bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite-Amplitude Motion of a Piston in a Shallow, Fluid-Filled Cavity
Authors: Blackstock David T.
Published: September 2005

A theoretical treatment of the motion of a piston in a fluid-filled cavity is presented. Emphasis is on the steady-state response of the piston to a sinusoidal driving force. Effects of finite amplitude and finite length of the cavity are taken into account; frictional damping is also considered. It is found that if the piston is driven hard enough in the neighborhood of resonance, the motion is markedly influenced by the nonlinearity of the equation of state (pressure-density relation) of the fluid. The fluid-filled cavity behaves as a nonlinear spring. The theoretical results show how measurements of the piston motion might be used to obtain data on the coefficients of the most important nonlinear terms in the equation of state of the fluid. Push-pull as well as single-sided piston-cavity systems are analyzed.
Measurements of Absorption Coefficients on Plates
Authors: Heckl Manfred
Published: September 2005

An analogy to architectural acoustics is used to characterize the localized damping at boundaries of structures in terms of absorption coefficients. These coefficients can be measured by a technique which has all the advantages and disadvantages of the reverberation chamber method of architectural acoustics. Experimental results show that the way in which absorption coefficients vary with frequency is primarily a function of the geometry of the boundary structure. Structures consisting of beams attached to plates, which are of practical importance, in some cases appear to dissipate energy by virtue of friction at the interface.
Response of Ribbed Panels to Reverberant Acoustic Fields
Authors: Maidanik Gideon
Published: September 2005

A statistical method for estimating the response of ribbed panels to acoustic excitation is discussed. It is shown that the acceleration spectrum of the vibrational field is related to the pressure spectrum by a coupling factor which is a simple function of the radiation and mechanical resistance of the structure. The radiation resistance of a ribbed panel is studied as a function of frequency. The analysis predicts that ribbing increases the radiation resistance of the panel and hence its coupling to the acoustic field. The effect of various panel-rib boundary conditions is also considered. The results of experiments which were conducted to test the theory are reported. The agreement between theory and experiments is shown to be satisfactory.
Some Aspects of Binaural Signal Selection
Authors: Schubert Earl D. , Schultz Martin C.
Published: September 2005

Two experiments are reported which measure the increase in intelligibility occasioned by listening binaurally to running speech imbedded in interfering signals. In the first experiment, the frequency range of the speech is restricted to one of three ranges: 200–1600, 880–2200, 1660–6100. The interfering signal is broad-band random noise. Under difficult listening (27% intelligibility for homophasic listening) the lowest range shows a binaural improvement of 33% for a change in interaural polarity, and of 28% for an interaural time disparity of 500 μsec. The middle- and high frequency ranges show less binaural gain, but do afford some advantage to two eared listening under difficult conditions.

The second experiment compares the effects of different speech waves masking the wanted speech in binaural listening. For the maskers used, the binaural system helps most when the interfering wave is the speaker's own voice or a multiple mixture of many voices. The measured differences between homophasic and binaural listening are small but statistically reliable. The interaural differences employed (time delay and polarity reversal) are no help when the interfering wave is a female voice, another male voice, or the multiple mixture played backward.
Vowel Formant Bandwidths and Synthetic Vowels
Authors: Tarnóczy Thomas H.
Published: September 2005

This letter summarizes previous paper by the author on the determination of vowel formant bandwidth from decay patterns of vowel cavities. Formant bandwidth, as well as frequency of formant, depends on the open or closed condition of the glottis. The tuning of the resonator cavities changes, therefore, during each vibration period within the natural intonation. This occurrence can play a part in constructing of the synthetic vowel.
Nonaxisymmetric Modes of Vibration of Thin Spherical Shells
Authors: Silbiger Alexander
Published: September 2005

Discussions of modes of vibration of thin spherical shells usually are restricted to axisymmetric vibrations. While nonaxisymmetric modes do exist, they are degenerate, that is, the frequencies are identical to the frequencies of the axisymmetric modes. This is shown to be a consequence of the spherical symmetry of the shell. The modes can be divided into three classes; for large mode numbers these classes correspond to extensional, shear, and flexural vibrations.
Simple Switching Device with Phase Synchronization
Authors: Belton Peter
Published: September 2005

A device capable of switching a pure tone of wide frequency range is described. The arrangement uses standard apparatus and permits a sine wave to be started and stopped precisely at any phase of its cycle.
Experiments Concerning the Sound-Sensitive Jet
Authors: Chanaud R. C. , Powell Alan
Published: September 2005

