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So I know that F0 need not be present for pitch to perceived (at least for men!) because the telephone filters out frequencies <300Hz (at least in the 90s, maybe there have been innovations in the filtering technique).

So how is F0 expressed over the phone?

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  • You've mis-phrased the question. F0 isn't "expressed" and it isn't present. Speakers can infer what F0 must have been. I suggest re-wording the question. – user6726 Aug 16 '16 at 14:52
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The fundamental forms the basis for the harmonic series: if F0 is 100 Hz, then harmonics are present at 200, 300, and so on. Humans can 'recover' (perhaps 'hallucinate') the original fundamental from the presence of these higher-frequency harmonics. This is also true for non-voice sounds. Here is a related Wikipedia reference.

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  • So the f0 is indeed filtered out through the phone for some reason, but the harmonics at other frequencies (e.g. F2 and F3 I guess) indicate something about the F0, correct? – Teusz Aug 16 '16 at 14:12
  • As far as I know, what you said about the limits of telephone frequencies is correct (i.e., about 300 to 3000). Because harmonics are multiples of the fundamental, you can calculate it by finding the greatest common divisor. Note that, per the Wikipedia reference, humans are also able to use this information to find additional missing harmonics. In the example there, harmonics at 300, 400, 500 allow recovery of both 100 and 200. – Jeremy Needle Aug 16 '16 at 14:21

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