Accession Number : ADA138008

Title :   A Recursive Linear Predictive Vocoder.

Descriptive Note : Master' thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Janssen,W A

PDF Url : ADA138008

Report Date : Dec 1983

Pagination or Media Count : 367

Abstract : A non-real time 10 pole recursive autocorrelation linear predictive coding vocoder was created for use in studying effects of recursive autocorrelation on speech. The vocoder is composed of two interchangeable pitch detectors, a speech analyzer, and speech synthesizer. The time between updating filter coefficients is allowed to vary from .125 msec to 20 msec. The best quality was found using .125 msec between each update. The greatest change in quality was noted when changing from 20 msec/update to 10 msec/update. Pitch period plots for the center clipping autocorrelation pitch detector and simplified inverse filtering technique are provided. Plots of speech into and out of the vocoder are given. Formant versus time three dimensional plots are shown. Effects of noise on pitch detection and formants are shown. Noise effects the voiced/unvoiced decision process causing voiced speech to be re-constructed as unvoiced. (Author)

Descriptors :   *Vocoders, *Mathematical prediction, *Autocorrelation, *Computer programs, Response, Speech recognition, Parametric analysis, Military applications, Pitch discrimination, Man machine systems, Recursive functions, Linear systems, Output, Data rate, Noise, User manuals, Theses

Subject Categories : Statistics and Probability
      Computer Programming and Software
      Voice Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE