Patent
1994-12-02
1997-08-19
MacDonald, Allen R.
395 209, 395 267, 395 271, 395 272, 395 273, 395 274, 395 275, 395 276, 395 277, 395 28, 395 286, 395 287, G10L 900
Patent
active
056596588
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method of converting speech, in which method samples are taken of a speech signal produced by a first speaker for the calculation of reflection coefficients.
BACKGROUND OF THE INVENTION
The speech of speech-handicapped persons is often unclear and sounds included therein are difficult to identify. The speech quality of speech-handicapped persons causes problems, especially when a communications device or network is used for transmitting and transferring a speech signal produced by a speech-handicapped person to a receiver. On account of the limited transmission capacity and acoustic properties of the communications network, the speech produced by the speech-handicapped person is then still more difficult to identify and understand for a listener. On the other hand, regardless of whether a communications device or network transferring speech signals is used, it is always difficult for a listener to identify and understand the speech of a speech-handicapped person.
In addition, at times there is a need to try to change speech produced by a speaker in such a way that the sounds of the speaker would be corrected to provide a better sound format, or that the sounds of the speech produced by that speaker would be converted into the same sounds of another speaker and then the speech of the first speaker would actually sound like the speech of the second speaker.
SUMMARY OF THE INVENTION
The object of this invention is to provide a method, by which a speech of a speaker can be changed or corrected in such a way that the speech heard by a listener or the corrected or changed speech signal obtained by a receiver corresponds either to speech produced by another speaker, or to the speech of the same speaker corrected in some desired manner.
This novel method of converting speech is provided by a method according to the invention, which is characterized by the following method steps: from the reflection coefficients are calculated characteristics of cross-sectional areas of cylinder portions of a lossless tube modelling the first speaker's vocal tract, those characteristics of the cross-sectional areas of the cylinder portions of the lossless tube of the first speaker are compared with at least one previous speaker's respective stored sound-specific characteristics of cross-sectional areas of cylinder portions of a lossless tube modelling the speaker's vocal tract for the identification of sounds, and for providing identified sounds with respective identifiers, differences between the stored characteristics of the cross-sectional areas of the cylinder portions of the lossless tube modelling the speaker's vocal tract for the respective sound and the respective following characteristics for the same sound are calculated, a second speaker's speaker-specific characteristics of cross-sectional areas of cylinder portions of a lossless tube modelling that speaker's vocal tract for the same sound are searched for in a memory on the basis of the identifier of the identified sound, a sum is formed by summing the aforementioned differences and the second speaker's speaker-specific characteristics of the cross-sectional areas of the cylinder portions of the lossless tube modelling that speaker's vocal tract for the same sound, new reflection coefficients are calculated from that sum and a new speech signal is produced from those new reflection coefficients.
The invention is based on the idea that a speech signal is analyzed by means of the LPC (Linear Prediction Coding) method, and a set of parameters modelling a speaker's vocal tract is created, which parameters typically are characteristics of reflection coefficients. According to the invention, sounds are then identified from the speech to be converted by comparing the cross-sectional areas of the cylinders of the lossless tube calculated from the reflection coefficients of the sound to be converted with several speakers' previously received respective cross-sectional areas of the cylinders calculated for the same sound.
REFERENCES:
patent: 3909533 (1975-09-01), Willimann
patent: 4624012 (1986-11-01), Lin et al.
patent: 5097511 (1992-03-01), Suda et al.
patent: 5522013 (1996-05-01), Vanska
patent: 5528726 (1996-06-01), Cook
MacDonald Allen R.
Nokia Telecommunications Oy
Opsasnick Michael N.
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