1. A method for concealing the effects of frame errors in frames to be decoded by a decoder in providing synthesized speech, the frames being provided over a communication channel to the decoder, each frame providing parameters used by the decoder in synthesizing speech, the method comprising the steps of: a) determining whether a frame is a bad frame; and b) providing a substitution for the parameters of the bad frame based on an at least partly adaptive mean of the spectral parameters of a predetermined number of the most recently received good frames.