MMethod for Adaptive Control and Equalization of Electroacoustic Channels
First Claim
1. A method for altering the soundfield in an electroacoustic channel in which a first audio signal is applied by a first electromechanical transducer to an acoustic space, causing changes in air pressure in the acoustic space, and a second audio signal is obtained by a second electromechanical transducer in response to changes in air pressure in the acoustic space, comprising:
- establishing, in response to the second audio signal and an audio input signal, a transfer function estimate of the electroacoustic channel, said transfer function estimate being adaptive in response to temporal variations in the transfer function of the electroacoustic channel,wherein the first audio signal is obtained on the basis of an additive combination of two signals, namely the audio input signal or a filtered version thereof, and a feedback signal, andwherein the establishing comprises;
filtering a signal obtained from the audio input signal by each of a plurality of parallel filters, wherein each filter from the plurality of parallel filters represents a transfer function from a group of transfer functions, and wherein the transfer functions of the group of transfer functions represent different variations in the transfer function of the electroacoustic channel;
subtractively combining the outputs of the plurality of parallel filters with a signal obtained from the second audio signal to obtain a plurality of error signals;
selecting one or a combination of transfer functions from said group of transfer functions based on the time-averaged mean-squared magnitude of the plurality of error signals; and
deriving said transfer function estimate from said one or said combination of transfer functions selected from said group of transfer functions; and
obtaining one or more filters whose transfer function is based on the transfer function estimate, and applying the first audio signal to the one or more filters.
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Accused Products
Abstract
An electroacoustic channel soundfield is altered. An audio signal is applied by an electromechanical transducer to an acoustic space, causing air pressure changes therein. Another audio signal is obtained by a second electromechanical transducer, responsive to air pressure changes in the acoustic space. A transfer function estimate of the electroacoustic channel is established, responsive to the second audio signal and part of the first audio signal. The transfer function estimate is derived to be adaptive to temporal variations in the electroacoustic channel transfer function. Filters are obtained with transfer functions based on the transfer function estimate. Part of the first audio signal is filtered therewith.
129 Citations
18 Claims
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1. A method for altering the soundfield in an electroacoustic channel in which a first audio signal is applied by a first electromechanical transducer to an acoustic space, causing changes in air pressure in the acoustic space, and a second audio signal is obtained by a second electromechanical transducer in response to changes in air pressure in the acoustic space, comprising:
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establishing, in response to the second audio signal and an audio input signal, a transfer function estimate of the electroacoustic channel, said transfer function estimate being adaptive in response to temporal variations in the transfer function of the electroacoustic channel, wherein the first audio signal is obtained on the basis of an additive combination of two signals, namely the audio input signal or a filtered version thereof, and a feedback signal, and wherein the establishing comprises; filtering a signal obtained from the audio input signal by each of a plurality of parallel filters, wherein each filter from the plurality of parallel filters represents a transfer function from a group of transfer functions, and wherein the transfer functions of the group of transfer functions represent different variations in the transfer function of the electroacoustic channel; subtractively combining the outputs of the plurality of parallel filters with a signal obtained from the second audio signal to obtain a plurality of error signals; selecting one or a combination of transfer functions from said group of transfer functions based on the time-averaged mean-squared magnitude of the plurality of error signals; and deriving said transfer function estimate from said one or said combination of transfer functions selected from said group of transfer functions; and obtaining one or more filters whose transfer function is based on the transfer function estimate, and applying the first audio signal to the one or more filters. - View Dependent Claims (2, 3)
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4. A method for altering the soundfield in an electroacoustic channel in which a first audio signal is applied by a first electromechanical transducer to an acoustic space, causing changes in air pressure in the acoustic space, and a second audio signal is obtained by a second electromechanical transducer in response to changes in air pressure in the acoustic space, comprising:
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establishing, in response to the second audio signal and the first audio signal, a transfer function estimate of the electroacoustic channel, said transfer function estimate being adaptive in response to temporal variations in the transfer function of the electroacoustic channel, wherein the establishing comprises; filtering a signal obtained from the first audio signal by each of a plurality of parallel filters, wherein each filter from the plurality of parallel filters represents a transfer function from a group of transfer functions, and wherein the transfer functions of the group of transfer functions represent different variations in the electroacoustic response of the electroacoustic channel; subtractively combining the outputs of the plurality of parallel filters with a signal obtained from the second audio signal to obtain a plurality of error signals; selecting one or a combination of transfer functions from said group of transfer functions based on the time-averaged mean-squared magnitude of the plurality of error signals; and deriving said transfer function estimate from said one or said combination of transfer functions selected from said group of transfer functions; and obtaining one or more filters whose transfer function is an inverted version of the transfer function estimate and filtering with the one or more filters a target response filtered input signal to obtain the first audio signal. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An apparatus for altering the soundfield in an electroacoustic channel in which a first audio signal is applied by a first electromechanical transducer to an acoustic space, causing changes in air pressure in the acoustic space, and a second audio signal is obtained by a second electromechanical transducer in response to changes in air pressure in the acoustic space, comprising:
