25. The vocoder device of claim 24 , further comprising: a receiver configured to receive the index values; a receive codebook configured to store the speech spectral parameters corresponding to the plurality of hypothesized speech spectral envelopes; and a synthesizer configured to synthesize human speech signals based on the speech spectral parameters indexed by the received index values.
24. A vocoder device comprising: a plurality of sensors for receiving signal segments; a transmit codebook configured to store speech spectral parameters corresponding to a plurality of hypothesized speech spectral envelopes; a discriminant function calculation component configured to evaluate a likelihood of the hypothesized speech spectral envelopes corresponding to the signal segments based on application of a likelihood function evaluated using a preconditioned conjugate gradient (PCG) process configured for block Toeplitz type matrices with a block size corresponding to the number of sensors and to output the most likely hypothesized spectral envelopes of the plurality of hypothesized speech spectral envelopes; and a transmitter configured to transmit index values corresponding to indexes of the most likely hypothesized speech spectral envelopes in the transmit codebook.