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Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic TestingLarge reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in the planning stages.
Document ID
20150008462
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Kolaini, Ali R.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
O'Connell, Michael R.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Tsoi, Wan B.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
May 19, 2015
Publication Date
October 12, 2009
Subject Category
Acoustics
Meeting Information
Meeting: Aerospace Testing Seminar
Location: Manhattan Beach, CA
Country: United States
Start Date: October 12, 2009
End Date: October 15, 2009
Sponsors: Aerospace Corp.
Distribution Limits
Public
Copyright
Other
Keywords
Reverberant acoustic field
acoustic/structural modal coupling
direct acoustic field
speakers
vibro-acoustic

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