A spectral gap in switched-off noise yields a tonal afterimage, not a noisy one

Evidence

An acoustic after effect was discovered in 1964 and later called the “Zwickertone”. The phenomenon can be described as follows: if sounds with a spectral gap are switched off, a faint tone lasting for several seconds can be heard. Its pitch strength (see Sect. 5.7) corresponds to the pitch strength of a pure tone of same pitch and sensation level. This result is at first astonishing, since after a broad-band noise with a spectral gap is switched off, one might expect a “negative acoustic afterimage” with a “noise quality” similar to a narrowband noise corresponding to the spectral gap. Contrary to this expectation, however, the afterimage has a clear tonal quality as evidenced by its pitch strength. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 756

Categorization

• DEFINE: Introduces and defines the Zwicker tone phenomenon and its counterintuitive tonal quality.
• QUESTION: What neural mechanism turns a spectral gap afterimage into a true tonal percept rather than narrowband noise?