Development of a portable sonic boom simulator for field use

•

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G~ .... '.~:"-;; .:::.<.._~ DE.VEWPMENT OF A PORI'ABLE SCNIC BCXM

l'I!.,:yvc;\/\,'JG 1 - C:- FT

SIMUIATOR FOR FIEID USE

1

m-,

1 ~,

by

N. D. E1lis, I. B. Rushwa1d and H. S. Ribner

July, 1974. urIAS Tedmica1 Note No. 190

"'#

DEVELOPMENI' OF A PORI'ABLE SCNIC BClCM

SIMULATOR POR FIEID USE

by

N. D. Ellis, I. B. Rushwald and H. S. Ribner

Subrnitted June,1974.

J

AcXnCMledgerrent

'Ihe authors wish te ~ress their appreciation te B. R. Ieigh, R. E. Gnoyke, J. J. Gottlieb, W. G. Ridlarz and G. Mungal for their as si stance in various phases of this project, and te the many volunteer subjects who toak part in the conparison-listening tests that served for the calibration of the Portable

Simu-lator.

This research was supported by the ei vil Aeronautics Branch of the eanadian Air Transportation Administration , Ministry of Transport.

..

Abstract

A portable senie bcx::m simulator has been developed for field tests on wildlife. Previous portable simulators have been rrobile only by truck or trailer;

the present device weighs 24.4 pounds ineluding peripherals and is easily earried by one person. It eonsists of a shock tube charged by a compressed air bottIe ,

coupled to an eJ<ponential hom. A ION-pass acoustic filter is rrounted in the ho:m; i t serves to control the rise tirre of the pressure signature~

The simulated senie boars mimie the loudness of typieal sonie booms and have corrparable overpressures and rise tirres. Calibration of the effecti ve loud-ness is by subjective carparison with idealized standard sonie boom (N-waves). '!he calibration is carried out in the reeently developed tJrIAS loudspeaker dri ven sonie boem booth. '!he loudspeakers aecurately reprcxluee the signatures to be

oorrpared which have been tape reeorded, and they are judged against the N-waves for equal loudness by an observer in the booth. The outcorre is expressed as equivalent senie boom overpressure (DI:» as a function of shock-tube driver pressure and

observer pos i tion relativeto the portable sinrulator .

'

.

1. 2. Table of Contents AcknCMledgerrents Abstract INTRODUCTION

RESEARCH ANI) DEVEIDPMENr

2.1 Shotgun as a Sonic Boom Simulator

2.2 Portable Shock-Tube as a Sonic Boom Simulator Increasing the Rise-Tirne

Final Design

APPENDIX A: Special Remarks Conceming Simulator Calibration

"

B: Field Measurerrents

" C: Calibration in Tenns of Fqui valent Sonic Boom OVerpressure

REFERENCES FIGURES iv Page # ii iii 1 1 1 2 3 4

1. INTRCDUcrICN

The recurring interest in supersonic transport, e.g., 1-3, has opened up the possibility of supersonie flights over the sparsely populated regions of Canada. As a result, adequate data are needed eoncerning the effects of sonie boans on Canadian wildlife. To faeili tate the gathering of this information , the develcprrent of a portable sonie boom simulator was ini tiated. 'Ibis field simu-lator device ~uld· be used in plaee of eJq?eI1si ve supersonic overflights.

'lhe major cbjective was a sirrn.llator light enough and ÇOI]paet enough to be earried by one man. Portable sirrnllatars developed else-;here4 ,5 are, because of their size and weight, permanently rrounted on either a truck bed or a trailer. Additionally, those simulators - employing uneorrected shock tubes - inherently have pressure signature "rise tirres" that except, near the grotmd, are very much shorter than these of real sonie boans; this ean invalidate the effecti ve loud-ness calibration.

The prirrary investigation 6 sought first to evaluate a shotgun and then a shock-tube as possible eandidates for developrrent. Eventtially the shock-tube was chosen over the shotgun on the basis of i ts better adaptabili ty to.vard sonie boom simulation and . i ts repeatabili ty . Developrrent has proceeded through fi ve major stages 7, . each stage being characterized by a significant change in the design configuration of the simulator. For eonvenience these have been designated Mark I, Mark 11... up to the present Mark

v.

A particular feature of the present scherre of sonie boem simulation is the calibration of the simulator ~ressure signal. The fixed-base loudspeaker-dri ven sonie boom simulator booth provides the rreans of calibration . A (human) sub jeet in the booth canpares the reprodueed simulator signal (FM-tape reeorded fran a microphone) wi th sonie boans (waves) and judges which arrpli tude of N-wave sounds equally loud.

2 • RESEARCH AND DEVELOPMENI'

2 .1 Shotgun as a Sonie Boem Sirrnllator

0Ur ini tial concept for a portable sonie baan simulator centered on the shotgun because of its portability and apparent convenience. During Sc:::m9 rronths of investigation several serious shortc:omings were uncovered, and the shotgun ooneept was disearded in favour of a shock-tube. Before going on to developrrents based on the shock-tube we will give an account of our experienee with the shotgun.

The test program wi th the shotgun covered approximately three rronths and involved sare 100 firings and their evaluation. The firearrn employed was a 12 gauge Cooey single shot. Nonnally loaded cartridges were ruled out by local police res-trietions as weIl as hazard; hence, the eartridges employed were hand-loaded, using table salt as ballast replacing the lead shot. This substi tution appeared to yield cx::nparably loud reports.

The rreasurerreilts were conducted in an open field wi th a Bruel & Kjaer 1/8 inch condenser microphone. The pressure signatures were recorded on a Bruel

& Kjaer FM taperecorder with frequency response from 0 to 20,000 Hz. A sanple

pressure signature is ShONn in Fig. 1 taken at an ooserver distance of 30.5 m. 'lhe peak ovel:pressure was in the range of 100-150 N/rrf for suecessi ve shots.

Sueeessive wavefor.ms showed extrerre variability. Beeause of the erratie 1

shapes, identification of characteristic features was of ten not possible. In favour-able cases, hCMever, the follCMing sequence could be discemed: a direct ballistic wave (a shock wi th a fairly linear decay) produced presumably by the errergence of

the salt charge, follCMed by a reflected ground wave (another shock), follCMed in turn by other disturbances arising presurnably frc:rn the canbustion gases energing fro!l1. the nozzle. But the trerrendous variability of the pressure signatures remained a very disturbing matter.

'Ihe shock waves in the pressure signature appear as approximately vertical jumps in the wavefoTIn. On an expanded tirre scale the "rise tirre" of these shock jumps is of the order of 0.01 ros. It is this short rise t:inE that accounts for the impuls i ve loud "crack" that characterizes the sound of a gunshot . According to loudness theory supported by subjective tests on humans, the' shorter the rise tirre

(the greater the high frequency content) the louder and rrore startling is the re-sulting "crack"; the effect is, hCMever, expected to level off for a given subject.

The 0.01 ros rise tine of the gunshot report fails to rnimic the 0.1 to 10 ros rise tirre of sonic boc:ms. This is not thought to be serious for htunanS and large grazing animaIs: their ears cannot follCM the shorter rise tine (wi th i ts higher frequencies), hence do not diff~rentiate in loudness (the levelling off process). But the ears of many small animals (e.g., guinea pigs) can indeed follow shocks with 0.01 ros rise time, and these shocks then sound substantially louder to them than sonic boc:rns that sound equally loud to humans.

The literature on the rrn..tffling of firearms was researched wi th a view to finding rreans for extending the rise tirre of the waveform. It was found, however, -as might be expected - that the devices were prirnarily effective in greatly reducing the wave anplitude, vbich ruled them out. Straight-forward absorptive rreans - e.g., a fibreglass shroud - would likely disintegrate soon because of the muzzle blast. In fact, no sui tab Ie rreans for extending the rise tirre of a shotgun pressure signa-ture was found.

'Ihus it was concluded that the shotgun has several serious shortccmings as a portable sonic boem simulator. First is the extrerrely poor repeatability of the pressure signatures. Second associated with this, but not rrentioned earlier -is the lack of a practicabIe rreans for controlling the signal arrpli tude: i t -is inconvenient to vary the charge in the field. 'Ihird, is the difficulty of correct-ing the ultra-short rise tirre of the shotgun pressure signature, which - for small

animals

at least - will falsify our calibration in tenns of equivalent sonic

boem

overpressure. There are two reasons for this: (i) the inability of humans - who will be the comparaters for the calibration - to respond te the extended high fre-quencies accessibIe te the hearing of the snall animaIs, and (ii) the inability of the reproductive system of the loudspeaker driven booth, used in the calibration, to reproduce these high frequencies.

2 .2 Portable Shock Tube as a Sonic Boom Simulator

In view of these shortcanings, the shotgun concept was put aside, and all further effort was expended on an approach based on a shock-tube coupled to a hom.

The shock-tube concept was attractive because of the good reproducibility of the signatures, the potential for strong signals (good range), and finally because it appeared to lend i tself te rreans for controlling the rise ~.

Developrrent of the shock-tube driven hom has progressed through fi ve

stages7 designated Mark I through Mark V. A brief description of the characteristics of each follavs.

Mark I pyramidal wcxxlen hom wi th one square foot exit area pyramidal driver wi th one square inch maxirrrum cross-sectional area

air supply not self-contained Mark II - hom as in Mark I

cylindrical driver with three square inch

cross-sectional area 2

foot p1.lIIp air source capabIe of 19.75 Kg/cm Mark III two-slope pyramidal hom wi th exit area of nine

square feet

- driver and air supply as in Mark II

Mark IV - Mark III configuration wi th divergent acoustic lens (helium filled beach balI) inserted in IIDUth of hom Mark V like Mark IV in concept, but corrpletely redesigned

and refabricated, wi th an exponential alurninum alloy hom replacing the two-slope pyramid

exit area 7.1 sq.ft.

pressure battle compressed air supply lav-pass acoustic filter

Increasing the Rise Tirre

A common undesired feature of all efforts to lengthen the rise tirre of the sirmllated sonic boom was a reduction of the overpressure . Ta counteract this

reduction for Mark II and subsequent IIDdels, larger driver cross-sections and

higher driver pressures were investigated. The ~k V driver uses a 55.5 cm2 cross-sectional area and pressures as high as 14.1 Kg/cm. The driver pressure is sup~lied by a small canpressed air bottIe with an allONable rraxirnum pressure of 155 Kg/cm •

A pranising approach to increasing the rise tirre was suggested by a paper of Davy and Blad<stock9 in mich the refraction and diffraction of short N-waves by soap bubbles filled with argon and helium were investigated. 'Ihe helium filled bubble behaves as a defocussing (divergent) acoustic lens at the higher frequencies. 'Ihus the broad-band effect is that of a ION-Pass filter. As might be expected from spec-trum considerations , this did indeed yield a substantial increase in the rise tirre of the N-waves that passed through the gas-filled bubble.

