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Interior and exterior sound field control using general two-dimensional first-order sources
1Industrial Research Ltd., P.O. Box 31-310, Lower Hutt, New Zealand. m.poletti@irl.cri.nz
The Journal of the Acoustical Society of America
|February 10, 2011
Summary
This study enhances sound field reproduction within circular loudspeaker arrays. Adding tangential dipoles improves interior accuracy and reduces exterior sound, extending the array
Area of Science:
- Acoustics
- Signal Processing
- Loudspeaker Array Technology
Background:
- Reproducing a specific sound field inside a circular loudspeaker array without external sound leakage is a persistent challenge across a wide frequency range.
- The Kirchhoff-Helmholtz integral, combined with specific loudspeaker responses, can achieve interior sound field control at low frequencies.
Purpose of the Study:
- To investigate the performance of circular discrete arrays of line-source loudspeakers incorporating tangential dipoles.
- To determine if tangential dipoles enhance interior sound field accuracy and reduce exterior sound radiation.
- To assess the impact of tangential dipoles on the operational frequency range of loudspeaker arrays.
Main Methods:
- Utilizing the Kirchhoff-Helmholtz integral with circular discrete arrays of line-source loudspeakers.
- Implementing loudspeakers with azimuthal polar responses, including combinations of 2D monopoles and radially oriented 2D dipoles.
- Introducing tangential dipoles to the array configuration and analyzing their effect on sound field reproduction.
Main Results:
- At low frequencies, tangential dipoles are not essential for accurate interior sound field reproduction.
- Near and above the Nyquist frequency, tangential dipoles significantly improve interior accuracy.
- The inclusion of tangential dipoles effectively reduces undesirable exterior sound fields.
- The addition of tangential dipoles extends the useful operational bandwidth of the loudspeaker array by approximately one octave.
Conclusions:
- Tangential dipoles are crucial for optimizing sound field reproduction in circular loudspeaker arrays, particularly at higher frequencies.
- These dipoles enhance the precision of the interior sound field while minimizing unwanted exterior sound.
- The findings demonstrate a practical method for broadening the effective frequency range of loudspeaker array systems.
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