basis the log2gain and voicing probability p v are used to estimate the signal to noise ratio snr in snr estimation block 230 fig8 further describes the estimation algorithm in convert to db block 800 the log2gain is converted to db the algorithm then computes an estimate of the active speech energy level sp_db and the background noise energy level bkgd_db the methods for these estimations are described in blocks 810 and 820 respectively finally the background noise level bkgd_db is subtracted from the speech energy level sp_db to obtain the estimate of the snr the snr and p v are used in the input characterization classifier block 240 the classifier outputs three parameters used to control the postfilter operation and the generation of the spectral components above p v the post filter attenuation factor pfaf is a binary switch controlling the postfilter if the snr is less than a threshold and p v is less than a threshold pfaf is set to disable the postfilter for the current frame the unvoiced suppression factor usf is used to adjust the relative energy level of the spectrum above p v the usf is perceptually tuned and is currently a constant value the synthesis.