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Nearfield broadband array design using a radially invariant modal expansion
Abhayapala1, Kennedy, Williamson
1Telecommunications Engineering Group, Research School of Information Sciences and Engineering, Australian National University, Canberra ACT, Australia.
The Journal of the Acoustical Society of America
|January 21, 2000
Summary
This study presents a new method for broadband beamforming, enabling precise control over both beampattern shape and nearfield focusing. The efficient parameterization allows arrays to adapt to desired source distances for applications like speech acquisition.
Area of Science:
- Signal Processing
- Acoustics
- Array Signal Processing
Background:
- Broadband beamforming is crucial for applications like speech acquisition.
- Nearfield beamforming presents unique challenges due to the dependence of wave propagation on source distance.
Purpose of the Study:
- To introduce an efficient parameterization for nearfield broadband beamforming.
- To enable independent control over beampattern shape and radial focusing.
Main Methods:
- Developed an orthogonal basis set of elementary beampatterns.
- Designed elementary beamformers and combined them with frequency and distance-dependent weights.
- Factored the beamformer into three filtering levels: elementary, shape-dependent, and radial focusing.
Main Results:
- Achieved a single parameter for radial focusing to a desired distance.
- Demonstrated a practical array design with a frequency-invariant beampattern (1:10 range).
- Successfully applied to nearfield scenarios with sources as close as three wavelengths at the lowest frequency.
Conclusions:
- The proposed parameterization offers efficient and flexible control for nearfield broadband beamforming.
- The method is suitable for practical applications such as microphone arrays for speech acquisition.
- Enables focusing to specific radial distances, enhancing performance in complex acoustic environments.