1. The problem statement, all variables and given/known data(adsbygoogle = window.adsbygoogle || []).push({});

(a) What is the pressure amplitude of a sound wave with an intensity level of 124.5 dB in air?

_____ N/m2

(b) What force does this exert on an eardrum of area 0.520 10-4 m2?

_____ mN

3. The attempt at a solution

if P is amplitude of pressure, then sound intensity (I) is proportional to P^2

I/Io = (P/Po)^2

dB = sound intensity level = 10 log[I/Io]

124.5 = 10 log[I/Io] = 10 log[P/Po]^2 = 20 log(P/Po)

log(P/Po) = 124.5/20 = 6.225

P = Po [10]^6.225

Po = reference pressure amplitude for human ear = 2*10^-5 N/m^2

P = 2*10^-5*[10]^6.225

P = 33.576 N/m^2

----------------

Force on eardrum = P * area = 33.576*0.52*10^4 N

F = 1.746 milli N

This is what I did. But it is not giving me the correct answer...can anyone help me?

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# Homework Help: Pressure Amplitude

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