It was decided

to

try this refracti ve approach in a MaJ:k IV version of the simulator. Instead of small soap bubbles, a 15-inch diameter beach balI was used. The size of the balI was mosen to be of the sarre order of magnitude as the wavelength of the pressure signature . The effect of introducing a helium filled balI into the rrouth of the horn was qui te dramatic . 'Ihe waves so produoed exhi-bi ted the desired extended rise-tirres of the order of 0.1 to 0.3 ros., Fig. 2. These rise-tirres are fairly typical of these in sonic baan. On the other hand, the rise-times exhibited in the absence of a heliumrfilled balI are typically 5

to

10

:fJ.Sec, mich are much toa short. 'Ihe introduction of an air-filled beach balI into the rrouth of the hom produoed na appreciable effec:r;indicating an ins igni fi

-cant influenee of the vinyl cover of the beach balI.

The heliumrfilled balI was initially used on the Mark V version of the simulator but was fotmd to be too weak to wi thstand the strong pressure wave and diaphragm debris from the new nore paverful driver. 'Ihus a much heavier balI made from gum rubber was instalIed, and it was found that this increased the rise time adequately even men deflated. Apparently the heavy gum rubber and protective

padding used in this reinforced balI blocked the higher frequency carponents of

the pressure wave and diffracted them to the sides; the diffracted signal was then absorbed to SOIre extent by 9bsoment material placed along the walls of the hom .

This thus achieved the desired low-pass filter effect by a different route not involving refraction by a gas lens.

Final Design

Photographic views of the current Mark V design fram difrerent angles are shawn in Figs. 3 to 5. The device is corrposed basically of a driver section, an exponential hom in mich a low-pass acoostic filter is nounted, and a portable oorrpressed air supply. Figure 5 shows the portable simulator with the heliurn-balI acoustic lens in place; this has since been replaced with the rubber barrier that, via diffraction and absorptive material along the walIs, serve3as a low-pass filter.

The shock-tube driver is cylindrical with a cross-sectional area of 55.5 square cm (8.6 square inches). 'Ihis increase in area over the Mark IV

(19.4 square cm or 3 square inches) ma.kes possible an approximate three-fold in-crease in the· overpressure at the exit plane of the hom. 'Ihe driver is fi tted with a pressure gauge (protected against :i.rrp~lsive changes of pressure) which reads to 200 potmds/square inch (14.06 kg/cm) and a quick-attach ooupling for pressurization as sham in Fig. 4.

Welded to the open end of the shock-tube is a plate which serves as a clamp for the diaphragm in conjunction with a similar plate on the exponential hom. 'l'he diaphragm is clanped between these plates by rreans of a quick-release system involving a two-way hinge and an over-centre locking rrechanism (Fig. 4). The quick-release rrechanism allows the diaphragm to be changed easily and does not require extra tools.

The hom expands fram an area of 55.5 sq.01l. (8.6 sq.in) at the throat to an area of 0.66 sq.m (7.1 sq.ft.) at the exit. A low-pass acoustic filter oorn-pcsed of a gum rubber barrier and fibreglass along the hom walls serves to extend the rise time by a rnechanism described earlier.

Pressurization of the shock-tube driver is p.a a small attached carpressed air bottIe (Figs. 3 to 5). 'Ihe capacity is 155 kg/cm (2200 psi), and i t is capabIe of delivering eight recharges to ~mum pressure (or more to lower pressures) • '!his small bottle can be refilled from a centrally located corrpressed air tank.

The (xmpressed air bottle was chosen over the manual purrp used wi th Mark IV be- J cause the

pump

required an unacceptably high effort from the operator.

'Ihe conplete sonic boom simulator is easily portable by one person,having a total weight of 11.1 kg (24.4 Th). Of this total, 2.6 kg (5.7 Th) is accounted for by the air bottIe. The overall length of the device is 1.00 m (39.5 inches) , with a maximum width at the nouth of the hom of 0.81 m (32 inches).

Operation of the simulator is tmcorrplicated. 'Ihe clamping plates are opened by unlatching the over-centre loek. A cellulose acetate diaphragm is placed

between the plates and locked in place wi th the over-centre elarrp and the two side elarrps. The nipple of the portable air supply is inserted into the socket on the driver and the valve is opened with a little care; air is slCMly admitted until the desired gauge pressure is attained. The diaphragm is then ruptured by operation of a plunger on the lCM pressure side: this is the "firing" aetion that initiates the "sonic boem".

A ccnplete description can be found in Ref. 10.

APPENDIX A: SPECIP<L REMARKSCCNCERNING SII'1UIATOR -CALIBRATICN

Basic to this portable sonie boom simulator is the concept of its eali-bration in terms of an equivalent sonie boom overpressure that sounds equally loud.

The judgerrent was made by subjects who individually listened

to

the reproduced sound in a booth. 'Ihe sonie booms used in the canparison all had 1 ros rise tirre.

