Patent ID: 9449610
Filing Date: 2016-09-20
CPC Classification: G10L

Claim Text:
1. A method of reducing noise in an audio signal received at a microphone for a wireless communications device having a transmitter, the audio signal being represented by a plurality of consecutive frames of data, each consecutive frame 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 the audio signal; calculating a first speech probability presence (SPP) factor for a first frame using a minimum mean square error (MMSE) calculation and a signal-to-noise ratio of the audio signal of the frame previous to the first frame, the first SPP factor for the first frame having a value ranging between a first minimum value and a second maximum value; modifying the first SPP factor for the first frame by a sigmoid function having a first shape and an output value ranging between a third minimum value and a fourth maximum value to provide a first warped SPP; changing the first shape of the sigmoid function after the step of modifying the first SPP factor for the first frame, to provide a sigmoid function having a second shape, which is different from the first shape; and calculating a second SPP factor for a second frame using the first warped SPP, the second SPP factor for the second frame having a value ranging between said first minimum value and said second maximum value; modifying the second SPP factor for the second frame by the sigmoid function having the second shape to provide a second warped SPP; adjusting a gain applied to the second frame by an amount corresponding to the second shape of the sigmoid function to reduce noise content in the second frame; converting the reduced noise content second frame to an audio signal; and providing the reduced noise content second frame to the transmitter of the wireless communications device; wherein the received signal comprises a plurality of frequency bands and wherein the steps of calculating a SPP and modifying the SPP are performed on each frequency band on a frequency band-by-frequency band basis and which provides a corresponding number of warped SPP values, the method further comprising: comparing each warped SPP value to a threshold value, which is substantially equal to a sum of the mean warped SPP values and at least one standard deviation of all warped SPP values; and if each warped SPP value is more than the threshold value, the value of the warped SPP value is substituted with a mean value of all warped SPP values.