Outer ear

The floppy part of the ear that protrudes from the human head is called the pinna. It mainly serves as a funnel for collecting sound waves and guiding them into the ear canal. It has the effect of amplifying sounds in the 1500 to 7500Hz frequency range [369]. It also performs subtle filtering of the sound, causing some variation in the high-frequency range that depends on the incoming direction of the sound source. This provides a powerful cue regarding the direction of a sound source.

After traveling down the ear canal, the sound waves cause the eardrum to vibrate. The eardrum is a cone-shaped membrane that separates the outer ear from the middle ear. Its covers only $ 55$mm$ ^2$ of area. If this were a camera, it would have a resolution of one pixel at this point because no additional spatial information exists other than what can be inferred from the membrane vibrations.

Steven M LaValle 2020-01-06