We have since earried out a study of the statistieal distribution of rise tirres of a large body of NASA sonie boom rreasurerrents, ei ted in Ref. 11. If this distribution isr,in effect, weighted according to louàness (using the ideas of Ref. 12 and the sone-phon relationship) ene ean deduce an effective average rise tirre; this carES out

to

be 4.2 ros. Fran the rreasurements of Shepherd and

Sutherland (Ref. 13) sonie boom N-waves of 4.2 InS and 1 ros rise tirres,respeetively,

must have arrplitudes in ratio 1.95

to

1 (5.8 dB) for equal loudness. 'Ihus it would seem that to oornpare the sinnllated boom of the portable device wi th a sonie boom of 4.2 ros rise time the equivalent overpressures in the calibration curves, Figs. C-5 to C-lO, should be multiplied by a factor of about 2.

We are, hcwever, reluetant to ae~pt this canelusion at face value. It inplies that a 1 ros sonie boom at 50 Nim overpressure (equivalent to about 100 N/m2 at 4.2 InS rise tirre) will be unacceptably annoying to about 40% of all listeners , according

to

social surveys (cf. e.g., Ref.14). Subjeetively, listen-ing

to

the sound reproduced in our booth, we do not find the 50

N/m2

level at 1 InS t~ be irrpressi vel y loud or annoying; the level has to be raised to about

62 Nim

to

be unaeceptably annoying. Thus, we believe it should be nore

justi-fiable (and conservative) to multiply the equivalent overpressures in the calibra-tion curves, Figs. C-5 to C-lO, by a factor 2.0/1.25

=

1.6 to apply to sonie bOOIT'S of average rise tirres. 'Ihis adjustment does not allcw for subject familiari -zation and lack of the elerrent of surprise; thus it eould be overconservative.

APPENDIX B: 'FIELD l'1EASUREMENTS

The pressure field produoedby

the

portable simulator has been investigated and is reported in this appendix. ,'Ihe tests were oonducted outdoors wi th a naninal terrperature of 70 Of' • The ground at the test' si te was flat wi th a short grass cover, the soil being darrp during the period of the' tests.

Test equiprrent used in these tests were 2 Bruel & Kjaer type 4135 1/4 inch free field microphones, a Tektronix rrodel 555 dual beam oscilloscope, and a triggering microphone • Recordings that were later used in the subjecti ve loudness calibration were made on a Bruel and Kjaer FM tape recorder rrodel 7001. A schema.tic layout of the experirrental apparatus is shawn in Fig. B-l.

To provide a canplete calibration of the characteristic waveforrns generated by the simulator two rnicrophone pos i tions were errployed. One rnicrophone was rrounted one inch and the other 50 inches above the ground. The pressures encountered at the laver rnicrophone position would be typical of the simulator perfornance for small

anirnals and birds at ground level. 'Ihe upper rnicrophone posi tion would provide data at a height typical of larger anirnals.

To establish the effect of ooserver position above ground level sene tests were perfonred using the device prior to installation of the low-pass acoustic

fil-ter. A typical result is shawn in Fig. B-2. The rise tirre of the upper trace is about 0.010 rns while that for the lower trace is 0.5 rns, both being reoorded simul-taneously. This difference in rise time resulting from height above ground Ireans that animals near the ground receive a simulated sonic boem which has a rise tiIre typical of aircraft generated sonic booms, while larger animals would recei ve an unrealistically sharp pressure wave. The cause of the variation of waveforrn wi th elevation has not been investigated but probabIe causes are refraction due to

tem-perature gradients and the aooustic inpedance of the ground. Af ter installation of the acoustic filter in the hom, the rise tirre of the elevated wave was extended to approximately 0.2 rrs as shavn in Fig. B-3 while the ground wave maintained aJ:::out a 0.5 rrs rise tirre. The changes of waveforrn shape wi th pressure and distance are srnall, however, the variation with azimuthal angle is rrore pronounoed as seen in Fig. B-4. The range from 00 _{(head on) to 90}0 _{(perpendicular) is covered with no} catastropie change in either peak overpressure or rise tirre with angle, only a gradual decrease in pressure and increase in rise time as the angle was increased.

Since the rise tirres of the pressure waves are reasonabl y constant, the pararreter rernalll1Ilg to be tabulated is the peak overpressure . Shock tube theory indicates that the increase in overpressure with driver pressure should be con-siderably less rapid than linear. This variation at specified distanees is shown in Figs. B-5 ani B-6. The distance of the observer from the device is another

im-portant parameter in the variation of the peak overpressure as illustrated in Figs. B-7 and B-8.

previously the change of peak overpressure with azimuthal angle was briefly discussed. 'Ibis variation is shawn for the elevated and ground rnicrophones respec-tively in Figs. B-9 and B-lO. The maximum angle at which this device yields useful overpressures is indicated by the azimuthal data at about ~ 300 from the hom axis.

The above data was collected under oonditions as consistent as possible in outdoor testing. There was an indication fran prelirninary data that with lower arrbient terrperatures (in the range of 40Üp) soIretlhat higher peak overpressures may result. In addition, a substantially different ground surface (e.g., dry loose

gravel) can rrodify the neasured wavefonns.

