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Formant Detector

IP.com Disclosure Number: IPCOM000094375D
Original Publication Date: 1966-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Buron, RB: AUTHOR

Abstract

This method and device detect the values of the formant frequencies in a voice signal. A coherent memory filter results in a mapping of the frequency domain into the time domain. In the coherent memory filter loop, the phase of each of the multiplicity of stored signals is adjusted in synchronism at a specified rate. The rate for each stored signal is a linear function of the time delay experienced by that stored signal, the linear function of all signals being the same. Consequently, wave reinforcement upon combination of these phase adjusted signals occurs at instant of time indicative of the frequency components of the input signal. In this way, the amplitude peaks in the output signal can be referenced to a time scale.

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Formant Detector

This method and device detect the values of the formant frequencies in a voice signal. A coherent memory filter results in a mapping of the frequency domain into the time domain. In the coherent memory filter loop, the phase of each of the multiplicity of stored signals is adjusted in synchronism at a specified rate. The rate for each stored signal is a linear function of the time delay experienced by that stored signal, the linear function of all signals being the same. Consequently, wave reinforcement upon combination of these phase adjusted signals occurs at instant of time indicative of the frequency components of the input signal. In this way, the amplitude peaks in the output signal can be referenced to a time scale. Thus there is effected a representation in which the instant of occurrence of each amplitude peak is indicative of the frequency of the signal causing that peak.

In case of pseudo periodic speech signal, i. e., pitch mode, the frequency spectrum of the speech signal is a line spectrum with different amplitude lines. Previously, after passing the voice signal through a coherent memory filter, the detection of the voice signal formant frequencies is performed on the lines of the treated frequency spectrum which were nearest the assumed envelope extrema. Therefore this measure was different from the exact values corresponding to this envelope extrema, i. e., formants. See the signal at point B. The exact values of the formants are to be obtained. The Hilbert transfo...