Term
-Compression: in hearing aid circuitry, nonlinear amplifier gain used either to limit ___ ___ (compression limiting) or to match amplifier gain to an individual’s ___ ___
-Compression provides MORE gain to ___ inputs (to increase audibility)
-Compression provides LESS gain to ___ inputs (to decrease the likelihood that LDLs are exceeded) |
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Definition
| maximum output; loudness growth (dynamic-range compression); softer; louder |
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Term
| lowest level (threshold) at which compression is activated; the point at which the input-output (I-O) function departs from linear |
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Definition
| Compression kneepoint (CK) |
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Term
| point at which the slope of I/O function changes |
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Definition
| CK: aka threshold kneepoint (TK) |
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Term
| input SPL when applied to HA gives a reduction in gain of 2 compared to linear mode |
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Definition
| Compression threshold (CT) |
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Term
| degree of gain reduction for signals above the compression kneepoint; Change in output relative to the change in input over a specified region |
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Definition
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Term
| No compression, CR=1:1. Every dB change in input results in a dB change in output |
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Definition
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Term
| once compression is activated, the resulting input-output function is ___. As input increases above the compression kneepoint, the compression ratio becomes ___ |
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Definition
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Term
| ___ ___: Compression circuitry takes some time to respond or compress the incoming signal that has suddenly increased in intensity |
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Definition
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Term
| time delay between the offset of an input loud enough to activate compression (input level falls below TK) & the resulting increase in gain |
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Definition
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Term
Adaptive Compression:
-Has ___ quick attack times
-Release times vary with length or duration of loud inputs: For sudden transient sounds, release time is ___. Release times are longer for inputs that are ___ in duration |
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Definition
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Term
static & dynamic characteristics of output limiting compression:
-High Kneepoint (>__dB SPL)
-High ratio (__:__)
-Fast time constants (__-__ msec) |
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Definition
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Term
Static & dynamic characteristics of wide-dynamic range compression (WDRC):
-Low Kneepoint (__-__ dB SPL)
-Low ratio (__:__ to __:__)
-Fast or slow time constants (__ msec to >__seconds) |
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Definition
| 35-45; 1.2:1 to 4:1; 20; 3 |
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Term
Applications for Compression:
-Maintain listening comfort (___ and "____” compression
-Maximize speech recognition (___-additional HF gain makes consonants more audible and reduces the upward spread of masking by vowels)
-Reduce adverse effects of noise (___-reduced LF gain at high input level)
-Limit HA ___ without distortion & minimize ___ ___.
-Optimize use of residual ___ range & restore normal ___ perception |
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Definition
| WDRC; mid-level; TILL; BILL; output; loudness discomfort; dynamic; loudness |
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Term
| What are the 2 types of WDRC? |
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Definition
-BILL: base increase at low frequency (or base decreasing at high level)
-TILL: treble increase at low level |
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Term
-BILL: ___-frequency gain is reduced for ___ input levels Why? To reduce the adverse effects of ___ (presumed to be
primarily low-frequency energy)
-TILL: High-frequency gain is ___ for ___ input levels • Why? To maximize ___ ___ |
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Definition
| Low; higher; noise; increased; lower; speech recognition |
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Term
-Expansion is what happens to the ___ of the left most kneepoint. For compression, its what happen to the ___ of the right most kneepoint.
-If expansion is used with WDRC, the greatest gain is delivered at (& only at) the ___- most TK
-For inputs less than TK, gain ___ as input level decreases |
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Definition
| left; right; left; decreases |
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Term
-Compression decreases gain for input levels ___ (to the right) the TK.
-Expansion decreases gain for input levels ___ (to the left) the TK |
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Definition
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Term
| What are some benefits of expansion? |
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Definition
-Quiets HA noise
-Quiets low-level noise. So when a refrigerator hums too loud you can activate expansion |
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