'!he pressure wavefonn at the operator positian for the maximum driver 2 pressure of 14.1 kgl square au (200 pounds/square inch) is approximately 400 Nim .

Figure B-ll shavs the pressure waveform recorded at the operator positicn for a driver pressure of 140 psig. '!he waveform differs cansiderably fran those encoun-tered in front of the hom. '!he peak anplitude of 400

n/square

m (8.4 poundsl square ft) while high could not be considered a hazardous level if ear protectors are wom by the cperator.

APPENDIX C:CALmRATION

o

m

TEm1S OF E;dUIVALENT SClUC BCX:l1 OVERPRESSURE

'lhe waveforms produced by the portable simulator are considerably different

in shape than that of a typical senic boom; hence I in order to have a significant

calibration of the device I an equivalent sonic boom overpressure for the variaus

field positions is required. Signatures were tape recorded for a variety of driver

pressures I d:>server distances I and azimuthal angles. These recorded waves were

re-produced in the UTIAS IDudspeaker-Driven Sanic Boom Booth Si:rrulator paired with

sonic bcx:m type N-waves (chosen wi th a 1 InS rise tirre and 100 rns duration) of

vary-ing arrpli tude. A jury of subjects ccnpared the loudness of the waveforrns in each

pair of signals

te

calibrate an equivalent senic baan overpressure .

To individually calibrate eadl data point presented in Appendix B was

irrpractical due to the tirre required for each calibration in the Booth SiImllator;

therefore , representative wavefonns (see Figs. C-l to C-4) were dlosen for

cali-bration on the basis of rise tiIre and overall shape. In the booth I the equivalent

overpressure (re an N-wave with 1 rns rise ~)was determined by a jury of subjects.

A :rrultiplication factor was cbtained for the different waveforrns by dividing the

equi valent overpressure by the rreasured overpressure. For sorre wavefonns this was repeated at different overpressures with the sarre :rrultiplication factor being

d:>tained. A single multiplying factor was cbtained for the data 1 inch abave ground.

Separate factors were found for the wavefonns 50 inches above ground at 15 and 30

rreter distance and at angles of 00 , 22-1/20 and 450 azimuth. The data at 60 and

120 rreters was scaled with the sarre factor as at 30 m and the data at 900 aziImlth

was scaled according te the 450 calibration. 'These multiplication factors were

then applied

te

the data presented in Appendix B to produce dlarts of eqUî valent

overpressure. The variation of this quantity with driver pressure at specified distances is ShONIl in Figs. C-5 and C-6. The data is cross-plotted in Figs. C-7

and C-8

te

shav the relationship between the equivalent overpressure and distance

with driver pressure constant. These calibrated overpressures Var::! with aziImlthal

angle as shONIl inFigs. C-9 and C-IO. If one wishes to compare these siImllated

waves with N-waves of 4.2 rns rise tiIre as was discussed in Appendix A., then the

equivalent overpressure of Figs. C-5 to 0-10 :rrust be multiplied by a factor of 1.6to 2.0.

In all cases the equivalent overpressure (based on an N-wave wi th 1 ms

rise tirre and 100 ms duration) was higher than the rreasured overpressure, due

primarily to the shorter ri se tirres (0.2 to 0.5 rns) and darrped oscillations

( ':::: 200 Hz) of the simulated sonic booms. Since hurnan subjects were used for the

calibration i t is strictly va lid only for animals whose hearing belav 5000 Hz does not differ significantly fran hurnan hearing. We have been told that this similarity

is approximated in the larger grazing animals and serre bird~. Small animals (e. g . I

guinea pigs , dlindlilla) have extended high frequency response (e.g. I to 50 KHz) I

but this shouldnot be a factor; the filtering in the hom wfts deliberately designed in to effectively eliminate all frequencies above 5 KHz.

-REFERENCES

1. Arlon. "US Supersonic Transport Program", Aviation Week and Spaee Tedmology, 92, No.l, Jan 5,1970, pp.26-88.

2. Arlon. ''New Studies for an Arrerican SST", New Seientis't, April 26, 1973, p.218.

3. Arlon. "A prelirninary Evaluation of 1) Noise, 2) Air Pollution, 3) Stratospherie Effects Related to SST Operations ", prepared by Aviatiori Planning &' Research

Division, Civil Aviation Branch, Canad. Air Transportation Administration, Report R71-1, April 1971.

4. Dahlke, H. E., Kantarges ,G .. T., Siddon, T. E., and Van Houten., J. J. "The Shock Expansion Tube and lts Application as a Sonie Boom Simulator!',' NASA

CR-I055, prepared by LTV Research Ctr., Western Division, Arlaheirn, Calif. 1968.

5 • Froobse, ~., Parrrentier.( G., and Mathieu, G., "Simulateur mcbile de bangs soniques a double tube a dloe pour étude des réaetions de sursaut.

Enregistrerrent des ondes de pression en fonetion des distanees ", Rapport-Technique RI' 16/71, lnstitute Franco-Allernan.d de Reserches de St. Louis, St. Louis, France, 1971.

6 . Ellis, N. D., Rushwald, I. B., and Ribern, H. S. "Prelirninary Evaluation of _ Shotgun and Shock Tube Driven Hom as Portable Deviees for Field Simulation of Sonie Boorrs", Univ. of Toronto, lnst. for Aerospaee Studies, prepared for CivilAeronauties, CMA, Ministry of Transport, Report UTIAS/CIV AERO #1 (1973).