An experimental study of laminar jets sensitive to sound was conducted both in air and in water at low Reynolds numbers, the water jet permitting visual determination of a condition of neutral stability. Plotted on a Reynolds-Strouhal diagram, the neutral contours show the unstable region to be bounded at high Strouhal numbers and low Reynolds numbers. The boundary is dependent on disturbance amplitude, enclosing a somewhat larger region for larger disturbances. The lower Strouhal number boundary, if it exists, must be extremely close to the Reynolds number axis. A qualitative comparison of the recent results of instability theory for pseudolaminar jets with the experimental results is made on the basis of local parameters, this making allowance for jet spreading which otherwise is a major cause of disparity. However, the velocity profiles, determined in the air jet, do not compare closely with the analytic ones for a slit jet which have been used in recent theoretical studies of laminar-jet instability, even at low Reynolds numbers. It appears that the embryo vortex, formed when the jet is disturbed, begins near the inflection point of the velocity profile and at a phase when the fluctuating velocity at the orifice is near maximum. Very long waves, which become quite unstable after an initially very small special rate of amplification, are considered as a possible cause of transition to turbulence in the jet.
New Procedure for Computing Finite-Amplitude Distortion
Authors: Cook Bill D.
Published: September 2005

An iterative process is described for the calculation of the distortion of plane finite-amplitude sound waves in a dissipative, nondispersive medium. The method of calculation is a discrete-interval process of considering the distortion of the wave while propagating through a small distance, correcting for absorption within this distance, and then considering this new wave, etc. It is necessary to use a high-speed electronic computer to obtain the spectral composition of the wave. The iterative process allows calculations beyond the “discontinuity distance.” The spatial change of the spectral composition is used for the calculation of “absorption coefficients” describing the energy loss from the total wave and from the fundamental component. These absorption coefficients, which are functions of distance from the source, are found to be remarkably different.
Study of Low-Frequency Sound Propagation in the Hartlen Point Region of the Scotian Shelf
Authors: Macpherson J. D. , Fothergill N. O.
Published: September 2005

From 1957 to 1960 a series of propagation experiments was carried out on the Scotion Shelf. A large seasonal systematic variation of attenuation was observed. This variation was apparently caused by a change in the vertical temperature structure. A ray theory is used to predict this variation and also to give information about the bottom reflection coefficient.
Interaural Phase and the Absolute Threshold for Tone
Authors: Diercks K. Jerome , Jeffress Lloyd A.
Published: September 2005

The present study agrees with earlier ones that the binaural absolute threshold is about 3 dB lower than the monaural. It also finds that reversing the interaural phase of the signal lowers the threshold still further. The findings are shown to indicate the likelihood that so-called absolute thresholds are really masked thresholds, with the masking noise present internally and exhibiting a small positive correlation. The close relation of our results to the earlier work of Hirsh on binaural masking phenomena is discussed.
Absolute Pitch
Authors: Jeffress Lloyd A.
Published: September 2005

It is suggested that absolute pitch. while found almost exclusively among musical families, is not inherited, but rather, that acquiring it partakes of the nature of “imprinting”—a peculiar type of early learning.
Interactions between Sound Waves
Authors: Dean L. Wallace
Published: September 2005

Exact solutions for the interaction between two concentric cylindrical waves and between two concentric spherical waves are presented. The scattered-pressure amplitude in the far field is shown to be constant in the cylindrical case and to be proportional to r−1 lnr in the spherical case, where r is the distance to the source of primary waves.

A near-field solution is derived for the scattered waves generated when two sharply defined, plane-wave beams of square cross section intersect at right angles. A comparison is made of the theory with recent experiments in which beams of circular cross section were used. It is concluded that if the scattered waves do exist, their amplitudes are at least 40 dB below those that are predicted by this theory.

