The speed of sound at 20C is 343.4 m/s, and as before:Originally Posted bybabygirl

,

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

,

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