7 . Ellis, N. D., Rushwald, I. B., and Ribner, H. S. "Progress Report. Developrrent of Portable Sonie Boom Sirrulator for Field Use", uni v. of Toronto, lnst. for Aerospace Studies, prepared for Cj. vil Aeronauties, CATA, Ministry of Transport, Report UTIAS/CIV AERO #2 (1973).

8. Glass, l . I . , Ribner, H. S., and Gottlieb, J. J. "Canadian Sonie Boan Simula-tion Faeilities". Canad. Aeronaut. & Space Jour., 18, No.8, pp.235-246,

Octcber 1972.

9 • Davy, B. A., and Blaekstock, D. T. "Measuranents of the Refraetion and Diffrae-tion of a Short N-wave by a Gas-Filled Soap Bubble". J. Acoust . Soc. Arrer. 49, pp.732-737 (1971).

10. Ellis, N. D., Ru.shwald, I. B., Ribner, H. S. "Development of Portable Sonie Boom Simulator for Field Use". univ. of Toronto, lnst. for Aerospace Studies, prepared for Civil Aeronauties, CATA, Ministry of Transport, Report urIAS/CIV AERO #3 (1974).

11. Pierce, A. D., Mag1ieri, D. J. "Effects of Atrnospherie Irregularities on Sonie-Boom Propagation " • proceedings of the Seeond Sonie Boom Symposium, Houston, 3 Nov, 1970, reprinted franJe Acoust. Soc. AlTer. 51, pp.695-701,

(1972) •

-12. Johnson, D. R., Rcbinsan, D. W. "Procedure for calculating the Loudness of Sonie Bangs". ACUSTICA, Vol. 21, pp.307-318, 1969.

13 • Shepherd, J. J., Suther land, W. W. "Re1ati ve Annoyanee and Loudness of Various Simu1ated Sonie Boom Waveforms". NASA CR-1192, Septenber, 1968.

14 . Ribner, H. S. "OVerview and Corrp1errentary Remarks". Proceedings of the Secand Sonie Boom Syrrposium, Houston, 3 Nov, 1970, reprinted from J. Aeoust. Soc. Amer. 51, pp.672-674 (1972).

FlGURE 2

'lYPlCAL WAVEFORM PRDOCED

BY MARK IV PORI'ABLE

SThUIA'IDR.

Driver Pressure

=

130

psig.

Distanoe

=

30 ffi.

Horizootal

= 1.0 ~/div.

Vertical

=

26

N/m

/di v •

FlGURE 1

. SAMPLE WAVEFORM PROOUCED

BY SHCID3UN BLAST.

Distanoe

=

30.5

m.

Horizontal

=

O.~/div.

Oscilloscope Signal Hicrophone Portable S~lator

I~=I

Trigger Mîcrophone Signal Hicrophone

FlGURE B-3

WAVEFORMS PRODUCED BY

SIMU-IATOR API'ER rnSTALLA.TICN OF

LeW-PASS FILTER.

Driver Pressure

=

80 psig. Distance

=

30 ffi.

Horizontal

=

0.5 ms/div. Vertical

=

50 N/m2

/di

v . Top Trace 50" above ground. Bottan Trace 1" above ground.

FlGURE I

B-a

WAVEFORMS PRODUCED BY

SIMU-IATOR PRIOR TO rnSTALLATlOO

OF UW-PASS Acc:vsrIC FILTER.

Driver Pressure

=

60 psig. Distanee

=

30 ffi.

Horizontal

=

O. 5 ~/di

v.

Vertical

=

100 Njm /div.

Top Trace 50" above ground. Bottom Trace 1" above grotmd.

FlGURE B-4 (b) 22-1/2°

VA..tUATICN OF WAVEFORM vITTH

AZIMU'IHAL ANGLE.

Driver Pressure

=

80 psig.

Distance

=

30 In. Horizontal

=

o.

5 ~/di v .

vertical

=

50 N/m

/di

v.

FlGURE B-4 (a) 0°

VARIATICN OF WAVEFORM

wrrn

AZIMJl'HAL ANGLE.

Driver Pressure

=

80 psig.

Distance

=

30 In.

Horizontal

=

0.5

WS/

div •

Vertica1

=

50

N/nf /di v.

FlGURE B-4 (d) 90°

VARIATICN OF WAVEFORM WITH AZ IMUTHAL ANGLE.

Driver Pressure

=

80 psig.

Distance

=

30 m.

Horizontal

=

0.5 rrs/di v.

Vertical

=

50 N/m2 /di v .

FlGURE

B-4 (c) 45°

VARIATICN OF WAVEFORM WITH AZIMUTHAL ANGLE.

Driver Pressure

=

80 psig.

Distance

=

30 m.

Horizontal

=

o.

5 ~/di v .

1• 15 30 na .... • • 60 • 120 • 320 ID 280 240

i:

₃ 200 ffi

I

G 160 120 0 80 40

Drl ver Presauno (po1g)

FlGURE B-5: OVERPRESSURE VS. DRIVER PRESSURE 50" AInVE GROUND

1

I

360 320 280 240

!

