Quadratic difference tones measured by cancellation originate primarily in the middle ear.

Evidence

Measurements of the cancellation level and cancellation phase for the quadratic difference tone as a function of the frequency region of the lower primary, have shown frequency independence at least for the first group showing almost regular quadratic distortion behaviour. This indicates that the quadratic difference tone measured by the cancellation method seems to be produced before the frequency-selective mechanism becomes effective, i.e. in the middle ear. The development of the quadratic difference tone for the second group seems to be rather complicated. A mixture of the nonlinear distortion produced in the middle ear and of that produced in the inner ear may be the reason. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1550

Categorization

• DEFINE: Clarifies that the site of quadratic difference-tone generation (middle vs. inner ear) can be inferred from frequency independence of cancellation parameters.