BSTJ 30: 3. July 1951: A Photographic Method for Displaying Sound Wave and Microwave Space Patterns. (Kock, W.E.; Harvey, F.K.)

11.4 MB·English

‘A Photographic Method for Displaying Sound Wave and
‘Microwave Space Patterns

by W. KOCK and FR. HARVEY

(Sonar Rac Oo 2108)
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In analyzing the perfomance of a scoustie or microwive redito Sis
tpl token the ay fn which he wave pee they ery ren
Ue suze, 1s hsb i ume cate tu have a pholopaplie rondo the
disttion of incenity im the field gener hy the retor. "THe per
drscrtes a simple mechanial scanning metho fr accomplishing his ent
For acoustic spali, pre microphone ix roves hack end orth Pre
te sound el to be explore a ra Jar ane the mere
‘When the output of the misrphone js cnet the lay Prough an
apie, the intensity ofthe igh sie acerdance with te end lve
“encountered by the probe microns A eimens ar sme reo
the wanton Hight intensity. To his wy the ie pcre Il
hy searing the snd Sal smeht ater Cae manne in whic a tevin
itage & fovmed* For apalyaing micronave fields she mieroptene ie re
plcsd with a tieronave pickup probe

semanttat

“The scamaing cevice ie showa in Fig. 1. The microphone i lerated athe
‘end ofthe rocking ann. Attached toi atthe let) is emall neon lamp

(Bevel fr cketwave peal by Tee rived Bic? oars
SSN) sila ens oe
SOUND WAVE AND MMEROWAvE SPACE PATTERNS sas

he is nero by the ampli stot of he microphone, the rocker
sn mers throng is veces! motion the enteastnly ncling the
nto and gene reducer i cause move slay toward the cea by the

sie po pong

‘ack ad siaiar show a: the left of the photograph, An acoustic le ie
Un is west pein Daten thee of he rocking arm and a eter
566 cum nae svete recnwweat. rman, Ls 1981

lect speaker win supplies single fequancy sound Geld. The Pena
Tred mers the beckground fs ben iva Icsase ts short evel
UND wae asus mUKOWAME See HarRENSE sor

next time of I mine allow the potogpaic recor 20 be inspected let
immediate siter the seensing eun has teen completed,

Aueutronn Pare

The Bet pots won cen tn determine he ape dstebson in
he foot mn af HP cr cmt le. Thi acon ene fe mle
ld ell ateps arranged in an open construction Figure 2 shows an
tail photograph in whisk Gh horizontal sotion of the sanning device

sate rai. The line sbacture of the sear is therfore vry eats bi

{be oe stucrue and focusing eet of the ler are eden. Figure # shows

iter ptetograph in which a finer aati scan with anger str
Provides « amooth searing pater

‘he matinton pero lang hoa wit & 8 aqusee spertute shown
in Wi. ahem aa rsquney of 9 KC. Asin Ce lens picture, minor lees
‘alc sec Toning atthe sides of the major lbe, mle severs mini
sea Stl in the central region next the aerial tr Fees
fe

‘The we-ncting papery of pis rade of sig stip i lusteted by
the supltade pattern in Fig. 5. In combination wth the tip in of ig
5, it ts the sound beam dowd awn rom thea. The ens ol
tesempleof a eacor ofcourse tthe im usally chose fo emen
S68 x LL svete sremueaL sounNan, JH 1951
ous WAVE AND MICHOWAVE 89868 PATTERNS oy

rate traction dn its simples frm, One ote, slg With the downorate
Tear il» dlinymelzy of te ain lobe structure, the upper be beng
qe peace

Auuaraos ov Puase

From this point, Une putea of phase wil beaded ta most the
ploy, This is apis by combining, with te inal pike up
by the phe mirrors, a eorsantpase constantamplitue sgn from
the cellar feeling Uhe source aud spesher. AP tho probe moves aay

TR Rea PE

for the ud scesker tnd Ken combination, the ase of the micophont
Sieve vires with mspect to the constant signal tom the oscar. Co
ftmictice snd destrutive intererene elke sd psturs eu 9 sa
Fig. 6 ae obtained. This i patter: fora progressive sourd wave (oat a
stunding wave) cneiging fo: thestrp least, in fc, the suie patter
sethatof Hig 3 except that pass fas bo ace ad the sina ieslly
Tee ementae, The cre wave rote converging tems the brighter
Fee pol see event snd the snl energy sess cong the eal
paint the wave fants bacme concave oucwaed. Figure 7 shows a similar
pattern but wit the intensity ofthe sel increased. Tais procedure brings
Up the intensity of the weaker field and ebows mone clesly the mtu hte

n

sryctte of the les. "The phase zevetsal at eal suerte minot labo ie
eal sen irom che fact dt th bright auc a Che rin lobes ine up
TUN the dak ana Oe arent ni,

