Humans can reportedly hear sounds as low as 31 Hz. If we consider the speed of sound in air to be 1125 feet per second, then a sound at 31 Hz will have a wavelength of about 36 feet.

Normally, to capture a sound or other wave, we need an antenna that is at least as long as the wavelength of the signal we are attempting to receive.

But with the ear this is plainly not possible. If the cochlea of a human ear were to be unrolled, it would have a length of about 1 inch. Thus, in the sense of being an "antenna" it would seem to be far too short to be able to receive a 31 Hz signal, yet somehow it does.

How does the ear sense such low frequency sounds?

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    $\begingroup$ "to capture a sound or other wave we need an antenna that is at least as long as the wavelength of the signal" - this is definitely not true for sound, it doesn't have to be anything special about an ear. I am also guessing your laptop/headset/cell phone doesn't have a 15-meter long antenna. $\endgroup$ – Bryan Krause Jun 7 '17 at 22:25
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    $\begingroup$ Possible duplicate of What causes the tonotopic organization of the inner ear? $\endgroup$ – Bryan Krause Jun 7 '17 at 22:29
  • $\begingroup$ Yep, no idea where you got that quote from, but obviously we can hear low frequency sounds. Try googling "basilar membrane dynamics", which should explain how sound frequencies are separated within the ear. $\endgroup$ – Oliver Houston Jun 7 '17 at 22:31
  • $\begingroup$ Besides that misconception, I voted to close as duplicate because another question asks about tonotopic organization in the ear and how different frequencies are 'mapped' to the basilar membrane. I think that answer is sufficient to answer your question. $\endgroup$ – Bryan Krause Jun 7 '17 at 22:31
  • $\begingroup$ I don't think this question is a dupe from What causes the tonotopic organization of the inner ear?. It has overlap, but the focus is different here. Overlapping questions scopes are fine and should not be closed. $\endgroup$ – AliceD Jun 9 '17 at 8:27

You are thinking of antennas for EM signals such as the dipole antenna. In this type of antenna, an external field (EM waves) excite the antenna (creating an electric current) which you then measure. There is thus something like a transduction step, which is more efficient if you can use the spatial scale of the wavelength.

In the case of hearing sound waves, the ear does not transduce the mechanical signal into another modality, but is directly modulated by the hair cells.


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