Vehicular automatic gain control (agc) microphone system and method for post processing optimization of a microphone signal
AssigneeGentex Corporation
InventorsMichael A. Bryson, Robert R. Turnbull
Life of this patent
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Abstract
A method for processing signals for reducing noise components in a vehicular microphone system (500A) compares (517) a plurality of noise component values (511, 513, 515) for at least one frequency band of plurality of frequency bands. At least one frequency band is then downwardly expanded (521) by a predetermined expansion ratio (523) for providing a noise reduced signal (535) when determining a value is below a predetermined threshold (519).
Claims20
A method for processing signals for reducing noise components in a vehicular microphone system comprising the steps of:
- comparing a plurality of noise component values for at least one frequency band of plurality of frequency bands;
- and
- downwardly expanding the at least one frequency band by a predetermined expansion ratio for providing a noise reduced signal when determining a value is below a predetermined threshold.
A method for processing voice signals in a vehicular microphone system comprising the steps of:
- converting the voice signals into a plurality of frequency bands in the frequency domain;
- comparing a long-term and short-term energy level from each frequency band;
- calculating a long-term average and short-term average from each respective short-term energy level and long-term energy level;
- comparing the short-term average to the long-term average;
- expanding the frequency band in a downward manner by a predetermined expansion ratio when the short-term average falls below the long-term average by a threshold value;
- converting the downwardly expanded signal into the time domain;
- and
- providing a noise reduced signal to an electronic device based on the expanded frequency band.
A method for providing an enhanced voice signal in a vehicular microphone system comprising the steps of:
- processing analog data from a beamformer microphone into a complex numerical value over at least one of a plurality of frequency bands using a filter bank;
- summing the square of both a real and imaginary portion of the complex value for each one of the plurality of frequency bands to produce a magnitude value;
- calculating a logarithmic value from the magnitude value;
- comparing a long-term and short-term energy levels from each frequency band;
- calculating short-term average from the short-term energy level;
- calculating a long-term average from the long-term energy level;
- comparing the short-term average to the long-term average;
- calculating a signal-to-noise ratio (SNR) of the logarithmic value;
- utilizing the SNR to determine a predetermine expansion ratio;
- expanding the frequency band in a downward manner by the predetermined expansion ratio when the short-term average falls below the long-term average by a threshold value;
- calculating a linear value for the noise reduced signal;
- gain smoothing the linear value of the noise reduced signal to provide a normalized signal;
- processing the normalized signal using an inverse filter bank for providing an analog noise reduced signal from the frequency domain into the time domain;
- and
- providing a noise reduced signal based on the expanded frequency band.
Dependencies are inferred from the claim text.