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AN ANALOG INTEGRATED-CIRCUIT VOCAL TRACT

PRESENTED BY:VINAY VENUGOPAL

NO 66

S7 E&C

GUIDED BY:Ms. NIMMY GEORGE

LECTURER

E&C

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OUTLINE Introduction Speech production Speech Locked Loop Circuit model of vocal tract Two port section Modeling of impedances Driving the vocal tract Conclusion

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INTRODUCTION First experimental Integrated-circuit vocal tract.

Bio-inspired model

Analysis-by-Synthesis

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SPEECH PRODUCTION

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Contd.. Vocal tract is a cavity in animals where the sound that is

produced is filtered

Consists of laryngeal cavity, pharynx, oral cavity, nasalcavity. Lungs act as power supply Larynx modulates the airflow from the lungs

Vocal tract spectrally shapes the source

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Contd.. Speech production is classified into 3 general

categories

1. Periodic2. Noisy3. Impulsive

Walls of the vocal tract controls the spectrum of thespeech radiated at the lips

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SPEECH LOCKED LOOP

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Contd.. Analysis-by synthesis method Speech is analyzed and parameters are extracted from it

to configure a speech synthesizer SLL is similar to PLL Measure of error is computed SLL locks to the input signal with the optimum vocal

tract profile

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CIRCUIT MODEL OF

VOCAL TRACT Vocal tract can be approximated as a non uniform

acoustic tube with time varying cross-sectional areas

The cross sectional area is varied by varying theimpedance at different points along the tube

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Contd.. Wave equation for 1d propagation of sound in a

uniform tube of circular cross section is

P-Sound pressureU-Volume velocity

Propagation of sound is accompanied by energy lossesdue to viscous friction and heat conduction by walls

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Contd.. Acoustic propagation is analogous to plane wave

propagation through electrical transmission line

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Contd..

Schematic dig of transmission line vocal tract

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Contd.. VT is represented as acoustic tubes (intra oral and oral

tract) using transmission line model (TL)

Concatenation of many acoustic tubes Each 2 port is a LC circuit element Current source is used as volume velocity source at the

glottis

Current source is implemented using a Wide LinearRange Operational Transconductance Amplifier

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This is converted to Tunable 2 port sections bygyrating RC network using WLROTA

Passive circuit model assuming rigid walls

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SNR is calculated to be 64,66,67 Db

ID-V

DSof typical N MOS for various gate voltages

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MODELLING OF

IMPEDANCES Glottal constriction resistance Zgc is implemented as

series of linear and nonlinear resistance

Implemented with MOS transistor Gate potential must be biased at the point given by

intersection of MOS device curve and desired I-V chara Linear Chara IV

Non-linear CharaIV

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CONTD..

Gm is varied by varying Igm

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DRIVING THE VOCAL

TRACT The area function space has large no of degrees of

freedom

To reduce dimensionality we use Maeda articulatorymodel

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Contd.. Maeda model describes the vocal tract profile using

seven component

1. Jaw height2. Tongue body position3. Tongue body shape4. Tongue tip5. Lip height6. Lip protrusion7. Larynx height

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Contd.. Articulatory codebook contains mapping from

articulatory and acoustic domains

Babble is produced using set of vocal tract profiles They are compiled into a look up table to produce

codebook- Babbling

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Contd..

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Contd.. Filter bank(130 to 6500) DCT( Discrete cosine transform) is applied to generate

a set of 12 Cepstral coefficients This is compared against the codebook Best match is found and corresponding articulatory

parameters are used to produce vocal tract area profile

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CONCLUSION Low power Analog vocal tract chip can be used in SLL

to generate speech

Cross sectional area of tube can be varied by varyingL/C It can be used in speech synthesis, speech recognition,

compression etc

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REFERENCES M. M. Sondhi and J. Schroeter, A hybrid time-frequency domain

articulatory speech synthesizer, IEEE Trans. Acoustics, SpeechSignal Process., vol. ASSP-35, no. 7, pp. 955967, Jul. 1987.

R. Sarpeshkar, M. W. Baker, C. D. Salthouse, J. Sit, L. Turicchia,and S. M. Zhak, An ultra-low-power programmable analog bionicear processor,IEEE Trans. Biomed. Eng., vol. 52, no. 4, pp. 711727, Apr.2005.

L. Turicchia and R. Sarpeshkar, A bio-inspired companding

strategy for spectral enhancement, IEEE Trans. Speech AudioProcess., vol.13, no. 2, pp. 243253, Mar. 2005.

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THANK YOU

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ANY QUESTIONS?