Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
1994-03-02
2001-09-11
Tsang, Fan (Department: 2645)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S201000
Reexamination Certificate
active
06289305
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for speech analysis and more specifically to an automatic process for the analysis of continuous speech. The results of the invention can be used for speech recognition and for speech synthesis etc. It is conventional to describe the wave form of speech using those resonant frequencies, so-called formants, which arise in the speech organ. The present invention presents a process for determining suitable frequencies for the formants from an utterance.
STATE OF THE ART
There already exist known methods for determining formants. One such method uses linear prediction, which provides frequencies included in the utterance at sampled time points. The centre of each vowel is determined using low energy peaks and is set as the starting point. Proceeding from the starting point, the frequencies are allocated to known, previously estimated, intervals for the formants. Subsequently a matching is made to surrounding frames, forwards and backwards, in order to join the formants together over the whole vowel sound.
One problem with this known method is that when each time point or frame is determined individually, it is easy for the wrong decision to be made in the allocation of the frequencies to the formants, because additional, incorrect, resonances arise, e.g. in the case of nasal sounds etc. The present invention removes this problem by delaying the decision on the allocation of frequencies to the formants until the whole utterance has been analyzed.
SUMMARY OF THE INVENTION
Thus, the present invention provides a process for speech analysis comprising the recording of an utterance using some suitable device. The utterance is divided into time frames and is analyzed by linear prediction in order to determine the roots for the denominator polynomial and thereby frequency values for each frame. The utterance is divided into voiced regions and in each voiced region the centres of vowel sounds are determined using a number of starting points.
In accordance with the invention, tracks are formed from the starting points by the roots being sorted from frame to frame, so that old and new roots are linked together. Factors of merit are calculated for the tracks relative to the formants and the tracks are distributed to the formants in accordance with the factors of merit. The factors of merit are preferably calculated using energy factors, continuity factors and correlation factors.
Further embodiments of the present invention are given in more detail in the subsequent patent claims.
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Parsons,Voice and Speech Processing, McGraw-Hill, New York, NY, (1987), p. 66,210-222.*
Nathan et al., “A Time-Varying Analysis Method for Rapid Transitions in Speech,” IEEE Transactions on Signal Processing, Apr. 1991, 39(4):815-24.*
IEEE Transaction on Communication, vol. COM26, No. 3, Mar. 1978, Chong Kwan Un, “A Low-Rate Digital Formant Vocoder pp. 344-354”, see II. system description.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Opsasnick Michael N.
Televerket
Tsang Fan
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