PESQ (Perceptual Evaluation of Speech Quality) is an ITU algorithm that is increasingly used to emulate MOS, which is "mean opinion score", a listening test for speech codecs. The objective is to automate and ensure reproducibility of measurement of degradation over telephony channels, due to speech compression, line conditions, delay/echo, etc. and obtain results that closely correlate with MOS human listening tests.

The AT&T website contains no published information about the AT&T Noise Preprocessor. Instead, below we provide the abstract of the AT&T patent:

The system and method of the invention relates to voice detection technology for determining instants of time at which a snapshot of noise characteristics results in improved adaptation of noise floors used in voice detection. The approach is based on the "lower envelope" of the smoothed input signal power. Incorporation of this approach in a simple time domain VAD (Voice Activity Detector) results in an effective low-complexity system which, on the basis of simulations, gives good performance down to SNR values of about 0 dB. In the invention the lower envelope also provides the updated value of the noise threshold during the presence of speech. The invention can also be embedded in other, more complex (e.g., frequency domain) VADs at low computational cost.

More information on the AT&T patent:

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