Interference Environment, The Bandwidth Of The Telephony Extension

Telephone speech often sounds muffled and thin due to its narrowband characteristics. With the increased availability of terminals capable of receiving wideband signals, extending the bandwidth of narrowband telephone speech at the receiver has drawn much research interest. Currently, there exist many methods that can provide good reconstructions of the wideband spectra from narrowband speech; however, they often lack robustness to different channel conditions, and their performances degrade when they operate in unknown environments.This thesis presents a bandwidth extension algorithm that mitigates the effects of adverse conditions. The proposed system is designed to work with noisy input speech and unknown channel frequency response. To maximize the naturalness of the reconstructedspeech, the algorithm estimates the channel and applies equalization to recover the attenuated bands. Artifacts are reduced by employing an adaptive and a fixed postfilters.Subjective test results suggest that the proposed scheme is not affected by channel conditions and is able to produce speech with enhanced quality in adverse environments.