Research Overview

Tinnitus and Zwicker tone may be produced by simple gain adaptation.

Listen to:
Audio re-synthesized from original powers
Audio re-synthesized from gain-adjusted powers

Zwicker tone: Here is some matlab code (zwicker.m) that will play band-gap noise, which should elicit a Zwicker tone in some subjects (assuming you have got the right hardware). Play this at 40-50dB -- roughly the level of natural speech in close proximity. Our data shows that about 1/3 of normal subjects will hear the Zwicker tone for at least one of the three band-gaps presented here. In contrast, subjects that report tinnitus are just about guaranteed to hear a Zwicker tone.
This is a sound file with three examples of notched noise that may elicit a Zwicker tone, followed by an additional segment with white noise which should not elicit the Zwicker tone.

Beware of the hardware: Most inexpensive sound cards on a PC or laptop will not be able to reproduce a sharp and deep notch as required. The same is tru for many headphones. We used a MAYA44 as sound card and Sony MDR-7506 headphones. We whiten the noise spectrum of the headphones using calibrated microphones to ensure uniform SPL across frequencies. Any 24 bit sound card should be fine. These specific Sony headphones are nice because they really don't seem to inject any noise in the band-gap. Most other headphones we tried had a 20dB noise floor in the band-gap.

Lucas C. Parra, Barak A. Pearlmutter, "Illusory percepts from auditory adaptation", Journal of the Acoustical Society of America, accepted for publication November 20, 2006.

Lucas Parra, Dec 12, 2006, updated Jun 9, 2008