Telefonaktiebolaget Lm Ericsson (Publ)

Google Inc.

Per Åhgren

Anders K Eriksson

Ivo Creusen

Tina Le Grand

Zohra Yermeche

Anders Eriksson

Methods and systems detect residual echo in an audio signal in a non-causal manner. A non-causal residual echo detector allows accurate detection of any residual echo from an AEC (acoustic echo canceller). The non-causally detected residual echo may be utilized to perform various actions such as selecting between different causal AECs, tuning a causal AEC, and/or characterizing the performance of the causal AEC. Aspects leverage an understanding that the information about residual echo being present in a signal does not have to be causal in the sense that it is acceptable and even advantageous to know some time afterwards (e.g., after a signal has undergone acoustic echo cancellation and is output for further processing or transmission) that a residual echo was present in the signal. Such an approach is different from the case of an AEC, which needs to know right away, with a fairly low signal delay involved, whether residual echo is present.

Residual echo detection based on non-causality

A harmonic echo power estimator estimates power of echo generated by harmonic loudspeaker nonlinearities in a user equipment having an echo path between a loudspeaker input and a microphone output. The estimator includes a frequency band mapper that maps each frequency band in a set of loudspeaker output signal frequency bands into a corresponding array of loudspeaker input signal frequency bands, where each frequency band in the set is mapped into several frequency bands in the corresponding array. A power estimator determines a power estimate of each input signal in each array of frequency bands. A power estimate combiner combines determined power estimates in each array of frequency bands into a corresponding estimate of loudspeaker input power generating harmonic loudspeaker nonlinearities. A power estimate transformer transforms the estimates of loudspeaker input power across the echo path into power estimates of the echo generated by the harmonic loudspeaker nonlinearities.

Estimation and suppression of harmonic loudspeaker nonlinearities

A method for suppressing noise of a first signal captured via a primary microphone is provided. A primary and a reference microphone are arranged on a communication device to capture noise and intermittent speech. A determination is made whether the first signal comprises non-stationary signal components or substantially stationary noise, and whether the first signal comprises substantially far-field noise in case it was determined that it comprises non-stationary signal components. A noise power spectrum estimate of the first signal is updated with a stationary noise power spectrum estimate if the first signal is considered to comprise substantially stationary noise or a far-field noise power spectrum estimate if the first signal is considered to comprise substantially far-field noise. A frequency response is computed on the basis of the estimated noise power spectrum. Noise from the first signal is suppressed by applying the frequency response on the first signal.

Noise suppressing method and a noise suppressor for applying the noise suppressing method

The present invention relates to a method and apparatus of a digital filter for noise suppression of a signal representing an acoustic recording. The method comprises determining a desired frequency response (H(&#x3c9;)) of the digital filter; and generating a noise suppression filter based on the desired frequency response. The desired frequency response is determined in a manner so that the desired frequency response does not exceed a maximum level, wherein the maximum level is determined in response to the signal to be filtered.

Noise suppression method and apparatus

One aspect of the invention provides a method for enhancing speech output by an electro-acoustical transducer in a noisy listening environment. In some embodiments, this method includes: filtering an input audio signal x(t) using a filter H(z) to produce a filtered audio signal x(t) formula (I), wherein x(t) formula (I)&#x2014;H(z)x(t); providing to an electro-acoustical transducer a signal corresponding to the filtered audio signal x(t) formula (I) to produce a sound wave corresponding to the filtered audio signal; and prior to filtering the audio signal using the filter, configuring the filter such that, with respect to one or more frequencies, the filtered audio signal has a higher signal level than the input audio signal, and such that the overall signal level of the filtered audio signal (sl) is substantially related to the overall signal level of the input signal (sl) such that si/=sl&#xd7;c.

Systems and methods for improving the intelligibility of speech in a noisy environment

Methods for filtering an input signal x(k) to produce an output signal y(k) such that the ratio of a power level of the output signal to a power level of the input signal is substantially equal to a desired value &#x3b3; are provided. The methods include forming a first corrected frequency response(&#x3c9;) based on a first correction value g(0) and a desired frequency response H(&#x3c9;); forming a first filter(z) from the first corrected frequency response(&#x3c9;); applying the first filter(z) to a first block of the input signal to produce a first output signal block; computing an amplificationcaused by the application of the filter(z); computing a value &#x3b3;, wherein &#x3b3;represents an amplification error; computing a second correction value g(1), where g(1) is a function of g(0) and &#x3b3;; forming a second corrected frequency response(&#x3c9;) based on the second correction value g(1) and the desired frequency response H(&#x3c9;); forming a second filter(z) from the second corrected frequency response(&#x3c9;); and applying the second filter(z) to a second block of the input signal to produce a second output signal block.

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Knivsta, Sweden

Per Åhgren