| 摘要 |
The system has a measuring circuit (3) coupled to a loudspeaker (1), used for detecting the microphone voltage, to determine the background noise level. The measuring circuit (3) may comprise a subtractor receiving the amplifier input signal and the loudspeaker input signal weighted by the amplification factor of the amplifier. - Alternately, the measuring circuit comprises a measuring resistance in series with the loudspeaker. A subtractor provides the difference between the voltage across the measuring resistance and the loudspeaker voltage. The output of the measuring circuit (3) is used for automatic adjustment of the volume and dynamics of the audio system.
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