IGNOIE & SOIM-COE06

ESTIMATION OF SOUND SOURCE POSITIONSUSING A SURROUNDING MICROPHONE ARRAY

T. Okamoto, R. Nishimura, Y. Iwaya
Research Institute of Electrical Communication,
Graduate School of Information Sciences,Tohoku University

Outline●Introduction●

Surrounding Microphone Array●

Estimation of Sound Source Positions–MUltiple Signal Classification (MUSIC) method (R. O. Schmidt et el. 1986)–Spatial Smoothing Technique (T. Shan et al. 1985)– Developing RAP-MUSIC●

Performance Evaluation●Conclusion
2Introduction●

FIR3 (FIeld Recording, Recognition andReproduction) system to record a sound field forlater reproduction

Reconstructing the sound informationin another place at another time3

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FIR Prototype
Recording Room

Reproduction RoomSoundinformation
Surrounding microphone array (157 ch)

Surrounding speaker array (157 ch)

B&K Type 4591 (157 ch)

FOSTEX FE38E (157 ch)

Today's our presentation,Reverberant time of both rooms : 0.15 s

Estimation of Sound Source Positions using a Surrounding
Microphone Array in a Reverberant Sound Field
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Surrounding Microphone Array●Ceiling 45 ch●Wall A 20 ch × 2●

Wall B 36 ch × 2

157 chArrangement of microphones

Spacing between microphones 50 cm 5

Estimation of Sound Source Positions●MUSIC method (R. O. Schmidt et al. 1986)

Input Signal

Spatial Correlation Matrix

Extraction

Base Vector of the orthogonal
complements from R

Steering Vector

Transfer Function between
microphone i and search point (x, y, z)MUSIC method(1)P has a peak because a isorthogonal to V if a fits thesource positions
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Estimation of Sound Source Positions
in Reverberant Sound Field●

MUSIC method (R. O. Schmidt et al. 1986)
Negative estimation in reverberant sound field !!!

●Spatial Smoothing Technique (T. Shan et al. 1985)–

Dividing the array into N subarray and calculating subarray's
spatial correlation matrices
(2)

MUSIC
Reducing negative effect of reflected sounds 7

RAP-MUSIC (RearrangementAnd Pre-smoothing for MUSIC)●RAP-MUSIC (Re-arrangement And Pre-smoothing for MUSIC)–

Making virtual channels from 4 channels at their median point–

Converting 4 signals at the real channels into 4 signals at thevirtual channels by both of amplitude and phase correlation(3)–

Averaging the signals at virtual channels
after synchronizing the phase(–Delay-and-Sum beamforming at virtualchannels)

Applying MUSIC method to averaged
signals
Reducing negative effect ofreflected sounds more effectively !!!

Keeping the phase of eachsignal at the virtual channel( Delay-and-Sum > Averaging spatial correlation matrices
8Performance Evaluation
Experiments of Estimation of Sound Source Positions●●Experimental Condition–Source 1 : male voice (a/i/kya/ku) 63.7 dB Lceq–

Source 2 : female voice (i/chi/yu/u) 50.4 dB Lceq–

Sampling frequency : 48000 Hz–

Time length of input signal : 1 s–Hamming window (512 points)–Frequency band : 500 ~ 8000 Hz

Evaluation value of the peak of Pk=

P at each search position(4)

P at the source position

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Experimental Condition

Using two equilateral 32-hedron point source loud-speakers(7 cm in diameter)10Arrangements of Microphones●

2-dimensional arrangement (Pattern 1)

Music (45 ch)●

Spatial Smoothing Technique / RAP-MUSIC(32 ch)

3-dimensional arrangement (Pattern 2)Music (45 ch)

Spatial Smoothing Technique / RAP-MUSIC(30 ch)
11Experimental Results●

Comparison of the performances of three methods
for Source 1 (Pattern 1)
Spatial Smoothing

MUSIC1234512345RAP-MUSIC

123↓
Only RAP-MUSIC succeeded inestimating correct position

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Experimental Results●Comparison of the performances of three methods
for Source 1 (Pattern 3)
Spatial Smoothing

MUSIC12345

1

2

3

45RAP-MUSIC

12345

↓

RAP-MUSIC is superior to MUSIC andSpatial Smoothing Techniquein a Reverberant Environment

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Conclusion●Developing an effective estimation methodof sound source positions using the3surrounding microphone array for FIR– Proposing RAP-MUSIC to reduce the influenceof reverberant waves

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