This paper deals with the importance of identifying and selecting the adequate speech denoising technique according to the desired quality. Three types and degradations are considered: the overall degradation, the speech distortion and the residual background noise. Different popular techniques of speech enhancement with and without perceptual tools are considered. Different criteria of quality evaluation well correlated with subjective tests and ITU-T recommendations are used. The analysis carried during this paper showed that, in terms of overall quality and residual noise evaluation, perceptual techniques lead to the better performances. In terms of speech distortion, the best performances are obtained with spectral subtraction and statistical techniques.