Browse Prior Art Database

Formant Tracking System

IP.com Disclosure Number: IPCOM000095221D
Original Publication Date: 1965-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Barber, RR: AUTHOR [+3]

Abstract

The frequency tracking system tracks a single vocal formant frequency.

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Formant Tracking System

The frequency tracking system tracks a single vocal formant frequency.

Bandpass filter 10 attenuates all frequency components outside the range of the desired formant frequency. Single-sideband modulator 11 translates the input upward by a constant frequency omega c. AGC amplifier 12 compresses the amplitude range of the translated input. Limiter 13 converts the translated signal into a series of essentially square waves. The pulse rate of these is detected by zero-crossing frequency detector 14.

The envelope of the speech signal is at a maximum within the glottal period, approximately when the glottis is closed. Envelope detector 15 is driven from the envelope of the output of amplifier 12. Detector 15 operates threshold detector 16 and logic circuitry 17 to drive sample and hold circuitry 18. Thus, the frequency detector 14 output is sampled only when the glottis is closed.

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