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A unique method to study acoustic transmission through ducts using signal synthesis and averaging of acoustic pulsesAn acoustic impulse technique using a loudspeaker driver is developed to measure the acoustic properties of a duct/nozzle system. A signal synthesis method is used to generate a desired single pulse with a flat spectrum. The convolution of the desired signal and the inverse Fourier transform of the reciprocal of the driver's response are then fed to the driver. A signal averaging process eliminates the jet mixing noise from the mixture of jet noise and the internal noise, thereby allowing very low intensity signals to be measured accurately, even for high velocity jets. A theoretical analysis is carried out to predict the incident sound field; this is used to help determine the number and locations of the induct measurement points to account for the contributions due to higher order modes present in the incident tube method. The impulse technique is validated by comparing experimentally determined acoustic characteristics of a duct-nozzle system with similar results obtained by the impedance tube method. Absolute agreement in the comparisons was poor, but the overall shapes of the time histories and spectral distributions were much alike.
Document ID
19810064200
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Salikuddin, M.
(Lockheed-Georgia Co. Marietta, GA, United States)
Ramakrishnan, R.
(Lockheed-Georgia Co. Marietta, GA, United States)
Ahuja, K. K.
(Lockheed-Georgia Co. Marietta, GA, United States)
Brown, W. H.
(Lockheed-Georgia Co. Marietta, GA, United States)
Date Acquired
August 11, 2013
Publication Date
October 1, 1981
Subject Category
Acoustics
Report/Patent Number
AIAA PAPER 81-1966
Meeting Information
Meeting: Aeroacoustics Conference
Location: Palo Alto, CA
Start Date: October 5, 1981
End Date: October 7, 1981
Sponsors: American Institute of Aeronautics and Astronautics
Accession Number
81A48604
Funding Number(s)
CONTRACT_GRANT: NAS3-20797
Distribution Limits
Public
Copyright
Other

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