1. A system for processing an audio signal having a number of frames, the system comprising: a decoder comprising: means for unquantizing at least a pitch period, a voicing probability, a mid-frame pitch period, and/or a mid-frame voicing probability of the audio signal and providing at least one output, where the means for unquantizing comprises means for generating at least one control parameter using at least the signal-to-noise ratio computed using a gain and the voicing probability of the audio signal; and means for analyzing the at least one output, including the at least one control parameter, to produce a synthetic speech signal corresponding to the input audio signal.