# Math Help - Help me!

1. ## Help me!

The size of your eardrum (the tympanum) partially determines the upper frequency limit of your audible region, usually between 16,000 Hz and 20,000 Hz. If the wavelength is about twice the diameter of the eardrum and the air temperature is 20oC, how wide is your eardrum? Is your answer reasonable?

2. Originally Posted by babygirl
The size of your eardrum (the tympanum) partially determines the upper frequency limit of your audible region, usually between 16,000 Hz and 20,000 Hz. If the wavelength is about twice the diameter of the eardrum and the air temperature is 20oC, how wide is your eardrum? Is your answer reasonable?
The speed of sound at 20C is 343.4 m/s, and as before:

$\lambda=c/f$,

Lets work with a cut-off frequency of 18000 Hz. Then the wavelength is:

$
\lambda=\frac{34304}{18000}\approx 0.019 \mbox{ m}
$
,

or about 2cm. So the eardrum dia would be half this or about 1cm. This seems
about the right sort of size (perhaps a little bigger than I would have expected).

RonL