27. A speech analysis device comprising: a plurality of sensors for receiving a signal segment; a speech codebook configured to store speech spectral parameters corresponding to a plurality of hypothesized speech spectral envelopes; a noise codebook configured to store noise spectral parameters corresponding to a plurality of hypothesized noise spectral envelopes; a combiner configured to combine the noise spectral parameters with the speech spectral parameters to obtain hypothesized power spectral density functions; and a discriminant function calculation component configured to evaluate a likelihood of the hypothesized power spectral density functions corresponding to the signal segment 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.
28. The speech analysis device of claim 27 , further comprising: a prior probability table configured to store prior conditional probabilities of first speech spectral envelopes following second speech spectral envelopes, wherein the discriminant function calculation component evaluates the likelihood of the hypothesized power spectral density functions corresponding to the signal segment based additionally on the prior conditional probabilities.