Patent ID: 8655653

Claim:
A method of encoding a speech signal according to a source-filter model whereby the speech signal is modeled to comprise a source signal filtered by a time-varying filter, the method comprising: utilizing at least one processor: generating a first signal representing a property of an input speech signal; subtracting from the first signal using a simulated random-noise signal, thus producing a second signal; quantizing the second signal based on a plurality of discrete representation levels, thus generating quantization values for transmission in an encoded speech signal, and also generating a third signal being a quantized version of the second signal; adding the simulated random noise signal to the third signal, thus generating a quantized output signal, wherein the generation of said first signal is based on feedback of the quantized output signal; transmitting said quantization values in the encoded speech signal over a transmission medium; and varying the magnitude of noise generated in the quantized output signal relative to said representation levels in dependence on whether the first signal is representative of: a property of a voiced interval of a modeled source signal having greater than a specified correlation between portions of the modeled source signal, or a property of an unvoiced interval of the modeled source signal having less than a specified correlation between portions of the modeled source signal.