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Mobile automatic volume control apparatus

  • US 4,864,246 A
  • Filed: 09/09/1988
  • Issued: 09/05/1989
  • Est. Priority Date: 11/25/1987
  • Status: Expired due to Term
First Claim
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1. A mobile automatic volume control apparatus comprising:

  • means for producing a signal corresponding to ambient noise;

    a noise detection section for detecting an ambient noise level comprising a low-pass filter having a cut-off frequency of substantially 10 Hertz for extracting low-frequency components from said signal corresponding to ambient noise;

    an audio signal detection section receiving an audio signal for detecting an input level of said audio signal;

    means for producing a control signal by subtracting a quantity of logarithmic change of an audio signal detection signal obtained from said audio signal detection section relative to a reference value from a value obtained by amplifying, with an amplification factor in a range of from 1.5 to 2.5 inclusive, a quantity of logarithmic change of a noise detection signal obtained from said noise detection section relative to a reference value; and

    a volume controller for increasing/decreasing an output level of said audio signal in response to said control signal.

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