Arraytechnik zur Geräuschreduktion bei Sprachübertragung

Noise reduction is used for speech transmission if intelligibility falls under the level of acceptance. One example for such a situation is given by mobile telephone for hand-set free use in cars. First noise reduction systems used either spectral subtraction or noise compensation. The latter requires a reference microphone for the noise signal which is available only specific situations. The drawback of spectral subtraction is the distortion of the peech signal, the relativ low signal-to-noise enhancement, and the musical tones. Improved techniques for signal enhancement use microphone arrays which a minimum of two microphones. Delay compensation and addition at their output signals delivers an enhanced speech signal. This approach can be extended to more microphone. In the paper a new system for 4 microphone is presented using spectral subtraction and post processing to estimate the speech signal. The signal enhancements is in the range at 10 dB, there are almost no musical tones due to post processing.