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Hearing aid device incorporating signal processing techniques

  • US 5,500,902 A
  • Filed: 07/08/1994
  • Issued: 03/19/1996
  • Est. Priority Date: 07/08/1994
  • Status: Expired due to Term
First Claim
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1. A hearing compensation system comprising:

  • an input transducer for converting acoustical information at an input thereof to electrical signals at an output thereof;

    an output transducer for converting electrical signals at an input thereof to acoustical information at an output thereof;

    a plurality of bandpass filters, each bandpass filter having an input connected to said output of said input transducer;

    a plurality of AGC circuits, each individual AGC circuit associated with a different one of said bandpass filters and having an input connected to the output of its associated bandpass filter and an output summed with the outputs of all other ones of said AGC circuits to form a summed output, said summed output connected to the input of said output transducer, wherein each of said AGC circuits comprises a first amplifier element having an input and an output, said first amplifier element having a having a gain of 1/emax, where emax is the maximum value of an audio envelope to be presented to said AGC circuit for which AGC amplification is to result, a logarithmic element having an input connected to said output of said first amplifier element, said logarithmic element having a first output carrying a signal indicating the sign of a signal at said input of said logarithic element and a second output carrying a signal proportional to the logarithm of the absolute value of said signal at said input, a filter having an input connected to said second output of said logarithmic element and an output, said filter having a throughput delay, a delay element having an input connected to said first output of said logarithmic element and an output, said delay element having a delay equal to said throughput delay, an exponential element having a first input connected to said output of said delay element, a second input connected to said output of said filter element, and an output, and a second amplifier element having an input and an output, said input of said second amplifier element connected to said output of said exponential element, said second amplifier having a gain of emax.

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