Low-frequency pressure wave propagation in liquid-filled, flexible tubes.

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Low-frequency pressure wave propagation in liquid-filled, flexible tubes. (A)
Bjørnø, Leif; Bjelland, C.
Published in:
Acoustical Society of America. Journal
Link to article, DOI:
10.1121/1.403122
Publication date:
1992
Document Version
Publisher's PDF, also known as Version of record
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Citation (APA):
Bjørnø, L., & Bjelland, C. (1992). Low-frequency pressure wave propagation in liquid-filled, flexible tubes. (A).
Acoustical Society of America. Journal, 91(4), 2441-2441. https://doi.org/10.1121/1.403122

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PROGRAM OF
The 123rd Meeting of the Acoustical Society of America
Salt Lake City Marriott ß Salt Lake City, Utah ß 11-15 May 1992
NOTE: All Journala rticlesa nd Letterst o the Editor are peer reviewedb eforep ublication.P rogram
abstractsh, owever,a re not reviewpeudb bliecfaotrioe ns, incew e are prohibitedb y time and schedule.
MONDAY MORNING, 11 MAY 1992 SALON G, 8:00 A.M. TO 12:15 P.M.
Session 0AO
Acoustical Oceanography:A coustical Studies of Upper Ocean Dynamic ProcessesI
Andrea ProsperertlC, hair
Departmenot f MechanicaEl ngineeringJ,o hns UniversityB, altimore,M aryland2 1218
Chair's Introduction--8:00
Invited Papers
8.'O5
0AO1. Low-frequencys oundr adiation and scatteringf rom bubble clouds. William M. Carey (Defense
Appl. Res.P rojectA gency,A rlington,V A 22202)
Recente xperimentael videnceh as shownt hat when wave breakingo ccurs,l ow-frequency
Hz) soundi s produceda nd LF scatterh asa differentc haracteristicth an expectedfr om roughs eas urface
scatteringT. hesee ffectsh ave beena ttributedt o the bubblesp roducedd uring wave breaking,w hich are
conveeredto depthb y the breakingt urbulencev, orficitya nd Langrnuirc irculationa s observedb y Thorpe
Thorpe,O ceanicW hiteC aps,e ditedb y E. Monahaha nd G. MacNiocaill( Reidel, Boston,1 986), pp.
57-58]. Whilet he radiationa nds catteringch aracteristicast frequenciegsr eatert han I kHz aree xplainedb y
incoherenstc atterfr om the observebdu bbles izea nds paced istributiontsh e lowerf requencyp henomenaar e
not easilye xplained.
8'30
0AO2. Low-frequencyb ncksc(cid:127)tter from denses ubmergedb ubblec louds.R onald A. Roy (Appl. Phys.
Lab., Univ. of WashingtonS, eattle,W A 98105), William Carey (DefenseA ppL Res. ProjectA gency,
Arlington,V A 22202), MichaelN icholasL, awrenceA . Crum, andJ effS chindall (Natl. Ctr. for Phys.
Acoust.,U niv. of MississippiU, niversityM, S 38677)
The frequency-dependcehnat racteristicosf the acousticb ackscattefrro ms ubmergebdu bblec loudsw as
studiedu singb othc onventionaaln dp arametrics ounds ourcesT.h e cloudsa, ll of whichp ossessead c har-
acteristliecn gtshc aloef 0 .5m ,a voidf ractioonf o rder1 0- 3, anda meanb ubblrea diuosf a pproximately
1.5 ram,w ereg enerate3d9 .2m beneathth e surfaceo f a freshwatelra ke (Lake SenecaN, Y) usinga n array
of hypodermicn eedlesd rivenw ith pulsedf low of compresseadi r. Backscatterintga rgets trengthsw ere
measuredfo r frequenciersa ngingf rom 300 Hz to 14 kHz. Resultso btainedu singc onventionaaln d para-
metrics ourcesw erec omparablew, ith targets trengthsfa llingi n the + 1 to - 10-ribr ange.S everalp eaks
wereo bservedin the targets trengthv ersusfr equencyd ata.L ow-frequenc(yl esst han 1 kHz) resultse xhibit
elevatedt arget strengthsth roughoutw, ith evidenceo f a broad peak at approximately5 00 Hz. Results
obtainedo ver the entire range of frequenciesw ill be comparedw ith theoreticalp redictionsb asedo n
coherent,r esonances cattering( > 1 kHz) and coherent,o ff-resonancsec attering( < 1 kHz) and collective
bubbleo scillation{s < 1 kHz). [Work supportedb y ONR, ONT, AEAS, and NUSC/IR.]
