Adaptive dynamic audio hum extractor and extraction process

A process for adaptively removing audio hum components from an input audio signal comprising the steps of:

• filtering the input audio signal with at least one notch filter at a fundamental hum frequency and with at least one additional harmonic multiple containing hum components;
• detecting the level of the input audio signal to provide a control signal;
• and
• dynamically varying the depth of the at least one notch filter in the input audio signal in response to the control signal to provide a maximum notch depth of the at least one notch filter when the input audio signal level is low and minimum notch depth of the at least one notch filter when the input audio signal level is high.

A process for adaptively removing audio hum components from an input audio signal comprising the steps of:

• dividing the spectrum of the input audio signal into a low-band audio signal and high-band audio signal;
• filtering the low-band audio signal with at least one notch filter at a fundamental hum frequency;
• detecting the level of the low-band audio signal to provide a low-band control signal;
• and
• dynamically varying the depth of the at least one notch filter in the low-band audio signal in response to the low-band control signal to provide a maximum notch depth of the at least one notch filter when the input audio signal level is low and a minimum notch depth of the at least one notch filter when the input audio signal level is high.

A process for adaptively removing audio hum components from an input audio signal comprising the steps of:

• dividing a spectrum of the input audio signal into a low-band audio signal, a band-pass audio signal and a high-band audio signal;
• filtering the low-band audio signal with at least one notch filter at a fundamental hum frequency;
• detecting the level of the low-band audio signal to provide a low-band control signal;
• dynamically varying the depth of the at least one notch filter in the low-band audio signal in response to the low-band control signal to provide a maximum notch depth of the at least one notch filter when the low-band audio signal level is low and a minimum notch depth of the at least one notch filter when the low-band audio signal level is high;
• filtering the band-pass audio signal with at least one notch filter at an interval of the fundamental hum frequency;
• detecting the level of the band-pass audio signal to provide a band-pass control signal;
• dynamically varying the depth of the at least one notch filter in the band-pass audio signal in response to the band-pass control signal to provide a maximum notch depth of the at least one notch filter in the band-pass audio signal when the band-pass audio signal level is low and a minimum notch depth of the at least one notch filter when the band-pass audio signal level is high.

A process for adaptively removing audio hum components from an input audio signal comprising the steps of:

• altering the input audio signal to provide a processed audio signal;
• dividing the spectrum of the input audio signal into a band-pass audio signal and a low-band audio signal;
• detecting the level of the low-band audio signal to provide a low-band control signal;
• detecting the level of the band-pass audio signal to provide a band-pass control signal;
• dividing the spectrum of the processed audio signal into low-band, band-pass and high-pass audio signal paths;
• filtering the output of the processed low-band audio signal path with at least one notch filter at a fundamental line frequency;
• dynamically varying the depth of the at least one notch filter in the low-band audio signal path in response to the low-band control signal to provide a maximum notch depth of the at least one notch filter in the low-band audio signal when the low-band audio signal level is low and a minimum notch depth of the at least one notch filter when the low-band audio signal level is high;
• filtering the output of the processed band-pass audio signal path with at least one notch filter at an interval of the fundamental line frequency;
• and
• dynamically varying the depth of the at least one notch filter in the band-pass audio signal in response to the band-pass control signal to provide a maximum notch depth of the at least one notch filter in the band-pass audio signal path when the band-pass audio signal level is low and a minimum notch depth of the at least one notch filter when the band-pass audio signal level is high.

A process for adaptively removing audio hum components from an input audio signal comprising the steps of:

• filtering the input audio signal with multiple independent notch filters at a fundamental hum frequency and each additional harmonic frequency at which hum components are audible;
• dividing the input audio signal into multiple frequency bands, a center of each frequency band being at the fundamental hum frequency or a harmonic frequency of the fundamental hum frequency at which hum components are audible;
• detecting the level of each of the multiple frequency bands at which hum components are audible to provide corresponding multiple control signals;
• and
• dynamically varying the depth of each independent notch filter in the input audio signal in response to the control signal corresponding to the same frequency as the notch filter to provide a maximum notch depth of each notch filter when the input audio signal level in each corresponding frequency band is low and a minimum notch depth of each notch filter when the input audio signal level is high.