Medium-level band-stop noise around 43 dB most reliably produces Zwicker tones

Evidence

The results displayed in Fig. 5.19 illustrate how frequently the Zwickertone phenomenon is found. Figure 5.19a and 5.19d show the spectral distributions of band-stop noises with spectral gaps at 1 and at 4 kHz. The distributions in Figs. 5.19b and 5.1ge show the probability of hearing a Zwicker tone as a function of the overall level of the noise. There is a clear maximum around medium levels of about 43 dB (density level around 0 dB). At these medium levels, more than 60% and more than 80% of the subjects can perceive a Zwicker tone for gaps in band-stop noise centred at 1 and 4 kHz, respectively. Figures 5.19c and 5.19f show probabilities of the durations of Zwicker tones when a band-stop noise with 43 dB overall level and 10 seconds duration is switched off. For both band-stop noises, the most likely duration is around 2 s, however durations longer than 6 s occur about 5% of the time. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 757

Categorization

• QUESTION: What mechanism makes medium overall levels optimal for Zwicker tone perception rather than louder levels?