How Do You Calculate Pressure Amplitude and Force on an Eardrum from dB Level?

[Jtappan]

Some one please help! Pressure Amplitude

Homework Statement

(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?

 

[Shooting Star]

This is pressure tactics, posting it three times.

33.5 N/m^2 seems to be correct. Are you getting both answers wrong?