Eli5:When one speaker is playing two (or more) frequencies of sound, think harmony in music) the resulting sine wave is an average of those two frequencies. How does the brain interpret it as two different notes when one speaker is playing the average of two frequencies?

Question

Eli5:When one speaker is playing two (or more) frequencies of sound, think harmony in music) the resulting sine wave is an average of those two frequencies. How does the brain interpret it as two different notes when one speaker is playing the average of two frequencies?

In: 11

Answer 1

Sound waves always overlap (superimpose). But the ear is able to isolate specific frequencies from the superimposed sound waves. Different parts of the inner ear cochlea (a snail shaped organ filled with fluid), and different groups of hair-like cells within the cochlea are (edit: relatively more) sensitive to different frequencies. This allows the sensory organ, and in-turn the brain, to isolate individual notes from the super-imposed wave.

You can find more details here: https://en.wikipedia.org/wiki/Auditory_system?wprov=sfla1

Also check the humans section here, for a relatively shorter and simpler explanation: https://en.wikipedia.org/wiki/Hearing_range?wprov=sfla1