VOCAL’s Constant Beamwidth Frequency Domain Broadband Beamformer software solution provides constant spatial discrimination performance across the full frequency band of the beamformer. Our beamformer software is available as a standalone algorithm or library. Custom designs are also available. Please contact us to discuss your beamforming requirements.
Constant Beamwidth Broadband Beamformer
Constant Beamwidth Broadband Beamformer improves upon a typical microphone array Delay and Sum beamformer which has a beamwidth inversely proportional to the source signal frequency. Using this type of narrowband beamformer for a broadband source signal such as speech would cause the signal to be low pass filtered whenever the beamformer steering direction is different from the source signal incident angle. A “spectral tilt” artifact is caused by noise and interference signals not being attenuated normally over the spectrum of the beamformer output.
A solution to this problem can be realized by considering a beamformer in the frequency domain and designing narrowband beamformers at discrete frequencies of a discrete fourier transform (DFT). The output of the Constant Beamwidth Broadband Beamformer is derived from the narrowband beamfomers using a filter and sum technique. The filters are derived to generate constant beamwidth beams over the full spectrum of the beamfomer.
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References
[1] J. Benesty, J. Chen, and Y. Huang, ”Microphone Array Signal Processing”, Berlin, Germany, Springer-Verlag, 2008