When a hard object is placed in the region of intersection, scattered waves are observed. This effect can be explained by the fact that with the addition of the hard object (a cylinder) the primary waves have components of the same symmetry. These components are the waves scattered from the primary beams by the object. Evidence is presented to show that these components, having the same symmetry, interact strongly in the volume surrounding the object.
Influence on the Behavior of a Linear Dynamical System of Some Imposed Rapid Motions of Small Amplitude
Authors: Bogdanoff John L.
Published: September 2005

Occasionally, linear dynamical system must operate under the influence of imposed motions of very small amplitude and high frequency which were not contemplated in its design. The influence of such motions on the behavior of the system is therefore of paramount interest. It is shown that, although the differential equations of motion are linear with oscillatory coefficients when the imposed motions are present, it is possible under certain conditions to determine the behavior in an average sense from the solution of a system of linear differential equations with constant coefficients. Criteria to determine the influence of the imposed motions on the stability and response to various inputs of the original system are easily found.
Flexural Vibration of Shallow Orthotropic Spherical Shells
Authors: Hoppmann W. H. , Miller C. E.
Published: September 2005

The paper presents a theoretical development of the equations of motion for the flexural vibrations of a shallow spherical shell of orthotropic material. For symmetrical vibrations, the motion is described by two ordinary sixth-order differential equations with variable coefficients. Factorization of the sixth-order operators into second-order operators is discussed and the details of solution are worked out for the case in which the equations are reduced to those for the isotropic shell. It is shown that equations for the latter case agree exactly with those derived previously by Reissner. A table of calculated frequencies is given along with some experimental results for steel shells.
Hydrophone Installation for the Study of Soniferous Marine Animals
Authors: Steinberg John C. , Kronengold Morton , Cummings William C.
Published: September 2005

A hydrophone assembly with terminals the Lerner Marine Laboratory, Bimini, Bahamas, has been installed on the east bank of the Straits of Florida in order to study the sounds produced by marine animals in the natural environment. Sounds from two bottom-mounted hydrophones, one in 100 ft of water and the other in 1200 it, were recorded on dual track, magnetic tape on a 24-h basis. The tapes were played back at eight times recording speed and monitored for sounds possibly of marine animal origin. More than 25 categories of sounds were observed during the initial period from November 1960 to July 1961. A number of the categories showed repetitive, diurnal patterns and possible seasonal patterns of soniferous activity. In general, sound categories the shallow and deep sites were different. Usually, only a single category was heard from a hydrophone at one time. Some tentative identifications have been made.
Studies on the Aural Reflex. III. Reflex Latency as Inferred from Reduction of Temporary Threshold Shift from Impulses
Authors: Ward W. Dixon
Published: September 2005

The effective protection provided by arousal of the acoustic reflex against temporary threshold shift (TTS) at 4 kc from exposure to impulse noise was studied by comparing the rate of growth of TTS produced by 2-min exposures to clicks of successively higher peak levels under two conditions: first, when the clicks were heard alone, and second, when each click was preceded at various intervals from 25 to 150 msec by a 1000-cps 100-dB pure tone presented to the contralateral ear. The results imply that the effective attenuation amounts to 1 dB at 25 msec, 5 dB at 62 msec, and 13 dB at 100 msec. Individual differences were large; some of the most slowly responding ears did not show significant protection until the delay reached 150 msec. The practical conclusion reached is that a reflex-arousal stimulus to be used to protect gun crews should precede firing by 150 msec or more. In regard to theory, the results support the hypothesis that the value of the acoustic impedance of an ear at any instant is an accurate indicator of the protection provided by the middle ear muscles. However, there is also evidence that part of the protection may stem from a change, with reflex arousal, in the peak-limiting characteristics of the middle ear.
Theory for Correlating Attenuation Data for Cylindrical Passages
Authors: Judd Frederick V. H.
Published: September 2005

The accepted method for correlating acoustic attenuation data for absorptive passages is in terms of dB/unit length. In this paper, we have derived a logarithmic theory that provides a better correlation for test data on cylindrical absorptive passages.
Radiation Loading on Pistons and Arrays of Pistons
Authors: Toulis Williams J.
Published: September 2005

Expressions are presented whereby the radiation load on a piston or an array of pistons may be determined from physical principles and factors illustrated by various types of well-known radiating surfaces, wave guides, and conical horns. On the assumption that the radiation loading on a piston may be defined sufficiently by its low- and high-frequency characteristics, then the total surface area and not the geometrical shape of the piston is the principal determining factor. In particular, the real component of the load on each unit area of a small piston is directly proportional to the vibrating surface area. The reactive component of the load, however, can be determined only within a factor between one and two in terms of the area. The infinite array of pistons on a plane and the finite array of pistons on a spherical surface are two examples for which accurate expressions of the radiation load are possible in terms of the characteristic properties of wave guides and conical horns. The principal term of the expression is proportional to the radiation load on the array if it is assumed that all of the array surface is vibrating actively. The factor of proportionality is the fractional portion of the surface that is actually active. The secondary term depends on the free-space characteristics of one of the units in the array and also on the spacing between the units.
Research and the Singing Voice
Authors: Oncley Paul B.
Published: September 2005

