Shane Switzer

Date of Award

12-1991

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Electrical and Computer Engineering

First Advisor

Matthew Kabrisky, PhD

Abstract

The major goal of this research was to investigate speech coding techniques in an attempt to achieve high quality speech transmittable at 4800 bits per second. The approach taken to achieve this goal was to code the frequency domain representation of speech. Speech was represented by a sparse set of frequency components. Four frequency selections schemes were implemented, and the resulting frequency coefficients (magnitude and phase) were coded in an efficient manner for transmission. Specific techniques involved in the speech coder included: (1) a recurrent neural architecture to make a periodic/noiselike decision, (2) the use of variable length windows for analysis and synthesis, and (3) a representation of noiselike speech using frequency banded energy information. The quality of the reconstructed speech was tested using listening tests which compared the different frequency selection schemes, along with original and sampled speech. The system did not achieve 'toll quality' speech; however, the resulting speech was highly intelligible. Specific quality degradation was noted at window transitions.

AFIT Designator

AFIT-GCE-ENG-91D-10

DTIC Accession Number

ADA243757

Comments

The author's Vita page is omitted.

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