CELP and speech enhancement

McLoughlin, PhD (1998). CELP and speech enhancement. University of Birmingham. Ph.D.

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Abstract

This thesis addresses the intelligibility enhancement of speech that is heard within an acoustically noisy environment. In particular, a realistic target situation of a police vehicle interior, with speech generated from a CELP (codebook-excited linear prediction) speech compression-based communication system, is adopted.
The research has centred on the role of the CELP speech compression algorithm, and its transmission parameters. In particular, novel methods of LSP-based (line spectral pair) speech analysis and speech modification are developed and described. CELP parameters have been utilised in the analysis and processing stages of a speech intelligibility enhancement system to minimise additional computational complexity over existing CELP coder requirements.
Details are given of the CELP analysis process and its effects on speech, the development of speech analysis and alteration algorithms coexisting with a CELP system, their effects and performance.
Both objective and subjective tests have been used to characterize the effectiveness of the analysis and processing methods. Subjective testing of a complete simulation enhancement system indicates its effectiveness under the tested conditions, and is extrapolated to predict real-life performance.
The developed system presents a novel integrated solution to the intelligibility enhancement of speech, and can provide a doubling, on average, of intelligibility under the tested conditions of very low intelligibility.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):