The patent's inventors are
This patent was filed on
From the background information supplied by the inventors, news correspondents obtained the following quote: "This disclosure relates to using paired microphones to reject noise.
"A headset for communicating through a telecommunication system, whether wired or wireless, will generally include a microphone for detecting the voice of the wearer. Such microphones are exposed to several types of noise, including ambient noise from the environment, such as other people talking, and wind noise caused by air moving past the microphone.
"FIG. 1 shows an in-ear headset 10 commercially available from
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "In general, in one aspect, a system for combining signals includes a first microphone generating a first input signal having a first voice component and a first noise component, a second microphone generating a second input signal having a second voice component and a second noise component, a mixing circuit, and an adaptive filter. The mixing circuit applies a first gain having a value .alpha. do the first input signal to produce a first scaled signal, applies a second gain having a value 1-.alpha. to the second input signal to produce a second scaled signal, and sums the first scaled signal and the second scaled signal to produce a summed signal. The adaptive filter computes an updated value of .alpha. to minimize the energy of the summed signal based on the summed signal, the first input signal and the second input signal, and provides the updated value of .alpha. to the mixing circuit.
"Implementations may include one or more of the following. The first noise component may have a greater contribution from ambient noise than from wind noise. The first microphone may include a pressure microphone. The second noise component may have a greater contribution from wind noise than from ambient noise. The first microphone may be more sensitive to ambient noise than to wind noise. The second microphone may be more sensitive to wind noise than to ambient noise. The second microphone may include a gradient microphone. The first microphone may include a pressure microphone, the second microphone may include a gradient microphone, and the first and second microphones may be located at a common location within the system.
"The adaptive filter may be configured to apply a least-mean-squared algorithm to compute the updated value of .alpha.. The adaptive filter may be implemented in a digital signal processor programmed to compute a difference between the first and second signals, multiply the summed signal by the difference and by a pre-determined step size value, and subtract the product from the current value of .alpha. to produce the updated value of .alpha.. The adaptive filter may be implemented in a digital signal processor programmed to decompose the summed signal and the first and second input signals into frequency bands and to minimize the energy of the summed signal in a first energy band. The mixing circuit may apply the first and second gains by applying different values of .alpha. and 1-.alpha., respectively, in different frequency bands.
"An equalizer may receive at least one of the first input signal or second input signal and equalize the received signal according to a pre-defined equalization curve to match the first voice component to the second voice component. The equalizer may include a first equalizer to apply a first equalization curve to the first input signal to produce a first equalized signal, and a second equalizer to apply a second equalization curve to the second input signal to produce a second equalized signal, the first and second equalized signals having matching voice components. The equalizer may include a single equalizer configured to apply an equalization curve to the first input signal to produce a first equalized signal, the first equalized signal having an equalized voice component matching the second voice component from the second input signal. A low-pass filter may filter the second input signal before the second input signal is provided to the adaptive filter. A second equalizer may be coupled to the output of the mixing circuit to optimize a voice response of the summed signal for use in a communications system.
"The mixing circuit may be further configured to apply a gain to at least one of the first input signal or the second input signal before providing the first and second input signals to the adaptive filter. Either or both of the mixing circuit and the adaptive filter may be implemented in a digital signal processor. The mixing circuit may include a first voltage-controlled amplifier configured to apply the first gain, and a second voltage-controlled amplifier configured to apply the second gain, the outputs of the first and second voltage-controlled amplifiers being coupled to produce the summed signal.
"In general, in one aspect, a device includes a windscreen in a first surface, a gradient microphone housed in a capsule having first and second outlets coupled to openings in a second surface displaced from the first surface, a pressure microphone mounted between the first and second surfaces, and circuitry coupled to the gradient microphone and the pressure microphone and operable to combine the signals of the microphones and provide a combined microphone signal.
"Implementations may include one or more of the following. The first surface and the second surface may be displaced a non-zero distance from each other. The first surface, the second surface, and at least one wall between the first surface and the second surface enclose a volume, and the openings in the second surface and a sensing element of the pressure microphone may both be coupled to the volume. The pressure microphone may be mounted in the wall between the first surface and the second surface.
"Advantages include rejecting noise in various environments, seamlessly combining signals from different microphones each best-suited for the noise found in different environments.
"Other features and advantages will be apparent from the description and the claims."
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