LETTERS
TO
THE
EDITOR
We would like to expressour thanks to Mr. W. H. Dingle,
TransducerGroup Leader, for his generousadviceand continued
interestthroughoutthe work.
395
/
f:98•
k½/s /
* This work arose as part of an investigation under Defence Research
Board Project No. D12-55-25-02 and is published with permission of the
T* IOOC.
Board.
• H. G. Baerwald and D. A. Berlincourt, J. Acoust. Soc. Am. 25,703-710
/
(1953).
2 Huelet, Neuhaus, and Kolb, J. Acoust. Soc. Am. 26,696-703 (1954).
* D. A. Berlincourt, "Aging in barium titanate ceramics," Brush Laboratory Company Technical Report No. 4.
•United Kingdom Provisional Patent Specification No. 11365, filed
April 24.1953.
• The samples were prepared by Mr. Ian F. Wright, Industrial Minerals
Division, Department of Mines and Technical Surveys.
6 Full details of the methods of preparation and measurement of the
constants of the samples will be published in a future paper.
7 C. B. Sawyer and C. H. Tower, Phys. Rev. 35,269-273 (1930).
/
/
Comments on "Mechanical
Mechanism of
Destructive Effects of Sound on Tissue"
FLOYD
DUNN
BioacousticsLaboratory, University of Illinois, Urbana, Illinois
(Received September 25, 1956)
A recently proposed theory to explain some of the nonthermal. noncavitation effects of intense high-frequency sound on living tissue is discussed in the light of more recent experiments. It is concluded that the
assumption of the theory that the observed effects are caused by unidirectional forces (proportional to the square of the particle velocity amplitude) of the acoustic field which create sufficiently great displacements in
structural members of the tissue to produce elastic failure. is not supported
by experimental results.
/
F•G. 1. The experimentally determined paralysis relation. This curve
displays the relationship between the reciprocal of the exposure time and
the square root of the acoustic intensity for the production of paralysis
of the hind legs of the irradiated young mice.
and a hydrostaticpressureof one atmosphere?
• A statistical
analysisof the data is madein orderto determinethe relationship
between the time duration of irradiation and the chosen acoustic
field variable.
A linear relationshipobtainsfor the paralysisrelation (the
reciprocalof the time durationof exposurefor the end point to
occuras a functionof the squareroot of the acousticintensity)
Narecent
paper
byWelkowitz
•aspecific
mechanical
mecha-
nism is proposedto explain some of the nonthermal, noncavitationeffectsof intensehigh-frequencysoundon living tissue.
The proposedtheory assumesthat the observedeffects are
producedby unidirectionalforcesproportionalto the squareof
the particle velocity amplitudeof the acousticwave. It is hypothesizedthat these forcescauseelastic failure in the system
when a structuralcomponentof the tissueis displacedfrom an
fromapproximately
48 w/cm• (30 sectimedurationof exposure)
to 160 w/cm• (0.8 sec time duration). The paralysisrelation is
shownin Fig. 1. A statisticalanalysisof the nine experimentally
determinedpointsin the linearportionyieldsa valuefor the
standarddeviationof the pointsfrom the straightline of bestfit
of 4-1.3%. An analysisperformedto determinethe degreeof nonregionyieldsa
equilibriumpositionto a secondpositionfrom which recovery linearityof the "linearportion"of the threshold
of suchmagnitudethat the deviationfrom
cannotoccur.The quantitativeformulationof theseassumptions quadraticcoefficient
linearcurveis considerably
lessthan
leadsto the followingrelationfor the irradiationtime, lB, required the statisticallydetermined
the standarddeviation.The paralysisrelation,therefore,possesses
for failure to occur,
an extensiveregion,whichis, to a highdegreeof accuracy,a linear
relationship
betweenthe reciprocal
of the exposure
time and the
t -\•-/J'
whereR is a viscousforcecoefficient,K is an elasticconstant,u0 is
the thresholdvalueof the particlevelocityamplitudebelowwhich
failure never occurs,and u is the particle velocityamplitudeat
whichfailureoccursin time tB. Welkowitzcitestwo examplesof
experimental
data, oneby Fry et al.• and anotherby Welkowitz
and Fryain orderto supporthis theory.The resultspresented
by
Fry et al. give the minimumirradiationtime as a functionof the
transducerdriving voltagerequiredto produceparalysisof the
hind legs of frogs irradiated in the lumbar enlargementof the
spinalcord.The work of Welkowitzand Fry givesthe minimum
irradiationtime requiredfor a 10% permanentreductionof the
action potential of excisedfrog muscle tissue as a function
of the sound pressureamplitude. For both sets of data, the
writer plots the minimum irradiation time as a function of
squareroot of the acousticintensity,i.e.,
t•0-• = m(u- u0),
(2)
wheret•0-t is the reciprocal
of the timedurationof exposure
corre-
sponding
to theparticlevelocityamplitude
u required
to produce
paralysis
ofthehindlegsof50%oftheanimals
andmis theslope
of the linear curve.
