Your phone can't play a man's voice. Your brain fills in the missing note.
Most telephones can't reproduce sounds below about 300 hertz, yet a typical male voice sits around 150. We still hear its true pitch, because the brain reconstructs a note from the pattern of its overtones, even when the note itself is absent. Audio engineers exploit this to fake bass.
Almost every musical sound is a stack of frequencies. A note with a pitch of 100 hertz contains energy at 100, 200, 300, 400 hertz and so on: a fundamental plus overtones at whole-number multiples. Remove the 100-hertz component entirely and, remarkably, listeners usually still hear a pitch of 100. This is the missing fundamental, sometimes called virtual pitch.
It was once thought the ear itself generated the absent note through physical distortion. But in 1954 J. C. R. Licklider reported that listeners still heard the missing pitch even when noise was added that would have masked any such distortions. The accepted view now is that the brain works out the fundamental from the regular pattern of the overtones. Exactly how is still debated. A leading idea involves comparing the timing of nerve impulses, but no neural delay mechanism of the kind that would require has been found.
Not everyone hears it the same way. Researchers at Heidelberg University found that with only a few harmonics, some people hear the missing fundamental while others hear the individual overtones, and that this preference correlated with which side of the brain handled pitch. The overtone listeners tended to be musicians.
Instruments and technology rely on the effect. A violin's body barely resonates below about 250 hertz, yet its open G string is below 200, and listeners seldom notice the weak fundamental. Timpani are tuned so that their overtones imply a note that is not strongly present, and some pipe organs use it to get very low notes from smaller pipes. Audio companies synthesise extra harmonics so that small speakers and earbuds seem to produce bass they cannot physically play; the 2001 hit 'Lady Marmalade' was mixed with one such processor.
Source: Wikipedia — Missing fundamental · Text summarised from Wikipedia (CC BY-SA 4.0)
