6926475986

84-1773

Review of Sound Induced by Vortex Shedding frocn Cylinder*

R.D. Blevins

GA Technologies, Inc., San Diego, CA 92138, J. Sound Vib., 22 (4). pp 455-470 (Feb 22. 1984) 8 figfs, 91 refs

Key Words: Cylinder*, Vortex ihedding, Sound generation

Sound induced by periodic vortex shedding from cylinder* ha* been studied mor* or lott continuoutly *ince the first quantrtative study by Strouhal in 1878. Meaiurement* have thown that vortex shedding i* a dipol* aource of sound. Theoretical model* for aeroacoustic sound in a fre* apace, mostly inspired by Lighthill'* work, have been developed which cen replicate the measurement* one* the vortex shedding force, coherence, and periodicity are experimentally measured. Vortex shedding from tubę* in heet exchanger tubę bundle* can reach da mag i ng intensłtias because the acoustic modę i* bound by the łower *peed of sound within the tubę bank itself. However, the amplitudę and occurrence of the resonence can only be approximately predicted at present.

84-1774

Noiae Aaaenment Guidełines

Bolt Beranek and Newman. Inc., Cambridge. MA, Rept. No. HUD-0002932, HUD/PDR-735, 36 pp (June 1983)

PB84-151133

Key Word*: Traffic noise, Airports

Thi* manuał deseribes thosa procedura* that have been devełoped so those wrthout technical training will be abl* to assess the exposure of a housing sita to present and futur* noise conditions. It prowides a means for asaessing separateły the noise produced by airport. highway, and railroed opera-ttons, as weil a* the means for aggregating their combined effort on the overall noise environment at a »lte. The text •xplains how to combin* sound l*v*l* In decibels and how the noise !evel on łarger sites may wary at different part* of the słte. Th* only materiał* required to make the noise assessment are a map of the area, a itraight edge ruler, a protractor, and a pencil.

Naval Underwater Systems Ctr., New London, CT, Rept. No. NUSC-TM-831145, 31 pp (Sept 14. 1983) AD-A135 494

Key Words: Underwater sound, Hydrophones, Buoys, Fast Fourier transform. Data Processing

A new multi-hydrophon* digital buoy system włth onboard FFT Processing has been dewloped. Acoustic data from aach of eight hydrophones is digitized and real time fest Fourier transformed by the buoy's micro-processor. Complax and ensemble averaged *>ectraf results are then written onto a high density digital cartridge tape. An instantaneous dynamie rangę of at least 72 dB is available over the frequency band 4-360 Hz. The first open ocean test of the system performed nearly flawłessly and was recowered intect. Over 75 hoursof acoustic data were acquked. including both ambient noise and CW tow measurement*. This technical memorandum presents a quick look review of the acoustic results of the saa test.

84-1776

Using Eigenvałue Analysis to Identify Interferencc in Ambient Sea Noiae YerticaJ Directionality Mea-aurementa

D.J. Kewley

Dept. of Defence, Weapons Systems Res. Lab., De-fence Res. Centre, Salisbury, South Australia 5108, J. Acoust. Soc. Amer., _75. (3), pp 826-833 (Mar 1984) 15 figs, 22 refs

Key Words: Underwater sound, Sound measurement, Eigen-value problem*

Ambient noise wertical directionality measurement* at Iow frequencies have shown that noise arrive* from k>ng dis-tance* at naar horizontai angles, from moderate distances at larger angles, and from to ca/ aources at high angles. Leveis of noise from different sources can be measured by examining vertical lineer array beam po wers & the appropriet* angles. However, when measurement* ar* madę, it is important to be able to distinguish between acoustic signals, ambient noise, and data contamination. Some exp*rimental results ar* *xamined, using conventionai and adaptive beamforming and eigenvalue - eigenvactor decomposition. and used to establish criteria useful in deciding whethter the maasure-ments ar* ambient noise or otherwise.

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W.

84-1775

SEACAL Digital Data Procetuig Buoy Acoustic Performance During BERMEX-83: Ouick Look Report

P.D. Hersteinand P.C. King 84-1777

Radiation and Diffraction of Underwater Acoustic Waves

Y.H. Pao. C.P. Chen, and G.C.C. Ku