Relative to the speech production and perception models, spectral envelopes play an important role in speech analysis, synthesis, and coding. Recently, spectral envelope estimation technique has made a rapid progress. There are several ways to obtain spectral envelope. These ways include SEEVOC technique, discrete cepstrum method, regularized discrete cepstum estimation, DAP, MVDR, etc. In this paper, we compared the different spectral estimation techniques by using the different spectral-distortion measures. It aims to compare the different envelope estimation techniques from some different perspective. The work is implemented in a low bit-rate coder based on the sinusoidal model by using the different techniques to captures the spectral amplitudes.