The ear itself generates audible nonlinear distortion tones from two simple inputs

Evidence

The nonlinear distortions produced by the ear can be made audible by playing a constant pure tone (here /1 = 1620 Hz) together with a short sine sweep of similar frequencies (here 12 = 1700 Hz to 3000 Hz). Although physically there are only two tones, a third descending tone with the frequency 2/1 - 12 can be clearly heard. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3352

Categorization

Category: Causal Relationships

• XREF: Connects to the reader’s reading on the ear’s nonlinear mechanics and combination-tone literature; also relates to the whistle experiment in 3354-55 proving the distortion is cochlear, not from equipment.
• SHARE: A great demo fact for anyone into audio engineering or hearing science: two pure tones make a third audible tone the ear itself manufactures.

Related

• Two physically present tones produce an audible third tone inside the ear (similarity 0.93)
• Two tones presented together produce audible combination tones in the ear (similarity 0.85)
• The ear itself generates distortion products even when equipment is clean (similarity 0.85)
• Combination tones arise from the hearing system’s own nonlinearity (similarity 0.85)
• Cubic difference tones arise inside the ear, not in the equipment (similarity 0.84)
• A healthy cochlea emits new frequencies when stimulated by two tones (similarity 0.83)
• Hearing’s own nonlinearity produces audible difference tones even in distortion-free equipment (similarity 0.83)
• Nonlinear distortion adds frequencies that were not in the original signal (similarity 0.83)
• The ear becomes less nonlinear as sound levels rise (similarity 0.82)
• Distorted audio gear can create phantom tones falsely attributed to the ear (similarity 0.82)
• Difference noise generated by ear nonlinearities can be heard before the test tone itself (similarity 0.81)
• The ear generates audible combination tones not present in the stimulus (similarity 0.81)
• Ear sensitivity depends jointly on frequency and on sound level (similarity 0.80)
• Regular distortion laws from electroacoustics describe hearing’s own nonlinear products (similarity 0.80)
• Two frequencies can mechanically generate sum and difference frequencies in the ear (similarity 0.80)