The human singing voice was one of the earliest subjects of acoustic investigation and has interested many of the great pioneers in the field. Yet today with well-developed research tools and techniques available, we still have only a superficial knowledge of the factors which contribute to the proper production of the singing voice, and the voice teacher is left with little more basic physical knowledge than he had before Helmholtz. This paper is devoted chiefly to a review of the current status of this subject, and a discussion of the contributions from speech work and of such researchers as Paget, Russell, Seashore, Bartholomew, Chiba and Kajiyama in Japan, Tarnóczy in Hungary, Gemelli, Sacerdote, and Bellussi in Italy, and the author.
Effect of Correlated Phase Fluctuation on Array Performance
Authors: Bordelon Derrill J.
Published: September 2005

It is shown that the expectation of the mean-square time-averaged response for a configuration of receivers is immediate from known statistical considerations.
Principal Considerations on the Artistic Qualities of Musical Sound
Authors: Thienhaus Erich
Published: September 2005

If one considers the transfer of vibratory energy from a musical instrument to the ear of a listener as a “transmission” in the most general sense, then one must consider each step at which there is a change in the original vibration characteristics (sounding board, room or part of the room, microphone, amplifier, disk record, etc.) as a separate element in the transmission chain. In principle, one must distinguish between active and passive transmission elements. As to whether a transmission system is active or passive, the magnitude of the transfer function (amplification or attenuation) is of less concern than the change in the phase angle with frequency (the slope of the phase characteristic). An unambiguous relationship between magnitude and phase characteristic exists only in the case of relatively simple networks, which are rarely found, however, in mechanical elements of musical instruments. Aesthetically satisfying musical sounds require active systems for certain parts of the transmission chain; in particular, the room (concert hall or recording studio) must possess certain “active” transmission properties.

Editor's note: By “active” the author means an element that modifies the phase characteristics of the signal; by “passive,” one that preserves phase. In this sense an “active” element modifies the wave form of the signal and a “passive” element does not.
Some Problems of Reproduction and Perception of Electronic Tape Music
Authors: Meyer-Eppler Werner
Published: September 2005

Composers working in the field of electronic tape music tend to use an acoustic repertory that may differ widely from the repertory used in traditional music. Features which so far had been more or less irrelevant or belonged to the emotional sphere become essential parts of the score now, as, e.g., transients and envelopes, statistical modulation, formant frequencies, noise colors, and reverberation characteristics. All these qualities and many others can be incorporated into the set of musical elements which form the building blocks of an electronic composition. The new musical language has two consequences: (1) the listener must learn to discriminate between acoustic elements he has no experience with, and (2) the reproducing device must be able to transform the magnetically stored composition into sound without adding unwanted elements or removing essential ones. The latter condition can be fulfilled only in acoustically dead rooms since the reverberation characteristic now belongs to the composer's tool unless he writes expressly for reproduction in living-rooms or concert halls.
Acoustical and Electrical Considerations in Approaching Facsimile Reproduction of the Symphony Orchestra
Authors: Selsted Walter T. , Snyder Ross H.
Published: September 2005

The paper describes the many considerations involved in attempting to reproduce the full symphony orchestra. The more important considerations covered in the paper were: frequency response of the over-all system, acoustical power requirements, spacial distribution of the loudspeaker system, maximum tolerable harmonic and intermodulation distortion, minimum allowable signal-to-noise ratio, and the number of separate record-reproduce channels necessary for proper musician location. A description is given of the methods of test and modification of the equipment to make it meet the performance requirements which were determined to be necessary. A description is also given of the program test conditions under which the finished system was demonstrated. A summary contains the various conclusions which were reached as a result of the experiment.
Effect of a Uniform Flow on Elastic Waves in a Porous, Saturated Elastic Solid
Authors: Jones J. P.
Published: September 2005

Elastic-wave propagation in a porous, saturated elastic solid is investigated for the situation in which there is a uniform flow velocity U0 in the fluid. Wave-velocity equations are set up for P and S waves, and the case of no viscous fluid coupling is investigated in detail.
Some Instrument Aids in Use in Western Germany for Checking Professional Standards in Audio Equipment
Authors: Franz Wilhelm
Published: September 2005

