University of Surrey

Nokia Corporation

Mulsys Ltd

Ahmet Kondoz

Stephane Villette

Khaldoon Taha Al-Naimi

Banu Gunel Hacihabiboglu

Huseyin Hacihabiboglu

Nilantha Nandima Katugampala

Kholdoon Taha Al-Naimi

St&eacute;phane Pierre Villette

A method of separating a mixture of acoustic signals from a plurality of sources comprises: providing pressure signals indicative of time-varying acoustic pressure in the mixture; defining a series of time windows; and for each time window: a) providing from the pressure signals a series of sample values of measured directional pressure gradient; b) identifying different frequency components of the pressure signals c) for each frequency component defining an associated direction; and d) from the frequency components and their associated directions generating a separated signal for one of the sources.

Acoustic source separation

A system for transmitting input data over a speech channel of a network comprising: a modulator arranged to produce a modulated waveform signal transforming the data for transmission over the network; a channel compensation filter arranged to filter the modulated waveform signal after it has been transmitted over the speech channel to compensate for the response of the speech channel; and a demodulator arranged to retrieve the data from the filtered waveform signal.

Data transmission

To alleviate problems of signal aliasing and to reduce complexity, Linear Predictive Coefficients (LPCS) are calculated from samples of audio signals and Line Spectral Frequency (LSF) vectors are extracted from the LPCs with a rate higher than a desired vector rate, the LSF vectors comprising values of different LSF parameters. Next, an LSF track is formed for at least one of the LSF parameters. At least one of the formed LSF tracks is then low pass filtered. Finally, decimated LSF vectors are reconstructed from the low pass filtered LSF tracks, the decimated number corresponding to the desired vector rate. The invention equally relates to a corresponding computer program, to corresponding devices and to a corresponding communication network.

Generating LSF vectors

A speech coder includes an encoder using an analysis and synthesis approach. The encoder uses a pitch determination algorithm requiring analysis in both the frequency domain and the time domain, a voicing determination algorithm and an algorithm for determining spectral amplitudes and means for quantising the values determined. A decoder is also described.

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Guildford, United Kingdom

Ahmet Kondoz