Patent ID: 8693699

Claim:
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, 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 physical variations in 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.