Adaptive noise reduction circuit for a sound reproduction system
First Claim
1. A noise reduction circuit for a sound reproduction system having a microphone for producing an input signal in response to sound in which a noise component is present, said circuit comprising:
- an adaptive filter including a variable filter responsive to the input signal for producing a noise-estimating signal and further including a first combining means responsive to the input signal and the noise-estimating signal for producing a composite signal;
said variable filter having parameters which are varied in response to the composite signal to change the operating characteristics thereof;
a second filter for filtering the noise-estimating signal to produce a filtered noise-estimating signal;
means for delaying the input signal to produce a delayed signal; and
second combining means for combining the delayed signal and the filtered noise-estimating signal to attenuate noise components in the delayed signal and for producing a noise-reduced output signal.
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Accused Products
Abstract
A noise reduction circuit for a hearing aid having an adaptive filter for producing a signal which estimates the noise components present in an input signal. The circuit includes a second filter for receiving the noise-estimating signal and modifying it as a function of a user'"'"'s preference or as a function of an expected noise environment. The circuit also includes a gain control for adjusting the magnitude of the modified noise-estimating signal, thereby allowing for the adjustment of the magnitude of the circuit response. The circuit also includes a signal combiner for combining the input signal with the adjusted noise-estimating signal to produce a noise reduced output signal.
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Citations
39 Claims
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1. A noise reduction circuit for a sound reproduction system having a microphone for producing an input signal in response to sound in which a noise component is present, said circuit comprising:
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an adaptive filter including a variable filter responsive to the input signal for producing a noise-estimating signal and further including a first combining means responsive to the input signal and the noise-estimating signal for producing a composite signal; said variable filter having parameters which are varied in response to the composite signal to change the operating characteristics thereof; a second filter for filtering the noise-estimating signal to produce a filtered noise-estimating signal; means for delaying the input signal to produce a delayed signal; and second combining means for combining the delayed signal and the filtered noise-estimating signal to attenuate noise components in the delayed signal and for producing a noise-reduced output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A sound reproduction system comprising:
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a microphone for producing an input signal in response to sound in which noise components are present; a variable filter responsive to the input signal to produce a noise-estimating signal; a first combining means responsive to the input signal and the noise-estimating signal for producing a composite signal; said variable filter having parameters which are varied in response to the composite signal to change the operating characteristics thereof; a second filter for filtering the noise-estimating signal to produce a filtered noise-estimating signal; means for delaying the input signal to produce a delayed signal; second combining means for combining the delayed signal and the filtered noise-estimating signal to attenuate noise components in the delayed signal and for producing a noise-reduced output signal; and a transducer for producing sound with a reduced level of noise components as a function of the noise-reduced output signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 29)
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19. A method of reducing noise components present in an input signal in the audible frequency range comprising the steps of:
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filtering the input signal with a variable filter to produce a noise-estimating signal; combining the input signal and the noise-estimating signal to produce a composite signal; varying the parameters of the variable filter in response to the composite signal; filtering the noise-estimating signal according to predetermined parameters to produce a filtered noise-estimating signal; delaying the input signal to produce a delayed signal; and combining the delayed signal and the filtered noise-estimating signal to attenuate noise components in the delayed signal to produce a noise-reduced output signal. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28)
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30. A hearing aid comprising:
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a microphone for producing an input signal in response to sound in which noise components are present; a variable filter responsive to the input signal to produce a noise-estimating signal; a first combining means responsive to the input signal and the noise-estimating signal for producing a composite signal; said variable filter having parameters which are varied in response to the composite signal to change the operating characteristics thereof; a second filter for filtering the noise-estimating signal to produce a filtered noise-estimating signal; means for delaying the input signal to produce a delayed signal; second combining means for combining the delayed signal and the filtered noise-estimating signal to attenuate noise components in the delayed signal and for producing a noise-reduce output signal; and a transducer for producing sound with a reduced level of noise components as a function of the noise-reduced output signal. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38)
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39. A noise reduction circuit for a sound reproduction system having a microphone for producing an input signal in response to sound in which a noise component is present, said circuit comprising:
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an adaptive filter including a variable filter responsive to the input signal for producing a noise-estimating signal and further including a first combining means responsive to the input signal and the noise-estimating signal for producing a composite signal; said variable filter having parameters which are varied in response to the composite signal to change the operating characteristics thereof; means for adjusting the amplitude of the noise-estimating signal to produce an amplitude adjusted signal; and second combining means for combining the input signal and the amplitude adjusted signal to attenuate noise components in the input signal and for producing a noise-reduced output signal.
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Specification