Limits in FIR subband beamforming for spatially spread near-field speech sources

Document type: Conference Papers
Peer reviewed: Yes
Full text:
Author(s): Nedelko Grbic, Sven Nordholm, Antonio Cantoni
Title: Limits in FIR subband beamforming for spatially spread near-field speech sources
Translated title: Gränser i FIR delbands beamforming för spatiellt spridda tal-källor i närfältet
Conference name: Proceedings of the 2003 International Symposium on Circuits and Systems
Year: 2003
Pagination: II-516 - II-519
ISBN: 0-7803-7761-3
Publisher: IEEE
City: Bangkok
Organization: Blekinge Institute of Technology
Department: Dept. of Signal Processing (Institutionen för signalbehandling)
Dept. of Signal Processing S-372 25 Ronneby
+46 455 38 50 00
Authors e-mail: ngr@bth.se
Language: English
Abstract: This paper analyses optimal subband beamforming performance mainly aimed at speech enhancement and acoustic echo suppression for personal communication devices, personal computers and wireless cellular telephones.
The focus is on theoretical limits of finite impulse response (FIR) beamformers for spatially spread sources in the array near-field. Performance of the Wiener solution is compared to the direct maximization of the array gain for different lengths of the FIR filters and different source interference spreads. The evaluation is performed individually in subbands with constant increasing logarithmic bandwidth. Results show that the difference between the Wiener solution and the direct array gain maximization is less than 2 dB in the measure of Signal-to-Noise plus Interference Ratio (SNIR), for small interference spread. With increasing interference spread the difference in SNIR performance increases, in favor of the array gain maximization.
Summary in Swedish: Performance of the Wiener solution is compared to the optimum signal-to-noise plus interference beamformer (SNIB) for different lengths of the FIR filters. The comparison includes different spatial spreading of the interference source. Results show that the difference in the measure of SNIR is small between the solutions in low frequency bands. It is also shown that the performance is close between the solutions when the spatial spread of the interference is small, i.e. the same size as the source. However, when the interference spread increases, the performance gain with the SNIB is significant, as much as 10~dB. By subdividing the fullband signals into constant increasing logarithmic bandwidth subbands, the number of FIR filter parameters needed is approximately 10-20 taps and it is nearly the same across the subbands.
Subject: Signal Processing\Beamforming
Signal Processing\Speech Enhancement
Keywords: Beamforming, near-field, spatial spread, subband
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