Strategies and Technologies for Minimizing Aircraft Noise: Multiple
Choice Questions
1. What is the relationship between sound intensity level (SIL) and sound pressure level (SPL)?
a) SIL = SPL + 10 dB
b) SIL = SPL - 10 dB
c) SIL = SPL
d) SIL = SPL + 20 dB
Answer: c) SIL = SPL
2. The sound pressure level (SPL) is given by the formula:
a) SPL = 20 log₁₀(p/pref)
b) SPL = 10 log₁₀(p/pref)
c) SPL = 20 log₁₀(p²/pref²)
d) SPL = 10 log₁₀(p²/pref²)
Where p is the measured sound pressure and pref is the reference pressure.
Answer: a) SPL = 20 log₁₀(p/pref)
3. What is the approximate reduction in sound pressure level when doubling the distance from a
point source?
a) 3 dB
b) 6 dB
c) 9 dB
d) 12 dB
Answer: b) 6 dB
4. The sound power level (SWL) is related to the sound intensity level (SIL) by:
a) SWL = SIL + 10 log₁₀(S)
b) SWL = SIL - 10 log₁₀(S)
c) SWL = SIL + 20 log₁₀(S)
d) SWL = SIL - 20 log₁₀(S)
Where S is the surface area of measurement.
Answer: a) SWL = SIL + 10 log₁₀(S)
5. The transmission loss (TL) of a single-leaf partition is given by the mass law:
a) TL = 20 log₁₀(mf) - 47
b) TL = 20 log₁₀(mf) + 47
c) TL = 10 log₁₀(mf) - 47
d) TL = 10 log₁₀(mf) + 47
Where m is the mass per unit area and f is the frequency.
Answer: b) TL = 20 log₁₀(mf) - 47
6. The critical frequency fc of a panel is given by:
a) fc = c²/(2π√(m/D))
b) fc = c²/(π√(m/D))
c) fc = c²/(4π√(m/D))
d) fc = c²/(8π√(m/D))
Where c is the speed of sound, m is the mass per unit area, and D is the bending stiffness.
Answer: b) fc = c²/(π√(m/D))
7. The sound absorption coefficient α of a material is defined as:
a) α = Absorbed energy / Incident energy
b) α = Reflected energy / Incident energy
c) α = Transmitted energy / Incident energy
d) α = (Absorbed energy + Reflected energy) / Incident energy
Answer: a) α = Absorbed energy / Incident energy
8. The Noise Reduction Coefficient (NRC) is calculated as:
a) NRC = (α250 + α500 + α1000 + α2000) / 4
b) NRC = (α125 + α250 + α500 + α1000) / 4
c) NRC = (α500 + α1000 + α2000 + α4000) / 4
d) NRC = (α125 + α250 + α500 + α1000 + α2000 + α4000) / 6
Where αx is the absorption coefficient at x Hz.
Answer: a) NRC = (α250 + α500 + α1000 + α2000) / 4
9. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
. The reverberation time T60 in a room is given by the Sabine formula:
a) T60 = 0.161V / A
b) T60 = 0.161A / V
c) T60 = 0.049V / A
d) T60 = 0.049A / V
Where V is the room volume and A is the total absorption.
Answer: a) T60 = 0.161V / A
10. The transmission loss (TL) of a double-leaf partition below the mass-air-mass resonance
frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
c) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
11. The mass-air-mass resonance frequency f0 for a double-leaf partition is given by:
a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
b) f0 = (1/2π) √((s/d)(m₁ + m₂))
c) f0 = (1/4π) √((s/d)(1/m₁ + 1/m₂))
d) f0 = (1/4π) √((s/d)(m₁ + m₂))
Where s is the stiffness of the air cavity, d is the cavity depth, and m₁ and m₂ are the masses per
unit area of the leaves.
Answer: a) f0 = (1/2π) √((s/d)(1/m₁ + 1/m₂))
12. The sound power level (SWL) of a jet engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁸
Where V is the jet velocity.
Answer: d) V⁸
13. The overall sound pressure level (OASPL) for N independent sources is given by:
a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
b) OASPL = 20 log₁₀(Σ 10^(SPLi/20))
c) OASPL = 10 log₁₀(Σ 10^(SPLi/20))
d) OASPL = 20 log₁₀(Σ 10^(SPLi/10))
Where SPLi is the sound pressure level of each source.
Answer: a) OASPL = 10 log₁₀(Σ 10^(SPLi/10))
14. The insertion loss (IL) of a noise control treatment is defined as:
a) IL = SPL_before - SPL_after
b) IL = SPL_after - SPL_before
c) IL = 10 log₁₀(SPL_before / SPL_after)
d) IL = 20 log₁₀(SPL_before / SPL_after)
Answer: a) IL = SPL_before - SPL_after
15. The noise reduction (NR) of a partition is related to its transmission loss (TL) by:
a) NR = TL + 10 log₁₀(S/A)
b) NR = TL - 10 log₁₀(S/A)
c) NR = TL + 20 log₁₀(S/A)
d) NR = TL - 20 log₁₀(S/A)
Where S is the partition area and A is the room absorption.
