Audio amplifier systems
First Claim
1. An audio amplifier system including a variable gain amplifier adapted to receive an input signal, means for detecting periods when the input signal falls below a predetermined level, sound transducer means arranged to provide a signal proportional to the ambient noise level in the area or a part thereof covered by the system for therewith controlling the gain of the amplifier, and inhibitor means controlled by said detecting means to prevent the change of the gain of said variable gain amplifier except during periods when the input signal falls below said predetermined level, wherein the sound transducer means comprises signal detecting means whose response time is short at the beginning of each said period and increases for the remainder thereof, and wherein the said latter signal detecting means comprises first and second capacitors arranged to be charged when the input signal falls below the said predetermined level and first and second level detectors arranged to detect when the voltage across the respective capacitors rises above a predetermined voltage level, the first capacitor charging at a faster rate than the second, and the first level detector controlling the response time of the signal detector of the sound transducer means.
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Abstract
An audio amplifier system is provided comprising a variable gain amplifier adapted to receive an input signal, means for detecting periods when the input signal falls below a predetermined level, and sound transducer means arranged to provide a signal proportional to the sound level in the area or part thereof covered by the system for controlling the gain of the amplifier. An inhibitor is provided which is arranged to be controlled by the detecting means so as to prevent any change of the gain of the variable gain amplifier except during periods when the input signal falls below the said predetermined level.
38 Citations
11 Claims
- 1. An audio amplifier system including a variable gain amplifier adapted to receive an input signal, means for detecting periods when the input signal falls below a predetermined level, sound transducer means arranged to provide a signal proportional to the ambient noise level in the area or a part thereof covered by the system for therewith controlling the gain of the amplifier, and inhibitor means controlled by said detecting means to prevent the change of the gain of said variable gain amplifier except during periods when the input signal falls below said predetermined level, wherein the sound transducer means comprises signal detecting means whose response time is short at the beginning of each said period and increases for the remainder thereof, and wherein the said latter signal detecting means comprises first and second capacitors arranged to be charged when the input signal falls below the said predetermined level and first and second level detectors arranged to detect when the voltage across the respective capacitors rises above a predetermined voltage level, the first capacitor charging at a faster rate than the second, and the first level detector controlling the response time of the signal detector of the sound transducer means.
Specification