Speech Enhancement using Excitation Source

Information

B. Yegnanarayana, S.R. Mahadeva Prasanna & K. Sreenivasa Rao

Department of Computer Science & Engineering Indian Institute of Technology Madras, India

Email: {yegna,prasanna,ksr}@cs.iitm.ernet.in

http://speech.cs.iitm.ernet.in

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• To enhance speech degraded by noise & reverberation using multiple microphone data

• Approach based on excitation source information

• Time-delay estimation using source information

• Coherent addition of Hilbert envelopes of LP residuals

• Derivation of weighted LP residual

• Synthesis of enhanced speech (Demonstration)

Objective & Organization

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Excitation Source Characteristics

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(LP residual & Hilbert Envelope (HE) of LP residual)

(a) LP residual, (b) Hilbert Transform & (c) Hilbert Envelope

HEs of LP Residuals of Speech

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LP residual & its HE of (a)-(b) Clean speech, (c)-(d) Degraded speech

Time-Delay Estimation

• Computing the HEs of two-microphone data

• Computing their cross-correlation

• Estimating time-delay

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Coherent Addition of HEs of LP Residuals

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(a) Microphone-1, (b) Microphone-2, (c) Microphone-3, (d) Coherently added & (e) Incoherently added

Basis for Speech Enhancement

• Nature of the coherently added Hilbert envelope is exploited to weight the residual

• Weighting of the LP residual e1(n) is done using

n e1(n) êc(n)e1M(n) =-------------------

n êc(n)

where, êc(n) is the coherently added HE & e1M(n) is the modified residual

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Results of Enhancement

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(a) LP residual of degraded speech, (b) Weighted LP residual, (c) Degraded speech & (d) Enhanced speech

Results of Enhancement

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Spectrogram of (a) Degraded speech, (b) Enhanced speech by proposed approach & (c) Coherently added signal

Summary & Conclusions • New approach for speech enhancement

• Using excitation source information in LP residual

• Coherent addition of HEs of LP residuals

• Enhancement using modified residual

• Need to derive suitable weight function for improvement in the quality of enhancement

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Paper #1582

Speech Enhancement

using Excitation

Source Information

B. Yegnanarayana

S.R. Mahadeva Prasanna &

K. Sreenivasa Rao

Department of Computer Science & Engineering

Indian Institute of Technology Madras, India

Email: {yegna,prasanna,ksr}@cs.iitm.ernet.in

http://speech.cs.iitm.ernet.in

ABSTRACTThis paper proposes an approach for processing speech from multiple microphones to enhance speech degraded by noise and reverberation. The approach is based on exploiting the features of excitation source in speech production. In particular, the characteristics of voiced speech can be used to derive a coherently added signal from the Linear prediction (LP) residuals of the degraded speech data from different microphones. A weight function is derived from the coherently added signal. For coherent addition the time delay between a pair of microphones is estimated using the knowledge of the source information present in the LP residual. The enhanced speech is generated by exciting the time varying all-pole filter with the weighted LP residual.