Accurate forward SNR estimation based on MMSE speech probability presence

摘要

Acoustic noise in an audio signal is reduced by calculating a speech probability presence (SPP) factor using minimum mean square error (MMSE). The SPP factor, which has a value typically ranging between zero and one, is modified or warped responsive to a value obtained from the evaluation of a sigmoid function, the shape of which is determined by a signal-to-noise ratio (SNR), which is obtained by an evaluation of the signal energy and noise energy output from a microphone over time. The shape and aggressiveness of the sigmoid function is determined using an extrinsically-determined SNR, not determined by the MMSE determination. The extrinsically-determined SNR is obtained from a long term history of previously-determined speech presence probabilities and a long term history of previously-determined noise histories.

主权项

1. A method of reducing noise in an audio signal received at a microphone for a speech-processing device, the audio signal, that is received at the microphone being represented by a plurality of consecutive frames of data, each consecutive frame of data representing a plurality of consecutive samples of the received audio signal, the method comprising:
converting the audio signal received at the microphone to a plurality of consecutive frames of data representing said audio signal; determining a signal to noise ratio (SNR) for a first frame responsive to energy generated by the microphone, and responsive to the determination of a softSNR and the determination of a realSNR for the first frame; determining a warped speech probability presence (SPP) factor for the first frame using a minimum mean square error (MMSE) determiner, which uses a SPP factor determined for the first frame, multiplied by a sigmoid function having a shape, the warped SPP factor for the first frame being determined by the determiner using the signal to noise ratio determined for the first frame; determining if the warped SPP factor is between pre-determined maximum and minimum values for the warped SPP factor; determining a re-warped SPP factor by adjusting the warped SPP factor responsive to the determination of whether the warped SPP factor is between the first and second pre-determined maximum and minimum values for the warped SPP factor; changing the shape of the sigmoid function responsive to the re-warped SPP factor; determining a SPP factor for a second frame based on the changed shape of the sigmoid function, the second frame following the first frame; reducing noise content in the second frame by adjusting gain applied to the second frame based on the SPP factor for the second frame; re-converting the reduced-noise content second frame to an audio signal; and providing the reduced noise content second frame to the speech-processing device.