Suppressor tones reveal tuning curves matching neural frequency selectivity

Evidence

Tones added to the ear in which the emission occurs can reduce the amplitude of the SOAE. A reduction of 50% in the sound pressure of the emission is possible, and the frequency variation of the SOAE in this case remains very small. Plotting the sound pressure level of an additional tone (the suppressor), which is necessary to reduce the level of the spontaneous emission - for example by 6 dB - as a function of the suppressor frequency, produces a suppression-tuning curve. Such a curve is illustrated in Fig. 3.13 for a relatively large SOAE. The curve shows great similarity to the neurophysiological tuning curves discussed in Sect. 3.1.3 and characterizes the frequency selectivity of the hearing system at lower levels. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 264