Synthesis of high-pitched sounds

Details Synthesis of high-pitched sounds Synthesis of high-pitched sounds

1996-08-14

2002-07-09

Korzuch, William (Department: 2641)

Data processing: speech signal processing, linguistics, language

Speech signal processing

For storage or transmission

C704S219000, C704S220000

Reexamination Certificate

active

06418406

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates to synthesis of sounds and more particularly to the synthesis of high-pitched sounds.
BACKGROUND OF THE INVENTION
The Mixed Signals Products group of Texas Instruments Semiconductor Division (SC/MSP) has an LPC (Linear Predicting Coding) synthesis semiconductor chip business with its family of TSP
50
C
1
X and MSP
50
C
3
X microprocessors. The synthesis is where a signal such as a human voice or sound effect such as animal or bird sound to be synthesized is first analyzed using a linear predictive coding analysis to extract spectral, pitch, voicing and gain parameters. This analysis is done using a Speech Development Station
10
as shown in
FIG. 1
which is a workstation with a Texas Instruments SDS5000. The SDS5000 consist of two circuit boards
10
a
plugged into two side by side slots of a personal computer (PC). The PC includes a CPU processor and a display and inputs
10
b
such as a keyboard, a mouse, a CD ROM drive and a floppy disk drive. Using one of the inputs like a CD ROM, the voice or sound to be synthesized is entered for analysis. The station also includes a speaker and the user editing can listen to the sound as well as view the display generated by the SDS5000. The analysis is typically done at a rate of 50-100 times per second. The display gives a time plot of the raw speech spectrum, pitch, energy level and LPC filter coefficients. These parameters may then be edited, if necessary, and quantized to a data rate of typically 1500-2400 bits/second. The data rate is kept low to reduce the memory needed to store the data in the product being created. The foregoing analysis is performed off-line and the LPC parameters are stored into the memory M of a synthesis product such as a talking toy or book shown in FIG.
2
. The book for example contains a microprocessor &mgr;P that is coupled to a ROM memory M that when a button is pressed processes using LPC model data producing the sound to a speaker S. The digital signal converted to analog signal and applied to a speaker in the book or toy. The coefficients for that sound corresponding to the button depressed are taken from the memory.
For high-pitched sounds, the LPC method does not provide a good spectral model. One such high-pitched sound may be a child's voice to be used in a talking book.
For high-pitched sounds, the LPC method instead of modeling the resonances of the vocal tract tends to model individual pitch harmonics. The resulting poor spectral modeling leads to poor synthesizer output quality. Any reasonable editing of spectral parameters will not, in general, solve the output quality problem.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention the synthesis of high-pitched sounds is improved by lowering the pitch of the original signal to be synthesized by a constant percentage. The lower pitch-shifted signal is then applied to an LPC analysis to extract the desired spectral parameters.


REFERENCES:
patent: 5536902 (1996-07-01), Serra et al.
patent: 5581652 (1996-12-01), Abe et al.
patent: 5641927 (1997-06-01), Pawate et al.

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