Voice Analysis Using the Bispectrum.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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The theory of the bispectrum has been studied, though very few practical applications have yet been considered in any depth. One application mentioned in the literature is the use of the bispectrum for voice signal processing. The aim of this thesis was to research the bispectrum towards the particular application of speech enhancement. The technique is based on the fact that the bispectrum is zero for a Gaussian white noise signal, arid the bispectrum of two signals added together is the sum of the two signal bispectra. Theoretically, processing signals in the bispectra domain should increase the signal-to-noise ratio of the speech signal. The signal can then be reconstructed from the bispectrum. Though the theory of the estimation techniques were proven, the applicability of the bispectrum to voice processing was questionable. Since any additive white noise is a random process, it will only be the expected value that is zero. With speech signal, the signal is considered stationary for only approximately 20 milliseconds. This does not allow a significant amount of the noise energy to be removed through the averaging process. Classical methods are just as effective.
- Voice Communications