A method and arrangement for echo cancellation of voice signals

Abstract

A method and arrangement for cancelling echoes in a communication terminal (400) during a voice call with an opposite party. The communication terminal (400) comprises an echo cancelling unit (416,600) adapted to produce an estimate of echo information in received speech signals coming from a microphone in the communication terminal (400), and subtract the estimate from the received microphone signals, before being transmitted to the opposite party. The estimate is produced based on down-sampled received microphone signals and down-sampled received speech signals from the opposite party. The down-sampled speech signals from the opposite party are filtered in a digital filter (606), and the output signals from the filter (606) are up-sampled to form the estimate. Performing echo cancelling based on down-sampled speech signals from the opposite party and down-sampled microphone signals, requires a reduced amount of processing capacity of the communication terminal, still resulting in a sufficiently high quality echo cancellation.

Description

technical field [0001] The present invention relates generally to echo cancellation in digital transmitted voice communications in which two or more terminals communicate. In particular, the invention can be used in voice communication between two parties via a mobile phone. Background technique [0002] In a digital voice communication system, speech is transmitted over a communication link between speaking and listening terminals. In this description, mobile terminals communicate with each other in a mobile communication system. However, the terminal may be any type of terminal for digitally transmitted voice communication using a microphone and a speaker. Furthermore, a voice communication system may be any type of system in which two or more parties communicate by voice by transmitting digitally encoded voice signals, such as wireless or non-wireless telephone systems, conference telephone systems, door intercoms in buildings Telephone system, walkie-talkie, etc. [...

AI Technical Summary

Problems solved by technology

However, there are some drawbacks: Temporary blocking of frequencies in background sounds, resulting in loss of naturalness

However, echo cancellers based on linear filtering also have certain drawbacks: since the digital filter cannot fully model the echo, a significant residual echo is left, and the digital filter requires a lot of processing capacity to achieve sufficient echo reduction

[0025] Another problem is that in the case of echo cancellers with band division, it is very complicated to design the accumulation function of the bands

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