1. A spectral frequency quantizer comprising: a digital signal processor adapted to operate, at least in part, as a finite impulse response filter, said finite impulse response filter comprising an input for receiving line spectral frequencies, and an output for providing smoothed quantized line spectral frequencies, said finite impulse response filter characterized by the transfer function: EQU H(z)=0.5+.DELTA.+(0.5-.DELTA.)z.sup.-1 wherein .DELTA. is determined by the formula: EQU .DELTA.=min(0.5,.gamma..vertline..function.(n)-.function.(n-1).vertline.) and wherein .function.(n) denotes a present input to said finite impulse response filter, and wherein .function.(n-1) denotes a previous input to said finite impulse response filter.