Question

A fan at a rock concert is 45.0 m from the stage, and at this point the sound intensity level is 108 dB. Sound is detected when a sound wave causes the tympanic membrane (the eardrum) to vibrate . Typically, the diameter of this membrane is about 8.40 m in humans


I solved for the intensity using Beta = (10 dB) log I/I_0

I got I to be 3.11*10^-5 W/m^2 45m away.

Then I found the energy to be 17.22*10^-11J

The answer wants it in micro joules but I'm not even sure if I've done the problem correctly.

Answers

bobpursley
I don't understand the diamter being 8meters. It makes no sense.

Secondly, What is the exact question?
oh sorry the diameter is 8.4mm

and the question is asking for the

How much energy is transferred to her eardrums each second ?
bobpursley
108=10 log(I/Io)
10.8=log( )

I= 10^10.8 * Io=10^10.8*1E-12=.063watts/m^2 check that.

Energy= areadrum*I= PI* .004^2*I above.
= .063watts/m^2*PI*16E-6=3.2 × 10-6 watts.

bobpursley
108=10 log(I/Io)
10.8=log( )

I= 10^10.8 * Io=10^10.8*1E-12=.063watts/m^2 check that.

power= areadrum*I= PI* .004^2*I above.
= .063watts/m^2*PI*16E-6=3.2 × 10-6 joules/sec

energy in one second= 3.2E-6joules

The range away from the stage doesn't matter?
the range doesnt matter because the relative intesity is already given in db

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