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Tracking Energy Flow Using a Volumetric Acoustic Intensity Imager (VAIM)A new measurement device has been invented at the Naval Research Laboratory which images instantaneously the intensity vector throughout a three-dimensional volume nearly a meter on a side. The measurement device consists of a nearly transparent spherical array of 50 inexpensive microphones optimally positioned on an imaginary spherical surface of radius 0.2m. Front-end signal processing uses coherence analysis to produce multiple, phase-coherent holograms in the frequency domain each related to references located on suspect sound sources in an aircraft cabin. The analysis uses either SVD or Cholesky decomposition methods using ensemble averages of the cross-spectral density with the fixed references. The holograms are mathematically processed using spherical NAH (nearfield acoustical holography) to convert the measured pressure field into a vector intensity field in the volume of maximum radius 0.4 m centered on the sphere origin. The utility of this probe is evaluated in a detailed analysis of a recent in-flight experiment in cooperation with Boeing and NASA on NASA s Aries 757 aircraft. In this experiment the trim panels and insulation were removed over a section of the aircraft and the bare panels and windows were instrumented with accelerometers to use as references for the VAIM. Results show excellent success at locating and identifying the sources of interior noise in-flight in the frequency range of 0 to 1400 Hz. This work was supported by NASA and the Office of Naval Research.
Document ID
20070002006
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Klos, Jacob (NASA Langley Research Center Hampton, VA, United States)
Williams, Earl G. (Naval Research Lab. Washington, DC, United States)
Valdivia, Nicolas P. (Naval Research Lab. Washington, DC, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2006
Subject Category
Acoustics
Meeting Information
Meeting: INTER-NOISE 2006 - 35th International Congress and Exposition on Noise Control Engineering
Location: Honolulu, HI
Country: United States
Start Date: December 3, 2006
End Date: December 6, 2006
Funding Number(s)
WBS: WBS 581.02.08.07
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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