Patent ID: 8965011
Filing Date: 2015-02-24
Classification: H03G

Abstract:
1. A method of attenuating an input signal to obtain an output signal; wherein the input signal is an audio signal; the method comprising: receiving the input signal; attenuating the input signal with a gain factor to obtain the output signal; applying a filter having a frequency response with a frequency-dependent filter gain to at least one of a copy of the input signal and a copy of the output signal to obtain a filtered signal, the frequency-dependent filter gain being arranged to emphasize frequencies within a number N of predetermined frequency ranges, N>1; wherein the filter comprises a sequence of N sub-filters, each one of the N sub-filters having a frequency response adapted to emphasize frequencies within a corresponding one of the N predetermined frequency ranges; wherein the frequency-dependent filter gain is arranged in consideration of a performance characteristic of a transducer; wherein the transducer comprises a speaker adapted to render a signal derived from the output signal; wherein the transducer is part of a device comprising a microphone adapted to sense the rendered signal, and an echo cancellation circuit adapted to predict the sensed signal from the signal derived from the output signal; wherein the performance characteristic is obtained from measuring a performance of the echo cancellation circuit vs. frequency; wherein the performance of the echo cancellation circuit is determined as the ratio of the power of the sensed signal after echo cancellation and the power of the sensed signal prior to echo cancellation; wherein the N predetermined frequency ranges are determined such that the performance characteristic comprises a local maximum within each one of the N predetermined frequency ranges; determining a signal strength of the filtered signal; and determining the gain factor from at least the signal strength.