The paper will be concerned with the description of tape recorder head measuring equipment type R-57 now in development, for checking performance standards of all professional tape recording and reproducing units. The R-57 unit does not require galvanic contact with the tape reproducing assembly. The R-57 permits inductive coupling to the head assembly and measures recording current, high-frequency bias, and frequency response of the reproduce head assembly at tape speeds of 30, 15, 712, and 334 in. per second. No test tape with its mechanical and electrical variations is required for this standard test. Special inductive pickup coil assemblies types K10 and K11 are briefly described. Tape reproducer equalization curves follow the norm of the CCIR recommendations No. 135. Further, disk reproducing equipment type EMT 930 will be briefly described in terms of very rigid disk reproducing standards in western Europe. The paper will also briefly touch upon a musical pitch generator producing the standard tone A at 440 cycles and will describe briefly circuitry in arriving at a typical oboe pitch at 440 cycles. A brief summary will be given of an instrument in use for accurate and direct measurement of wow and flutter as frequency modulated and amplitude modulated variations in reproducing equipment.
Effect of Sound Reinforcement System in a Room on the Reverberation Time and Clearness
Authors: Nimura Tadamoto , Kido Ken'iti
Published: September 2005

The sound reinforcement system in a room lengthens the reverberation time of the room by acoustic feedback. The extension of Sabine's equation in such a case is introduced mathematically, where m microphones and n loudspeakers having arbitrary directional patterns are located in the room. The fundamental standpoint of this mathematical treatment is the same as Sabine's. By the result of this analysis, the directional patterns of the loudspeakers are more important than those of the microphones in avoiding singing due to acoustic feedback. If some combinations of the loudspeakers having suitable directional patterns are directed to absorbing surfaces, especially to the audience, and if the directivity gain in the direction of reflecting surfaces can be decreased, the clearness may be remarkably improved, though the room is reverberant when empty. The theoretical consideration in such a case is described in terms of the change in the apparent room constants. The possibility of electronic control of the acoustic behavior of a room is suggested.
Sound Radiation from a Beam Attached to a Plate
Authors: Lyon Richard H.
Published: September 2005

The sound power radiated by acoustically slow waves scattered by a beam is computed. An acoustic radiation resistance per unit length of beam is computed based on the radiated power and the mean-square transverse plate velocity in the absence of the beam. For a diffuse reverberant vibrational field and supported, clamped, or edge supported lines, explicit expressions for the radiation resistance are obtained. The reduction of radiation coupling due to beam vibration is also computed.
Listeners Can Be Seduced to Perceive the Paradoxical Ratio 51:87 as Either One or Another Truly Melodical Interval
Authors: Meyer Max F.
Published: September 2005

The ratio 51:87 (1,706), musically paradoxical, is found to be interpreted as 4:7 when surrounded by the terms 63, 76, and 101; and interpreted as 3:5 when surrounded by the terms 34 and 68.
Békéy's Audiometer
Authors: Hirsh Ira J.
Published: September 2005

The audiometer that Békésy described in 1947 and the audiometric technique have permitted the measurement of auditory thresholds as a continuous function of frequency or of time, and have simultaneously provided a measure of the listener's variability. The clinical value of the instrument is seen in the detailed frequency characteristics of the threshold and other features that appear to have diagnostic significance. In the laboratory, the principles of the audiometer have been incorporated in ways that have permitted new kinds of problems to be studied. Particular reference is made to masked audiograms as a function of frequency and continuous recovery curves after exposure to sound.
Study of High-Level Pressure Fluctuations by Acoustic Methods
Authors: Michaud P. , Mattei J.
Published: September 2005

Pressure measurements in an intermediate range between acoustic (low pressures and zero average motion) and aerodynamic field (high pressures with no variations or with step variations) are necessary in aeronautical research. A very wide pass-band measuring chain having no signal drift is necessary for the correct recording of these pressure variations. For some other tests, it will be necessary to measure pressure variations in a continuous flow without creating supplementary aerodynamic noise; finally, a dynamical calibration of this measuring chain must be possible. To this end, O.N.E.R.A. is studying systems including piezoelectric transducers (ammonium phosphate, barium titanate) and condensers (with FM circuits). The surface of these microphones is flat and without any roughness and may be fitted either on the surface of a model or on the wall of wind tunnel or shock-tube. The placing of these transducers no aerial vehicles enabled us to study the structure of shock waves from missiles of different kinds. They are also used in connection with studies of transonic and supersonic phenomena in shock-tubes and wind tunnels. The dynamic calibration of the pressure transducers is studied either from a known shock wave or from a source giving a rectangular pressure variation.
Aerodynamic Mixing in a High-Intensity Standing-Wave Sound Field
Authors: Mickelsen William R. , Baldwin Lionel V.
Published: September 2005