The alton of pease makes it posse to ain motion pcan of
Drogresive wave motion. Hy ting wraeive movie “stile, i whith the
[Pst Fent patir is slvancel oregvth of a wavelemglh, » complete
tle i stained, Thi series! win picture then epee natin ene
sonable lengli of lop af si tan

‘An example of the retarding eect caused by « delay ee is shown in
1g. 8. This wee potiem ipa compote (ove expe) pictare and wa
obtsned in the olewing way the left side of the photo was sane ith
only the te! orn ati ene removed). Te en was thea putin place ad
the pi eortinued to scar the area toe vig. A the sp ofthe pot,
the circle ave fronts ze scent he enous feat the hath vy ut
inthe sadow region behind the lens the wavefronts ae tale One
sows that che igerton of te ls has enue ely equal to bat cme
‘eavelanth along the ai, This remlta na curves we front craig
{fom the es al ronnie facing asion,

‘An aczust: x: miseowase) "wo in whic the dey eset uns dante
ties sir is eauseucion to a venetian blind! hi i Fe. The
Feed Rom is he sine at iat in Fig. 8 ac et at he focus of thi lens
sas lo price tt rather than covesving ps font athe arena
veave. Ar the diction getter of the fed hom would inate (Fie 8),

heventer portion ofthisiensis rater sry “hwninted,” but the eval
ing ence veicentrtion, i passing thao the lem, hited wards
by the guiding ation of the slater inten The realingslasymmetay of
‘he wetcal amplitude distinc a the spectre ofthis eu lice Ip
the increased thidaos f che phe lie the per sein of he pase
raph en ege par response fr the never! intl ste

fare as mpored= The stztgitnes of the pls ine, home, lisa
thet the ene nas conversed the ier wav fants font haa i he
Hi plane oe rant

‘The rndesmble caneentetion of ety at. the venter orton of the le
cam be meray rer fy eubaitatng oe Use sal fet For of Fig
{ull euial local Having is threat atthe focal pont of the lene
The eveay distibution caring the lene then Gin uaues aa the
Sank patescne~e ony a slighs dissymmetey inthe arapitude dsteibaton
Gf the emerging wave as shown in Fig. 10. The ettibution of such
5 “shied” leas i the horizon plese, however even mone fom
Since't isnot skewed ¥y the sant pte a tis ple (Fy. 1,
372 tue wus sverme mmemazeas jours, OLY 1951

i, 10h et Be so 9 we tn

In sma acouri invesiatons i ie dssitble 16 neve + neue of plane
waves of esto ane. igus IDand 11 sow tat» sik aes ens
provides simple way of tcieving this result. The broad Dad natre of
Se AVE ‘009 MICROWAVE SPACE. PATTERNS 33

he slant plate Jens easures that plase wave fons wil be produce from
LKC down tthe lovestfequency contemplate for us, a lines sry
size car be employed since microwave lesee of 10 and 20 foot apertures!
hee Rees but sid Sou quite aif

nthe thee precaing plop, vatatioes in the intensity of the
serergng waves ‘earinton inthe thisknees ofthe phase line) ean be ob
Serva To show this ees more seria to indinte the symmetry of
‘hse smpltade variations, Fig 11 was retaken with the phasing signal

moved 0 a6 to obit a pare saplitude pattern. Fig. 12). As mention
ty connect wih Vi. 3, hese pallens ply show the tateusy var
on we ate ala guest in the losin ot Prat! fel of auy pase
tsnve sone having rite cros-sectonal extent, For given wevelength
sac crn sti ciensin, thee variation van le called fom
‘ection theory ad evaluated with the ad of Corns pital Te intrest
ng to compte Fy, 12 with Fig 13 which fa Seller poto of Ce sue
ie in fst wf elton aes tat of HE wavlongissperte
dimension! Ahoagh the aperure dinansions in wavelengts inthe ten
(ses ate cleat aul the actual wavcengts ar ite diflsent, Lee bet

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