Two frequencies can mechanically generate sum and difference frequencies in the ear

Evidence

When two pure tones are heard together, other tones with frequencies lower than the frequencies of either of the two pure tones themselves may be heard also. These lower tones are not acoustically present in the stimulating signal, and they occur as a result of the stimulus consisting of a “combination” of at least two pure tones; they are known as “combination tones.” The frequency of one such combination tone that is usually quite easily perceived is the difference (higher minus the lower) between the frequencies of the two tones; this is known as the “difference tone”: where fd = frequency of the difference tone fh = frequency of the higher-frequency pure tone and fl = frequency of the lower-frequency pure tone Notice that this is the beat frequency when the frequency difference is less than approximately 12. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1571 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Combination tones arise from the hearing system’s own nonlinearity — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 430; The ear generates audible combination tones not present in the stimulus; Cubic difference tones arise inside the ear, not in the equipment — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3354 (+4 more)

Related

• The ear generates audible combination tones not present in the stimulus (similarity 0.94)
• Two simultaneous tones generate audible lower tones absent from the stimulus (similarity 0.94)
• Combination tones become audible only above roughly 70 dB primary level (similarity 0.88)
• Combination tones arise from the hearing system’s own nonlinearity (similarity 0.87)
• Two tones presented together generate an audible combination (difference) tone not physically present. (similarity 0.87)
• Difference noise generated by ear nonlinearities can be heard before the test tone itself (similarity 0.87)
• Cubic difference tones arise inside the ear, not in the equipment (similarity 0.86)
• Combination tones fill in missing harmonics of a perceived fundamental (similarity 0.86)
• Combination tones beat against other near-pitched instruments unless masked (similarity 0.86)
• Two inaudible high tones can produce audible low phantom tones that interfere (similarity 0.86)
• Only some combination tones are readily perceived, and none by all listeners. (similarity 0.85)
• Cubic difference tones reveal nonlinear cochlear mechanics even at low sound levels (similarity 0.85)
• Combination tones exist below both source tones and vary in audibility (similarity 0.85)
• Hearing’s own nonlinearity produces audible difference tones even in distortion-free equipment (similarity 0.84)
• Phantom tones are heard despite being absent from the presented sound (similarity 0.84)

Broader Connections

• Two simultaneous tones generate audible lower tones absent from the stimulus #corroborates (0.92) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1571