FromFig. 1 it is clearthat the valueof uo,the particlevelocity
amplitude
belowwhichfailureneveroccurs,
cannotcorrespond
to
a valueof I• greaterthan 7.0, i.e., the lowestexperimentalpoint
--ln[1--(uo/u) •] and obtains a reasonably linear relation from
which the constant(R/K) of Eq. (1) can be evaluated.
One of the major projectscurrentlybeingconductedat this
laboratoryis a comprehensive
investigation
involvingthe determination of ultrasonicdosagerelationsfor a given functional
endpointin a youngmammal3• The purposeof this study is to
obtainexperimental
resultswhichwill befruitful in the elucidation
of the physicalmechanism
involvedin producingthe observed
i
functionalchange.Although this study is still in an early stage,
someinterestingresultshave alreadybeenobtained.The relation
betweenthe reciprocal
of the time durationof exposure
for paralysis of the hind legsof youngmice and the squareroot of the
acousticintensity has been determinedwith a high degreeof
accuracyfor a frequencyof 982 kcps,a basetemperatureof 10øC
FzG.2. The experiment• paralysisrelationplottedin accordance
with the eqoation ia • --(R/•)
In(! --Ie/Z).
396
ACOUSTICAL
SOCIETY
NEWS
on the linearportionof the paralysiscurve.The maximumvalue
of u0 which need be considered,therefore,correspondsto an
intensityof 49 w/cm•.
Figure 2 showsthe experimentallydeterminedpaxalysisdata
considerably
restrictedby comparison
with the work on the
linearrelationship
betweenthe exposure
time (to produceparalysisof the hind legsof the animalsirradiated)and the function
•W. Welkowitz. J. Acoust. Soc. Am. 2?. 1142 (1955).
• Fry, Tucker, Fry. and Wulff. J. Acoust. Soe. Am. 23, $64 (1951).
a %r. •Velkowitz and V•. J. Fry. J. Cellular Comp. Ph¾•iol. 48, (1956).
• W'. J. Fry and Fo Dunn. J. Aeoust. Soc. Am. 28. 129 (1956).
a F. Dunn and W. J. Fry. Paper HD-6.2nd I.C.A. Congress,Cambridge,
Ma•aehusetts. (June 21.1956).
mousespinalcord.
It is, therefore, concludedthat the theory proposedby
Welkowitz, which assumesthat the observedeffectsare produced
plottedin accordance
with Eq. (1) for twovaluesof u0.The cases by unidirectionalforcesproportionalto the squareof the particle
considered
correspond
to valuesof uoof 49 w/cm• (planetraveling velocityamplitudeof the soundwave and that theseforcescause
wave case),the value indicatedabove, and 46 w/cm•. The two elastic failure in the system when a structural componentis
curvesareshownplottedto includethe full rangeof valuescovered displaced
from an equilibriumpositionto a secondpositionfrom
by the experimental
measurements
for whichthe linearparalysis wldchrecoverycannotoccur,is not supportedby morerecentand
relation was obtained. It is clear from the curvesof Fig. 2, that a
moreaccurateexperimenta•results.
--in(1--Io/I)
is not obtained,for the factor (R/K) constant,as
postulatedby Welkowit•..The curvewhichcorresponds
to the
46 w/cm2 value illustratesthe greaterdeviationfrom the linear
form requiredby the theoryof Welkowitzwhenvaluesof u0 less
th•n that corresponding
to an intensityvalue of 49 w/cm2 are
chosen for the threshold value.
Concerning
the experimental
verificationof the theoryproposed
by Welkowitz, the following considerationsshould be noted.
