Noise reduction by application of two thresholds in each frequency band in audio signals

A computer-implemented method to reduce noise in a signal, the method comprising:

• obtaining an audio signal;
• separating the audio signal into frequency components in each of a plurality of frequency bands;
• obtaining a first threshold for a first frequency band of the plurality of frequency bands;
• obtaining a second threshold for the first frequency band;
• calculating a first envelope of first frequency components in the first frequency band during a first time frame;
• calculating a second envelope of the first frequency components during a second time frame that is after the first time frame;
• calculating a first signal-to-noise ratio based on a difference between a magnitude of the first envelope and a magnitude of the second envelope;
• in response to the first signal-to-noise ratio being greater than the first threshold and less than the second threshold, attenuating the first frequency components by an amount based on interpolation of the first signal-to-noise ratio between the first threshold and the second threshold;
• and
• combining the frequency components, including the attenuated first frequency components, to produce an output audio signal.

A computer-implemented method to reduce noise in a signal, the method comprising:

• obtaining an audio signal that includes speech;
• separating the audio signal into frequency components in each of a plurality of frequency bands;
• obtaining a first noise threshold that is based on one or more characteristics of human speech in a first frequency band of the plurality of frequency bands;
• obtaining a second noise threshold that is based on one or more characteristics of human speech in a second frequency band of the plurality of frequency bands, the second noise threshold being different than the first noise threshold;
• calculating a first signal envelope for first frequency components in the first frequency band and a second signal envelope for second frequency components in the second frequency band for a first duration of time;
• calculating a third signal envelope for the first frequency components and a fourth signal envelope for the second frequency components for a second duration of time that is longer than the first duration of time and overlaps the first duration of time;
• calculating a first noise ratio for the first frequency components using the first signal envelope and the third signal envelope;
• calculating a second noise ratio for the second frequency components using the second signal envelope and the fourth signal envelope;
• in response to the first noise ratio being less than the first noise threshold, attenuating the first frequency components by an amount based on interpolation of the first noise ratio between the first noise threshold and a third noise threshold;
• in response to the second noise ratio being less than the second noise threshold, attenuating the second frequency components;
• and
• combining the plurality of frequency bands, including the attenuated first frequency components and the attenuated second frequency components, to produce an output audio signal.