Systems, methods, apparatus, and computer-readable media for adaptive active noise cancellation
First Claim
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1. A method for active noise cancellation, said method comprising:
- in a first clock domain, applying a digital filter to a reference noise signal to produce an anti-noise signal; and
during said applying the digital filter, and in a second clock domain that has a lower frequency than the first clock domain, producing updates to the digital filter that are based on downsampling a first input signal and a second input signal into the second clock domain,wherein the reference noise signal is based on a signal produced by a reference microphone, andwherein the first input signal is based on information from the signal produced by the reference microphone, andwherein the second input signal is based on information from a signal produced by an error microphone.
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Abstract
An adaptive active noise cancellation apparatus performs a filtering operation in a first digital domain and performs adaptation of the filtering operation in a second digital domain.
79 Citations
137 Claims
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1. A method for active noise cancellation, said method comprising:
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in a first clock domain, applying a digital filter to a reference noise signal to produce an anti-noise signal; and during said applying the digital filter, and in a second clock domain that has a lower frequency than the first clock domain, producing updates to the digital filter that are based on downsampling a first input signal and a second input signal into the second clock domain, wherein the reference noise signal is based on a signal produced by a reference microphone, and wherein the first input signal is based on information from the signal produced by the reference microphone, and wherein the second input signal is based on information from a signal produced by an error microphone. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 87)
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19. An apparatus for active noise cancellation, said apparatus comprising:
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a reference microphone configured to produce a reference microphone signal in response to a first acoustic signal; a first analog-to-digital converter (ADC) that is coupled to the reference microphone and configured to produce a first output signal that is based on the reference microphone signal at a first sampling rate; an error microphone configured to produce an error microphone signal in response to a second acoustic signal; a second ADC that is coupled to the error microphone and configured to produce a second output signal that is based on the error microphone signal; a control block that (A) has a first input that is coupled to the first ADC to receive a first downsampled signal at a second sampling rate lower than the first sampling rate, (B) has a second input, at the second sampling rate, that is coupled to the second ADC, and (C) is configured to provide updates based on the first and second inputs; and a digital filter that is arranged to receive the updates from the control block and configured to filter a reference noise signal that is based on the first output signal, at the first sampling rate, to produce an anti-noise signal. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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58. An apparatus for active noise cancellation, said apparatus comprising:
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a reference microphone configured to produce a reference microphone signal in response to a first acoustic signal; a first analog-to-digital converter (ADC) that is coupled to the reference microphone and configured to produce a first output signal that is based on the reference microphone signal at a first sampling rate; an error microphone configured to produce an error microphone signal in response to a second acoustic signal; a second ADC that is coupled to the error microphone and configured to produce a second output signal that is based on the error microphone signal; a control block (A) having a first input coupled to the first ADC to receive a first downsampled signal at a second sampling rate based on the first output signal, the second sampling rate lower than the first sampling rate and a second input coupled to the second ADC to receive a second downsampled signal at the second sampling rate based on the second output signal, the first input and the second input each having a first bit width, and (B) configured to provide updates based on the first and second inputs; and a digital filter that is coupled to the first ADC, arranged to receive the updates from the control block, and configured to filter a reference noise signal that is based on the first output signal and has a second bit width that is less than the first bit width to produce an anti-noise signal. - View Dependent Claims (59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 88, 89, 90, 91, 92, 93, 94, 95, 96)
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97. An apparatus for active noise cancellation, said apparatus comprising:
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a reference microphone configured to produce a reference microphone signal in response to a first acoustic signal; a first analog-to-digital converter (ADC) that is coupled to the reference microphone and configured to produce a first output signal that is based on the reference microphone signal at a first sampling rate; an error microphone configured to produce an error microphone signal in response to a second acoustic signal; a second ADC that is coupled to the error microphone and configured to produce a second output signal that is based on the error microphone signal; a control block (A) having a first input, in a pulse-code modulation (PCM) domain, that is coupled to the first ADC to receive a first downsampled signal at a second sampling rate based on the first output signal, the second sampling rate lower than the first sampling rate and a second input, in the PCM domain, that is coupled to the second ADC to receive a second downsampled signal at the second sampling rate based on the second output signal and (B) configured to provide updates based on the first and second inputs; and a digital filter that is coupled to the first ADC, arranged to receive the updates from the control block, and configured to filter, in a pulse density modulation (PDM) domain, a reference noise signal that is based on the first output signal to produce an anti-noise signal. - View Dependent Claims (98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137)
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Specification