Flint, the two setsof experimentsusedby the author to support
his proposedtheoryXawere not earfled out with precisionand
accuracycomparableto that of the morerecentwork.ASSecond,
the rangeof the parametemstudiedby Wetkowitzand Frys was
THE
JOURNAL
OF THE
ACOUSTICAL
SOCIETY
OF AMERICA
Erratum: Equivalent Circuit for Spherical
Radiation
in a Solid
[J. Acoust. Soc. Am. 28. 724 (1956)'[
V.
SAL•O•
$,anford Research Institute. ,•!enlo Park. California
N theillustration,
the denominator
of the expressiou
for the
complianceC is in error. For 2(l--a) reaA2(1--2a).
VOLUME
29. NUMBER
3
MARCH.
1957
AcousticalSociety News
Special Summer Program on Noise Reduction at
the Massachusetts Institute of Technology,
August, 1957
(1) What can typologicalstudiescontributeto historicalcomparative linguistics?
(2) The importanceof distributionversusother criteria in
linguisticanalysis.
A Spedal SummerProgram on Noise Reduction,under the
(3) To what extent can meaningbe saidto be structured?
(4) What can the new techniquesof acousticalphonetics
contributeto linguistics?
instructingstaff of M.I.T. anddistinguished
industrialengineers,
is beingofferedat M.I.T. in August,1957.The programcomprises Therewill be in additionmeetingsat whichspecialproblems
two one-weekunits. From Monday, August12 throughFriday, will be treatedin detail.Of interestto readersof the Journalare
August 16, the fundamentalsof noisereductionwill be taught, the sectionsentitled "Mathematical linguistics"and "New
and from Monday, August 19 throughFriday, August 23, new
electro-acoustical
equipment of value to linguists. Practical
advancesin the scienceof noisecontrolwill be taught
applications:
machinetranslation,phonetictypewriters,synthetic
The programis directedtowardthe manwith a noiseproblem, speech."
rather than toward noiseexperts.In the first week, the behavior
Attendanceat the Congress
is restrictedto thoseinvited by the
directiou of Professor Leo L. Beranek with assistance from the
of sound waves, instrtm•entationfor noise measurement,fundamentals of hearing, soundin enclosures,acousticalmaterials, and
principlesof vibration isolation will be discussed.In the second
week, criteria for noise control, ventilation system quieting,
quieting of officebuildingsand homes,designof mufflers,instrumentationfor vibration measurement,machineand shopquieting,
train and automobilequieting,noisefrom air jets and jet engines,
quietingin the aviationindustry,instrumentationfor measurement of high intensity noise fields, and case historieswill be
presented.
Studentsmay attend either or both of the weeks.
Exhibits, a field trip, and entertainmentfeaturesare provided
for, in addition to the formal material. Low-cost dormitory
facilitiesfor individualsor couplesand cafeteriasare available.For
information,write to the Director of the SummerSession,MassachusettsInstitute of Technology,Cambridge39, Massachusetts.
•)IRECTOR O1• THE S•R
MASSACHUSETTS INSTITUTE
SESSION
OF TECHNOLOC.¾
CAM'BRII)C.E
39, MASSACHUSETTS
organ/zingcommittee. Personswho are interestedin attending the
Congressbut who have not receivedinvitations are requestedto
apply for invitations and further informationto the Secretaryof
the Congress:
Miss Eva Sivertsen
Kirkeveien 98 AIII
Oslo NV
Norway
International Symposiumon the Phonatory
Function of the Larynx
Dr. R. B. Vallancien,Head of the Laboratoryof Oto-POlinOLaryngologyof the Faculty of Medicineof Paris,summarizes,
as
follows,the recent International Symposiumon the Phonatory
Functionof the Larynx, held in Paris, October20-21, 1956.
The Symposium
wasorganizedby ProfessorAubin of the Chair
of Oto-Laryngologyof the Faculty of Medicine of Paris.
After two anatomiccommunications
by Dr. Truffert and Pro-
lessorRethi about the new researches
relatingto vocalmuscles
and their innervation,Dr. van den Bergg•ve a critiqueof the
The EighthInternationalCongress
of Linguistswill takeplace nenrochronaxic
theory.Despitethe author'sarguments,
and on
in Oslo,Norway, from August5th to 9th, 1957.In its plenary the basisof his own electromyographic
experimentation,
he calls
scssious
the followingfour topicswill be treated:
into questiontheir experimentalconclusions.
Congressof Linguists