12.5 - Low Power Speech Enhancement

David HalupkaPh.D. CandidateElectronics Group

June 24th, 2005

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Motivation

Today’s recognition systems can achieve a 95%+ recognition accuracy after extensive training

Research systems: same accuracy with no training Typically: 10% accuracy in the presence of noise,

reverberations, and conflicting conversations Humans are equipped to deal with noisy environments

Two ears → let us localize and focus on a single speaker

Complex noise: one sensor doesn’t cut it Multiple microphones → superhuman noise filtering

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Step 1: Sound Localization

dx+τν

x

t

tm2(t)

m1(t)Time-Based Cross-Correlation

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Step 2: Speech Enhancement

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A Hard Case for Hardware

Localization is a exhaustive linear search Gradient search, etc. not applicable

Each time delay must be checked Each likelihood can be evaluated in parallel

1 GHz Intel Pentium III needed just for real-time localization → consumes 35 W

Speech interface is beneficial for handheld devices, but battery life is limited. Palm M100 → 150 mW

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Results – 0.18 μm CMOS

Die Size: 2.51 mm x 2.51 mmPower Utilization: 29 mW

Die Size: 1.51 mm x 1.38 mmPower Utilization: 3.45 mWFPGA: 184 mWDSP: 650 mW