: The document provides a detailed description and analysis of the recognition algorithms used in the Vicens-Reddy speech recognition system

Description and Analysis of the Vicens-Reddy Recognition Algorithms

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According to an acoustical theory of speech production, the spectra of voiceless fricatives can be characterized by poles and zeros whose frequency locations are dependent on the vocal‐tract configuration and on the location of the source of excitation within the vocal tract. The locations of the important poles and zeros in the spectra of fricatives can be determined by a matching process whereby comparison spectra synthesized by electric circuits are matched against the spectra under analysis. This method has been used to determine the frequencies and bandwidths of the important poles and zeros for several versions of /f/, /s/, and /∫/. Based on these findings, a simplified electrical model is developed for the synthesis of voiceless fricatives. The model consists of a noise‐excited electric circuit characterized by a pole and a zero whose frequency locations can be varied. Stimuli generated by this model, both in isolation and in syllables, are presented to listeners for identification. The results of the listening tests are consistent with the data from the acoustic analyses and with the findings of other investigators.

On the Properties of Voiceless Fricative Consonants

The two major cues for stop consonants, the burst of the stop release and the formant transitions in the adjacent vowel, were investigated. Detailed energy density spectra of the bursts were prepared. The transitions were studied by means of sonagrams. Possible criteria for identification were developed and tested. In order to assess the efficacy of the two types of cue, perceptual tests were conducted with isolated segments that contained either stop bursts or vowel transitions alone. Common acoustical properties of bursts and formant transitions are noted; differences as well as similarities are discussed in the light of different varieties of pitch judgments.

Acoustic Properties of Stop Consonants

As a first step toward a general speech recognition computer program, a program has been developed to recognize ten Eng.ish vowels in isolated words of the form /b/—bowel—/t/. Input to the computer was real time spectral data obtained through the input system described at these meetings in May, 1958, by Forgie and Hughes. The program was developed from the study of spectral data from five speakers. The program was tried on new speakers, the errors analyzed, and the program modified. The program, as finally evolved by this process, first determines the rough location of the first two formants. The remaining confusions are resolved by combinations of the following, as required: (1) position of F3, (2) the slopes of F1 and F2, (3) an estimate of pitch, and (4) the energy in the frequency band between F1 and F2. Whenever the over‐all power is above an arbitrary threshold, each 6‐msec scan of the filtered data is classified as one of the ten possible vowels. A tally at the end of the word determines the final ...

Description and Analysis of the Vicens-Reddy Recognition Algorithms

References

On the Properties of Voiceless Fricative Consonants

Acoustic Properties of Stop Consonants

Results Obtained from a Vowel Recognition Computer Program

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