The aerodynamic mixing of mass and heat is of fundamental importance in fuel-air preparation, combustion, and exhaust-gas mixing in jet-engine combustors. Although combustors commonly have intense sound fields, little attention has been given to the effect of sound on aerodynamic mixing. This paper describes a theoretical and experimental investigation of the aerodynamic mixing of heat (or mass) downstream from a line source in a transverse standing-wave sound field. Kinematic analysis shows that sinusoidal standing sound waves displace the molecular-diffusion-wake in a manner similar to the displacement of a vibrating string. Nodal points occur at distances downstream which are whole number multiples of (stream velocity)/(sound wave frequency). The maximum wake displacement occurs at the antinodal distances and is equal to (√⋅rms of particle velocity)/(π⋅sound wave frequency). Theoretical analysis shows that intense sound fields may deform the molecular-diffusion-wake to such an extent that both the instantaneous and time-mean temperature field is substantially affected. When the deformation is slight, the temperature field is only changed in the time-mean sense. The analysis shows that the criteria for wake deformation are stretching of the wake, and the ratio of wake radius of curvature to wake thickness.
Electrochemical Applications for Ultrasonic Waves
Authors: Yeager Ernest
Published: September 2005

Ultrasonic waves at intensities sufficient for cavitation have been found to produce relatively large effects on such electrochemical processes as the corrosion of metals in electrolytic solutions, the anodic dissolution of metals, the formation of gases at electrodes during electrolyses, the electrodeposition of metals, and electrodialysis. A systematic study of several of these effects has been made in order to establish the fundamental nature of the effects. Ranked in order of importance, the basic mechanisms are as follows: (1) the disruption of concentration gradients at the electrode surfaces, (2) the partial destruction or removal of surface layers such as oxides on the electrode surfaces through cavitation, and (3) the partial degassing of the solution immediately adjacent to the electrode surface. The actual and potential practical significance of these various electrochemical effects will be evaluated. [Based in part on research supported by the Office of Naval Research.]
Direct Comparisons between the Sensations Produced by Frequency Modulation and Amplitude Modulation
Authors: Zwicker Eberhard
Published: September 2005

Subjective comparisons of the sensations produced by frequency- and amplitude-modulated octave-band noises were made by the method of adjustment. The results indicate a general correlation between the sensations produced by the two kinds of modulation. Expressed in changes of level (ΔL) and shifts (Δz) along the critical-band function, ΔL seems to be equal to C⋅Δz, where C = 10 dB/1.6 Bark. A second experiment shows the possibility of increasing and decreasing the sensation produced by amplitude modulation by adding in-phase or out-of-phase frequency modulation. The conclusion is reached that at least for noises the sensation produced by amplitude changes and that produced by frequency changes are based on the same mechanism.
Loudness, Reciprocality, and Partition Scales
Authors: Stevens S. S. , Guirao Miguelina
Published: September 2005

By the methods of magnitude estimation and magnitude production, judgments of softness were shown to be the reciprocal of judgments of loudness. The instruction to judge “distance” produces the same results as instructions to judge softness. Attempts to partition a segment of the loudness continuum into equal-appearing intervals results in a systematic error that is greater the more variable are the judgments.
Measurements of Gas Temperatures in Combustion Engines by Ultrasound
Authors: Rona Thomas P.
Published: September 2005

The possibility of measuring gas temperatures in internal combustion engines during actual operation has been studied at the Sloan Laboratories for Automotive and Aircraft Engines under the supervision of Professor C. F. Taylor. Barium titanate transducers are used at 2 mcps to produce short ultrasonic pulses in the combustion chamber through metallic coupling rods. The transit time of the sound signal is measured electronically and related to the absolute temperature of the gas mixture. The accuracy of temperature measurement in the unburned charge at about 1500°F is about 20°F. No complete evaluation of the accuracy has yet been made inside of the flame region. Sonic temperature measurements are expected to be particularly useful in studies of the antiknock properties of fuel. Real-gas behavior and thermal relaxation are the limiting factors in other applications. [This work was initiated by the Coordinating Research Council, Inc. and has been carried out with the support of the U. S. Army Ordnance.]
The Phonon-Photon Concept
Authors: Post E. J.
Published: September 2005

