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UBC Theses and Dissertations

Efficient speech storage via compression of silence periods Gan, Cheong Kuoon


An adaptive optimal silence detector is designed and implemented in four speech coding schemes: N-bit PCM (N = 5 to 12), N-bit A-law PCM (N = 4 to 8), N-bit ADPCM (N = 3 to 8) and ADM (Adaptive Delta Modulation) for bit-rates of 16Kps, 24Kps and 32Kps. The amount of compression is approximately 35% for voice recordings such as radio newscasts, highly active conversations and readings from prepared texts. Subjective evaluation shows that the silence-edited versions (silence played back as absolute silence) have acceptability scores of 1.07 lower than the unedited versions with respect to a specific coding scheme for a score range of 1 to 5. With noise-edited versions (silence replaced by random noise during playback) the score degradation is 0.5.

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