Apparatus and method for suppressing noise from voice signal by adaptively updating Wiener filter coefficient by means of coherence

A method for suppressing a noise component of an input voice signal by a voice signal processor, the voice signal processor including

• a hardware computing device, and
• a storage medium having program instructions stored thereon, execution of which by the hardware computing device causes the voice signal processor to provide functions of a signal generator, a coherence calculator, a targeted voice section detector, a coherence behavior calculator, a Wiener filter (WF) adapter and a WF coefficient multiplier, said method comprising:
• forming, by the hardware computing device via the function of the signal generator, a first directivity signal having a directivity pattern substantially being null in a first direction, using first and second input signals that correspond to a plurality of signals in a temporal section;
• forming, by the hardware computing device via the function of the signal generator a second directivity signal having a directivity pattern substantially being null in a second direction, using the first and second input signals that correspond to the plurality of signals in the temporal section;
• using the first and second directivity signals by the hardware computing device via the function of the coherence calculator to calculate a coherence value;
• determining, by the hardware computing device via the function of the target voice section detector, based on the coherence value, whether the temporal section is a targeted voice section, in which the plurality of signals arrive from a targeted direction, or an untargeted voice section, in which the plurality of signals arrive from an untargeted direction;
• maintaining an average of all coherence values determined to correspond to the untargeted voice section, and upon detecting that an instantaneous coherence value calculated by the coherence calculator corresponds to the untargeted voice section, obtaining a difference between the instantaneous coherence value and the average by the hardware computing device via the function of the coherence behavior calculator;
• comparing, by the hardware computing device via the function of the WF adapter, the difference with a predetermined threshold, and upon detecting that the difference is smaller than the threshold, determining that the temporal section is a background noise section that substantially contains no voice signal, and using signal characteristics of the signals in the background noise section to calculate a new WF coefficient;
• updating a WF coefficient when the new WF coefficient is obtained;
• and
• multiplying the first input signal by the WF coefficient by the hardware computing device via the function of the WF coefficient multiplier.

A non-transitory computer-readable medium on which is stored a program for having a computer operate as a voice signal processor, wherein said program, when running on the computer, controls the computer to function as:

• a first directivity signal generator forming a first directivity signal having a directivity pattern substantially being null in a first direction, using first and second input signals that correspond to a plurality of signals in a temporal section;
• a second directivity signal generator forming a second directivity signal having a directivity pattern substantially being null in a second direction, using the first and second input signals that correspond to the plurality of signals in the temporal section;
• a coherence calculator using the first and second directivity signals to obtain a coherence value;
• a targeted voice section detector determining, based on the coherence value, whether the temporal section is a targeted voice section, in which the plurality of signals arrive from a targeted direction, or an untargeted voice section, in which the plurality of signals arrive from an untargeted direction different from the targeted direction;
• a coherence behavior calculator maintaining an average of all coherence values determined to correspond to the untargeted voice section, and upon detecting that an instantaneous coherence value obtained by the coherence calculator corresponds to the untargeted voice section, obtaining a difference between the instantaneous coherence value and the average;
• a Wiener filter (WF) adapter
• comparing the difference obtained in the coherence behavior calculator with a predetermined threshold, and
• upon detecting that the difference is smaller than the threshold, determining that the temporal section is a background noise section that substantially contains no voice signal, and using signal characteristics of the signals in the background noise section to update a WF coefficient;
• and
• a WF coefficient multiplier multiplying the first input signal by the WF coefficient from the WF adapter.