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US 5,687,189 AGranted
Method of noise reduction for an ADPCM signal
AssigneeMotorola, Inc.
InventorsSybren D. Smith, Paul D. Marko, Craig P. Wadin
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Abstract
Noise in an ADPCM signal is muted or suppressed by modifying the magnitude of the ADPCM information during noisy conditions. In one method, the ADPCM data is changed to a predetermined magnitude value. In another method, the magnitude is reduced by a predetermined amount.
Claims1
A method of noise suppression of an ADPCM signal comprising the steps of:
- receiving a radio ADPCM voice signal transmission;
- demodulating the radio ADPCM voice signal transmission to recover an ADPCM data;
- detecting the presence of noise on the radio ADPCM voice signal transmission;
- and
- for a portion of the ADPCM data which includes noise, modifying a magnitude of the ADPCM data to mitigate the noise by substituting a predetermined magnitude value for the ADPCM data, the predetermined magnitude value being selected from a hexadecimal group consisting of the values "3" and "C", depending on the hexadecimal value of the received signal.
2 more elements
Dependencies are inferred from the claim text.