Answer: b) NR = TL - 10 log₁₀(S/A)
16. The Sound Transmission Class (STC) rating is approximately related to the average transmission
loss (TL) by:
a) STC ≈ TLavg - 5
b) STC ≈ TLavg
c) STC ≈ TLavg + 5
d) STC ≈ TLavg + 10
Answer: c) STC ≈ TLavg + 5
17. The frequency of maximum radiation efficiency for a simply supported panel occurs at:
a) f = c² / (4fcL)
b) f = c² / (2fcL)
c) f = c² / (fcL)
d) f = 2c² / (fcL)
Where c is the speed of sound, fc is the critical frequency, and L is the panel dimension.
Answer: c) f = c² / (fcL)
18. The transmission loss (TL) of a double-leaf partition above the mass-air-mass resonance
frequency and below the critical frequency is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 20 log₁₀(fd) + 29
d) TL = TL₁ + TL₂ + 40 log₁₀(fd) + 29
Where TL₁ and TL₂ are the transmission losses of individual leaves, f is frequency, and d is the cavity
depth.
Answer: b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
19. The sound power level (SWL) of a propeller is proportional to:
a) N³D²
b) N⁴D²
c) N⁵D²
d) N⁶D²
Where N is the rotational speed and D is the propeller diameter.
Answer: d) N⁶D²
20. The wavelength λ of sound at a frequency f is given by:
a) λ = c/f
b) λ = cf
c) λ = c²/f
d) λ = f/c
Where c is the speed of sound.
Answer: a) λ = c/f
21. The sound pressure level (SPL) at a distance r from a point source with sound power level (SWL) is
given by:
a) SPL = SWL - 20 log₁₀(r) - 11
b) SPL = SWL - 10 log₁₀(r) - 11
c) SPL = SWL - 20 log₁₀(r) + 11
d) SPL = SWL - 10 log₁₀(r) + 11
Answer: a) SPL = SWL - 20 log₁₀(r) - 11
22. The transmission loss (TL) of a single-leaf partition at the critical frequency fc is approximately:
a) TL = 20 log₁₀(mfc) - 44
b) TL = 20 log₁₀(mfc) - 47
c) TL = 20 log₁₀(mfc) - 50
d) TL = 20 log₁₀(mfc) - 53
Where m is the mass per unit area.
Answer: b) TL = 20 log₁₀(mfc) - 47
23. The sound absorption coefficient α of a porous material of thickness d at normal incidence is
given by:
a) α = 1 - |R|²
b) α = |R|²
c) α = 1 + |R|²
d) α = 1 / |R|²
Where R is the reflection coefficient.
Answer: a) α = 1 - |R|²
24. The transmission loss (TL) of a single-leaf partition above the critical frequency fc is
approximately:
a) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 44
b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
c) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 44
d) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 20 log₁₀(f/fc) - 47
Where m is the mass per unit area, f is frequency, η is the loss factor.
Answer: b) TL = 20 log₁₀(mf) - 10 log₁₀(η) + 10 log₁₀(f/fc) - 47
25. The sound power level (SWL) of a turbofan engine is proportional to:
a) V³
b) V⁴
c) V⁵
d) V⁶
Where V is the exhaust velocity.
Answer: c) V⁵
26. The coincidence frequency fc for a panel of thickness h is given by:
a) fc = c² / (1.8h√(E/ρ))
b) fc = c² / (1.8h√(ρ/E))
c) fc = c² / (3.6h√(E/ρ))
d) fc = c² / (3.6h√(ρ/E))
Where c is the speed of sound, E is Young's modulus, and ρ is the density.
Answer: a) fc = c² / (1.8h√(E/ρ))
27. The sound pressure level (SPL) reduction due to a single noise barrier is approximated by:
a) ΔL = 10 log₁₀(3 + 20N)
b) ΔL = 20 log₁₀(3 + 20N)
c) ΔL = 10 log₁₀(3 + 40N)
d) ΔL = 20 log₁₀(3 + 40N)
Where N is the Fresnel number.
Answer: b) ΔL = 20 log₁₀(3 + 20N)
28. The sound power level (SWL) of a fan is proportional to:
a) N³D⁴
b) N⁴D⁵
c) N⁵D⁶
d) N⁶D⁷
Where N is the rotational speed and D is the fan diameter.
Answer: c) N⁵D⁶
29. The transmission loss (TL) of a double-leaf partition at frequencies well above the mass-air-mass
resonance is approximately:
a) TL = TL₁ + TL₂ + 20 log₁₀(fd) - 29
b) TL = TL₁ + TL₂ + 40 log₁₀(fd) - 29
c) TL = TL₁ + TL₂ + 60 log₁₀(fd) - 29
d) TL = TL₁ + TL₂ + 80 log₁₀(f
