A sound wave in air at 20 degree celsius has a frequency of 155 Hz and a displacement amplitude of 4.60×10−3 mm.
For this sound wave calculate the pressure amplitude (in Pa).
Use 1.42×105 Pa for the adiabatic bulk modulus.
Q1: Pmax = ? Pa
Find the intensity of the wave.
Use 1.20 kg/m^3 for the density of air.
Q2: I = ? W/m^2
Q3: Find the sound intensity level (in decibels).
Use 1.00×10^−12 W/m^2 for the reference intensity.
? dB
physics problem
2012-11-30 9:44 am
回答 (1)
2012-11-30 4:39 pm
✔ 最佳答案
Take the speed of sound in air at 20'C be 343 m/sPressure amplitude = square-root[1.42 x 10^5 x 1.2] x (2.pi x 155) x 4.6x10^-6 Pa = 1.85 Pa
(B) Wave inensity = (1/2) x 1.2 x 343 x [(2.pi x 155) x 4.6x10^-6]^2 W/m^2
= 4.13 x 10^-3 W/m^2
(C) Sound intensity level
= 10.log(4.13x10^-3/10^-12) dB = 96 dB
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