In the recent past, broadband speech coders have been used at a bit rate of between 8 kbps and 32 kbps. Current studies are focusing on the robustness of these coders (and their variants), which have standard settings in various mobile phone applications. This robustness is assessed in two clearly defined ways.


The first way consists of the addition of a noise reduction step (or steps) to overcome possible background noises present in speech. This means trying, in the event of noisy speech reception, to make the output of the speech coder resemble the output for a clear voice (without noise) as closely as possible.


The second way consists in assessing the degradation experienced by certain coders when there are bit error rates in the transmission channel. In mobile telephone systems, a margin of error is allowed for in the bit error rate during the transmission of speech channels, which results in the degradation of decoded speech or reconstructed speech in the receiver. In view of this assumption, the aim is to reduce coders

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