16 u @ 15 ""tres

~

30 • .. 60 " 120 • o o 60 Driver

_ure

(1'019)

320 ® 200 pdg driver pressure & 150" " " (!) ua )( 80 o 60 310 ~ ~

:

240 120 80 30 60 90 120 Distance (1'1)

FlGURE B-7: OVERP~SURE VS. DISTANCE 50" 'ABQVE GROUND

360 320 ~ 200 ps!g driver pressure 150" " " o 120 )( 80 0 60 280 W 40 + 20 240

~

I

200 160 120 80 40 30 90 DistanQ! (m)

.---

-f!) 15 f"Ctres. 20 psig driver pressure

(i) 3 0 " 80" " " 0 6 0 " BO" 60 50 20 10 30

FlGURE B-9: OVERPRESSURE VS. AZIMUTHAL ANGLE 50" ABOVE GROUND

90

BO

o 15 rretres, 20 psig driver pressure

0 3 0 " B O " " "

o

60 BD " 70 10 30 60 90 _{lIZ_thalllngle} (0)

FlGURE B-11 WAVEFORM MEASURED AT OPERATOR POSITICN

Driver Pressure

=

140 psig.

Horizontal

=

1

rns/~v.

.

-FlGURE C-2

REPRFSENTATIVE y,.1AVEFORM USED FOR CALIBRATICN OF PORTABLE SIMUIA'IDR.

Driver Pressure

=

80 psig.

Distance

= 30 m.

Horizontal

=

5 ms~div.

Vertical

=

25 N/m /div.

FlGURE C-l

REPRESENTATIVE ~"lAVEFORM

USED FOR CALIBRATICN OF PORI'ABLE SIMULATOR.

Driver Pressure

=

20 psig.

Distanee

=

15 m.

Horizontal

=

5

ITEidi

v . Vertical

=

25 N/m

/di

v •

FlGURE C-4

~RESENTATIVE WAVEFORM

USED FDR CALIBRATICN' OF

PORI'ABIE SIMULATOR.

Driver Pressure

=

80 psig. Distanee

=

30 ffi. Azirnutha1 Ang1e

=

45° Horizontal

=

5rns/div. vertical

=

25 N/m2/div. FlGURE C-3 REPRESENTATIVE WAVEFORM

USED FOR CALIBRATICN OF

PORI'ABIE SIMULATOR.

Driver Pressure

=

80 psig. Distance

=

30 m.

Azirnutha1 Img1e

=

22-1/2° Horizontal

=

5 msLdiv. Vertica1

=

25 N/mf/div.

1

~

~

~ 450 300 lSO o 15 ITetres o 30 6 60 + uo 30 60 o

8

0 --~---+-90 120 lSO UlO

Driver Pressure (pBig)

FlGURE C-5: EFFECTIVE OVERPRESSURE VS. DRIVER PRFSSURE 50" ABOVE GROOND

450 O lSrtetres o 30 6 60 +uo 0 300 0 N~ 2;

i

lSO

Driver Pressure (psiq)

450

300

lSO

20 40

o 200 PRi9 driver pressure o lSO Cl 120 + 80

o

60 " 40 X 20 60 80 100 120 Diotanoo (~)

FIGURE C-7: EFF'EX:I'IVE OVERPRESSURE VS. DISTANCE 50" ABOVE GROOND

450

300

150

o 200 psig driver pressure Cl lSO o 120 l( 80 0 60 " 40 + 20 60 90 120 Diftt.>oe (m)

100

o 15 rretres, 20 psig driver pressure

o

30 80 " 6 60 80 "

o 30 60 90

)\zimlthal Mgle (')

FlGURE C-9: EFFECrIVE OVERPRFSSURE VS. AZIMUTHAL ANGLE 50" ABO\lE GROUND

o 15 rretres, 20 psig driver pressure

o 30 80 <9 60 80 " 40 20 o 30 60 o I\ziruthal JIngle (')

urIAS TroINlCAL NCIl'E NO. 190

Institute for Aerospace Studies, University of T oronto

DEllEIDPMENr OF A PCRTABLE OCNIC BOCM SJMJIAroR FCR FIEID USE

Ellis, N.O., Rushwald, I. B., Ribner, H. S. 11 pages 26 flgures 1. Senie Boan 2. Simulator-Portable 3. Faeility

1. Ellis, N.O., Rushwald, l.B., Ribner, H. S. I l. urIAS TechnicalNote No.190

A portable sonie bo::xn simulator has been developed for field tests on wildlife. Previous portable sümlators have been rriXlile only by truck or trailer; the present device weighs 24.4 potmds including peripherals and is easily carried by ene parsan. It consists of a shock ttbe charged by a OCIlPressed air bottle, coupled to an exponential hom. A lew-pass acoustic filter is ITOWlted in the hom; it serves to contral the rise ti.ne of the pressure

signature . The silTUlated senie bocms mimie the loudness of typical sonie bocms and have

crnparable overpressures and rise tirres. Calibration of the effective loudness is by sub

-jeetive eooparison with idealized standard senie bocrns (N-waves). The calibration is carried out in the recently developed urIAS loudspeaker dri ven senie boan booth. The loudspeakers

aecurately reproduoe the signatures to be ea>pared which have been tape reoorded, and they

are judged against the N-waves ·for equal loudness by an cbserver in the booth. The outcare

is e><pressed as equivalent sonie baan overpressure (LIp) as a functian of shock-tube driver

pressure and cbserver position relativeto the portable simllator.

