| 摘要 |
The invention relates to an automatic volume control system which adjusts the level of an audio electrical signal in dependence on ambient noise level. A filter derives low frequency components from the audio signals and these components are then applied to a gate where they are intermittently gated. An electrical signal produced from ambient noise detected by a sensor is sampled by a further gate during the gating periods and a sampled level of the noise signal is maintained from one gating period until the next gating period and is applied to a gain control circuit to control the level of the audio electrical signal in dependence on each sampled level of the noise signal. The gating and sampling actions preferably occur at irregular time intervals under the control of a logic and timing circuit assessing circuit and clock.
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