Noise Cancellation Using Segmented, Frequency-Dependent Phase Cancellation

A method of noise abatement within a signal stream containing unwanted signal referred to as noise, comprising:

• acquiring a digitized noise signal from an environment in which the signal stream is present;
• dividing, by a digital processor circuit, the digitized noise signal into a set of different frequency ranges;
• subdividing at least one frequency range in the set of frequency ranges into a plurality of noise segments;
• computing, by a digital processor circuit, a frequency domain representation for the digitized noise signal, where the computation of the frequency domain representation occurs before or after the steps of dividing and subdividing;
• individually shifting the frequency domain representation of one or more of the noise segments which comprise the digitized noise signal in time using the digital processor circuit, where quantity of time shift is dependent on a selected frequency in the frequency domain representation and takes in account both an in-air propagation time of the noise signal and a system propagation time associated with the throughput speed of the digital processor circuit and any associated equipment, where the in-air propagation time is transit time for a signal to travel though air from an input microphone to a feedback microphone;
• converting the frequency domain representation for each noise segment of the digitized noise signal to time domain to form an anti-noise signal;
• and
• outputting the anti-noise signal into the signal stream to abate the noise through destructive interference.

A system for noise abatement in an audio signal stream which contains a noise signal, comprising:

• a microphone configured to acquire a noise signal from an environment in which the audio signal stream is present;
• an analog-to-digital converter configured to receive the noise signal from the microphone and operate to convert the noise signal to a digitized noise signal;
• a digital signal processor configured to receive the digitized noise signal from the analog-to-digital converter and process the digitized noise signal by
• dividing, by a digital processor circuit, the digitized noise signal into a set of different frequency ranges,
• subdividing at least one frequency range in the set of frequency ranges into a plurality of noise segments,
• computing a frequency domain representation of the digitized noise signal in frequency domain, where the computation of the frequency domain representation occurs before or after the steps of dividing and subdividing,
• shifting the frequency domain representation of one or more noise segments which comprise the digitized noise signal in time, thereby producing a shifted frequency domain representation of the digitized noise signal, where quantity of the time shift is dependent on a selected frequency in the frequency domain representation and takes in account both an in-air propagation time of the noise signal and a system propagation time associated with the throughput speed of the digital processor circuit, where the in-air propagation time is transit time for a signal to travel through air from the microphone to a feedback microphone, and
• converting the shifted frequency domain representation for each noise segment of the digitized noise signal to time domain to form an anti-noise signal;
• and
• a digital-to-analog converter configured to receive the anti-noise signal from the digital signal processor and operate to convert the anti-noise signal to an analog anti-noise signal.