Back to results
US 7,248,708 B2Granted
Noise canceling microphone
AssigneeAdaptive Technologies, Inc.
InventorsMichael A. Vaudrey, William R. Saunders
Life of this patent
Estimating the term…
Abstract
An improved noise canceling microphone is provided including robust design features and advanced noise control and speech discrimination convergence characteristics. Two adaptive controllers are used to ensure robust performance in quickly changing acoustic environments ensuring an acceptable minimum performance characteristic. Additionally, a new real-time spectral estimation procedure is applied to a noise canceling communications microphone platform that permits continued and optimal adaptation of non-voice bandwidth frequencies during speech transients.
Claims31
An adaptive noise canceling microphone system comprising:
- a first microphone for generating a first microphone signal containing primarily speech and noise;
- a second microphone for generating a second microphone signal containing primarily noise;
- a first adaptive filter comprising a single filter coefficient wherein the first adaptive filter is adapted to:
- generate a first output signal from the second microphone signal;
- and
- generate a first error signal, wherein the first error signal is generated by subtracting the first output signal from the first microphone signal;
- a second adaptive filter comprising multiple filter coefficients, wherein the second adaptive filter is adapted to:
- generate a second output signal from the second microphone signal;
- and
- generate a second error signal, wherein the second error signal is generated by subtracting the second output signal from the first error signal:
- and
- first and second adaptive convergence controllers, wherein the first adaptive convergence controller is adapted to change a rate of convergence of the first adaptive filter based on the first error signal and the second adaptive convergence controller is adapted to change a rate of convergence of the second adaptive filter based on the second error signal.
9 more elements
An adaptive noise canceling microphone control method comprising:
- generating at a first microphone a first microphone signal containing primarily speech and noise;
- generating at a second microphone a second microphone signal containing primarily noise;
- generating a first output signal by filtering the second microphone signal with the first adaptive filter;
- generating a first error signal by subtracting the first output signal from the first microphone signal;
- sending the first error signal to a first convergence controller;
- generating a second output signal by filtering the second microphone signal with the second adaptive filter;
- generating a second error signal by subtracting the second output signal from the first error signal;
- sending the second error signal to a second convergence controller;
- changing a rate of convergence of the first adaptive filter based on the first error signal;
- and
- setting a second convergence parameter changing a rate of convergence of the second filter based on the second error signal.
8 more elements
An adaptive noise canceling microphone control system comprising:
- a first microphone, wherein the first microphone generates a first microphone signal containing primarily speech and noise,
- a second microphone, wherein the second microphone generates a second microphone signal containing primarily noise,
- a single-weight adaptive filter having a single filter coefficient, wherein the single weight adaptive filter is adapted to:
- generate a first output signal from the second microphone signal;
- and
- generate a first error signal, wherein the first error signal is generated by
- a frequency domain controller comprising a series of stored frequency domain threshold values each associated with a frequency;
- and
- a frequency domain adaptive filter having multiple filter coefficients, wherein the frequency domain adaptive filter is adapted to:
- generate a second output signal from the second microphone signal;
- and
- generate a second error signal, wherein the second error signal is generated by subtracting the second output signal from the first error signal,
- wherein the first error signal is used to update the first adaptive filter, and the second error signal is used to update the frequency domain adaptive filter, and
- wherein the second error signal represents primarily speech;
- a gain comparator adapted to:
- determine whether the first error signal exceeds any one of the series of stored frequency domain threshold values;
- and
- if the first error signal exceeds any one of the series of stored frequency domain threshold values, then send the switch a switching signal for the frequency associated with the one of the series of stored frequency domain threshold values;
- and a switch, wherein the switch is adapted to:
- receive the switch signal;
- and
- In response to the switch signal, set a convergence parameter of the single-weight adaptive filter to zero.
19 more elements
An adaptive noise canceling microphone control method comprising:
- generating at a first microphone a first microphone signal containing primarily speech and noise
- generating at a second microphone a second microphone signal containing primarily noise,
- generating a first output signal at a first adaptive filter from the second microphone signal;
- generating a second output signal at a second adaptive filter from the second microphone signal,
- generating a first error signal by subtracting the first output signal from the first microphone signal;
- generating a second error signal by subtracting the second output signal from the first error signal;
- comparing at a frequency domain comparator a Fourier transform of the second error signal to a set of frequency domain threshold values;
- selecting a first convergence parameter for controlling a rate of convergence of the first adaptive filter based on the first error signal;
- and
- selecting a set of second convergence parameters for controlling a rate of convergence of the second adaptive filter based on the set of frequency domain threshold values.
7 more elements
An adaptive noise canceling microphone system comprising:
- a first microphone for generating a first microphone signal containing primarily speech and noise;
- a second microphone for generating a second microphone signal containing primarily noise;
- a first adaptive filter comprising:
- a single filter coefficient wherein the first adaptive filter is adapted to:
- generate a first output signal from the second microphone signal;
- and generate a first error signal, wherein the first error signal is generated
- by subtracting the first output signal from the first microphone signal;
- a gain comparator and a switch connected thereto and wherein the gain comparator is adapted to:
- determine whether the first error signal exceeds a predetermined threshold;
- if first error signal exceeds a predetermined threshold, then send the switch a switching signal;
- and
- wherein the switch is adapted to:
- receive the switching signal;
- and
- in response to the switching signal, set a convergence parameter of the first adaptive filter to zero;
- and
- a second adaptive filter comprising multiple filter coefficients, wherein the second adaptive filter is adapted to:
- generate a second output signal from the second microphone signal;
- and
- generate a second error signal, wherein the second error signal is generated by subtracting the second output signal from the first error signal;
- and
- first and second adaptive convergence controllers, wherein the first adaptive convergence controller is adapted to control the rate of convergence of the first adaptive filter and the second adaptive convergence controller is adapted to control the rate of convergence of the second adaptive filter.
19 more elements
Dependencies are inferred from the claim text.