TECHNICAL NOTES AND RESEARCH BRIEFS

une Flamme," Czechoslovak J. Phys., Sec. B, B22, No. 5, 394-397 (1972)-1. Acoustic waves have been excited in a flame seeded with potassium. It is shown that the amplitude of the excited wave is proportional to the frequency of a harmonic perturbation imposed on the plasma. This suggests a means of ultrasonic excitation, the limitations of which are analyzed. [Order No. N72-32660.-]

Conditions of Coherence in Diffraction Spectra Produced in Liqu.i.ds on Ultrasonic Standing Waves--R. Baer •Translation of "Uber die Koh•irenzverh•iltnisse in den an stehenden Ultra- schallwellen in Fltissigkeiten erzeugten Beugungsspektren," Hel- vetica Phys. Acta 8, No. 7, 591-600 (1935)•. Experiments, ducted to determine which of the different diffraction spectra produced on ultrasonic standing waves in liquids through the diffraction of light are coherent, i.e., can be brought to interfere with each other, are described. The result is the following: any arbitrary pairing of two spectra with even ordinal numbers (including zero order) possesses at least one common component of coherent light; the same is true for any pairing from the group of spectra with odd ordinal numbers. On the other hand, any spectrum of the first group is completely incoherent in combina- tion with any spectrum of the second group. The patterns of ultrasonic standing waves produced by the superposition of several or all of the diffraction spectra may also be explained by such coherence properties. Experimentally determined coherence properties are exactly those obtained from the assumption that higher diffraction spectra originate in multiple diffraction (Bril- louin theory). •Order No. N73-11713.•

Certain Experiments to Demonstrate the Diffractio..n of Light by Ultrasonic Waves--R. Baer [Translation of "Uber einige Demonstrationsversuche zur Beugung des Lichtes an Ultraschall- wellen," Helvetica Phys. Acta 6, No. 8, 570-580 (1933)3. Photo- graphs of diffraction spectra originating in the diffraction of light by ultrasonic waves are reproduced. They show that the intensity at which individual diffraction spectra occur is a function of the ordinal number, ' which exhibits maxima and minima. The position of the r•axima and minima depends on the intensity of the sound beam, the value of the sound wavelength/light wave- length and on the length of the path of the light beam within the sound wave. With an experimental arrangement described by Barand Meyer to record fields of ultrasonic waves in liquids, the diffraction of waves by a wire screen and the refraction and re- flection of an ultrasonic beam at the interface of two liquids are examined. [Order No. N73-11714.-]

Loudness of Uniform Noises--E. Zwicker and R. Feldtkeller [Translation of "Ueber die Lautstaerke von Gleichfoermigen Geraeuschen," Acustica 5, 303-316 (1955)•. With the aid of equal loudness contours (loudness in zones as a parameter), of the measured width of the frequency groups and reduction of loud- ness in neighboring frequency groups, the level of sustained noises with given spectra can be calculated. The aural analysis of a sound into bands of definite size (frequency groups), already demonstrated for the hearing threshold, masking, and phase detection, appears meaningful in the investigation of noise levels. Loudness is estimated from the sound intensity in the frequency groups, acting separately at low intensifies but with considerable throttling of one group by neighboring ones at high intensifies. [Order No. N73-11715.•

16.7

How Noise Affects Aggression Many situational factors directly affect human aggression.

Researchers at Louisiana State University have shown that an environmental factor, noise, can increase aggressive action.

In groups of three, 36 students took part in an experiment in which they were allowed to throw foam rubber balls at one of the experimenters. The subjects thought they were testing the

passive resistance of their target and knew nothing of the true aim of the experiment. Test sessions took place under one of three conditions: no noise, unlabeled white noise (a mixture of noise of various frequencies) or crowd noise labeled as cheering at a prize fight. Noise levels were set at 45 dB above the ambient noise level of the room. The prize-fight noise was included to test the hypothesis that aggressive noise would elicit more aggression than unlabeled noise. Videotapes were made of the three-minute ball-throwing sessions and judges rated aggressive behavior ac- cording to how many balls were thrown and how close the subject stood to the victim when throwing the balls.

John Knipmeyer and Perry Prestholdt report that subjects in the white-noise and crowd-noise conditions exhibited significantly greater aggression' than did those in the no-noise control groups. The crowd-noise conditions, however, produced no higher levels of aggression than the white noise. [Science News 103, 272 (28 April 1973).3

3.1

Technical Reports The following technical reports are available from National

Technical Information Service, Springfield, Virginia 22151, under the order numbers shown.

Additional Sonic Boom Data Related to Tests Conducted at White Sands, N.M., and Edwards Air Force Base- L. A. Lee, John A. Blume and Associates, 130 Jessie St., San Francisco, Calif. 94105, September 1972. Data in the form of notes and recordings which were compiled during the White Sands and Edwards Air Force Base Sonic Boom Test Programs and which are presently available in files at the Blume offices were reviewed to present window-mounted strain-gauge readings with related overpressures during the 1965. White Sands tests and window sizes of the Edwards AFB 1966 test structures. These

data are to be used by FAA in current studies. [Order No. AD-751934.-]

An Investigation of the Acoustic Energy of Underwater Explosions of Gaseous Hydrogen and Oxygen in a Gas-Water Resonator--J. F. Miles and J. C. Patrick, Jr., Naval Postgraduate School, Monterey, Calif. 1962. In recent years at the U.S. Naval Postgraduate school, a great deal of interest has been exhibited in the use of hydrogen-oxygen explosions in semienclosed cham- bers as an underwater acoustic signal source. The basic intent of this thesis was investigation of the amount of acoustic energy available from such a controlled explosion and its dependence on various mixtures of gas, including excess amounts of hydrogen, oxygen and nitrogen. The low energy yields obtained were both unexpected and disappointing and the efficiency of conversion from chemical to acoustic energy was astonishingly low--so low that the value of the process as a source of acoustic signals is confidered to be of doubtful significance. Frequency spectra and time domain photographs of each explosion and a short section on variation of energy with depth of explosion are included. [Order No. AD-753242.-]

A Simple Model of Shock Cell Noise Generation and its Reduction--Y. Y. Chan, National Aeronautical Establishment, Ottawa, Canada, October 1972. Based on the data of nearfield surveys of the sound pressure from a choked jet, a simple model is proposed for the mechanism of the screech generation. A con- vected wave propagates downstrekm along the jet boundary and is modulated by its interaction with the shock-expansion waves of the jet. These interactions generate strong dipole radiations. Using this model, an excellent reproduction of the essential fea- tures of the experimental results is obtained. By preventing the formation of shock waves inside the jet, the strong dipole radia- tion and hence the screech noise can be eliminated. Design data for perforated nozzles to achieve full •xpansion of the jet are

556 Volume 54 Number 2 1973

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