Homework Help: Physics

Posted by Kyle on Friday, May 4, 2012 at 9:37pm.

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.

Physics - bobpursley, Friday, May 4, 2012 at 9:45pm
I dont understand the diamter being 8meters. It makes no sense.

Secondly, What is the exact question?
Physics - Kyle, Friday, May 4, 2012 at 10:24pm
oh sorry the diameter is 8.4mm

and the question is asking for the

How much energy is transferred to her eardrums each second ?
Physics - bobpursley, Friday, May 4, 2012 at 11:11pm
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.
Physics - bobpursley, Friday, May 4, 2012 at 11:12pm
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
Physics - Kyle, Friday, May 4, 2012 at 11:25pm
The range away from the stage doesn't matter?
Physics - Marshall, Monday, September 17, 2012 at 1:05am
the range doesnt matter because the relative intesity is already given in db

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