In the application of acoustic echo cancellation the adapta tion process is disturbed by local background noise as well as by the speech of the local speaker. Furthennore, the loudspeaker enclosure-microphone (LEM) system has time-variant nature. There fore, adaptation control is absolutely necessary. If fast algorithms like affine projection arc applied also numerical stability problems caused by matrix inversion arise. In this contribution both prob lems are addressed and by introducing a pseudo-optimal regular ization a common solution is derived.

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Artificial bandwidth extension methods have been developed to improve the quality and intelligibility of narrowband telephone speech and to reduce the difference with wideband speech. Such methods have commonly been evaluated with objective measures or subjective listening-only tests, but conversational evaluations have been rare. This article presents a conversational evaluation of two methods for the artificial bandwidth extension of telephone speech. Bandwidth-extended narrowband speech is compared with narrowband and wideband speech in a test setting including a simulated telephone connection, realistic conversation tasks, and various background noise conditions. The responses of the subjects indicate that speech processed with one of the methods is preferred to narrowband speech in noise, but wideband speech is superior to both narrowband and bandwidth-extended speech. Bandwidth extension was found to be beneficial for telephone conversation in noisy listening conditions.

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