# Sound wave question

stuti911

## Homework Statement

Sound is detected when a sound wave causes the eardrum to vibrate. Typically, the diameter of the eardrum is about 8.4mm in humans. When someone speaks to you in a normal tone of voice, the sound intensity at your ear is approximately 1 * 10^-6 W/m^2. How much energy is delivered to your eardrum each second?

I = P/(4pi*r^2)

## The Attempt at a Solution

I tried using the equation and I got 2.20×10^−10 W as my answer, but it is wrong. I cannot understand why, because the question seems really simple.
Any help is appreciated, thanks!

Homework Helper
Gold Member
I tried using the equation and I got 2.20×10^−10 W as my answer, but it is wrong. I cannot understand why, because the question seems really simple.
Any help is appreciated, thanks!
The diameter of the eardrum is about 8.4 mm. Which means the radius is half that.

[Edit: And welcome to Physics Forums!]

Last edited:
Gold Member
yes, so if you take proper radius you will get the answer.

stuti911
yes, i did take the radius
this is my calculation:
(10^-6)*(0.00001764*4*pi) which gives my the answer above
can any of you try the question?
thanks!

Gold Member

Gold Member
first of all, take eardrum as a circle, not sphere, and so use area as pi*r^2

stuti911
allright.. i got it!
thanks a whole bunch :)

Gold Member
welcome Stuti...would you accept my friend request?

Mandeep Deka
welcome Stuti...would you accept my friend request?