In a paper presented March 14 to the American Physical Society, MSU physicist Michael Harrison outlined for the first time the explanation for this phenomenon. Basically, size does count - when it comes to ears.
Ears are the holding pens for all matter of sound.
It long has been known that human ears can register pure tones better than monkey ears can. The human ear is a remarkable thing. That, Harrison discovered, is where the differences in ear design become apparent. Monkey ears are shaped much like humans, except they are smaller in the cylinder extending from the eardrum to the outer part of the external ear. That smaller shape makes the monkey ear behave more like a seashell.