8:55
0AO3. Laboratory experimentso n bubble-cloudo scillations. LawrenceA . Crum, Michael Nicholas, Ali
Kolaini (Natl. Ctr. for Phys. Acoust.,U niv. of MississippiO, xford, MS 38677), and Ronald A. Roy
(Univ. of WashingtonS, eattle,W A 98105)
A varietyo f experimentsth at haveb eenu ndertakent o investigateth e acousticc haracteristicosf bubble
cloudsw ill be describedT. hese experimentsh ave involvedb oth passivea coustice missioni,n which the
radiatedn oisei s measuredfr om a bubblec loudt hat is beingp roduceda, nd activea coustics catteringi,n
which soundw avesa rc scatteredfr om a similarlyp roducedb ubblec loud after it has ceasedt o radiate
emissionsIt. appearsth at the dominanta cousticc haracteristiocf thesec loudsis that theyr eadilye mit,a nd
can easilyb e stimulatedin to emitting,l ow-frequencsyo undb y the collectiveo scillationosf the bubbles
within the cloud.T his modeo f oscillation[s eep apersb y Prosperettain d by Careya nd Browningin Sea
SurfaceS ounde, ditedb y B. R. Kerman( KluwerA cademicD, ordrecht1, 988)]a ppca(cid:127). to providea
physicaml echanismfo r a broadr angeo f ambientn oisee missionisn the oceana nd may play an important
role in low-frequencayc tives catteringfr om the oceans urface[. Work supportedb y ONR and ONT.]
0AO4. Two-dimensional imaging of bubble cloud distribution. David M. Farmer and Mark Trevorrow
(Inst. of OceanS ei., P.O. Box 1600, Sidney,B C VSL 4B2, Canada)
Observationo f bubblec loud organizationw ith sidescans onarsh avingf ixed orientationi s now a well
establishetde chniqueth at has revealeda spectso f bubblec loudb ehaviorr elevantt o the studyo f low-
frequencya eonstics catteringL, angrnuirc irculation,a nd relatedt opics.A difficultyw ith this approachi s
that thes ignafl roma fixeds onaris limitedt o whatevedr riftst hroughth ef ieldo f view,s ot hatt emporaal nd
spatiale volutiono f the patternsm ustb e inferredf rom the time-dependenot,n e-dimensionsailg nal.O bser-
vationsh aven ow beeno btainedw ith an azimuthallys cannings onart hat can acquireb ubblec loudi magery
every 30-40 s through3 60' over a disk of radiusa pproximately3 00 m. Bubblec loud evolutioni s slow
relativet o this scarfingra te, so that successivirea agesfo rm a movie of the evolvingb ubblec loudp atterns.
Suchi magecsa nb e usedto determinteh eirl engtha nds tabilitya, ndt he wayi n (cid:127)/hich adjacenctl ouds
amalgamate[W. ork supportebdy ONR.]
0AO5. Us/nata coustics cattering(h igh frequencyt)o predicta coustics cattering(l ow frequency). Frank
S. Henycy (Appl. Phys. Lab., Univ. of Washington,1 013 4Oth St. NE, Seattle,W A 98105), David
Farmer (Inst. of Ocean SciencesS, idney,B C, Canada), and SveinV agle (Bergen Sci. Ctr., Bergen,
Norway )
Modelso f low-frequencrye verberationfr om tenuousb ubblec loudsh avem adea ssumptionasb outt he
geometryo f the cloudsS. omeo f thosea ssumptionasre replacedw ith propertierse motglym easuredu sing
high-frequencsyc atteringT.h is approachis appliedto the measuremenmtsa ded uringt he CST-7e xperi-
ment,w hichi s the firste xperimenitn cludingb othh igh-a nd low-frequencmy easurementAsl.s o discussed
is the useo f oceanin formatioonb tainedfr omt heh igh-frequencsyc atterinign additionto the geometroyf
thec loudsto helpi nferl ow-frequencrye verberatiocnh aracteristic[sw. ork supportebdy theO fficeo f Naval
Research.]
2314 J. Acoust.S oc. Am., VoL 91, No. 4, Pt. 2, Apdl 1992 123rd Meeting:A cousticaSl ocietyo f America 2314
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10:10-10:.25
Break
10:2(cid:127)
0AO6. Fractal chantcterization of the near-surfaceo ceanic bubble layer from deep-oceanr everberation
measurementsK. ennethE . Gilbert (GraduateP rogrami n Acousticsa nd Appl. Res. Lab., PennS tate
Univ., P.O. Box3 0, StateC ollegeP, A 16804)a nd LintaoW ang (Natl. Ctr. for Phys.A coust.U, niversity,
MS 38677)
At high seas tatesa nd low grazinga ngles,i t hasb eenh ypothesizedth at surfacer everberationis dom-
inated by backscattefrr om the bubblel ayer beneatht he seas urface.A ssumingt he hypothesisis true, a
simples tochastibcu bble-layebra ckscattemr odelh asb eenu sedt o analyzes urfacer everberatiodna ta from
four differentd eep-oceaanr eas.I n everya rea, the inferredw ave-numbesrp ectrumfo r the horizontal
structuoref theb ubbllea yeris a ni nverspeo welra wo f thef ormP (K) = .4K- (cid:127), wher.e4 i sa constanKt ,
is the horizontawl aven umbero f the structurea, nd 3 f(cid:127)<(cid:127)4. The existencoef power-laww ave-number
spectrain dicatesth at the horizontasl tructureo f the bubblel ayeri s fractal.U singD = 4 - fi/2 for the
fractald imension2, (cid:127)< D (cid:127) 2.5 is obtainedfo r measuremenatsn alyzeds of ar. Fractals tructurein the bubble
layeri mpliesth at horizontailn homogeneiteiexsis to n a wider angeo f scaleasn dp ossesssc alein variance.
