Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
1998-10-27
2001-01-09
Hudspeth, David R. (Department: 2741)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S220000, C704S226000, C704S208000
Reexamination Certificate
active
06173256
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method according to the preamble of claim
1
. LPC coding has been in wide use for low-cost applications. Therefore, performance to some extent has been compromised. Such methods have often caused a kind of so-called buzzy-ness in the reproduced speech which is represented by certain unnatural sounds that may occur over the whole frequency range and that are experienced by listeners as annoying; the problem also appears in a spectrogram. The state of the art is represented by Alan V. McCree et al, A Mixed Excitation LPC Vocoder Model for Low Bit Rate Speech Coding, IEEE Trans. on Speech and Audio Processing, Vol.3, No.4, July 1995, pp.242-250. Although the reference has taken certain measures to decrease the effects of the buzzy-ness, it was only successive in part.
SUMMARY OF THE INVENTION
In consequence, it is an object of the present invention to improve speech quality by suppressing or otherwise rendering inaudible such buzzy-ness; the solution found has been to carefully apply noise to the speech signal. The necessary measures should require only relatively little processing effort, in view of the low-end character of LPC speech generation. Now, according to one of its aspects, the invention is characterized as recited in the characterizing part of claim
1
. Both the spectrogram and human listener tests show the improvement.
The invention also relates to an apparatus for outputting speech so coded. Various further advantageous aspects of the invention are recited in dependent Claims.
REFERENCES:
patent: 4969192 (1990-11-01), Chen et al.
patent: 5479564 (1995-12-01), Vogten et al.
patent: 5611002 (1997-03-01), Vogten et al.
patent: 6009384 (1999-12-01), Veldhuis et al.
Alan V. McCree et al: “A Mixed Excitation LPC Vocoder Model for Low Bit Rate Speech Coding”, in IEEE Trans. on Speech and Audio Processing, vol. 3, No. 4, Jul. 1995, pp. 242-250.
Hudspeth David R.
Piotrowski Daniel J.
U.S. Philips Corporation
Wieland Susan
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