The subjective assessment of speech and sound codecs requires anchor signals to ensure its reliability. The reference system currently used is Modulated Noise Reference Unit (MNRU) which simulates only quantization noise. Now, the new generations of codecs present other impairments. In this study, we consider speech quality as a multidimensional phenomenon and use dimensional reduction techniques to project codecs' impairments in a four dimensional space, each axis of the perceptive space corresponding to one of them. A verbalization test allowed characterizing two of these dimensions by the following attributes: “muffle” and “background noise” anchor signals were designed for these two dimensions, and a statistical analysis allowed validating the accuracy of at least one of these signals.
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