Several branches in physics have led to the concept of walls which characterize a difference in state of adjacent regions in a medium. Examples are the natural Bloch walls separating the Weisz domains in ferromagnetics or the artificial porous powder props which are used in the experimental technique of helium II for separating ground state and excited components of the fluid. Another almost trivial example is a mirror (in empty space) intercepting an electromagnetic disturbance. All examples, whether natural or artificial, have the common feature of being impermeable for the state at either side of the wall. The constituent particles of the medium (if any) pass through on condition that they change their state. This suggests, in analogy with the well-known semipermeable membrane in classical physics, the definition of another semipermeable membrane or wall, which is permeable for matter (if any) but impermeable for its excitations. An analysis of the dynamics of such membranes provides a coherent picture of the classical concepts of acoustic and electromagnetic momentum together with their nonclassical counterparts: phonon and photon momentum. It leads in addition to an interpretation of the photon concept in a material medium, which corresponds to Minkowski's definition of electromagnetic momentum in matter.
Motion of a Transient Cavity in a Compressible Liquid
Authors: Flynn Hugh Guthrie
Published: September 2005

An iterative, approximate solution has been found for a nonlinear differential equation describing the collapse of a transient, spherical cavity in a compressible liquid. The cavity contains vapor and a small amount of gas. The differential equation was first derived by Gilmore, who obtained a solution for a cavity containing only vapor. The analysis, which yields the radial speed of the interface in terms of tabulated functions, was carried out to provide a partial description of a gas-filled bubble that collapses to less than a few percent of its initial radius, and then rebounds. The method of solution permits the use of experimental or theoretical numerical data as equations of state for both the liquid and cavity contents without any assumption of algebraic relations between thermodynamic variables of state. The compression of the cavity contents is assumed to be initially isothermal, then adiabatic until heat transfer by conduction becomes important in the final stage of collapse. For this final phase, a second solution that takes account of heat transfer has been found. The effects of viscosity, surface tension, and heat conduction in the liquid have been neglected, but their probable importance has been assessed. [This work was supported by the Office of Naval Research.]
Bore-Hole Coupling Experiment
Authors: Angona F. A. , White J. E.
Published: September 2005

Many measurements of the earth's elastic properties are best made through the use of a fluid-filled bore hole. A theory describing the mechanism by which elastic waves in a solid generate bore-hole signals was published by White [J. Acoust. Soc. Am. 25, 906 (1953)]. This paper is concerned with the experimental verification of the bore-hole coupling theory. A model consisting of a metal rod loosely coupled to a metal pipe was used. An elastic pulse was generated at one end of the rod and permitted to travel along the rod. During the course of travel down the rod, energy from the pulse is transferred to the pipe and can be measured. The rod corresponds to the earth and the pipe to the fluid in the bore hole. Since the same mechanism for transfer of energy applies to the rod-pipe model as to the earth-bore-hole system, the bore-hole coupling theory is applied to the model and the computed wave forms compared to the experimentally observed signals.
Diffraction Pattern near the Focal Line of a Converging Cylindrical Wave
Authors: Kanevsky I. N. , Rosenberg L. D.
Published: September 2005

Assuming a small value of the ratio of the wavelength λ to the dimensions of the radiator, expressions are found for pressure and velocity distribution near the axis of a convergent cylindrical wave front. For some concrete cases (ceramic transducer with radial polarization, ceramic transducer with axial polarization, and a reflector in the form of a parabolic cylinder), focusing factors, gain and focal width for pressure and velocities are calculated. A constant angular distribution of the amplitude on the surface of the converging front gives maximum value of the pressure focusing factor. In this case the following expression gives the width l0 of the focal strip: (κl0)2 = αm2(αm2/2) − (αm/4) sin2αm −4 sin4(αm/2), where κ = 2π/λ and αm is the aperture angle. The approximate expression l0/λ = 0, 5/sinαm is accurate enough for the most practical purposes. Corresponding expressions for different cases are obtained. Finally, some equations are quoted connecting the pressure on the axis with the focusing factor and total incident energy. It is shown that, in the case of a finite length of radiator, the obtained results are valid on the whole length of the axis except small portions at the ends measuring about √λf where f is focal distance.
Dispersal of Particulate Matter in a Liquid Medium by Means of Sonic and Ultrasonic Waves
Authors: Collet M.
Published: September 2005

