scholarly journals Microphone array beamforming with near‐field correlated sources.

2009 ◽  
Vol 125 (4) ◽  
pp. 2545-2545
Author(s):  
Jonathan L. Odom ◽  
Jeffery Krolik
Keyword(s):  
Microphone Array ◽  
Near Field ◽  
Correlated Sources ◽  
Array Beamforming

scholarly journals Instability wave models for the near-field fluctuations of turbulent jets

2011 ◽  
Vol 689 ◽  
pp. 97-128 ◽  
Author(s):  
K. Gudmundsson ◽  
Tim Colonius
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Microphone Array ◽  
Near Field ◽  
Turbulent Jets ◽  
Instability Wave ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Scale Structures

AbstractPrevious work has shown that aspects of the evolution of large-scale structures, particularly in forced and transitional mixing layers and jets, can be described by linear and nonlinear stability theories. However, questions persist as to the choice of the basic (steady) flow field to perturb, and the extent to which disturbances in natural (unforced), initially turbulent jets may be modelled with the theory. For unforced jets, identification is made difficult by the lack of a phase reference that would permit a portion of the signal associated with the instability wave to be isolated from other, uncorrelated fluctuations. In this paper, we investigate the extent to which pressure and velocity fluctuations in subsonic, turbulent round jets can be described aslinearperturbations to the mean flow field. The disturbances are expanded about the experimentally measured jet mean flow field, and evolved using linear parabolized stability equations (PSE) that account, in an approximate way, for the weakly non-parallel jet mean flow field. We utilize data from an extensive microphone array that measures pressure fluctuations just outside the jet shear layer to show that, up to an unknown initial disturbance spectrum, the phase, wavelength, and amplitude envelope of convecting wavepackets agree well with PSE solutions at frequencies and azimuthal wavenumbers that can be accurately measured with the array. We next apply the proper orthogonal decomposition to near-field velocity fluctuations measured with particle image velocimetry, and show that the structure of the most energetic modes is also similar to eigenfunctions from the linear theory. Importantly, the amplitudes of the modes inferred from the velocity fluctuations are in reasonable agreement with those identified from the microphone array. The results therefore suggest that, to predict, with reasonable accuracy, the evolution of the largest-scale structures that comprise the most energetic portion of the turbulent spectrum of natural jets, nonlinear effects need only be indirectly accounted for by considering perturbations to the mean turbulent flow field, while neglecting any non-zero frequency disturbance interactions.

Spherical Microphone Array Beamforming

2010 ◽  
pp. 281-305 ◽  
Author(s):  
Boaz Rafaely ◽  
Yotam Peled ◽  
Morag Agmon ◽  
Dima Khaykin ◽  
Etan Fisher
Keyword(s):  
Microphone Array ◽  
Array Beamforming

Near‐field broadband array beamforming using wave equation transformation

1996 ◽  
Vol 100 (4) ◽  
pp. 2696-2696
Author(s):  
Rodney A. Kennedy ◽  
P. Thushara ◽  
D. Abhayapala ◽  
Darren B. Ward
Keyword(s):  
Wave Equation ◽  
Near Field ◽  
Equation Transformation ◽  
Array Beamforming

scholarly journals Effects of a near-field rigid sphere scatterer on the performance of linear microphone array beamformers

2016 ◽  
Vol 140 (2) ◽  
pp. 924-935
Author(s):  
Yuxiang Hu ◽  
Haoran Zhou ◽  
Jing Lu ◽  
Xiaojun Qiu
Keyword(s):  
Microphone Array ◽  
Near Field ◽  
Rigid Sphere

Considerations for near‐field acoustical inverse measurements on partially correlated sources.

2010 ◽  
Vol 128 (4) ◽  
pp. 2285-2285
Author(s):  
Alan T. Wall ◽  
Kent L. Gee ◽  
Tracianne B. Neilsen ◽  
Michael M. James
Keyword(s):  
Near Field ◽  
Correlated Sources

A beamforming paradox: Using far‐field techniques to design a near‐field microphone array

1997 ◽  
Vol 102 (5) ◽  
pp. 3208-3208
Author(s):  
Darren B. Ward ◽  
Rodney A. Kennedy ◽  
Thushara Abhayapala
Keyword(s):  
Microphone Array ◽  
Near Field ◽  
Far Field ◽  
Field Techniques
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