View Full Version : Sound wave and energy...can you help me?


kingwinner
03-16-07, 09:15 AM
A sound wave with intensity 2x10^(-3) W/m^2 is perceived to be modestly loud. Your eardrum is 6.0 mm in diameter. How much energy will be transferred to your eardrum while listening to this sound for 1.0 min?

P=IA=(intensity)(area)
=2x10^(-3) * (pi (6x10^-3)^2)
=2.2610x10^-7 W

P=delta E/ delta t
=2.2610x10^-7 J/s * 60 s
=1.3572x10^-5 J

But this is not the right answer. I have no idea what I did wrong. Can someone please help me? Any help is greatly appreciated! Thanks!

1100f
03-16-07, 09:54 AM
A sound wave with intensity 2x10^(-3) W/m^2 is perceived to be modestly loud. Your eardrum is 6.0 mm in diameter. How much energy will be transferred to your eardrum while listening to this sound for 1.0 min?

P=IA=(intensity)(area)
=2x10^(-3) * (pi (6x10^-3)^2)
=2.2610x10^-7 W

P=delta E/ delta t
=2.2610x10^-7 J/s * 60 s
=1.3572x10^-5 J

But this is not the right answer. I have no idea what I did wrong. Can someone please help me? Any help is greatly appreciated! Thanks!


The area is not equal to pi*d^2 but pi*r^2

kingwinner
03-16-07, 06:40 PM
Thanks for pointing it out! I rarely make this kind of silly mistake:rolleyes: