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FROMDistribution: Further dissemination onlyas directed by Commanding Officer, NavalOrdnance Laboratory, White Oak, MD., Nov1953, or higher DoD authority.

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USNOL ltr, 29 Aug 1974

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meaniing ofthe- E~spionuge Act, ,O'USC, 31 and 32.e% nelfad~r. lts.l ý*

of ts conltents. in any manner to an unauthorý,zedperson.. is prohz~bitee b-, 'aw.

Reprodu.ction of this rnstster in' any to Irrr-A by othf-erthan naval activities ix not authorized except by-sp.aCific &pprovoI of the Secretary of the Navv.

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IrIV1

a.a htrx1.'ns bis- msý 1ototyp-

I tics W~re Theasflzrd fov'. th7*0$L'pI v Ir e thiS ~t t'bu". dif" T' 'Jin .'th type o~~t11aTg.Z~~

~~eens erei~aýe lsn' x1~a m ples of Pauli typDo cfrutbp~rtien lon vs s. of Ppf r.iZ', I nJulkie, e t

'Phef tie'.hniq U eona'iS ted 0• tms ;ictn tbO tnt p 1,t to

i-ý SOJA zln a'h~~ otatting~lprobe 'hydropho,ýeTe

tes t ";p neý wes iý~s .,pe v c ~f2Ct11g IS.t -7,3t0-"'-1O a tZd refle C ito r. By 'th is- -methc-

wa zs isible to, 1A~ o'j.-ýl the' lel1 hd t on ihte ns i tzy as a

L~;r~t~r .r~j abs~orpic'n C cvtmputadý'-' An 1i~ e

C.X A.Ž xo. wt a multipl dima~l 3c,: a a tlte best

C a 1 1 0 ich.o C c 'h mct rx s t iz or. i1'S str~es t6Std over. arnz b v t 250 1,C ' tL or, V:i szi

ý Q: t~otr2.& aomlt!' "powar re,2.GC C- ' It-, thea total ýinci& c; tý:t es t A-20 Th A;1'; tiýfrii.qulacy, 'rangs.coed r

:~~~xV'~w Lt2~t la t e.t I"0~-o7?it ote ri*s 4~v* ýSr o.2t

ItI

RDOW Report 2989 1 vrbr13

This ,rsport de~c'ibas the results of a rcesawc'.> progr:Cur,support,~ by Foundational Resea.rc fit,-riciS L.nder ,h' o.vP .54 -r1 is conceamod with an ivestigattion Of' severa~l

my'e$ c souird absorbent panels for use as IiIi-Ings in.

of'tho.a bst wide bani1 vneahl- lining reportesl to ch` irktl-e literature of' uttxasofics.. This ~report is initended forthe information of .!cientifLic..perscrne1 concexne1d with, thepiroblem nf doing underwater~ ultrasonics reercordeveloipment m.td te-tiflg vork~

JEDWAM~ L. WOODY ARDCaptedin,, USN

*42

BY Airect*.a

Trot.

( rs l=) Is T.~ Atct-e sbt.a Z nd Aon~ 22~ Iew Y

~ rwvn Msyr clt- ni., Sqtm.d Abopto a~nd Souni Abscrbera Li.water', BUS~nI~pst DoJ? ~h~U

* f) A!ercatt Stindardz Assoc le.tflo' .Inr,, Atoo'tiCp2. Tarmnpc~c

(~)1.%~ KndI an' R F.~t~er, A Stiplif ied Y!etb~cd for'Determiziintx1 Tr~ansducer' Dlire,&1VX*itjyndex" J. Acoust. Sm.Ain, 9 Z3 69~ 14)'

(h) ýL F. X -ý1Uxc and. A.. Fe,~a~nnuso.- A~ometics.NT1hn 11400& SOnB, Tit,6 Wefw TO-rCe 1950)., -S

(iIN--al'oz'dnpne ltboratory,'ý- OTlso-ze~tloal. Stu.dy of Underwatav-3clare. Absor'bing U.axelw, UAVO) M. pOrt 2903, Jun 1953

Zv '71Ak.r c.d .~ f'r -ftsiorbleg e*rjajSe.

-. a7 ', In 0-4igni 140=3 idrat ion ~~11-, ~~ p~C -~','J; Aeott. So*. Ai,2 10(L9)

'- -I AnwlhcV

Labc-O~t~rvj 'In U-d-r~e Cr

W, Ne )son and F.H-, H ibbard, "Ab~sorbi$ng, Vctd.8 f,7! U4we tor Sound Maasxing Tr nks end Baf fes", ;in5 f

c) Adml.ralty Researceh Lzboratoi-y (Teddington) Asti:c , Acoustic Energy by R~ubber Loaded Haevy ýýsrt~cles".,.A.RL?/N.1/195O5D,, Aug 1",9 (see)

,p) Office Seienltifi Research and Deveopm~ent* Sectlorn 6.#Div. 6-1, "A Calibration Syst~m in th~ ~e~ loaAegacy<ýIl19ange"l Aug 1944 (Submitte~d by Be1ll 'Telaphore labcretr'.1,9for the Western Electric Comparq ard. Corntv-z-ct .

-A

1. Inltroducti.onl1I. Lining Requ~irements O~ri 'am~s

II.Selection. of Sam~ples f or 'MasilnomenA* SL-1ectior. of 4t'!terial * 4

B. Select'an of" Structu:-c .c seme.

IV. Laboratory Apparatuts ~e.*V. M~asireuments

A* Meastirement Prograim ~a**.oe**9~. ~- Bo Theor7 of Measurem~ents 6* 94e.*

Co Application of' the Technique *eem.e,.*

71. Diseussion of Resiul~ts .. * .* 2 .. * I'

CourparixOn o6f Barples from 50 to 250 ke 4......Measureme nts Constddering, p'e-codic~ity in V1. ..... 4

Bro~freuL~nc)T Ran')e, Measureme.nts -S~wple

Intw-Pretatic.n amd IRellab11±ty of. IR emz1Ls 76..II.Acknowled~&s~7

V1

ILL~JQh.2ION,

?tue .That Sample of Ln,,a.j¶0l Butyl Ri-ubber w11th a ofLattice Surfnac 2

Figure 2, Meaeurt-mtnt TarAkl Lt,1ned wltb cts~w cn

? we3a ftagrum of a Flat LininrY fland wth'aReflector .... ..

~I~ur 4. ~iagrm ofa -lst Liing Frecedo-d by a

Impedance týýanoition Xediur .. * *-*

Ytgure 5.Worisal Reflectivity tndem for Loa-dad Butvc.y-lI Kb b 6r

Samples with Meta.1 Load Irvs-Alumtlf Pon= &n

Figure 6 XoaXRefloc-ctvity Indextfor _ýocdad Butyit, IRtbberSamIp3les with 'Metal £oadtne44a& Powder4 *,-

Pigure 7-. laa elcivt ne o.r Loaded Dtztyl lub~berZ&=:0lt9s:wvth Metal IcoaCl=ng.aad Powder (ýBlowing

iptgu 8 Toot Samnple, of 3r5.tiebfti X*hj Lnin& C

Figure 9, tnt &amplns or Insulkrottt Tank L~ining.- p 5

2igu81re IlO~ ~ta ttwv of' Fafnir Structure

irw'~U DiUOra WImieatlng Trnnett,- on Oroa s S-ect'Z.ri of

Figture 32, Dtavan Tnidieating Trans .ttton Cross -Saoetton ofi

?Lg4zro 13. TyplotIl vicnsof Gon0 tt1o4ttOtl0400Dvc 20

14 tt0 Oisn xtatJ ~ tt Oas-Stien of

Aacs=t laAbsomtltontit..m. 25

1 "- 6,, Arnngtsmnt (ozt .ýr par~ ~~ 26

AVY

~ire 20. Dlagram of fGhonetriec Rclatior)-,hip of ?:'ojectov10canto$ ar,(.1ThPn'rc

F igura 231. Restriction on '?roIdter)3 e nwid~th I~oj~ry

F1igtu'e 22. et~J~~~ on Frollootor Bea Width ,avs Frtuerncy. i-;. J

P~ue23, Typ1~cn Re.Pl~etlvit7 Patt 1nFqleIy00 ke -

Plato FT-4uOr*CY 50. to 250 kc . . . . . .

Refl~ectio.n CharactueisiS~~c verviu3 Fr equ~no y

FI-for ;5 ampi~ ow Sr . -

F igure P 5 Sampl.e Xo 11

F1igurs6ý twoipe is...,z 4

28.l Sampl No 2

F~~~~ ~ ~ I zue0M`4' o

F,,.Furs Z4' ple~; NO, 3

41 YO.I

00 . *

and ýI fo -m'aN, 21

sapl 410 2 - .

Pigure 59. r~lvction cbtsra-cterltric Z F~- ifl .th n ezv y 'oSampl NO 21

Zig~ur* 43, Comnilecton. f e loort it t~ iv Itt £Ind~ wean

Fr~z2. al, to, 4C .60

SarspHof ŽouiQlt -!-a of Sap* .t- 21 'cz

?i~~~~'an~~e qua noprlo o- Ncz-taa Relctvtyi nqt) 1Reflectl~vit77.ndesna R).Siampll NO~ 22 ve

OtrEcc 9 1 .~o Ber A eA"Nt 75

"ýteurze' 47- rflefls'ftcv- Ohaiaý-.eriLatbtoovs' treq'iency, Seriple

~~o."j 21 Inznc IO n~ FsI, a *7

4Tab9 Io 1 F!!7ect -,)f nC:'1n3sr,ý,tn cm) th4ý Rtsf1;v~,IonQ~f BrIil~s~h TFtnir .. *

* t~ ~IQ

)ýcvn1

IF.

All ~Te area reproesnt-ing, the totalnormalized powor zfotdt'a~S.A '(SEa 1a.4. )

P cm/sec Pase velolcity

Thiq4kriC Se of' l.Jning- 1av,,r

hiknse3S Of tGran-sitio0n layor

DPcm Distance fro . Mprojcctor to stan Is

cm Sam ple width

* Dflisn* in. plane Of aa.pl betres:!n;tetohailf-powo r points or tho0

'0t antenty r ef lected from smple at a

andg.4I1n the'. plane, _W= 9tv-Q,

argre 2m:. 01Se ~bi, ixzsptWi

f c. ctead from reference.p1at. tafv ditnor atapolv~r alOrW,0 (G` aMd In thepne~

W !0.6

az. fl, *11-!

rjvtden on aY aur1<1

Pdynos/rcm2 Effetif.9rve pressvr fcure. a+,

incidente fon a suxrtac ep

dSmx Cyno$/CM2 Ptessure reflected from p1mptecorresponding to : max,

P or/searofleclted pwrr-

Perg/set flI'm tM: powfertdfotr fer .~-

orgse P*owr, ref lected from, reierenle~ 't

Itdb ?The ntlocefIk 'etIIIi ty Index, which Is the:ret~ctohcoe 1iien't't, % expressaci

enrgy., ref lected -frQTT tS u~c on th&X-de of Incidence to the "incident

db Normal 1Aef lectivity IMuX, the ratio ofsound evtergy rotleotodi normally Tr=sat nurrfaedto the inotiorit energy,. which.,

1,01o Az Or v t'nsi.u

~p~~cin ;I/' Psi-

tX

L 13T OV 0 74

frwm sbnrle to~ the n:r~alizedlee Ild from, a re- '~ ferA

expressed in db_

-~db eh scftý,ttring, index fr -prle'odie in ~

,.oumlt pressure to m,.U-ticle volocit

dynelsec/cm 3 lmpedan~e of infini t~e thickness

T- dyne/see/m ýIxuoft,edae At a 'Point x In atadi. tioa otidiufla

desofe4CiD3 Sý6ciiie- a~c~sU61 mpedanCe or ve te

Anepersa/cu Attitflaloito - onxita itt, the ri 4t Iof, ýtbe' abtita*L wOpagatiox

A3 degreesy cr Polaer anglýe rvesure d ~r oo the aaoust-Icradians' axis of a "IS~tOn daiator~.

degrees. orI ?Pola? zigle Corresponding, -tbeý 6radians pow~er 'pplntý:~g~ 2)cf

z'a dis tor

derraasý or -0 tzh3~e tAO ~e~~~~~~radias sditi54 frozm a Maton radjiator -Is,

wm4, The ra ti oc

s~~y ~~etriea 1.;rfac I'Sof ~R ad Sequo3. to RqSnd A

rr.!ý T, ct JAI 1

L'. 0 WSM)ý(

db r,,,,. oe~c~I x 'cr P e le

degreesý,jg *.rt a1r jg"4e rnsasmri fet th.a

rad ias ris~±e. xs

* ~!-,Nve len~gth ofb sownd

/'gm/r S jeific .density

4'dogr~oas or ~ d angle or the mG;surerP-nt pzn"radiaw h 44crm~id by the x ax-IS

and a line 1which is the' interan-ti~cMof' the masurordeiit ,e v ndnormas 1 t, thie a xIs

1 ".,11 CD 10,7'T tON

.~A pz'obIlezi of pr lct!.cq 1.%tcýcrz in tho xr f ~mC~u~tie tabe daelop~jent of 'Linings or coatinj53 vho

'"Sd 14 a- so td re e vt V)r.3 t Applioa10 one of sound4 eb2rb,3rxdnLs Include e-verL-ift f'or iimder'wster ordnance nmlrtl'.Inn *-: do fater acoustip, tanks,. and soun~d b-fler !ulrierwaeiar acoustic devices of all typoz.

.2 The vozrc r'aported here I& a prellimnary istudy of the useof an aibsorbent )4,ning wi.th ,a atruct,_,red aurfao6 desflgned te.reduce 'the reri,6tion of- =drwatier sourAnd. 'The surfacestrueture of thiis lInit'g 'es1t -t a i lyaeed latt-'eof Un'.J.orz right, a~lruarx'eon-:, (Fi.gute 1). M e basic mae-IsC .t"f--- which the stut~ue e'ei~mde wer'e metal-1oaded bulu-1r'X',bera. V-n~ee apaclmsmo i`wara m~s~a red havine, thie strietur-a

bý!ta-,7 rubber, Cocmpa'a W 6- su~ureit nt 9,re ý`~on-salIp.Levs of: esobý of tbe abov~i *material*,, and oz G'rman Faf nL-,

oo-,red ass frcm 50G kd to, Z50 ke for 'all Samplaes'L Uowleve",.Ir'r the mioat isorpbezt ýaamplep wsurements were mad I'rrm 20

ii. raruvo lmpmreý FOR TANKSZ

ý.ez'watsi' acoustle mesa~r~nts t o. Bl1it-ate froe, X1.41A c~n-'ictls eartal..n 1equenecr ranges, Frepi',a tar*_,.bailng, mensLons 5 x' 5 7 3.0 ft and lined wi Gerqa*^ afn1r,Is, Ill use at t~hit lebox'tory at t'he "P'rf ain~t W11uf s{~wTho f'ioquency irange of the iei isnr<ytaei thic

tx&ara T'foum stout~ 50ý lxloe-y lea to 7lieve"i62 "re~acivlea. i xi*.t'hnique ar'e Ured toý MMilittiz tbe, tnt _-usd~rteelations from t~he Val, ýD the~ Ms~nk& he u's of -the pu3.#e

~ t 'bi~tyto sePar~to waVtl refectionsXrot

't,.M abnrpcticrn ;er rufls'~cz5... n ced n o grea h pa'

L1

I..

FIG. .TEST SAMPLE OF LOADFl

BUTYL RU.BBER. LINING WITHA CONW LATTICE SURFACE

"I.-4.2"

I/ii

N AV Oli R F, C4I

'tt4

4,i NrR

Vy~ the lirizig, part tstiarly when lett (A'c t~h#~de2-cetn~aU1y 2.onglr than ~.~ttit path length

SW&~ e~r~ no time fln- A ")rat~fjr.

'~ '- al.~ f~ a) e2 fraquencl.esa.c &Z'rk ': ' 2zrit 04 z-u 414C kcý rt:r vrirt

-e deiair-td sv. .1-nce the puli n reocded foa- rood~~q~aeny re~chJ~ ~ of the samr e' stetirI i,~.r

Mleastiiemeonts n~ad, this f~ei'~ b ecomre p-rlresa ivek -.~redificut raq,, ilre speeial tieca'itiona.,) T!o allevlt&';dU ~f'ficulty the 11ning musnt be suffleient'7 atsorbent tc

redu~ce the init"al reflections f~rom all walls to a riegig611 rvalue relative to the desi.red sipnal.

5,. It Ins instructive to consider a spherical, ab~sorbefltly-lined. eneloemre with a radiue eq~ual to atm multiple half ~v~lazigth ot tbe aouxvl and ni aimple aoarca located at 1the cernter'-The stes0'-'state total Intensi.ty at 'Gh center, I~ Is given ty

where 'Is- the sourew in'etoiit~r &M'1 is the ref led t 101Coo ieriei.e*r

The n t12-o rd e taro In "the ýererie Sived the cr~v.lbutlon tothe Intensity 1,ý of the nth, iref I Oeti'ozn if ýonly~ tbhe .'It order

term Re, i co~ld redas eontr tibi I21 to .the. relfletted, intaren it 1t7.the " Indri, o i

/ .- s

Tht ~ ~ ~ __ rsl .rte--aiert h ie

Th tI hR voix In oon INb IngonI 4 t8JIk I-*t f~ I0C tt Ih Oen~

ngir gidblo ilm-#it t~owtr t.o- sm order th o~~t ti" ~,meter.i; ofg 1oc0fr1,tohe- C-n the flist b bet b.r-Of SC, wI Cb 11,e~. & 1,45potaty 1~c a ~te .r~et

.e~tivonsI 1,,, r tiS~n. C;x ro~ 1;~t TI 0re dI'f' fta ez

lanel 1inin4, backed by~ a gi rto 4E £ T

thfcoreti.c~l atpproach slm.lisr to thNt o9 .:i c 1,e (.CCa),t

or ref1rzted toircident pressturý, At L!-. 3irfrjcc )r V-

Z.-

vhes'e ZO is the acoustic imrjedance of the lining slarfaceg anaZ~, is the accustic, impedanee of the water0,

Inside the i~ning thm impedance at any point i~s given bLy efollowing eqUatioii Which is discussed in considerable detaii iT.

referenice (h):

where frIs the excs 'ess iix's e at x

'V- Is the. vazttc1Q VelOity at x

AP~~~ is the V tte nuaU0 ber san~ois the f CIV

'S ne th_(MAwcet

bcIs thm .',Ph I* veathe,freaten" is K with

rrloae~ed. buly rý6bera thig bas not 7et beoM ý4detmn

~. Ter~fo~ ~ s th liing ~ S., the aeomstS?Z~dace rt. t ine.n

__ W(8) reum"

ti~ nzl ~:3Jy~rt ~u~y r

*t*1+

ap Txf.VACh'sS n(9,)r

111 11 q

- FF ;F 13A

4 < Vflr. I at tho awntD t~it o' nV! Ot.

-lid vma'v *;tatn a hutghlty ablbn~ bIntng -ri &k Lautw Rowove -ver a M uL ,, irl Iht I~~ra f t nz crna

1 0o fn U'. ~mto-L)a I stnjRtd atr.(Z'z 1% v 'hrt woul to r n Ll 01.m

If ir soe etisfilea the ccxi.t ioni tha~t tho) product ;% .4 el&arge by -making o( very 1srge YI3)sA~ then the cxpl'vutc:tor the lmpedfrceL Ato

Although thbis :n~padanrace is com~plex aniid t heiieao of wateraS rea1IT Ine caanmtnlimtz !'/k by sqruatIngteabot ~m

op t1"hassý iitpedaneoOS ro aconsatant vsluo of 0(1/ onleYazt

Thew minltmwi v alue' C'f te IS 9 therefore

tr~Tr

o r

/-Uo*A Ili "

7, *f7~t7. 7774 qRUME-WRWS M-11

H'V NJ) lii7/1v .

t Olal) 71 A 1a 'A /

I IfW

~t~OR LETLk EE

Ins ýt XeAE: Af1SflptO OfE th I1-,

&gL~O T~i~odn~A ~nt UU and -at, (Di f

the vat.'ue %i Z( Inda -qual.- to -Z a~ ~t x

-csAcal n olcin

-~ ct

shae u dh etut'r e ff ta d7Oatd Of n~ tn- ~ ~ ~ ~ ~ r I. iCO tr r'c 2i '-. ..... 5)V K .1.

MRtcia rtt~' b C~ttrI inos htrr 'j IroaC': K C "

38nP88 o . di ffrn tnr6-o of ~ r~~ :'.)- cI r~o e.n 5'. r, !'t

wereSP~ioyi~tA1 S1/1ec1*iont of 2 1.¶teic. IadIa,

'Wa usaeod to4ranmi Eube ulsv~erialute Prior tora toe sthistt3 cflatwirJsu_:cor n the ithutu-hcij3'ies, nor al ý rc±ieTheMon".%or eaurezents a bomnanmde em a *niar'.7 o cnnttc..ri the sml2 f

Safthple nofma'.diffrenlete tpi ot eta frm1.0at e& rubbtrt . Thwere ppro QM.tl re~ tae WC1,. 2 1/2o tnh same 6nomet cross.z

ns ued t tras oi the pulseevu-ted waviue normao= the rom'g~to.etirgsraeadtorziv h .t~ca atnab Theoneb-

of, meaureen c~niteda evztmnttatly s of' oomparns the' "_Peýugthte Aorta1ureete puz' fro "h msa-bce 'unl. t) .-

-refstln frmtbh utJ.dto ae, norma rs

* ztaatty i3 derAdin this report, S#3 S thnoMel.- ro-!1tectivity index.4ý Tha meaeuredoede not neceu$2:r~li$ reptresent

;nt' te nuatle x: In, the matrta 31UO thea Impedance, mismiatch atrz:-e wotrapeilarTe iistn sou whih can, erntwr tbe~=;tert-a1,. tinz er toScondilolttna tihoieaslng the thickntess, offthe11 eamele dcsi& riot nezir4ncraethe, observied loea83.

ThI'e resul-snw of, these ,valoia Wouftia treh Ol~o ~PI1'ýed, as a basia for tihi seleotton of lo:;ided.-rubber mcite.rkh~

psetae-

S. -*rp-tr 4 t or sc ten s Ideread In -th Ia eiAd_

-f .. I A..2, Who avizfz...OV.

7ie vJ r... P"'3,tdoVeqil Pr8b

et d ~crir 4 95p of 0rfr

- ý, -.S . tr 2 w5 troo

NAVORD REJ'OPA 2989

FIG. 5 NORMAIl#L REFLECTIVITY INDEX OF

LOADED BUTYL RUBBER FLAT DISK SAMPLES

METAL LOADING, ALUMINUM POWDER

VARIED PARAMETER :METAL PROPORTION

PROPOR lYONSAMfPL.Z (BY WFIGHT)

.,A 25 PTS/1008 100 PTS/IOOC 200 PTS/100

OA UNLOADED501

-s 20

20

Z1 5 .- -

6o 100o0 400 600 1000F1PEOUSENCY (KC)

~~io

NAVORD REFPORT 2999

FIG. 6 NORMAL REFLECTIVITY INDEX OF

LOADED BUTYL RUBBER FLAT DISK SAMPLES

METAL LOADING: LEAD POWDER (95 PTS/tO0)

VARIED PARAMETER: CUMAR AND 3L.OWING AGENT

SSAMPLE PROPORTION (BY WCIGHT)

9.25 PTS/1O0 CUMAR0.1 PTS/100 BLOWING AGENT9.25 PTS/t0O CUMAR

E 1.0 PTS/i00 BLOWING AGENT

F 9.25 PTS/100 CUMAR2.0 PTS/100 BLOWING AGENT

OA UNLOADED

25I

E 20

'A

200 400 600. !000FREQUENCY (KC)

NAV ORD REPcOR 2989

FIG. 7 NORMAL REFLECTIVITY INDEX OF

LOADED BUTYL RUBBER FLAT DISK SAMPLES

METAL LOADING: LEAD POWDERVARIED PARAMETER: METAL PROPORTION

PROPORTION

SAMPL E (.Y WEIGHT)

G 160 PTS/IO0

H 25 PTS/tO0

SI 320 PTS/1O0

OA UNLOADED25

/

,

II

2 0 \H

/. 0-A /15 :--

.00

I0

•0O0 200 400 600 ICOFREQUENCY QKC)

12

X',,s.

I I 4•1

m r

98 te*aI,,he

•'or the wedge oje!:Iort vGi,-j ?fr.ir) in the exist~,nrgl .. ining (Uiýgure 2) Is prolh).Fb,,m "~r~ S" rubber This 11 r,

w~forn-,rly 1-.sed In an nnsec~hal- 11- n G ern~n -ny s n. d p r i cr t oini ta 11a' lo~i in our tank, wos zt~orpd in 8ir for a nxz.-b-r of' e

Exaitu "on o t-he wteges inlate- that 141e rubbo-' has detc;mrJioce ted aznd *is r&eltively hard, Rasult~s of -measurmnertz or ,.iUnrIng ean, therefore, be interpz'oLed, only as 01't~~tico,ýx1ating Insta~lltioil and not necessnrily 4t-hat of Fafnlr r In ts,

3 J2MilJ Condit4Cnw

16,, The besic "-teriel of tho wedge elemcnts ident-ified in thIs-r-epor.t as 13'.!tish Fafnir, Fi.g!1te P7, ".s but-Y." riAbber. Since thfez-?0wedges were I.n good condition,, the resti 4 's shoul.d be rpe~~e~.Oft thAIS rriterial,

17, Imsulk-rete 1.9 a rmteriel rezde from :!oarse sardust and cemnent*i-i the proportion of 4 tol P igure q. This m~terial -is being

,aetd lby rmderwater -Sound Refre'nee Teýboratory (WSRL). as a liningfeor'eac (ih);es- rtank' Reults of easurervents M~ade 9+1 UHkJ

B ratherlow, of~ the .'rder, of- -20 10.1 compar'ed to~a. raeferenaaerpflcto plater~~nyrag considereda lwi T-hia

za teris I the n constitutim one of " the types mentionied t n -thep~ecedinzb sel:tiorn which has a relatively lowA ebsoc'ptiorn p*er tun't

S S ut. prmt f4' t-1b goad. Match at the Interfae -

toLioar y liig n Sal o"k, - The ma*'iýz'A.3 e~

ec-an C)Stm fro U-e Cdi LtI

b-' -dr~~ "No~rT two is e rdanly C or rI 1 et. 4i

-oil c." rltrc. -A nt sounzd eccoimtera a grad-mlopt -r i.. e.. ll tls "rnStio a9 ol, rmt±Oti =

n C "TIYý th

I POOT

'44

I P

I. *d:iIL N IN

"'if. 3l

It

*1 4F

rt to'i i

* 4..t.I

II

j0V--fL fLJP H T 3

AI

CANA OR DUCT

SECTION AON

F IG. 10TY~'PIAL VIE'NS OF* FAFiR STRUCTURE

I fn.i,

&v Fvý'i

NAVORDI R4eport 2989

requirt--.ont thnt th cThiqngc of' section anrv1 rte of c1hnng,, Of'sactioni occutr tin c. giadiil ,!ntinuois -manenwr thirorqjioit t1Cotransiti~on length,, inclndlng the houndvri(ý.o3, roertenct-1d1'hon, a Uso, as inhrn tj-1ory, oneO c.-,a sty:"- 4that surzh of$S"2tIOTI I.rIpUOS8 j- gr,,)d i 1c n t ir-ou otir -ch: nz(- oF' in Jc 6

20,-, Gor'mn Fa~njr~. The Dr inc iple of' grn.t' .D13 t re n., ;I ori has beer,SuccessN1u2y applied to thcexperimental -v-ý`pr!~ent of 3ound-in-air aýbsorbent lining~s, and nore rece- i , r e p urt " yMeyer ini reference (e) to the davolopiz,~ -.ndprma ter s oundabs-orbent linings,, In the development seUnderwrlte!' aouflllinings,, various materiali~ with elastic rozjte~resis anid variousshaped 3tructures were triepI., The I'infil version of the-li~i~ng,ralled lfarnir, was constructod of flat triangular rubber wedgeswith included air spaces,.

21,. The structure consis4.-s of~ rows of% these elements m~ountedon a ~wood backing plus tho vatrr canal~s or ducts in the spacesbetween the rows, (see. Figiw.-z 2 an 1)f.

2- . IG 7M z

~~~ d~r-z frc on a mtu~d of thle varlat'.oý. ' :c ~z2

o te ateofcbunJ4' crosi section., Tho i -) zl eli

b e st fin wh i c. a s 1 n Cie p or vs1 v'- w var i f-4 w 1ý '" ~ 7 -hold constant. For n vzdg craon~ sttlof o"f 25%, o,16 the t~ot"Iarea at x a Ot the stutr, rllcovd.n 'to r'e-once (e' rex;,1t-inl ?Te~et1,v pressures of It% of those of the Lnidet orwave. This reduction~ held bcveen a 1ortmr cl.toff f~nqu~ency for'whicih the vedge length equals a hair swavt lezigtb airr- la vppe:' C-.t-off frequency for which the zpr-Ang or th6 canzals waa i eja1l toa half vave length. It was 4indleated in reference (e,' thbat "'beproperties of the ca~nals sfleet the 1.ewer and bighcerNear the lowier viatofT freavexcy, the Small. ratio Of 3P%½Ln towxVo lengeth cauased the velocity of vsttr in the can'aGla to -be4ecressed which, in. t a a."- iedatee st ~t ',-i tir oftb*e wede-.6 Alt the h1gh-fr :~~c:~~rte creased ral f* pacIne to wave lenagth C ='~d cwd* to~ enp the Ptrctmze an ,,.c tbe reflected fro~i ther 1et.ýd backi~igý At array cmiotis4i1 of4 aa~equence of two rows of vec3ges Ii. em lon.g sxmd I* C_ 1ht' 7el ,-* a row ot 'vedges 25,"'r 1~ CM L~t thic~$k arnd splikratel3v 3 ýcmi ap~oxt wag S irn ; efrej (e, tc 1 0rease the ba'r.vid th , so that the J;P*xix; av t~tetivt' fr'om 40kArnother -fivtor cors14et~ I'll -M O~ergel410 (e)~ and usý 4- det'ji.izarea of, ved ge Of' 50% 461 the týul' 'arp,6.Qt x 0;, the Off"'It Ofth'e backrinZ vas pot vprcs~ e~ridge _Iorgt~sl. z~ to or

introu~~nga_!,'TPP~C!abe.ine r'ease ins the Offoo~t 0: tht j!iSLýzorntlz~ty at X =,_Dwe11 ~esere ya ~raeireato~ of cba=*g of ~~ei~~t

* Qlderto iZ*VStigateL the- e$$ke-''ofLn:as-'re tbP cross, ý"ectiloz- OAr aprxmtU6

-*or w Fofe&: r iflt: Ix thh !afj 2,r juei~ that e

~C eT hedimen5s 0 FV'rnp; .ý'Zum 7thetFai f Z. inlThe1d i h Nv tan'x1nlaec

zhý~~~~~~~~~~~~~4 '-7a"'a rte egs flnts1 A~ a.

11rntea or th dimenions mn .loro,ji,th

4, ,Q I~ -,

vnl10 cm correllponC141 othnneloTý re v J ou 'The incluc ed a ir ~ ~ bTmrallel to thie base, Irefr,-)nce (0) ~.In -le r~re, cnt rnaT,12r'

1, at.r w of th 4.I ;, IAt. - -- f tt

Lý1• a wjedge percallel to the rm~s. The c~~ ¶fcrn,2(d lop-wear thet

lwedgez are tlm narrowe to th h~;o r ,*lei~vur~t oz al.('¶ut

one tm wch~c should mis %`.,- iiper c-&-to fre;,uency ýoapp~rax~trt-ely 170 kc. '.Me r,-u=tjF cogssectionfl are ver3u5

di1stance fromn the wedge backdixw plate Is sŽ-icrn in Firgurp 2

RODS

SI&BF)X:

1-T

-A

Dz~vlllb; MMM K .=MM O 'M

T T B1

77*p dlrot~jt ef:ie:ýrs above'½ Vh

it0)sdrbyrf'ek-Lyt~

a *,W-31-av*inO .. *.1 *rvqu.Ita D,7lnarae

t ~NAVCUHD REPOkfl 2989

IB

A :ELEVATION

---- mI

SECTION A-A SECTION 8-,B

FIG. 13~TYPICAL VIVEWS OF CONE LATTICE STRUCTURE.

20

7 T T-ý

tono1, ,t v~tetU1 by ý' e .1 t&'~ 13v LO~ 1):"ut-itir'd ~stO~Ar'I&'tY ei.,OzA f~gt &-t& ~ 1e IIC~.b The Cones &nr

bteking czwinvSit of onog ri'dx unni'tt0 1of oded butyl rabber. Thediwetl*13 o of the cone elervrjmtlý- ware eelected by ,iiing thepretults of r*ferance !4e) t,, a ienara1 guide, A lenr;tb of 37cr was chosen~, which c'otrr,ý.ponds to a lover cutof'f 1'requcrecyof arprosizatt.,y 10 kc. The cone gereratinp anile was cbo~erias small as practic&1, 'nam~ely 1r;. Tbe radius ci' the cone baiseis approximately one cm.ý The 'test panels are approxirztely 22 zr.squ~are "n 5 cm deep wbich incl.udes a 'thickn~ess of 1.25 cm forthe base. In Fig~ure 13 1t will be observed that each cone issv&x-1oiwrded by uix: ta~ngent cones. The exposed areas of the pl-ebacking approximate .small triangles. The percentage of urzea*:tpose4 Is approximately 9% of the total section. Although itIs possible to eliminate this flat area with the associateddiscoritimaity,' it was felt that, for t~he purposes of' thispr lim1rnary Investigation it would be instructive to Meavurne thiereflection characteristics with the discontirnut7r present and~ tonote the frequency at which th. Offe'ot of the discontinuit7becomes zicticeabla* F'rom referents (a) one might expect this"~requoincy to-be around 250 ko, since at this frequency themadimam dimension of =ne of. the "tani'gles't Is equal to a hall'wave 1engtho' Also one would expect the level of the reflectedsound to be of the order of4 1,0 db'below tbat ior a f lo, t Sxanpleof ' the 3Ame material., This lo biased ozi 1he percent of tolf.alarea axnravedo An additional conside'ratiorn In the selectiren'of,this structure was 'the timple geometriesl reh';ionshIp betweensurface and violtme versus dirtrneze fl~om the cone tips whichvo=ld be of value --In any fnturo. that lStty: of' tbemathansivm oft gradual transiti ot,-

WATA

1000

~~ X~v

-1+

'If

1;a~"S-Z=1CMOF IC 1T"11Z 11NW1

Z F ?i r~ur 14. e v the oro s z t,: or&tirc, 1 ersiu~ dint-anceft the LSZ tct U- o the iruliptli core salM2.e. Observe that;the-V in smiooib transitiort ,at tht, cone~ ti~ (x w-(D + DI.,'both the change of section~ and~ the rate oiC ch~nre of sctionsproxirate zero at this p~o~nt,, Tlio p2lnrip aresa at the back ofthe strueture (X. ~Is ro'1I'ced to ap roximExtely one-severithe that shcmwn in ?Firu~rr. 1.2. -ro-r German PaJNir and can be!rraotically ellmin~ ted by Incorporating ccrnical holes in thetxposed sectionis of the bacIcnsr (note dot'"tedz line's). The 3cct1i.--of' water nineuded between t.be cones frAdi'taily tapers with li'Prom the vedte tips so that the discontinuity encamtered with theFafnir linings due to theo cavials Is not present.

25# It Is realized that the structuzres studied here are proposedfor use at uuch lower wave length-to-diumeniaioc ratios than thosoincluded In PA71cighe's 'ork (m gradual transition. The phAsesurfaces at these frequencies are nio longer' plane and thesecharlsm of saw~d transmihssion from water ;.xnto the material isVer7 tomplicated both b~cause of the Involved shape of thestructure anid tb* coumplez behavior of the 1!Iterialo Hence, thisinvestira~tin bas bee~n essentially experimental.

* 26. The physical charaeteristics of the samples. studied ares~uarized in Table 1., "The table also Civet, acr, numbers ared£rlzre numbers, 'iiich L11ustrats the respective oa~mleso The

* first digit of the tiode number refers ýto the samaple' material=d the stcorA di1git donates -doen~c physical cbhaacteristicswhere pactibil,

NAVORD REPORT 2989

MIX3 I I CtIW&L AI 1Ion or LaxIMI~ Uxn"1J

f Io - -mi 8I1MJCIJR un"c-TI

121 Z . ws04o03 PUM 0'103MS m06o

PIM45 AS 0.3 WAM 291 VIT 0.6 am

1I& U3 MMCXI RUM~ 3.751 . 223. 5 IDl~13 omC!A) m

114 3L ATIT03Rion 1.75 2.0 21 22 5 1"40S2. . 2.7s

13 om CU)BU

S 413 F(h0) 10) 5. 1.0 40 Dt10M 2101 A0

32 51 A Lu25 IX40 1.M PD& 1.63

9~~a iS 2 45 s

S& 41 n 1"M) WM 51ý 50m xw"am -1m

6. 1 1-40 (1 f) -

=SMXN= Dean IN M

I~V. LAORATOR~Y A">PARA'JMJ

of TAhe appsir;. tutj fer rrodl.uCing,normsll 11,,r.t, sound wave.,z andi~ ""or rthG rOfloovit~y pattern is illi-Lt~ratod in Figure >

28., A ý.e];Ayki trigge'A from a'Tktaronlx o3cif.1lostopeg Type 512,1'n'tlatz-t a squniro palse which ~rodul-tes the ozarrier fror. the,319na]. Ž.~ o~ This puilse-modulated wave is arplified andthen drIves the projector through a ratching, network, Thepro.jecto-, produces a narrow bean of' pulse-umodula ted souind waveswhich are normally incident on the specim~en. Rleflections f'ror,the specirien are received by the rrýti.ng probe hydrophone andthe vol I'toae generated is sent tIbr a ratehing netwcark to thegated receiver which is triggered , the oscilloscope- Thereceivin~g gate can be set t-o correspond to the beginning of' thadesired reflected :sIgnsl by an adjustable tirte delay.. Afteran'pliftc&-tion, the 'J~gnals are applied to tho polar recopder hcis designed to:: ,*ndu ' 'conitinuou~s it,:arl .th~ic plot. T~ho reposition. indlcrted'b thie.!'ecorder i4m ~de tcG corresnond to th~ehydrophorm orintio by the use, 6f a selsyn systow'-*

29. ArrenrS nt ..of Aym~ar,,t12ule, Thý, arrlangemnt of' t~he apparatzzsis illustrated in -Figi eq 16 abd 17. Ref'erence ref2lection pl.ateswere made of' 1/6'1xieh brass alate backed by 1/4 inch corprenaý

* They were sinsperled -velErtlc*ýliy from. the. rotati on framework by a12 inch wire rope,, 'The p~late *-S held verticeil by a weight

'IV 80 1~ coeeUt 8nd-absi*xbentý:ateria.1, Th apacirr%aI;e to the ecleting Plýta by-gwaUm-r-a r bands. Thlo

center of' the sarqp'le va S1 s oI t i oi at*: e elw h s,5cof the -water to *allvi -Por- approx.immte. _ce#nteriftg of' -the sam'plo-betvween t~he water surfaece' find theý positioning weight t.which wascovered withart zýoust-ý,a absor~ber)X

~Q ~ eat~r;~tat ~ra~ om iad o~fi he, f our partq outlWroSAll mea Suraene#ts veri, made' withý sourd ýiorinllv incident~ On

Th1o : s.I a'.e n f'req!.ýaan%1 r aP.ga%, r c 250 kc irertsof' 50 Xc~

0ru;V 7af"'Ifl am in the radial p.aw 0Ln$&-'f.e chr ctcristitc, ap hedbý

ý:7r uýt-j (f the s,-i-~r1U ztirf(ace.

NAVORD REPORT 29E39

0

_ _ _ _ _ _ _ _ - ---

CL q-a 0

0. -

w 2 'rr 0 1a. z

ccv

J w-I.

w

~j~- W-1

i -£ .

atI

z 0

41 - J -Z

o -0 An

10- 00 Q M

-0 wz 0z 0~L.

~La td -- j

00

tI Iqr

NAVORL) R-.PORT 29 U9

.4

raa

NAVORtD REPORT e-m9

F.1G. 17ARRANJGEME:NT OF SAMPLE AND

UNDE~RWATER EQUItPMENT

_7 n27

"-M -W

j4AVThC3t~ort298'Q

et The neta.ureflfeft of terort prOmtincng etrtictiir&;!vL ri Ii&N~o. 211 tlhe ntiprliwaonce,:Yý W ccrrestpon:11e FatV

detaileek ifcwrrAtion on the rý-fl~ectioncarte1sisntufrequency in the roegion between tht' 50 kc ap~ot !2 ',epxenvitr

d.n ?%axirement of -Sample No. 21 at points 50 icc apart cvtafrequency range fro= 20 kc (the lowest, practlcal frequaency)

to I Mc, to determine th4 ox-pected usefufl frequency ranco of c atank lined with this material..

B3. Theory of Meoasurements

3.3l The Method or izeasvring, the reftlection coefficient o as c r iŽ*eicin pararraph 8 1ih practical if the reflectivity pattern of. the

ý-ic~lm is1 not :nibstentially diffrerent frotm the reflec'ýw1_ttypat'tern of the plate; thi8 was thŽ,% *asu- for the iltsan"ýie$prevflously dl'scnssedt, ii1-ovever, za structvrv~d specimezt carnintroduce a nabstrantial changge in the rzesfiectiv-itypttrh Treflectx.vity pattern Is cr"itically dependent on 'the pz'opepr

ainetor pzjco n ample, and this is difficult toachieve. Yaxtzm= teflection does'not, ordLinarily occur normal to

the sample* Flurthermore, thi~re la sufficient scatterting so tWhavt'-even if we compared -this nxizu, reflection t.teratrr

0 ~reflection from a plate 'it 'wonld not. accurately i-ndicate the,etbserption oharacterUtles6r! the spesmen0 A techniqrue devivedto take aocivcutof these' diffticulties consists of ýwztiOLIPýtng a

*se-arate hydrophoce for WeasUrS.Dg t'he-reflccvted signals.s The_hydrophmon is ro1tated 1n, a $par.i~iicVlh passes throuigh the axis,of symmetry. ot the Proleetor =6 non~al ~to, the aple or refereunce-plate, Figure ±a19. T%6 rl~fUetvt vatternsL thJPtzs obt&inedt . fI rstLwith a reflecting lt xdta iha pcmn oehrwtt-he valves of maxim=t reflection, are' used for CsIc:clcIlath the-A P

ri~ctiCn and scattering 'z=1tti ciefts from the structured. saptes',

32,'If tmm2&rth, ?2ect. -alon a ;.urfact, the ýreflectc~d

I-S t121e Polar anUgle Ae~tr~. frOM the projector axis ofar ti T,. t the su.;rface of the sair-le.

't~p radii) jf7, 'ue from, t~he) axis In the plane

-th Ivy - ofbt

"', j tnA tnhe A.AJlect..6.g nfCoP-e

8 W1-0M LNAVORD REPORT 2989

0I0

CL zw

I cr

w 0

-J0C-J

29GN&A Sffp

wxil be 3yally symtrtric abD, tf-~~~~~ the re vcase~ pntt.7.

inwtal retern is t~ of VmIStdpw

31,Ai1~Smmti aps For a s~rmple for which cne c-=.rassume axially synmetric, ref ectionst the refleeted. power, P.,19 simllar¶.y

T( )in eq~iatiOns (18)' Qnd. (119) may be' measwee.'by r otaIt in g th.,e.

probe. hyrophofle shiowr. In 'Figur'e 18, in th-_e _.t Pj1lbO_ £ro OM t

7'/2,D Accordina t1o referience.(i') the reflection coeffi~ientis dif ined as: ."The sounzd, reflectionl Coeffiie±nt _e a surfacenot a reniezatori tie riti 'cf `the 'ate of-,,~o soimd. energy7relt~eetd from:tesra the th sd o neide0:e toD theImeident rate of rlowl thii veta1 reftt renCe r)leite is a7vrect ref lectorA t'he refl~ecte'd power P. L S eqju~ _.t*o theinoident power. lb relectlor cerCi~efi nrt, Rý nay be thend~ufined as

.s*'on (20' a-re re laced ~y ';he dotube inte~r~in ape~

'Kr~~ -)r -- esr rafernce (g) mhie devised mes-o el..Z;-,-pati~;7 the ptwcm radinl~te f r.= an axtalliy _q ~frcs,

a~ v'~n y o~wt~~n5u~or (2V91, by a e cetr T-ea.sure-M,ý of ara ra a zhfectit7 'lnttOrn CjnWIE'0'~ j

,)ar~er IeF~rs 3.9), The mijle in z theAL5r. leg.res and #cle In termsA'o theŽ

* c:-~cr ~~ ~~dto exp Sr

.~in,

ýýG 19 ILLUSTRATION 'SHOWING USE OF POWER 'HARTSFOR~ CALLU!LATING REFLECTIN INDICES.RCAAND

FREOUENC-Y, 1O i<CSAMPLE No 21 ALUMI'NUM LOADC.Q ROT(L RUBBERSTRUCTURE CON'E LATTIE

-,A '1 E NI0 SAUPLE NO 2ZI b-~ 8 ldt~ Ff~.C I A'IERS ý4 REýRW u 4 ,I

pBEQ NO 0;-i,,

(RVElGLEVEL 331kdiONE TNAT CF T"E REFMCNCE PLA. L

~~1~"--

S)

ffOw a 3

~~~,-- ---..... a....bILLLgTRATIVE GOMpuTA-iioN

1L L

%&"I % W ,7V I:va clapcn$o A NC

t .0'ci..4

or for brevity

E~xpressed in db,

V 10 10g, /1 +0: (3

~A ~ (24)

w here R is the. re'flectivity 'Jide.T (he ref lectior'. C'oeff iclentL-ýPresb~d ±nJ- db)-

V14~ the frirst' te~rmAn G uIn ,n

Sis the, Scatfcring lindeX - the tecond term i r eqtý:.titon. (2<

3,5. it is eobv±6us, tha~ I.. f t 'Cle tli.6i qtantltjes, RAa and ýsOaly two ar'e, Independent.-: Fo~r. 93mple~ fn J.~tia~iw'iid coix*3 a str'ong reflatio. a~~ th jý; 4' to 0e~x . w -ithout-a - PArc;Lably Increasin~g 7. -ould M-er'ain ."Mcrease, and a~4i~c-oepionding decrease in' Z' *The to Ie tter'. rateshnI-~iet Ln a general way thed~istribition of -3 rtlclinrod~x red by the l.ining, Thpp, pak d .

tr~dic-Stes thes aixmi #eto 'ihme~ ~~as~arq r epreseat~s specula reUtfet.Lon~

~r~it*,I;- p181e, the Sc~tter:Lný ,t)r~ c& wc-ides, ao:reS are.w Offdhe -o'-.ton from reuIl ciior of Solind 're~fletted,

TISO'SU Of tht) sbhrptlocný Ine -4IY obtair teabsorption lossIn nn--the

<K -7;

P f7 F

low'

Irln'oxirated poi~e t i. tc- !(u mis-li pa'tf.: -Mbyf' v

171s the number of' incrertentwsdqin a hall, per±io.

f, s a superscript irndice'teS t'hat valu~es of' the pa'ene~ter ar-er~e:1surXed ir. the r2,anie of ý

Thotg3z Drocedtlra 3±ir~ar to that folicved for thn L7,1ally9ymmetrIc case the newv.reflecti-Aty- irdex I? is,

t~he ace-tefr~g -- ie ' -

V (27)

d t

'1 `-04*, 2'Ca ba th~lught 0;' ani P,:?,- r v~i~ c

Q q ui to a fnd S~ epcvv h .t. '~1tuPk-re1'1ect~vi~ty ovasurad for anky anl V;~ - or P. tJ el~3z.,,plo Tho nu.zber c tniýrea-criltS, 7 f~s~~c~r ai nseclle~a cc~vr3 cy depends on~ froq,ýccy., tbe ý*h aic2 ~r c t P ,- t c~Of' ki hydrop~hono, nux4 the )i:tn oi- tli se ~tiirp; t'h,5 tra V 0uJrtsrrnined exMerimeta3lly. A Iso, sUrmTemetc mjý4y be zi

the ,)olin er 9.e rang 1ror.n f7- j;( 77,/, .ý I Th V.-, t'espi.1ififid by the rad1lal annle ~4, The r;ults c~c:reSzponct"iklng vn average W,' two r,ýesuxements at equal"~u~ n:al 3-1 swinls of' this experinient. T 11e 1 -1t te 9 1 r0C 0?AU 7-C- 1~3' 1 Sto Comz'pensate for errors du~e to i-isall~gnine-r.t..

-7.Per oicitv of Sel!ectcdac~ -It may Na notc'dtt ~(canela~t-tice strnctiirs TFigurp 13)h lis n anr a~~j&r > ý;okt inV/' of -0/3d, A mneasuremnent'5 in the Plane o~f 53o)ýtion A-A sthen to, the average of two m-easu~er~emts 0r' th type,~a n,1" a mtevaiirement '%n the p",hne of' the 3`,tion, D3-I t,, 'tlhrŽor two inevasurnernents for x X"=(l 7*-) 9 whezs n~ is aninteger., These two measureinents wer'e assumed to be s%,.iCeýrst

* ~to indicate approximately the varletion of thw reflect.Zouchs~racterls ties with-W for the cone-la~ttice struetitrG-,

38. The-. periodicity- 1n. f for the Fafnir saimples is ifIf eCjUzCl n-cr mont Srwe~p "' d ed one.. should 't.I rz oretcramenl~ .,,or tft~e FL, k^n -sample because, of, its larger period,* Hwevr~~ae nt~~eonly mwde. -i~n-lanes at 90 defr-;s,

fo this výT1,31mihary' i. .estl'setion tC:Oresponi4n fl? to J:Ace 'ror

,. A~pplestion of' t-he 'Techn~ique

391- The factocrs vwhic.7- 1w,.'2u'ee c.thh c~h~oe ,)I measuremient~e~sin P Practic~al apiý,ir o the technique diesri~bad

a7 a r th~e 3oxt.anda geo-mtx'ical c~harceiriaties of thz~ inensthe tazlk2 the iransdu.clr3 'and the nrqeny, rsne

over h Wt-*Lii'nts ar de-Siroid,. th6 fraquen^_y rarlae-zonr5tde::6,d is from 2u 'kc tr, 1 M--, IUea~u:ý.eMents zt,,freqtuencjes

S2 k-- are ot' .inters7zt but could not-be rsde satis.Oaet%ýzly

reuirelmn tsŽ '4*c g--.verr the selzt~tcn &the size of the proalectGW Fir'st,

-. - .Lio~ n~ee Surele~nt afO-~ -~. -.- *.- . Th: tan lin~. ~ rs.iabl

-~ ~ ~~~~~~~~~ +--~...~~ 049JC~Oe.~T~

_ _ r .r A-

;-h- "

..............

wIhore % is the distance from projector to s1pvles

the wav e1.ength of sound in weter.. For the cone,.struc.ts, A-.

Vinimurn width of uniform illwuArntion was selected at about %

cm - the width of four cones, That this constitutes a sufficient

portion of the lining was verified exPer"Lmen'tal 1 .y, The width of

uniform illumination for a piston source vas taken to be that

between the half-power points, indicated by the angle 5 in

F-ý.gure 20 The pressure versus the polar ang-le3jr fr{ t piston

source for aIIsances for whioch equetion (30) i va.Ud, is giV-fl

in reference (h) as

The press94jt iV6'.n" - f'o? ,.3 ,O a.' decreases with tncreaSI,

polor angle' 'nd, reahehs the ha!l'-poW4r',ýOoini t when

/ i .(32)

and passes t Iii when

.te tha distanco in. the, -plana Olta 'e sampe between the

-. : r'- iri:a: on over th-e sample, it 4S s to-`, .:d,Atanse fror 14-he 9rroj e Ct 0 to the -sgr'ne, &sr

S. ... ... ,',=.k :, "re -,-.,i in 0 7"ertoeZ - qarTl.klto ,f eC ',

-9..

NiAdokH 0 HPOH T P4H4

0 c

K \ 0

(L_U-3

I jj

/W C

IN 0AsA

N 4L

a. 0

"IL

36

~PVD Repoirt 2989u ryt~ < ~(324) crin 'OC!

Thet requirement given, by eqv tUer (30),T httb mphae in the Fraunhofer region, can now be ertprvssed I.trsoDw, D%, atnd ,_ as follows:

IA)

41. The second requirement CM the sitze of the prc'ec-tor isthat the intensity of the sowad incident on the walls of the'tank or the water surface be lowo. This is necessary bcc-u~sc etth,a relatively low-level reflection's from the sarapiLesQ Thýecerditioa -that the main beam not; illnnttnte the nidcs of thetank or the water surfaceb Utwetve the p:rojector aM. the sazirmle

* can be nxpre-ssed as

ý' -'D is t--ie workr~nt ~r4th Or de 0pth, these, being approzimatC'-ý~alI f or zh±3 t'n a ?y ufLnz the relatioridhlip bbtctwom the nt

tye A~X zi i" ýJ Otztls (32 )r aa2 33 by -ýzsk q'&'3•),~~~~ ti 7-pT~rz~ 0.-.1ed -by eq=.tz~it 3l'hibpse

:_ comenlient to enrpro';S ZD roatt to ýthe ma MlI VIAAth

1 Thtn a 1 (348) Ceflm be- M"Ztttcn

irt C tb¶\: 15r"% n~¶ l a,-$-&

It u5, C(.~ w hcu cab-xm at

*394J - -176

Z2 If, terms.* of' te;cetrradA±-s~ the aeb-07 :crAt

4 c

fro eqat~ms(3) EMr (0J; enditf ýtte nuuericel mlaes listedabcm ar-,,j fled, t)* res-itricttot on the projector radius Is

_ ..N1-93

*raklý .-n Jru.e t'tri tXtI ¾oOn tVe taxplb; dc*srot ete~ei~y~i~r 6X &~ 7U 'zcC n.t' thc~ sazap'e T~hQ 1w'5zve

0.mneatzt!zý zen rt-te-a y thes ratio LD12 where

hr>1~r tus ~tben~dett mafl or thaw tmttarzlty of illnmirwt, -,.i'O Jz~ 'na.SA ;.0 aprct 1 ateot 0daFor the lettermtra.Terat"us ci :.rohnees mntMb

NAVORD REPOHT 2989

LIMITING EQUATION' 0.394 X • rw K 177

22 CM SAMPLE

10rw> 0.394 • DEFINES THE FRAUNHOFER REGION

5 EFF•CTIVE TANK WIDTH

2 "rw 2 1.77

4 COE SAEWOr.~ .. n.- .b. _ 4

aq* h-

SFIG. "2t

SRESTRICTIONS ON PROi•Gt,,73- J EAM WIDTH•iBEAM WIDTH vs FREQUENCY

-0.9

7r

NAVORD REPORT 29819-lo LIMITING EQUATION'. 6.65 FYŽa .93X

* L -INDiCATES FREQUENCY RANG5 FORF~GIVEN TRANSDUCERS

50SAMPLE: 22 GM

6.65 I20-

iso

0.5

0.

0.15

40

4% f .," '7''

It mnly be observed that the ti'm W'Idth 01 hydro~hone a 9;ýXesded th"Le bearM Width 01P all of the projtctors 4xcenrt t---7 E-Pwhich "as used *at the~ high ffrequancies, For these higherfrequency m~easw~emhents the hydrophone- bean width was app oxlirtelya third of' that of the E4 The minimnum hydrophorte beam width(st I. Me) was such that 4Lt intc.,rcepted soiind from an. ar'ea ~ia dilimeter equal to the width at the base of f'our ad~acent cane:This was tentatively accepted as the rnini~mi width to get- v,re pre sentsil Live. ref'lection masu~roment._

4.5- Thce pulse length in we ter should noil-~c~ddouble the,,distance f'rom the lhydrophonte to the, specim;.ý~;order th~t the tail of the inciftr1- N~~ ould not I.ntezere

44ithl this ref1eatiom, Ai~tw'ly i1t was oidtomore connna-M;. bout7 t*01 third!7 of, 7h, 5,~r~ ~ Ad3tp ýls -xa1~tiofl 0iS abtt C; TI:-Ae~~h

e~~ton~cecuip1menlt-,, The d*Y'rOPjon'a roteti'On ýieS~9e*td12 R?If to 0 alcm sif f icie nt pulsesi rer enof hydrophone

tr-Ovel (artproxiwately 9,0) for goocd pttern' roittPall

i~e(, ~ ~r'r e h~w i,' ,,C nf c,~~2¾k~- 2

c~Sai~2. n 21 and of ,a refý.rorce plate wr', c:K, c n :.)r Avexamplsc. The pattezr. nwber is nna un of' '- 'ne c-cvi~(see Table 1) f*ollowed by a dash and a serialidn1ctGnumber,, The special cordiLrl:3t- Pape. referred to rv7SlIs designed to cover ~-300 to --:,30 (Cbart ý3) and -0.400 t~o + 900

Chart A~ The latter usz ed only ovts iýde thxe anr;g cý'V 171atThe u-se of the expanded scaeI o~f Chprt B -1nereased the r-curayof the power dete-rmination., After redraw'Iing the polar ploton ornthis special paper a planineter Is used to determiine tho earza!I:r~der theo Clirves, A for the re~ference pIote and A., for thiiýsamiple as indica6- in~ Figure 19,~ The peak, -press's ues from these-up~le and fricn the referenre piat. tire also redoff thePetterns- 3ncd thien S? an,- R1'te as S--aoz.,r.-'n th:

(C _Mrnaison of -,ip.1ea po -50 tc 250 k-

47 Hege.C'iýJLg .4? $ 88M Pe at~r~. A com-parigV7the patte.-.ns, for all'samples- at, 1O,~iiven in Flgvir;, 2:,-.T1his fl.gtira is arr~angrd Ato show the refietlvity ý,pat".erns

struotwrec rubb'ei s"atples on the loftt si~t and aU .oth-er sat1on the right~..'~ i itidicated on~ ea'pt~rvh itdentit*,Acode num~ber fron. Table X 1 the, rteriail.~, tlhe, st~ruettixre and thelý:

values ~ ~ ofRan .. The refetefiet i'Pt4 ,t ref 1ectivity pattomNoý 01-136 shown-'in Figure 24. was' L"Sed, P tha ref'erance ptfor these cconputatldns6,

4P, The~ effect of s a.r r Ie -mntwo.r Ia , u h~ 1 re flec tivity. pattern:_may ba noted by cv~pa-Aing Ilke wt e ~srcu~~bt

7~u'~ 3. ~ntitt~Such a grop r-le id.d butyll mterit"~~ ~ ~ ~ ~~~~~~O dc ria*~-vr c.- t .. &,. ,.4.

-~~ pa t terni/~- fo Sspe'Ný 31f.t htdA, WU.~

O- C- .Sml' itr ~w1n'

2, ht.-....a

0)~.L i.!>t

7A 7 -'r -7

PZIG, 23 TYPIC.AL. REFLECTIVITY PATTERNS:-IWLUENCf K)OK',,9P~OECTOR OERC

i.OAL' D BVT ~tRUER 'C4 LAT'I C.E SAMPLES LOAC)Etý Buj'YL PVFýFtR ý .hfA

: ý t $'. SlV,1

54-.5 -3 d I V

LEADLOAED . -72 b 6E/& LOADED ar.

Il

~' '.0

FANRSAPE INS'WEAN AVS W*

S7 32d 119&S ~m

A.Ildjt. L R T_ --TRt-S6 db 0"ELTW-RS

S-/eb s/v.Sa AVA .aýf

Z) tL' S(_ i. L 7 o

vv 4 -M7t3tUUf ry

ci~ Lu roxc f; o~~z 1, 7rr.C

flt' cisnm,*de of' the: aos m;t: r2n .aia at 100 Qc isL shwnI t'a1

vales endr~t aloxI ýnert ¶)2 vst:hsIC) !rvos of. loadin-3,9 nr-sf or the,'leardrrtr blw 1 r, a 4. en~ct. .s t,)* O

49.. A couipariso ofd samle havin aw_ Lcrs~ittO ~-:3rflat~~~~~~~~~,, cm.e rtes~ aeilb ato 100inca hw- ~ h

upmpler, port ion ofFree 23n Thbe dif thercnc ztrscattersh :zj;;Lrp'ethe twog lyeas v of asurfaces agetucizd vtlhes~l minus ie t r wnleua.a) tr.,m alsoeicred coe wtilth- h3adi~s ofe-t :ofdiandt3-S dbai' ortelead- wt lo wingS'M11L densityo 2,61"s +,4 aut..

noted ithat zthe a b'lowt . gn iate os ost

had an ano~tzlous density of 12'3, These resu_'lts .5ndicotett'S vn ' aeia ff.~ the. 3caýttvering ind~ex,

50,. It will be noted, that tne ýkt 5ish nTh tmi r tRtteN -1, -3 *c12Ct.7rzosursd in the plane cif $ection B-Bjiva' re 10,; sce&es "Len c.rct -

,,)onounctnd scattýering off the acons~tir. ~ixi krth t.2.~:es Fgur 2. T: r~u~;ts bo'"nr2 mv by the Qz-k7t Z'zav

"tte Brit.ý,pe efi hcad a high ac~Yettrinig index 'S 7A a~ atIOr,; k0, In factl tihis value' of S was the highe-st (a%~ t'%4s

xfreAuency) fr~ all of the, sawples- tested

51- The poattern for the, Gertan Pat;ni~r Semn1.e Noý 7?1 shcar'n in?tce231 'Is not. necenssr%17 tyrel" 4 tUhl; struetr're nar

're r t orwcm th i11vmira4wnt too ,3mllI GZ -F- ý4.O Zing CX~if tci~e CýO~ntvs an-i thef Theertotm.eZ

Et p12 . i- - ti-T fAt row 2, Ito a c:naI-'-r aI t.. e

S. S-R d J&S

LU"

7- - 77 777 '1,7 77 -

ýA The rnecRýtlty for usirlg the Prcsa~n$ technirjuc- n in I I laSscatt rin-~ anfd nbsorpticn 0., Sttexilsture o

.ýecirnens is evident from tLhe fact that 1st~ral spradirng ~~Zfor most of th,,e patterns,, and that the imsxiwts occur at aigleý! of•,tcrzAl for several of the struct -urad sam~ples. 71-e use of 't-hnnrmal~& -. flctivi5ty index, Rn, Instead of R a-, sn indicat'.-on o.1aý-sorptic-a would re'sult In an error of 7,5 d'a for t;;he Br~ti~zh

55- LatterT .3 Versus FMt gX Reflectivjlty patterns 'orSample No,. 21 are compred in Figure 2.4 with of:s I thlere~feren;-- plvtc at corresponding frequpncss, Thp sattrnildex, shown or 'Pattern NIo, 21-161,, is a a-x~ t 15C. k-, a1o.n

* -~~reseat both endsa of the frequencey band, The decrease &

* Te ~f~~cyend~ mey be attributed tc- the "wi~asze of:lerith reltve 'to theý dIL~erSion:3 ^f thne ejGMsent-* 71he ~a t the an h:Leqay r, probebly caused by r~oflct~on !otha flat portion of' the sam.1 as dseussea i Seectin T

56& Reflection Nrsmneters vs Flawc-odd uX V4baSaI~z fat or' t1he scattar~uig 01.ncdex 5-t peaký rorecltvityýndcix a t r± refIo71ct~vity 1mdex,,R, for the variont* 1oede4-:*:iblbe samples are p'i.Mtted in F~gures 25 t!,hrough 3, 'rany

-,- opsthese -th~ pararaeters- .ar plottel3d on.ta.8

urv~. ,.. *.t;.. *ar p os e

p A Is!OT *:Iittý) or, a p T of .gtV A ~(-,kl t. te

"h4- 11--ý,e a o- u. .v d t

W .nCBnntn f2 bw h

j *hu-.

ai h

16, 4 R7FLýEG T IVII Y PATTERNS OF~ SAM PLE ANUWEF R F 'FENICE P ;FF OUFNC0 00 TO M5 KCPROJE:CTORt QBGSAMPLE NO 2! ALUMINUM LOADEDO BU1 Y. RIJBU3IS)TRUCTURE: CONE LA TTICE

-,AM.PLE NO) 21 REFFLFILNGE PLATF NO ý')l

NNY

t 4 S.

/Jb I I

...- 405db

6--39,94b ýw Ke

'5 R -336 4b

S s- 6.3 49b 0-13

46.

.NA'VUfRC) REPOF"

* ~REFLECTIVITY INDEX (R)

PEAK REFLLCCM4VITY INDEX (A) X-

SCATTERING INDEX (s) 0- 3

-10 - -

~-20

X

-4050 10020 0

FREQUENICY (KC)LEAD LOADED, BL/TYL R11,880CONE LAT TI GE *$TRUGTURE

FIG. 25

REF LECTI ON CHARACTER ISTICSvs FREQUENCY FOR SAMPLE NO. 11

VA: O e al ! ' tt C"- ~ ~ b hJ "

~gtnts; mples a !.&honz. .n '±gr qs~ 6.':.. rsod ftrom Iprd4~Y' to 0A d.u ,- ht' .; l;ycPYtfI

-~~eý 1*16actionL ecbarac tAristies of. the alu&*2Tit 4 i s &u:i

No 21.~ Q~L4A~n ~ arc an own 1A Figts-ý rfncer~

-u tlats sample ,m s 1l1o,,w th ir o g ho ut the f£ra-quenvz.y reange V th* 'itv~t;Index decreasing frrom -24- (3b at .50 he to 3

&c.-. simztsitybetwen tht =-ure Ff4 titfor' thLA t).cldd teris1 No,. 131 is thint 'thc =najor partiora oZ the 4f~rccL;,t-c>:cllrs ,twen 100 and 150 k~One diffe--ance9 hoýwovor.4' Is- -the

aprarent 1nw'=Aef PI ... 1aZZ Ctý5ipeM-?fl'Dpared to th~e reltirely high slope ftecuv o t c~L

Itded s~mpls.O "The peak reflectivIty -q ndez o tpeN~2~h~sa iAniuit PAt 150 ke but the index Ssý bl~dc-uj-" &

theO treqvency rornger A1soT Rt 1$0 k= the SL~atterlatt Is sxno-ximnm, 9 db; and:;&r'p-s to ppproximalteiy 4 dý at both theý l10-& nd high ends, off the '0treqtenoy ranget.

59. The rtleinhast4t-.tt. hta cone,4aettice aamppLeof lead-lmoa*4 "ýbu4y1 ýrubber with: bi""ing agent, Samplea No, 3^'ý~ s3hown 'in' ?$ir&27? Both tbte~ftleetivl.y and tho peek

r'3tectrit Inict asfairly constautt with freguianer-. Trho

rsogaitive naltil bute tar sea tft~fgtr'l fr~equeneiesezcpt t 1 t '' t,01y be. ebasl~4i~ tt the: mnlaut nelw Of

asq Sameflr . W Ot the~ . .. `.r

60,4 l ta a'L S 6, 1222and 32 eac afrcrr bwiyl nbber ýbtt *i. w *t1Xe5siltra to

- ~ ~ ~ ~ p e±@t~~~j2?O-- ?i~iw Zt ~ *A- th r 'Sec* wr~tr~tc fcw CS

heivy ze4c'dfnl Tht slettt , 3 atr1-1=,at~ t Q 4 db tt 120 Ice, Zt ny0a not'b.

C' sc;t.t; iti1Y lot. th C tizeple ~sa tisihsw" the$'Ot Cor, -Urrt. [4!~ 45w t:~prn tt thrr~twc l~l~~fSf

at 1-0 .'flirf a4l~

- -c !2~w~ dtdr; zvlr rwb3 5 22ATerolcbt"WA W, Shoun,"~ .rs~ta..,CA. lA*41.$f

r~iv *zy t.' 4,x nary

NAVORO PR PCPT .

REFLECTiV!TY INDEX (R) o----

PEAK REFLECT'V!TY INDEX (A) X- X

SCATTERING INDEX (S) 0-O, 0

0

S-I0

-J

_J

-20

(=- i (R)R

"30

"-4 0 - A ' A... I ... I•_ t =,. ... ._

so to20 302FREQUENCY- (KC)

ALUMINUM LOADED BUTYL RUBBERCONE •ATT"cE STRUTcURE

FIG. 26

REFLECTION CHARACTERISTICS"s FREQUENCY FOR SAMPLE NO. 21

49

REFLECTIVITY INDEX (R) --PEAK REF1 --CTIVITY INDEX W~ x--X

-to

(R)

-30-50 too 200 300

FREQUENCY N(KC)

LEA0 AND &.IOW/N( AGEW LOADW- BUT-YLRUiRREW COME LATT.C( STRUCJ07.*V4E

FIG. 27

REFLECTION CHARACTERISTICS

Vs FREQUENCY FOR SAMPLE NO.,31

05

REFLECTIVITY INDEX (R) o-oPEAK REFLECTIVITY INDEX (a) X---.X

SSCATTERING INDEX (S) O------c

10

.- 0 I - . .X, ,(S)

-10

(R)

-20 -- I-. I -l50 100 200 300

FREQUENCY (KC)

LEAD LOADED BUTYL RUBBER FLAT SAMPLE

FIG. 28

REFLECTION CHARACTERISTICS

vs FREQUENCY FOR SAMPLE NO. 12

e5

NAVORD REPORT 2~

REFLECTIVITY INDEX (R) -

PEAK REFLECTIVITY INDEX (a) X---

SCATTERING INDEX (S) oc

-104(R)

50 100 200 300FREQUENCY (KGý)

ALUMINUIM LOADED SU7YrL RUDDER FLAT SAMPLEFIG. Z9

-. REFLECTION CHARACTERIST ICSVS FREQ'INCY FOR SAMPLE NO. 22

¶ ..

a stt rob;hs thcun,2. S7¶ ltrt. Iceulc'

j' atj thej ~L~Ot£reoe S0~ c rchtee f s of Di

sat Of t flCa t ssmple.. Thlew poor a. !as ac~Žrto ee.*'~tio empl'L t hs ½2oaekd mstc-2a at

-, I'.sest r eq 'ances I t a he 2...f 1 1 ctdAd*~~AOv Sape 2cean :,.. 0Z ab;)pz. <11

I7?the ranws-, trom 50 to Ire,0 It~ ½my l~ notcx 12 toS ccy'v-c? Io tf fe renr.t -,; *wter.,iso13 tre c-much m±ti'a oloselIy grc-pths.42 fQ½-

Tial.'t &"iples than f'or thei c':nen-!htt&Acr samp.tr t,.

$a m Dpie6, Nc,, 211 wer Soleotedi f1or P, ?u"rther nitudy on, t-he bPt- r~~~W !ziUzh 0au 1of absorptiorn tharoulglhut. the rocw;mg

hAceitC qi' gs8mnse other ther, Icedod butyl r ui~ b" t-

in- Figaros 31 thrn-ngh r4k I I Sh Ffr: Sv'w f Lr

3,w'.the m.ost. caoba .r be-ant; ; ,ý'ý r; -,wterZ-c

z;tk' ires mremeto.re, vr.ieC: .:ldcy2 'x'v~ az tch az

¶~n s la S-0 cgerŽG thet tbs' w,'2 IW 4,

1ý I M. t-at'tp.-£ "'a'it: ½ Ts fr~z~yr~~r fgyytrh kt "

- 4' 7' ~.. &~~44~''rr ~ftt~ 4 c~ %,.

ll. f~ C* at~.k ngi)2 f4' -i.7

vs ~~ ~ ~ ~ ~ ~ A F" " ~ ' 4 i h v~ lt.* . , ,* cr4"',c 7v

i's -.. rc 7 z~ ri.2.! C

.7" 4.7" 7 "'1- 4.-' 49A

v 4 ¶ 4

t7r.-.4 4 . S4~ 7

NAVORD REPORT 2989

REFLECTIVITY INDEX (R) 0--0

PEAK REFLECTIVITY INDEX (a) X -- x

SCATTERING INDEX (S) O--

to

10

FREQUENCY (KC)

LEAD AND BLOWING AGENT LOADED BUTYLRUBBER FLAT SAMPLE

FIG. 30

REFLECTION CHARACTERISTICSvs FREQUENCY FOR SAMPLE NO" 32

5S

NAVORD REPORT 2989

REFLECTIVITY INDEX (R)o---OPEAK REFLECTIVITY INDEX (A)X---X

SCATTERING INDEX (S) D---f)

20

0 BRI TISH FAFN/R

. -I0-

-J

w (/

-40 -,-

SAM-OLE NO. 41'"

50 ;00 200 300FREQUENCY (KC)

FIG. 31

REFLECT;ON CHARACTERISTICS vs FREQUENCY55

NAVORD REPORT 2989SAMPLE NO.:

51 CONE LATTICE IMMERSED AND HEATED X

52 FLAT53 FLAT IMMERSED 054 FLAT IMMERSED AND HEATED 0

"-MEAN FOR ALL SAMPLES10

0 0

ooA-o 0 x

(S)

0J-10

-20 0

PEAK REFLECTIVITY INDEX (&)

SCATTERING INDEX ,(S)

-J x= -i - (R3 - -•5 -

00

REFLECTIV1TY I.NDEX (RI

50 100 200 300FREQUENCY I KC)

!/NS UL KRE TEFIG. 32

REFL~ECTON CHARACTERISTICS vs FREQUENCY

56

d the, J ., t

.vr o trt 3 c d ýhe a~~' r~ vne -s- §Fr ", ~~

"e ot The ds ricpa t f I ~ n,~tcv.t ~~d> the zw r- az L-, n, 7A Y rciý db g 1 ~fI -1-f

ofc~ Samyt1a N'Fo. 53 i~s adjusted for the I5e' i t2.1ume of mat-rivi . it' d-e--44aý;on Is sl~o a fii d~ 7-ýSlcc th-":7activity Iro &re se bout 6 db and th-u n,:atter~ig iný,X~rre~~abouit 6 d", 'he rea34c -eflec-1IUty 1. r -:57 ,*reaý -

spproximtely 12 db ove the ifrequenvy range used ThiL mlue ofthe reflectivity index measured 'at 50 icc llpraimast-A;- 5 db) -Dz.zample3 5 =m thick a grees with' me~surew-,nts ~zede by Tr,, andDarnier, refrews~ (/b) on sample~s 12 in tshick which i.;~a r'eflectioni coaffi4oient of about on~e per~eent oz- & ref'J-e-CUvityindex of 40 dbo, It is evidant frcm this areement~Z and elc f'rM~t~he insignificanit effect of a cone-lattie e tirf~eia- --,rt;-ur*that for fint samplea. of TnrWsuaret0 the absorptl.on, Is inol§ZO 'UV"*by wurfaee, zý2.swtch,, Thsw J~th a~frfit ij~oloaded buityl1 rubbev.,

66 Figtwe-33 s~hOYR the tef2eto 190 braeteristics, of the p1J.*at*,eCna!, $ao1 It& 61sflri Dotewe *rants ware made the sample

V*51are imce!6 1n*fter A: l83"P: f=I ,tý*fom days to ra~v es =:~r~ta~p~ sr a pO~ibl DwT , ?fle~t.Lvity inrlex i3 betwman -ýý

~nA -~ 4I or. 1h 'req at-icy re~g*, Ths ning bad essentiallyM~ atC'fet &t!4s,.f scaftterar tk c~ttering index w ryiz4gbetwveon twill- bdgt ve ard npiit4 ~v~wTis SamPl wa

1:4d ý ,~tb ,e too's -zlm0,,U bas 1en trj.ed as 'a i: thp

Stile ro~1t! vtylnde iýSbqtt -4 db lt is of!'

Stb6 ter* I 4~W~7~n

-14I

"=oi 'k

-Roo

NAVORO REPORT 2989

REFLECTIVITY INDEX (R) 0O---o-

PEAK REFLECTIVITY INDEX (a) X-~

SCATTERING INDEX ~S)D-

1~0 ,

-10100200 300

FREQUENCY (KC)

PLEA TEED CANVAS

FIG. 33

*REFLECTION CHARACTERISTICS

vs FREQUENCY FOR SAMPLE NO. 61

50

NAVORD REPORT 2989

- MEAN OF 'TWO SAMPLES

SAMPLE NO.71 X

SAMPLE NO. 72 0

REFLECTIVITY INDEX (R)

PEAK REFLECTIViTY INDEX (L6)

SCATTERING INDEX (S)

I0

x(S)

xo 0

-14

ýxx

- 0 1 1

50 I00 200, FREQUENCY (KC)

GERAON rAF'WIR SAMPLES (ENLh OF TANK)

FIG. 34r

REFLECTION -CHARACTERISTICS vs-FREQUENCY

59C,•L

-- 1

68- I c'~ tu e C,

airt 2 rie, aInTI O&-1-ne in geea hz SMýISa

Yssuemnt Ceaureeni r~ rin Peri-ltty

were male to obtaxn acopsn between xreýslt s Za~ a SisIorlantat-Ion and vrftbaton two 'Žricr-tat'ons. For th? eor

orlnteicn, the samp.les Wr :zeasure~d in r planu>mTV?.Th~theo.ys t*s~~srje~z sicveŽir

Tr~ -7- t- 3?o try -O

> ~ ~ Y' 0sQ4 the -ruso B ,a&Sreved to cGe5note theP

Pr? 4~' ~ Srare use&d to- denocte reflection caatr~izi

the ¶-- etteToer.zThese avereage a~bt~ are&iCr.A qv-t 2 t2 2.z 29, M.ct~azrrents wec z7akc

7< ~am2 hrwl IV~ and the SCsrr-an i'afnlr raxl>- rcaze fr: 5ct Le co2( 'm

tsr~~~~~ a1rrzrt; n] t 250 lkc,ý -he @-4 rerý~ 's-~~ 2~rthe ;cnee 2.-att!s,--e aazyre a pla~netrog

¾O thesc~rllel surfaces ef the%* wed MetnSt& x s2.r O ancI fcr the British

71~~ M 7(,

A" th t te .

NAVORO REPORT 2989

0z

ZI~J w

00

4 cc w

00

8 crf

ww

4:4:

0Z

04 w 0 0

NqP) 13A3 L

6?

NAVORD REPORT 2989

o 0

T-n,

z

.0

LU

X Lw

o00 0 0 0 •t

I ! I

l.0

100U')-

x00

IOU/V z

4-o

hi >

9) -,3A3-1

c-2

NAVORD REPORT 2989

00

Co~ 0

C\3~ LU* .)

w UJ LL

to pl 00jw-4 U.

0-

0 (nNP) 033

It)

r0 W

z Z

I--4

-0 0

C4J

6(3i~ -40

NAVORD REPORT ?2989

Ua

Z <

,CL

Z "" S '

z I•S-'- 4 ' -

OLUL,

QLIJ0.i z

F-2ccD 4v_juJ0 N

> W

=)) -

W I Wo --

_j L =W O --

w0CC

ZN

NAVORD REPORT 2983A t A G E .- o

r X . .X

-25 ! PEAK REFLECTIVITY ISPEY (A)

-30

-40

- 4 t ---------------______1_.. .

-20-l +FLECTIVITY INDEX M)

w. -25,0

L -151tOATiTERIW INDEX (S

;o

00 V.00 .300

/~~~~~~~~~ ONC I/~II~ ~. ~ V ~h A T Wr

0~~~~~i N: C ýlAMAUEET

cm, pm r4, rnrrwr44.-Kyt-

S J..' gLly -t it i7C

m~xinrn cv .4 ca av r ot73b a t1V& ir ~xtta ~

the offe-t t so* it. t ht"Yrct't':r -. n~c & hc n I~fl r

71 ~~~wo 40ý, c4:r::ar a ?er0;e.'1,4, chbrsctc.¶z Srr&

72t .. Tables T1rn2' tie th~aez values of 2the C'¼rV'c~9 -n ,

tbc 0ffcft u avrtin Orweltp.to fon the~t whfeoichho e

2) ;st SL~vC~ V-

72 abeU ~esteavrz2vlu5o t 26, (Assctr p.erlnr tpt

tor 3,4tmr'~ or gri!, epn~ tt r5 Intc0 p

£tfee n, In isnt'tion o t he eRM'eet3*iongo emr

Chtisra chterpzt~e ofrritish Fe f'a'i

sm1I ~ ~ ~U4 Sr Ot t 9.isietq 2

is~~~Vs ?'iur 3%wre 3-~ 'b~nt~e tose'~ Tbio l t Rir ff.mrovet a tdbe

8f&&iriW&W 1 A LNAVORD REPORýT 2989

AVERAGE r-

1kx X-x

-10

15 -0

-20-

-20-

PEEAK IIT RFLCINDEX INDX A

-25o

10,

wp -

REoFtLEZCTiViTY INDEX (R)

-20 'r Si A

FIG 4

x.MT 1S

NAVORO REPORT 2989

cc

>-

-i w 'J"

XXK

-i -jk. U.

IL4W

00

.'qP) 13A3-1

thesane b.iat Vary as muc., dý) it a f'rieq-ne,yitri& rA an R bo twon -ýtaues intar -' .ls of' 50 kiý

7~4, I curve for 1. tho~'v -*,oyjerc~. ariat'Ion -iitbhfroq-jncy from 150 14o 2CO k,.: !>-t, ^ro:, 200. to '45 k.c TI u

75. Figure 42 zhows the retfleation characteristics of, 5:a t peNei 21v h cone-1a~ttce 92rple corresponding to the 1'suifrucee 3ernnle No, 22,, reaured at kc irncroments over t~hefrequenev range from 140 t.o 26-0 kc,. The seatlo-ering i nd ex forrth!.ý conM aarnpe 13 appirowlt~3y ?. db at 1.40 ke and doereos~sto a vali-ae ol" abou.t 4 db at 2260 ka 'is has boern irantionedDr,ýviouzl> Ithis decrease in scattering I.s believed to be caused

by. *t-h inrae of -refrlection wilth T're ue'ny f om 'Che £iatr,ý-z betw~en the cone bses T1he peak reflectivity Index..

b et- 140 koc and Increases to, -34 db at 2.60 kc, The rai'1ect.A~it-i;ndx9 i~s approxirately -30 db at both ends of' the !'requ:.-,,ý

W) ý4 ke and 260 kc) and as~ nlnirl `.-37 db) at 2150 k,ý;

Coaio ofR 84d igures 4.3 and -44 show the r,- aSi1.ectlvity index, nq favr the fat sample An~d the ~cne1t'tic~ssar~ple , v'espectively, , The car~ra3pondlng eurve for th.e re`L-eectvity

Lndex R . l P1tted-on,-eaeh I 'ize f'or eom bfl..n 17t may ICeobe-ýd- *hat rj moft ,;ar q~ t rr flat sa "P3

t anf.,r the st 8=u&4*p!9 721m necessityr fozr using theP #ent~ techii STi 'ui sztfdompe ra e r~

~'1a tha ~# ~ffr~nc bet~e~the t~iioutves shownIIn. Fi" 4A to.ibsou 26 db 'at the -low-frequency' end.,

~~~~~~~~Sml No.,y ~x~g a we~t - 21

'77 mx.uets-ve d iii on Campie ft,~ 2-1. thisi'almin=-Sb4,tyl rt~bb' a P,.eWith a cone-1attice struczture overth

ýr~srge from 20 ka. ta Mei kc6 i jncmements 0~ ~~KLA~ 1 ~ VM1,V used 4 rf order -to c'e

~ ~ f~n~.yrange, F~ig=*' 2.1 shows tbe .beam widths 's

T',)_ 2" S l2

d te ý71d. -,c 4tr S~ I S!ne _I V81U.)3 of RKý4 ~~~not agee. 1,1 aV

*~.9*?.3 ~C k~~ 2COkc, t S id, 'w th ti

tt$,3:1p

NAVORO REPORT 2989

-30

-34

0,.X-xX "Y%, X- X"

X-A-40 - AP~ 'ex

K: 40 ISO ISO 20C 220 -240 260FREQUENCY (KG)

ALUMINUM L C4DEO 6uTY RLIBGER cowC L rricE sAmp4Ei

OREFLECTION CHARACTERISTICS vs FREQUENCYIFOR SAMPLE NO. 21

FIG. 4 2

7'

NAVOPD REPORT 2989

-4J1

"-I I

>! xw- '

• ~N-12 -

| I

-16 . .. .• _ _ •!1 !

140 !60 1 60 200 2•0 240 260FREQUENCY (KC)

ALUMINUM LOADED BUTYL RUBBER FLAT SAMPLE

COMPARISON OF NORMAL REFLECTIVITY INDEX, RN-AND THE REFLECTIVITY INDEX, R, OF SAMPLE NO. 22

FIG. 45

$7

NAVORD REPORT 2989

R -R---R-26 1

X-X*\ x~ xJ..-

-.34

"-38k

-J

> -42-

-RJ-- 6

-54

-58 n a [l200 220 -240 260

FREIGUENCY (KC)

ALUMINUM LOADED BUTYL RUBBER GONE LATTICE SAMPLE

COMPARISON OF NORMAL REDUCTIVITY INDEX, RN ANDTHE REFLECTIVITY INDEX, R OF SAMPLE NO. 21

FIG. 44

72

RF.3 45 REFLECTIVIIY PArTF-t7NS OF SAMPLE: ANC) REFEU ENCE R. TE.

FREQUEN-Cy 35 KC T~OIWUAMP1.E No 21: ALUMINUM LOA(Ot) BUT'Yt RV88ERI.;TRUrTUFE GON~E LATTiCE

SAMPLE NO 2 REPEREWCE PLATE N~O C4

.:2 '2db

KC3KC --

NO

I-A

15 S- liabz!wC K ' 2*-92*b - - -

~4A ~ ZT6* X84 )e 44

SO / / /a

a /3J

jVat

750

A-a v 1: 01;0.1 5T v. "maw-~r,

rag k. I= ,-- ZI

ýmoac,ýs rojrjjm---v d~t~fori-nt s~mos ýhcurvies reprasento an aigc e o. a11l available pw~OI.3 t'h-aPeIntt miirkcod X-. Th!D l*ý.tzr s*oa for th1. rozedThe aurves thut5 repres~a*,t mcsir#n~~d i. ~n

SIi~ consIarsd4 probabl.e thato th,ý leress ±In S a rd the Imeasin4 and- R 07~er tala Mnge from 200W k to 300 ke &r-r cau±-ed brv

the Planz portiow~ of~ the sta'uCtIZ~ betwecm t~he com~a, Thpa~ag 7eau3 oft R is be.low -20 db fo thý artt1m rsage and th~e

a8#rage V.-t of A is be3lew -25 db for ati but the two Imowst,Tequezeie. T'h Inc-ma~oe Inl sme~te1..rinf from~ 2< kc to 150,, ke :12

~ are~re~,wlitth t~he thieo~r7 giv~en by R~ayleigh mrweipng ecor-,rr~ptzd Surfaces, refreence* WX 141ws of Rt/ t~ and S8 i~ at~wo hlghist. fraqmneies are eocrwev't doubtf'U bs-aaiz# of Utorro'w hyt!lroions, pattern,

51 The o~vra1I syst-ti wwo chie*okp for, 1,mi'itty, ead drift as

a PPw ox ir-i '6e y 1/2I db Um0 Iv ý1y thxe I rer'm tot. 4odw±via ý"io Tersius oscillator C-atpuit (o i*.1 oablock-

;0 pu* ..- -,~

'k'

CIDAS the

1-ý~~ Z-tz r I "r

-. ~~-'t

7, 74

.7x h 1e

V '*ýr~' l~

FIG 46 REF-L.ECTIVITY PATTERNS OF SAMPLE NO 21

PROJECTOR BEAM WIDTH

SAMPLE NO 21 ALUMINUM LOADED BUTYL RUBBER MATER!,V-STRUCTURE CONE LATTICE

NARROW BEAM BROAD BEAM,

POENN 21-259, 5,34 21-120FRtaEOt4CY.50 KC o a4*?73d 50OKCPRO.JECTOR 08E R -23.8* 0G -25---

1 -40

90 20 --- 'c

2' -159S. 28Adb 21-M -5m

23-V3.5 24-244500;cc AV "- ZTA db 500 KC .0S.'1

E- -29,

;~J /OF

~. \ \ TS

)s- r% . "

NAVORD REPORT 2989

PRJ9Q• T SYMBOL080 0 0XB41A + 0E8 0OBE 0 0QBG X /2

- AVERAGE OF ALL POINTS FOR *o PLANE-15j

_ 20-0x

-25 0 0 + IV

w +w+

-J-30

-35

-40 L.

- 5

4 w 0

O5 . - ,, I

x

- 15t

to-w0w 4

.5.

20 50 00 500 1000FREQUENCY (KG)

ALUMINUM LOADED CONE LATTICE

REFLECTION CHARACTERISTICS vs FREQUENCYFOR SAMPLE NO. 21

FIG. 47

761

¾' -,'ntry .k be >or'Gt i&

o4 v 4 L

re~rg~vtrPw Ž2aC to lt c, "A t'l'x; WcIuQ r~be! use 's ~*;

Sre z b-,-e e by InimL ti ng tt d1isco 0nt nu 4ty caie yth ~~

-'Orticn ,)r the linaing-' RwesU.s ±rA~cto thratre'cto2rothe-Se r-su 11 zl~ane s urflie%,a s -r! s ignt!1.ca nt v't f-,roqu-en t'ý far

t> th, wcldtb 0o' th-,s fltt s3urfce, Is. gr~e-B'e thanr a hJSfnxvc leng~th of the scamd, F-,r, $agjpje go,, ?2i tx, teuo~vas abolir ZOO ke.. Thesa pis Te sm-lYcss covAl be replh-tvd byproperly shrpod depressions,

bE ?rth~.'Itprovemont of the lining at low tr~quonciez willprobittly be M; 4O-cA;l thb-n at high. frequzencies, Gina00331t,111tY Is. to use inclcded air spýaces to peniit more deformattion

* of *e m-t.r:Q and in tu'rn incroarse this loss,, This metohod was.tise4 erfecti'"nLy for ftfntr40 '

* 7.Anotheir Possible m08fl2 f tr isiproving the absorpti on of hsmet±3 e low fraures ist inees the lengt ofthCtfl',3 Th sw3CCid pn'ttt Mv7eaT tI'e ivitera t rmts ge of

ieuimt ctet at t~he Ic"Wet f'erquckn~cie moTe d i a&almwz-sa' t mtsc~h a linIng *c&CL-. PVOlipy riorG. 3p!aC3e--.3l{

~ ~ robb~sthat *bs!,rptitncab irne soestatyto~ Canevao or totawttcriasLd ab oew-a terle

tod ws a~le* tm%:t Xs em..ct 'tt ittt pnLe.' 6n.

rxr ~ ~ ~ 7ýl to m-r'4c* *~e~ttioe a'erpt2~.". t co~.c

m4 p b pmm4-rO

Z-V S 0 t~4v~ aiý,t IC. F7

1: ^v saývw.Cc~ctc' fmt~ 4 y~t

n F

ri.:u bi I'~d i x- of >c: e tv- n, the 11. s

~.The mxias'urc~t -- reflecticn vatic U

bt The owaure-met ef nor-ndM !efli~ction Ireduct'-wrIM -Maipr'essure,. These rneasurements would indjc.3ats the app11cvo1'Aityof linings for use in acoustlc pressure tak.

SThe measurement of reflection evh,.ralcter-istics biolcw20 kel Re3ults of these mneasurements wou.ld irniic~te the lowerfreqmoney limit, of a tank lined with a cons ltti(oo ztr~u,ý,ue,

ACKNOWLEEDGIENTS

90ý. The author wishes' to expres~s his appreciatln to thefollmaing- individuals ofý, t1%e Adoustie~s.Researc~h Division-,

Ur.a.'cob Pomeraritz for. ecrnts and. -help throughout ther orlk or. theory, aW~ssa~peiietation; M~iss FrncesFezi~t~ for thew compUts-ti, 6n arM Preparation. Of the graphs;Mr. A, T. ;aquees and IVr` Ifv, $ 53?)ý ri'o h~f~SW9g~txIn in-tc~rPret~ng the results., Thq loaded butyl ruibber vss.

..he Chemistry Divrisi~n.,.