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means for establishing, in response to the second audio signal and the first audio signal, a transfer function estimate of the electroacoustic channel, said transfer function estimate being adaptive in response to temporal variations in the transfer function of the electroacoustic channel, wherein the establishing comprising; means for filtering a signal obtained from the first audio signal by each of a plurality of parallel filters, wherein each filter from the plurality of parallel filters represents a transfer function from a group of transfer functions, and wherein the transfer functions of the group of transfer functions represent different variations in the electroacoustic response of the electroacoustic channel; means for subtractively combining the outputs of the plurality of parallel filters with a signal obtained from the second audio signal to obtain a plurality of error signals; means for selecting one or a combination of transfer functions from said group of transfer functions based on the time-averaged mean-squared magnitude of the plurality of error signals; and means for deriving said transfer function estimate from said one or said combination of transfer functions selected from said group of transfer functions; and means for obtaining one or more filters whose transfer function is an inverted version of the transfer function estimate and filtering with the one or more filters a target response filtered input signal to obtain the first audio signal
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17. A computer readable storage medium product comprising encoded instructions which, when executing with one or more processors, controls the processors to perform process steps for altering the soundfield in an electroacoustic channel in which a first audio signal is applied by a first electromechanical transducer to an acoustic space, causing changes in air pressure in the acoustic space, and a second audio signal is obtained by a second electromechanical transducer in response to changes in air pressure in the acoustic space, the process steps comprising:
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establishing, in response to the second audio signal and the first audio signal, a transfer function estimate of the electroacoustic channel, said transfer function estimate being adaptive in response to temporal variations in the transfer function of the electroacoustic channel, wherein the establishing comprising; filtering a signal obtained from the first audio signal by each of a plurality of parallel filters, wherein each filter from the plurality of parallel filters represents a transfer function from a group of transfer functions, and wherein the transfer functions of the group of transfer functions represent different variations in the electroacoustic response of the electroacoustic channel; subtractively combining the outputs of the plurality of parallel filters with a signal obtained from the second audio signal to obtain a plurality of error signals; selecting one or a combination of transfer functions from said group of transfer functions based on the time-averaged mean-squared magnitude of the plurality of error signals; and deriving said transfer function estimate from said one or said combination of transfer functions selected from said group of transfer functions; and obtaining one or more filters whose transfer function is an inverted version of the transfer function estimate and filtering with the one or more filters a target response filtered input signal to obtain the first audio signal
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18. A processor based system, for altering the soundfield in an electroacoustic channel in which a first audio signal is applied by a first electromechanical transducer to an acoustic space, causing changes in air pressure in the acoustic space, and a second audio signal is obtained by a second electromechanical transducer in response to changes in air pressure in the acoustic space, comprising:
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an estimator, which functions in response to the second audio signal and the first audio signal, to establish a transfer function estimate of the electroacoustic channel, said transfer function estimate being adaptive in response to temporal variations in the transfer function of the electroacoustic channel, wherein the establishing comprising; a plurality of parallel filters, for filtering a signal obtained from the first audio signal by each of the plurality of parallel filters, wherein each filter from the plurality of parallel filters represents a transfer function from a group of transfer functions, and wherein the transfer functions of the group of transfer functions represent different variations in the electroacoustic response of the electroacoustic channel; a subtractor, for subtractively combining the outputs of the plurality of parallel filters with a signal obtained from the second audio signal to obtain a plurality of error signals; a selector, for selecting one or a combination of transfer functions from said group of transfer functions based on the time-averaged mean-squared magnitude of the plurality of error signals; and an estimator, for deriving said transfer function estimate from said one or said combination of transfer functions selected from said group of transfer functions; and a filter selector, for obtaining one or more filters whose transfer function is an inverted version of the transfer function estimate and filtering with the one or more filters a target response filtered input signal to obtain the first audio signal
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Specification