The ear itself generates distortion products even when equipment is clean

Evidence

A transmission system containing a nonlinearity produces harmonics when transmitting a pure tone. Such distortion products are often neither annoying nor audible, because they match almost totally with the fundamental. Musical tones are complex tones and consist of several harmonics. In this case, the nonlinearity changes the amplitude of these harmonics somewhat. This change is also rarely detected. Further, masking, which is stronger above the frequency of the tone, leads to the fact that strong fundamentals mask the higher harmonics produced by the nonlinear transmission system. Difference tones, produced by the nonlinearity when two tones (the primaries) are presented, are easier to detect. The difference tones are produced at frequencies below those of the primaries. The masking effect at medium and high levels is much smaller, and the difference tones are more easily detected. The frequencies of the difference tones may appear unharmonically related to the primaries and may therefore be annoying, if audible. Even when using highquality electroacoustic equipment that does not produce audible nonlinear distortion products, we still hear difference tones that are produced by the nonlinearity of our hearing system. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1520

Categorization

Category: Causal Relationships

• DEFINE: Defines what difference tones and combination tones are and why they are detectable where harmonics are not.
• XREF: Mirrors the concept of cochlear nonlinearity / otoacoustic emissions in auditory neuroscience; connects to distortion-product otoacoustic emissions (DPOAEs) used clinically.

Related

• Hearing’s own nonlinearity produces audible difference tones even in distortion-free equipment (similarity 0.94)
• Combination tones arise from the hearing system’s own nonlinearity (similarity 0.87)
• Difference noise generated by ear nonlinearities can be heard before the test tone itself (similarity 0.85)
• Distorted audio gear can create phantom tones falsely attributed to the ear (similarity 0.85)
• The ear itself generates audible nonlinear distortion tones from two simple inputs (similarity 0.85)
• Combination tones beat against other near-pitched instruments unless masked (similarity 0.84)
• Cubic difference tones arise inside the ear, not in the equipment (similarity 0.84)
• The ear generates audible combination tones not present in the stimulus (similarity 0.83)
• Humans perceive extended sound sources poorly when their parts emit identical tones (similarity 0.83)
• Noise-induced high-frequency threshold shifts can make previously inaudible difference tones audible (similarity 0.82)
• Nonlinear distortion adds frequencies that were not in the original signal (similarity 0.82)
• Cancellation equalizes internally produced combination tones with an external tone (similarity 0.82)
• Two tones presented together produce audible combination tones in the ear (similarity 0.82)
• Distortion product emissions arise only in a live ear, not passive cavities (similarity 0.82)
• Nonlinear cochlear mechanics make listeners perceive nonexistent difference tones (similarity 0.81)