Compressors, limiters, and expanders each apply different gain rules to signal level.

Evidence

Dynamic aspects of cochlear mechanical compression were studied by recording basilar membrane (BM) vibrations evoked by tone pairs (“beat stimuli”) in the 11–19 kHz region of the gerbil cochlea. The frequencies of the stimulus components were varied to produce a range of “beat rates” at or near the characteristic frequency (CF) of the BM site under study, and the amplitudes of the components were balanced to produce near perfect periodic cancellations, visible as sharp notches in the envelope of the BM response. We found a compressive relation between instantaneous stimulus intensity and BM response magnitude that was strongest at low beat rates (e.g., 10–100 Hz). At higher beat rates, the amount of compression reduced progressively (i.e. the responses became linearized), and the rising and falling flanks of the response envelope showed increasing amounts of hysteresis; the rising flank becoming steeper than the falling flank. This hysteresis indicates that cochlear mechanical compression is not instantaneous, and is suggestive of a gain control mechanism having finite attack and release times. In gain control terms, the linearization that occurs at higher beat rates occurs because the instantaneous gain becomes smoothened, or low-pass filtered, with respect to the magnitude fluctuations in the stimulus. In terms of peripheral processing, the linearization corresponds to an enhanced coding, or decompression, of rapid amplitude modulations. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3625 (#expands, via linked claim)

Categorization

• XREF: connects to: Cochlear compression operates via a gain control with finite attack and release times. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3625

Related

• Cochlear compression operates via a gain control with finite attack and release times. (similarity 0.93)
• The cochlea compresses a 100 dB input range into about 57 dB of response. (similarity 0.91)
• Cochlear compression shows hysteresis with faster attack than decay at high modulation rates. (similarity 0.89)
• Cochlear mechanical compression is not instantaneous but has finite timing (similarity 0.89)
• Cochlear compression delay implies automatic gain control circuitry (similarity 0.86)
• The cochlea may regulate gain slowly rather than compress sound instantly (similarity 0.85)
• Fast amplitude modulations skip cochlear compression and get enhanced coding (similarity 0.84)
• The cochlea’s compressive nonlinearity may act as a time-averaging gain control, not instantaneously. (similarity 0.84)
• Cochlear compression shows asymmetric envelope at high beat rates. (similarity 0.84)
• Cochlear compression makes response gain peak near the moment of maximal two-tone cancellation (similarity 0.83)
• Cochlear gain control tracks intensity changes only up to about 1 kHz (similarity 0.83)
• Faster-fluctuating sounds trigger less cochlear compression, trading sensitivity for better dynamic encoding (similarity 0.83)
• Basal cochlear gain control is fast but limited to about 1 kHz bandwidth. (similarity 0.82)
• Cochlear envelope gain is low-pass filtered and decreases with faster beats (similarity 0.81)
• The cochlea cannot track dynamic intensity changes above roughly 1 kHz (similarity 0.81)

Broader Connections

• Cochlear compression operates via a gain control with finite attack and release times. #expands (0.78) — Dijk, Pim van, Physiology, Psychoacoustics and…, 3625