How can a vibrating eardrum convey the rich symphony that we hear? Why don鈥檛 the various frequencies interfere with each other?
James Stone
University of Sheffield, UK
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The clue to the answer is in the second part of the question, which mentions 鈥渧arious frequencies鈥�.
In 1822, French mathematician and philosopher Joseph Fourier effectively proved that every sound can be represented as the sum of sinusoidal waves, each with a different frequency.
A sinusoidal wave is a pure tone and sounds like a single note on a whistle. As an example, if five sinusoidal waves with different frequencies are added together, they produce a complex wave. It is obvious this consists of five sinusoidal waves because that is how it was made.
Once we know this, we should be unsurprised to learn that a part of the inner ear called the cochlea essentially separates out the various sinusoidal waves in any complex sound.
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