Hence,o n the average,t he mediuml ookst he samea t all scalesb etweens omei nner scale and outer
scale. (Presentlyt,h e inner and outer scalesa re not known.) In this papers omep hysicapl rocesseasr e
consideredth at could generatef ractal structurei n the bubblel ayer and somee xperimentaml eansa re
suggestefdo r identifyingth e processe[sW. ork supportedb y ONR.]
10:(cid:127)0
0AO7. A critique on the relationshipb etweenb ark, sca(cid:127)ering and environmentalm easurements. R.R.
Goodman (Appi. Res. Lab., Penn StateU niv.. P.O. Box 30, StateC ollege,P A 16804)
In the paperb y Gilbert that was presentede arlieri n this sessionit was shownt hat, by the useo f the
first-orderB orn approximationa nd a plaosiblea ssumptiona boutt he verticald istributiono f bubblcsb, ack-
scatterings trengthm easuremenitns severael xperimentysi eld horizontalw ave-numbepro wers pectraf or
bubbldee nsitioefst h ef ormP (Ks)= .4K(cid:127) (cid:127). Thev alueosf /(cid:127) werefo undto l iea pproximatbeelytw ee3n a nd
4. Sincea givenv alueo f (cid:127) requiresth at the oceanographpicro cessepsr oducea bubbled istributionth at
obeyso, n the averagea, specifics calingin Yariancei,t is interestinst hen, to seei f therea re any correlations
betweent he oceanographic/atmospheoribcs ervationasn d the valueso f B for the experimentsth at were
analyzed.I t is the purposeo f this paper to examinet he resultso f each of the experimentsfr om the
standpoinot f acousticasn de nvironmentaolb servation(cid:127)ns ordert o seekc lues to thec orrelationo f(cid:127) with
oceanographic/atmosphoebrisce rvationIst .w ill be cleart hat noneo f the experimentcso ntainedm easure-
meats that are suffcientt o yield specificc onnectionbs etweent he environmentaml easurementasn d the
ContributedP aper
11:15
( 1962)] and othersa t low grazinga nglesG. as volumef ractionso f the
ordero f 1%, lineard imensionosf the ordero f I m, and surfacec overage
0AOg. Enhanced backgoatferingf rom b bble cloud distributions on
of the order of 1% (the latter of which agreesw ith the experimentally
the oceans urface, AndreaP rosperertal nd KausikS arkar (Dept. of
measuredv aluesf or 10 m/s winds) are sufficientto give an excellent
Mech.E ng.,T he IohnsH opkinsU niv., BaitmoreM, D 21218)
matcho f the dataa sa functiono f frequencyin the range0 .1-2 kHz and
wind speedsfr om 5 to 25 m/s. In the previousw ork the cloudsw ere
It has been showni n earlier studies[ ProsperertlL, u, and Kim;
treateda s independenstc atterersIn. the presenwt ork the previousre -
Sarkar and Prospercttib. oth submittedto L Acoust.S oc.A m.] that
suitsa rer efinedt o includelo west-ordemr ultiples catteringef fectsa long
bubblec loudsp roducedb y breakingw avesa t the ocean'ss urfacec an
the lineso f Foldy[ PhysR. ev.6 7, 107( 1945} ] andB iot [J. AcoustS. oc.
expla(cid:127)int he unexpectedlhyi gh backscatterinlge velso bservede xperi-
Am. 44, 1616( 1968}].[ Work supportebdy ONR.]
mentally by Chapmana nd Harris [J. Acoust. Soc. Am. 34, 1592
2315 J. Acoust.S oc. Am., Vol. 91, No. 4, Pt. 2, April 1992 123rd Meeting:A cousticaSl ocietyo f America 2315
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Panel Discussion
PANEL MODERATOR: Andrea Prosperetti
PANEL MEMBERS: William M. Carey
Lawrence A. Crum
David M. Farmer
Kenneth E. Gilbert
Ralph R. Goodman
Frank S. Henyey
Ronald A. Roy
2316 J. Acoust.S oc. Am.,V ol. 91, No. 4, Pt. 2, April1 992 123rdM eeting:A cousticaSl ocietyo f America 2316
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MONDAY AFTERNOON, 11 MAY 1992 SALON G, 1:30T O 6:00 P.M.
Session 1AO
AcousticalO ceanography:A cousticalS tudies of Upper Ocean Dynamic ProcessesII
Ralph R. Goodman,C hair
(cid:127)4ppliedR esearcLha boratoryP, ennsylvanSiata teU niversityP,. O.B ox$ 0, StateC ollegeP, ennsylvan1ia6 804
Chair's Introduction1:30
Invited Papers
1:35
IAOI. The proposedK ulgbt Inlet surfaceh ackscatteringe xperiment. T. Ewart, D. Farmer, F. Henycy,
D. Jackson,P . Kaczkowski,L . Olson, and E. Thorsos (Univ. of Washington,S eattle,W A 98105)
An experimenits plannedf or the 93-95 time framet o measures urfaceb ackscatterinagt 400 Hz using
a pencil beam sourcea nd receiverc urrentlyu nderd evelopmentT. he acousticse xperimenwt ill be con-
ducteds imultaneouslwy ith surfacez one environmentaml easurement(sn otably, surfaceh eights tatistics
and bubbled ensitiesc) ontributedb y variouss cientistisn the air-seaa cousticsp rogram.I nitial operationin
the fjord allowst he equipmentt o be installeda t low wind speedsa, nd the apparatusc an be connectedb y
cablet o the protectedw aterso f a smallb ay. In this way operationo f the equipmenot vera widev arietyo f
wind conditioncsa nb e achieveds afelyp rior to openo ceand eployment(.H igh windsa re commonin the
confinedc hanneol f the fjord.) As the principalg oal,t he apparatusw ill be usedt o determineth e regime
wherer oughs urfaces catterintgh eoryd oesn ot adequateldye scribteh e observationasn, dt o determineth e
dominanmt echanismIsn. thiss catterinrge gimeth e measuremenwtsil l focuso n the relativeim portancoef
thev ariouss urfacezo nep henomen(ab ubbleisn theird ifferenitn carnationsp)r edictedto yielda n enhanced
surfaceb ackscatterinsgig natureT. he rationalea ndd esigno f the experimenwt ill be discusseTdh. e exper-
imentw ill provideth ee xperiencree quiredb eforeo peno ceanm easuremenctasn b eu ndertaken.
2.'00
IAO2. Wave brenblng, turbulence, and related similnrity Inw(cid:127)A review of wind-wave research nt
Tohoku University. Y. Toba, H. Kawamura, and N. Ebuchi (Dept. of Geophys.,T ohoku Univ., Sendai,
980 Japan)
Researcho n wind wavesm adeb y our groupa t TohokuU niversityis reviewedw ith emphasios n wave
breakingt,u rbulencea,n d the underlyingsi milarityla ws.D etailedd ynamicapl rocesseresl atedt o wind
wavesi,n cludingo rderedm otionsa ndt urbulencien the air andw ater,h aveb eeni nvestigateind a tank,
usingq uantitativfelo wv isualizatiotne chniquecso mbinewd ith thed irectm easuremeonft t urbulenftl ows.
Conspicuouesv entss, ucha s airflows eparationf,o rmationo f a high-vorticityla yera t the wavec rest,w ave
breakinga,n db urstingin air andw atera ref oundi n thev icinityo f thew aters urfaceT. heya rer elatedto one
anothetro e xplainm omentutmra nsfefrr omt hea irflowa ndt urbulencgee neratiownh.,i chm ayb ea ssociated
with soundg enerationat the water surfaceS. imilarityl awse xist,w hichc orrespontdo the relationship
betweenw avesa nd turbulenceb elowa nd abovet he interfaced, escribintgh e grossn atureo f the wind-wave
fieldA. parametue(cid:127)/rv o(cid:127), isi ntroducteodd escriobvee rapllr ocesosefw si nd-wabvree akinwgh, itecapping,
and drop productionI.t is suggestetdh at this parametemr ay describea lsot he overalli ntensityo f bubble
formation in the sea.
2:25
IAO3. The effect of the rough (cid:127)dr-(cid:127)e(cid:127) interfaceo n sc(cid:127)ttering from tenuousb ubblec louds.E ric I.
Thorsos (App]. Phys.L ab., Univ. of WashingtonS,c atticW, /, 98]05)
Hcnycyh asd evelopead t heoryf or ]ow-frcqueocsyc atterinfgr omt enuoubs obblec loudsIF . S. Hcnyey,
J. Acoust.S oc.A m. 90, 399-405 ( ]990)]. The bubblyw ater is treateda s an effectivem edium,d escribed
with a spatiallyv aryingi ndex of refraction,a nd the scatteringis found usinga perturbationt heory ap-
proachT. hism odeal ppliesto bubblec loudsw ith sufficientlloy wa ir volumefr actionth atb uoyancfyo rces
aren egligibleth; eb ubblec loudsa ret husr eferredto ast enuousH. enyeys implifiedh isa nalysibs y assuming
that the air-seai nterfaceis fiat. Here the effecto f includings urfacer oughnesiss examinedfo r the 2-D
problem(I -D surfacreo ughnessb)u, t otherwisHee nyey'asp proacihs followedT.h e integrael quation
methodi s usedt o obtaint he exacta cousticfi eldsn ear the roughs urfacew, hicha re thene mployedin the
2317 J. Acoust.S oc. Am., Vol. 91, No. 4, Pt. 2, April1 992 123rd Meeting:A cousticaSl ocietyo f America 2317
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bubbles catteringc alculationsu singp erturbationth eory.R esultsc omparingb obbles catteringw ith rough
and fiat seas urfacess howt hat the averages catteredin tensityi s not mucha ffectedb y surfacer oughnessb,o t
the statisticadl istributiono f intensitiesc an be significantlya ffected.l eadingi n somec asest o a hightailed
intensityd istribution( spikes)w hen the surfaceis rough.I mplicationsfo r the time dependencoef the
scatterinagn df or the Dopplers pectrumw ill alsob ed iscusse[dW. orks upportebdy ONR.]
IAO4, Acousticd aylight:I.m agingt he oe(cid:127)m with ambientn ul(cid:127)e. Michael J. Buckingham,B roderickV .
Berkhout (Marine Phys. Lab., ScrippsI nst. of Oceanogr.,L a Jolla, CA 92093-0213), and StewartA .
L. Giegg (Dept. of OceanE ng.,F loridaA tlanticU niv., BocaR aton,F L 33431)
For manyy earst he principalm eanso f probingt he oceanu sings oundh asb eent hrought he useo f either
active or passive techniqueWs. ith an actives ystema, n objectis illuminatedb y a pulseo f sounda ndi ts
presencien ferredf rom thee choi t producesw, hereasth e passivea pproachin volvess implyl isteningfo r the
soundt hat the objecti tselfe mits.H ere a new methodo f employings oundi n the oceani s reported,w hich
is neitherp assivneo r activeI.t relieso n the naturallyo ccurringi,n coherenatm biennt oisef ieldi n the ocean
as the soles ourceo f acousticil lumination.B y analogyw ith daylighti n the atmospherea,m bientn oise
scatteredfr oma n objecti n the oceanc anb e focusedo ntoa n imagep lane,a ndf rom thisa cousticim age,w ith
appropriatsei gnapl rocessinag ,v isuali magec anb e producedo n a television-typmeo nitoro f the object
spacei n the ocean.T o testt his concepts, everals implee xperimenthsa veb eenc onductedin the oceano ff
Scrippsp ier,w ith a singlep arabolicre flectoar ctinga s an acousticle ns,w hichc onfirmt hat objectsil lumi-
natedo ulyb y ambiennt oisec ani ndeedb e seen overa frequencbya ndb etween5 and 50 kHz. [Work
supportedb y ONR.]
3:15-3'30
Break
3:30
IAO$. Bubble Idumee choe(cid:127) from convergenczeo ne ranges,B . E. McDonald, G. L Orris, and Michael
D. Collins (Naval Res. Lab., WashingtonD, C 20375)
Surfacer everberatiofnr om bubblep lumesa t longr anges( one or two convergenczeo nes) is modeledb y
combininga Born approximations catterm odel [McDonald, L Acoust.S oc. Am. 89, 617-622 (1990)],
which has givena greementw ith surfaceb ackscatterd ata at closer anges( much lesst han a convergence
zone), and an efficienmt ethodf or couplingt he scatteringa nd propagationas pectso f the problem[ Collins
and Werby,L Acoust.S oc.A m. 85, 1895-1902( 1989)]. A signalf rom a point sourcen ear the surfaceis
propagatedth rougha realistically(cid:127)fr active oceant o convergencew,h erei t incoherentlyiu sondieas seto f
bubblep lumes.T hese are representeda s verticallya lignedc ylindricalp atchesc ontaininga sound-speed
defectt hat diminishese xponentiallyw ith depth. For low frequencies(o n the order of 100 Hz), the hy-
pothesitsh at backscatteisr duea lmoste ntirelyt o deeplye ntrainedb ubblesli,k elyr esultingfr omL angmuir
circulation cells, is examined.
