beats between tones and subjective tones

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Re Beats between tones and subjective tones.

Tonal monaural diplacusis is a common effect. To hear it, you
adjust the frequency of a sine tone with the level within about
10 dB of threshold and find a frequency where beating or roughness
appears. The recommended frequency range is near the octave from
1 to 2 kHz where threshold microstructure is strong. Any background
noise, linearizing the cochlea, may destroy the effect.

The sensation can be quite striking as one tunes to the right
frequency ... pure tone sound, and then, suddenly, roughness or buzzing.

Tonal monaural diplacusis and threshold microstructure are both
associated with cochlear emissions. Dips in the microstructure and
TMD occur for signals close in frequency to the emissions.

Unfortunately, these emissions are not the same as tinnitus. The case
of  the piano tuner experiencing beats for high level tones still
seems rather mysterious to me.

Bill Hartmann