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US 4,061,874 AGranted
System for reproducing sound information
OwnerJ. P. Fricke, Ulrich R. Mullerinventors
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Abstract
In an environment of acoustic noise, such as a car radio playing in traffic or engine noise, both the volume (AGC) and dynamic range (Compression) of the audio amplifier are controlled by a local ambient acoustic noise sensor, such that gain is increased and dynamic range decreased simultaneously with increased ambient noise.
Claims8
A system for reproducing sound information in an environment impaired by noise of varying level, said system comprising:
- A signal processing circuit having input means for receiving an input signal conveying audio information, output means for providing an output signal conveying processed audio information, and at least one signal path coupling said input and output means, said audio information occupying a given frequency band and having a given dynamic range;
- and
- a control signal source providing a control signal related to said noise level;
- said signal path comprising amplifier means operative in at least a first portion of said frequency band to amplify said input signal,
- first means responsive to said control signal to vary the amplification provided by said amplifier means as a first direct function of said noise level,
- signal compressor means operative in at least a second portion of said frequency band, and
- second means responsive to said control signal to reduce the dynamic range of the signal in said at least second portion as a second direct function of said noise level, to provide an output signal which is boosted and dynamically compressed in at least a portion of said frequency band.
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Dependencies are inferred from the claim text.