1. A speech analysis device comprising: a plurality of sensors for receiving a signal segment; a codebook configured to store parameters corresponding to a plurality of hypothesized speech power spectral density functions; and a discriminant function calculation component configured to evaluate a likelihood of at least one of the hypothesized speech power spectral density functions corresponding to the signal segment based on application of a discriminant 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.