IAO6. Acousticr adiationd uet o surfacew aveb r(cid:127)lt;ng. RobertM . Kennedy (Naval UnderwaterS ystems
Ctr., AUTEC, West Palm Beach,F L 33402-7517) and StewartA . L. Glegg (Florida Atlantic Univ.,
Boca Raton, FL 33431)
While waveb reakingis continuallyo ccurringa t the seas urfacei,t s transienat nd s(cid:127)xm(cid:127)zlic naturem akes
it difficultt o measureE. xperimentarl esultsa re presentedth at showh ow acousticm ethodsc an be useda s
a remote sensoro f this fundamentalp rocessS. ea surface-generateadc ousticr adiation (40 to 4000 Hz) is
directlyr elatedt o a quantitativem easureo f the boundaryd ynamicsi;. e., the Toba variable.T he frequency
spectrumo f the radiationr emainsr emarkablyu nchangedo vera wide rangeo f environmentacl onditionsb ut
the correlationb etweent he soundp ressurele vela nd the Toba variableu ndergoeasn abruptc hangew hen
spillingb reakerss tartt o occur.R esultss upportth e useo f acoustictso remotelym easureth e rateo f energy
beingd issipatebdy waveb reakinga ndt hew avelengtho f the dominantg ravityw avec omponenTt.h eoretical
studiesh ave related the field measurementtso analyticala nd laboratoryr esultsc ited in the literature
indicatingt hat remotem onitoringo f the rate of occurrencaen d size distributiono f infant (freshly
entrained)b ubblesm ay be possibleif splasheosn the surfaced o not radiates ignificanst ound.S ignal
proceasinaglg orithmsfo r the remotem easuremendtsis cusseadb ovea ree nhancedb y eigenstructuraen alysis
of the measuredc ross-spectrdael nsitym atrix. [Work sponsorebdy ONR and NUSC.]
2318 J. Acoust.S oc. Am., Vol. 91, No. 4, Pt. 2, April 1992 123rd Meeting:A cousticaSl ocietyo f America 2318
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1AO7. Hi,h-frequencys urface(cid:127)c attertng phenomenian hlgh (cid:127)ea states.K erry W. Commander (Coastal
SystemsS tation,P (cid:127)arna City, FL 32407-5000)
The determinatioonf acoustics catteringfr om a roughs eas urfaceh asr eceivedc onsiderabalet tentionin
recenty ears.K nowledgeo f whitecapc haracteristic[sJ . Wu, IEEE J. OceanicE ng. 17, 150-158 ( 1992) ] has
led to a betteru nderstandinogf surfaces catteringp henomena[D . F. McCaramona nd S. T. McDaniel,
IEEE J. OceanicE ng. 15, 95-100 ( 1990)]. For thiss tudya substantiaalm ounto f backscatterindga ta was
acquiredw ith autonomouusn derwatevr ehiclesru nningb etween5 0 and 100f t of the surfaceT. hesev ehicles
useda shortp ulsel engths onaro peratinga t 215 kHz. The useo f a high-frequencsyo nara llowsd eep
penetratioonf denselyp opulatedb ubblep lumesB. ecausoef theh ighr epetitionra te,g oods patiavl ariation
of backscatterinsgtr engthfr om breakingw avesh asb eeno btainedP. reviousm easuremenbtsy others cien-
tists of bubbled istributionf unctionsi n breakingw avesa llows an approximatec onversiono f scattering
strengtha t the sonarf requencyto mostf requencieosf interestT. he databaseh erec onsistosf measurements
madei n deepw atere nvironmentws ith seasr angingf rom seas tate0 to 3. The spatialv ariationo f scattering
strengthd ue to the seas urfacea nd bubblep lur0esfr om breakingw avesi s discusseads a functiono f wind
speed.
ContributedP apers
4:4(cid:127) attenuationw ith decreasinpgu lsele ngthm ighth aveb eene xpectedN. o
effect was observed for two different but well defined bubble distribu-
IAOS. Short pulse acoustic transmission through marine
tions.[ Work supportedb y DRA Maritime.]
microbubblesA. !astairC owley (DefenceR es.A gencyM, aritimeD iv.,
Portland, UK), Nicholas G. Pace, and Tony Campbell (Bath
University, Avon, UK)
5.-OO
Whena bubbleis exciteda t or neari ts naturalf requencyit is a very
IAO9. Nonlinear wind-wave effects in backscatter. R. H. Meilen and
effectives catterera nd absorbero f sound. In fact, at resonances, catter-
i. A. Leykin (Marine Sci. Inst., Univ. of Connecticut, Groton, CT
ing and absorptioncr osss ectionasr e of the ordero f 1000t imesg reater
O634O)
than the geometricc rosss ectionf or typicalm arinem icrobubblesA.s
with anyr esonanst ystema, bubblet akesa finitea lbeits hortt ime to ring In backscatteerx perimentsn,o nlinearw ind-wavee ffectsh aveb een
up to steadys tateo scillationa nd continuesto oscillatefo r a finitet ime observedin Doppler spectraa nd azimuthala symmetryo f scattering
after the drivingf orcec easesA. numbero f studiesh aveb eenc arriedo ut strength.B oth effectsh aveb eena scribedto spatials kewnesass sociated
to attemptt o describeh ow acoustica bsorptiona nd backscattedr epend with nonlinears teepeninogf the wavefrontsB. icoherencaen alysiso f
upont he durationo f the drivingf orce.M ost notableo f thesea re the wavegaugem easurementsin a laboratory flume supportst his mecha-
backscatterm easurementf or short pulses in near surface seawater nism.H owever,s tandards tatisticaml ethodsr evealo nly averagep rop-
[Akulicheve t aL, Soy. Phys. Acoust.2 3, 177-180 (1986)] and the erties.I n a recentp aper[ N. E. Huang, NonlinearW ater WavesW ork-
forwardt ransmissionla boratorym easurementfso r short pulsel engths shop,B ristol,U . K. ( 1991) ], Huang reportedo n the useo f phase/time
at 120k Hz [H. R. Suiter,J . Acoust.S oc.A m. 91, 1383-1387 (1992)]. analysiso f the analyticw ave functiont o obtaina dditionali nformation
Akulichevo bserveda decreasein acousticb ackscattefro r short pulses on local propertiesa nd analyzedw ave-buoyd ata by this method.H is
at three discretef requenciesw, hereasS uiter found no corresponding resultss howede videnceo fwave groups in additiont o possiblefr actal
enhancemenint forwardt ransmissioant 120 kHz. This paperd etailsa propertiest,h e spectrao f the phasef luctuationbse ingc onsistenwt ith a
comprehenssivtued yth atm easureadc oustiact tenuatiotnh rougha well self-similapr rocesosf fractald imension(cid:127) 1.4. Phase/timea nalysiso f
definebdu bblec loudo vert hef requencrya nge2 0-200k Hz andf or pulse the laboratoryf lumed ata is reportedh erew ith similarr esultsa nd this
lengthsfr om2 0 cyclesd ownt o a singlec ycleu singa parametrictr ans- appearsto supporftr actalb ehavioor f the wave groups. Someo f the
mitter.T he experimensti mulatedth ec onditionfso r whicha decreasien implicationsfo r backscattear re considered.
5:15-6:00
Panel Discussion
PANEL MODERATOR: Ralph R. Goodman
PANEL MEMBERS: MichaelJ . Buckingham
Kerry W. Commander
Terry E. Ewart
Robert M. Kennedy
B. E. McDonald
Eric I. Thorsos
Y. Toba
2319 J. AcousLS oc. Am., VoL 91, No. 4, Pt. 2, April 1992 123rd Meeting:A cousticalS ocietyo f America 2319
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MONDAY EVENING, 11 MAY 1992 SALON F, 7:00 TO 9:00 P.M.
Session lid
Tutorial on Digital Audio
Mauro Piemcei, Chair
Departmenot f (cid:127)lerospacea nd EngineerinMg echanicsS, an DiegoS tate University,
San Diego, California 92182
Chair's Introductions7:00
Invited Paper
7:05
IIDI. Digitaal udio.T homaGs . StockhamJr,. (ElecE. ng.D ept.U, niv.o f Utah,S altL akeC ity,U T
84112)
This tutoriala ddresseasn audiencew ith no backgroundin digitala udioa nd buildsa basica nd funda-
mentalu nderstandinogf the subjectT. he presentatiocno versa seto f topicst hat definea digitala udioc hain
from inputt o output.T he topicsa re signalp reparations, amplingd, igitizationr, ecording/correctiosni,g nal
processinge,d iting,p laybacke, rror detection/correctiond,e codinga, nd signalr econstructionT.h is set of
conceptsp rovidess ubstantiailn sighti nto digital audio acrossa broads pectrumo f applicationsfr om the
lowestq ualityv oicet o the highestq ualitym usic.
2320 J. Acoust.S ac. Am.,V ol. 91, No. 4, Pt. 2, April1 992 123rdM eeting:A cousticaSl ocietyo f America 2320
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TUESDAY MORNIN(3, 12 MAY 1992 SALON (3, 8:00 A.M. TO 12:15 P.M.
Session 2AO
AcousticalO ceanographyA: cousticalS tudieso f Upper Ocean Dynamic ProcessesII I
Terry E. Ewart, Chair
AppliedP hysicLsa boratoryU, niversitoyf (cid:127)Vashington1, 013E ast4 0thS treet,S eattle,W ashingto9n8 195
Chairs Introduetion---8:00
Invited Papers
8.'O5
2AOI. Uppero ceand iagnosticdsu ringr ainfall. HermanM edwin (Phys. Dept., Naval Postgraduate
SchoolM, onterey,C A 93943}
Laboratorym easuremenhtsa veb eenm adeo f the soundr adiatedb y the completes izer angeo f acous-
tically significants, ingler aindropsf,a llinga t terminals peedso nto the surfaceo f an anechoicw ater envi-
ronmentT. hish asp rovidedth es ourcein formatiofno r thed etaileda nalysios f manye ffectos f lightt o heavy
rainfalla t sea.T he threea cousticalldyi stinctives ubrangeasr e defineda s small drops( equivalendt iam-
eter, 0.8-1.1 ram}, midsize drops (I.I-2.2 ram}, and large drops (> 2.2 ram). Theses ubranges
correspontdo dropst hat are oblatee llipsoidss, lightlyf iat-bottomeedl lipsoidsa, nd completelyfi at or
concave-bottomeeldli psoidjsu st beforet heyh it the waters urfaceT. heir l(cid:127)netration throught he air-water
interfacere sultsin underwatesrp ectraw hich,r espectivelhya, vep eaksa round1 5k Hz, are veryb roadband,
and havep cakst hat decreasefr om 10 to 2 kHz as the drop diameteri ncreasefsr om 2.2 to 5 ram. This
knowledgoef the acousticaslo urceast the surfaceh asn owm adei t possiblteo determined, uringr ainfall,
sucho ceanp arametersa s:g ast ransferb y activem icrobubblesb,u bblep opulationsu ndert he seas urface,
rmso ceans loper, aindrops ized istributiont,o talr ainfallr ate.r, aindropt emperaturea,n de vent he typec loud
and its baseh eightf rom whicht he rain came.S omer esultsw ill be presented[W. ork supportedb y the
ONR.]
8:30
2AO2. An inversiont echniqueto measurer ain usingu nderwatesr ound.J effreyA . Nystuena nd Leo H.
OstwaldJr, ? (Depto. f OeeanogNr.a, vaPl ostgraduSacteh ooMl, ontereCy,A 93943)
Laboratorym easuremenotsf t he soundg eneratebdy individuarl aindropss trikinga t terminalv elocity
showd istincts pectrasl ignaturefso r drops izesf rom 2.2-4.6 mm diameterT. heses pectrasl ignaturefso rm
a basiso f a lineari nversiona lgorithmt hat allowst he larged rops ized istributionin rain to be estimatedfr om
the measuredu nderwaters oundS l(cid:127)ctrum. As larged ropsc omprisem osto f the water volume,t he estimate
of rainfall rate shouldb e very good. Exampleso f both the forward problem--estimatingth e underwater
sounds pectrumg ivent he drop size distribution--andt he inversep roblem---estimatintgh e drop sized is-
tributiong ivent he sounds pectrum--wilbl ep resenteadn dc omparedta fieldo bservation[sW. ork supported
by NOARL andN PS.] a(cid:127)Lt., USN.
8:55
2AO3. Rain noise.J ohnE . Ffowcs-Wiiliamasn d Hugh C. Pumphrey( Eng. Dept., CambridgeU niv.,
TrumpingtonS t., CambridgeC B2 IPZ, England)
This talk will reviewt he progresms adeo vert he last4 0 yearsi n the understandinogf the soundm ade
by rain fallingo ntoa waters urfaceM. easurementwse rem adei n the early 1950'sb, ut the storyr eallyb egins
whenF ranz [J. Acoust.S ee.A m. 31, 1080-1096( 1959)] showedth at a raindropc an makes oundi n two
differentw ays:b y a water hammera t the momento f impact,a nd by entraininga bubbles omet ens of
millisecondasft er.S ubsequewnto rk hasl argelyc onsisteodf a longc ontroversoyv erw hicho f thesee ffects
wasm osts ignificanatt variousf requenciesF.r anz wasn ot reallyi n a positionto drawa validc onclusioans
he had no g(cid:127)3ocdi ata for real rain. a situationw hichp ersistedu ntil the mid-1980'sw. henN ystuen[ J. Acoust.
Sec.A m. 79, 972-987( 1986)] andS crimge[tN ature3 18, 647-649 (1985)] separateldyi scoveretdh at the
powers pectrumo f rain noiseh asa largep eaka t 14 kHz. Nystuent riedi nitiallyt o explaint he peaki n terms
of the initial impact sound,b ut one of the presenta uthors[ Pumphreye t al., J. Acoust.S oc. Am.
1518-1526( 1986}]s howedth at it is duet o bubblese ntrainedb y a procestsh at wasn ot knowna boutb efore
that date. Since then, this processh as been extensivelys tudieda nd is fairly well understoodfr om an
2321 J. Acoust.S oc. Am., Vol. 91, No. 4, Pt. 2, April 1992 123rd Meeting:A cousticaSl ocietyo f America 2321
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