~

Available co pies of th is report are limited. Return this card to UTIAS, if you require a copy.

urIAS TroINlCAL Nare NO. 190

Insl:itute for Aerospace Sl:udies, Universil:y of T oronl:o

DEl/EWPMENr OF A PORTABLE SCNIC BOCM SIMUIA'lIJR FOR FIElD USE

Ellis, N. 0., Rushwald, I. B., Ribner, H. S. 11 pages 26 figures

1. Sonie Boon 2. Simulator-Portable 3. Faeility

I. Ellis, N.O., Rushwald, l.B., Ribner, H. S. Ir. urIliS Technical Note NO.190

A portable sonie bo::xn simulator has been developed for field tests on wildlife. Previous

portable simulators have been rrobile only by truck or trailer; the present device weighs 24.4 pounds including peripherals and is easily earried by one person. It consists of a

shock tube charged by a OCIlPressed air bottle, coupled to an exponential hom. A la;-pass

aooustic filter is ITOWlted in the hom; it serves to contral the rise t.i.rre of the pressure signature . The sinulated senie bcx:lns mimic the loudness of typical senie bcoms and have

eooparable overpressures and rise tirres. Calibration of the effecti ve loudness is by sub

-jective ccrrparison with idealized starrlard senie boans (N-waves). The calibration is carried

oot in the recently developed urIAS loudspeaker driven sonie boem booth. The loudspeakers

a=ately reproduoe the signatures to be eCJ'Pared which have been tape reoorded, and they are jtrlged against the N-\yaves for equal lou:::1r.ess by an oosezver in the booth. 111e outa::ne is e><pressed as equivalent sonie boom overpressure (LIp) as a function of shock-tube driver

pressure and cbserver positian relative to the portable simllator.

~

_V

Available copies of th is report are limil:ed: Return this card to UTIAS, if you require a copy.

urIAS TroINlCAL NOlE NO. 190

Instil:ul:e for Aerospace Sl:udies, Universil:y of T oronl:o

DEVELOPMENr OF A PORTABLE SCNIC BOCM SIMJIA'IDR FOR FIEID USE

E11is, N. 0., Rushwald, I. B., Ribner, H. S. 11 pages 26 figures 1. Senie Boan 2. Simulator-Portable 3. Faeility

I. Ellis, N.O., Rushwald, l.B., Ribner, H. S. Il. urIAS Technieal Note No.190 A portable senie bOClll simulator has been developed for field tests on wildlife. Previous

portable sinulators have been nDbile only by truck or trailer; the present device weighs 24.4 PÇ>unds including peripherals and is easily carried by one parsOI1. It consists of a shock ttbe eharged by a OCIlPressed air bottle, coupled to an-exponential hom. A lew-pass

aooustic filter is rrounted in the hom; it serves to control the rise tirre of the pressure

signature • The siJTUlated sonie bocms mimie the loudness of typical senie boons and have

eooparable overpressures and rise tirres. Calibration of the effective loudness is by sub

-jective OCIlParison with idealized standard senie bocrns (N-waves). The calibration is earried

oot in the recently developed urIAS loudspeaker driven senie bOClll booth. The loudspeakers

a=ately reproduoe the signatures to be e~ which have been tape reoorded, and they

are j udged against the N-waves ·for equal loudness by an cbserver in the booth. The outcare

is e><pressed as equivalent sonie baan ooerpressure ~p) as a function of shock-tube driver pressure and cbserver posi tian relativeto the portable simllator.

~

Available CO pies of this report are limited. Return this card to UTIAS, if you require a copy.

urIAS TroINlCAL Nare NO. 190

Insl:itul:e for Aerospace Sl:udies, Universil:y of T oronl:o

DEl/EWPMENr OF A PCRI'ABLE SCNIC BOCM SIMUIA'lIJR FOR FIEID USE.

Ellis, N. 0., Rushwald, I. B., Ribner, H. S. 11 pages 26 figures

1. Sonie Boon 2. Simulator-Portable 3. Faeility

I. Ellis, N.O., Rushwald, l.B., Ribner, H. S. Ir. urIAS Technical Nate No.190

A portable sonie bo::xn simulator has been developed for field tests on wildlife. Previous

portable sinn.>1ators have been rrobile only by truck or trailer; the present device weighs

24.4 pounds ineluding peripherals and is easily carried by one person. It consists of a

shock ttbe charged by a OCIlPressed air bottle, coupled to an exponential hom. A la;-pass

aooustic filter is rrounted in the hom; it serves to contral the rise tirre of the pressure signature . The siJTUlated sonie bocms mimic the loodness of typical senie boons and have

eooparable overpressures and rise tirres. Calibration of the effective loudness is by

sub-jeetive carparison wi th idealized starrlard sanic bcx:rns (N-waves). The calibration is earried oot in the recently developed urIAS loudspeaker driven sonie boem booth. The loudspeakers

a=ately reproduoe the signatures to be ea>pared which have been tape reoorded, and they

are judged against the N-waves for equal loudness by an cbserver in the booth. The outocrre is expressed as equivalent sonie boan overpressure (LIp) as a function of shock-tube driver pressure and cbserver positian relative to the portable simllator.

~

_V

.

"~

I

'