Conventional methods do not generally meet the physical requirements for efficient dispersal of agglomerated particulate matter in a liquid medium. Simple stirring techniques do not induce the relative motion necessary for the dispersal and require an excessive amount of mechanical power, long mixing times, bulky containers, and batch operation. With sonic and ultrasonic waves direct effects may be produced in a simple and inexpensive way by submitting the components of the suspension to strong relative motion. The particulate matter will then be rapidly dispersed due to the erosion and disaggregation processes. Theoretical studies and laboratory results have led to the development of an efficient, inexpensive, and essentially simple process. Industrial performances are possible and with low transducer power results superior to those obtained with standard apparatus may be obtained.
A Method for Determining the Radiation Characteristics of Aircraft in Flight
Authors: Cole John N. , Kyrazis Demos T.
Published: September 2005

Information on the basic characteristics of aircraft noise sources during flight requires that a methodology be established which can adequately determine total acoustic power, directivity, and frequency characteristics from sound pressure measurements. A procedure is presented for transposing from sound-pressure-time information received at a stationary ground point to information on the radiation characteristics of the moving source. Included are such physical mechanisms as propagation time lags, energy losses through a diverging sound field, atmospheric absorption losses, and Doppler shifts in frequency. A graphical approach is utilized wherever feasible to facilitate calculation. The method is equally applicable to cases where the microphone is in motion parallel to the axis of an axially symmetrical sound source at rest.
Noise Radiation from Jet Aircraft in Flight
Authors: von Gierke Henning E. , Cole John N. , Eldred Kenneth M. , Fass Martin , Hoeft Lothar O. , Kyrazis Demos T.
Published: September 2005

The radiation characteristics of a jet aircraft in flight (directivity patterns for octave bands) have been determined as a function of flight speed. Accurate control of flight path and velocity and correlation of the aircraft's momentary position with each moment of the pressure time curve had to be achieved before reliable results were obtained. The maximum over-all sound pressure level, which occurs for a stationary jet at an angle of 140° to 150° from the aircraft's nose, decreases with increasing flight speed with a reduction of the total sound power output by up to 6 db. This decrease in noise power output is less than expected theoretically from the reduced relative velocity of the gas jet to the surrounding atmosphere. The noise radiated toward the front of the aircraft increases with increasing speed and above Mach number 0.7 the maximum of the over-all sound pressure appears at an angle of 20° to 30° from the aircraft's nose. This is accompanied by an increase in the total noise output, which is attributed to radiation from the turbulent flow generated by the moving aircraft as demonstrated by high-speed glides.
Differential Path Method for Measuring Ultrasonic Velocities in Glasses at High Temperatures
Authors: Krause J. T.
Published: September 2005

A method is described for measuring longitudinal and shear mode velocities in glasses over a wide temperature range at frequencies in the 10–20 Mc range. Use is made of a differential path technique in which measurements are made on a heated portion of a short rod-form sample. Transducer and bond are kept outside the furnace and thus are kept at normal operating temperatures.

Also described is a pulsed oscillator unique to the method of measurement and responsible for the high degree of resolution and accuracy.

Data for a commercial glass showing large changes in unit delay time as temperatures approach the softening point of the glass are illustrative of the method described.
Transient Response of a Thin Elastic Cylindrical Shell to a Moving Shock Wave
Authors: Bhuta Pravin G.
Published: September 2005

Using the theory of thin elastic shells, the transient response of a finite cylindrical shell of circular cross section subjected to a moving pressure discontinuity obtained for the axisymmetric case. The response to a moving shock front with a decaying pressure intensity behind the front may be obtained from this solution by the superposition integral. From the solution for the moving pressure discontinuity, the response of the shell, due to an impulsive load applied simultaneously over the entire shell, is obtained by the use of a limiting procedure. The upper bounds for the dynamic loading factors are given as functions of the shell parameter β = l2/rh.
Form of Analytical Expressions for Mechanical Impedance and Mobility
Authors: Levy S.
Published: September 2005

A useful form is shown of an analytical expression for mechanical impedance and mobility. The form lends itself to determination of its parameters by measurement of resonant and antiresonant frequencies and of amplitude at those frequencies.
Fatigue Tests of a Resonant Structure with Random Excitation
Authors: Smith P. W. , Malme C. I.
Published: September 2005

Fatigue tests were made on resonant cantilever beams excited at the base clamp by sinusoidal or band-limited random forces of constant rms value. Cracks appeared at the edge of a 1/8-in. hole on the long axis of each beam. Tests were made on bare and Alclad 2024 aluminum alloy. Lifetimes ranged from 104 to 106 cycles at a frequency of 185 cps. Data from the literature for fatigue without strain concentration are compared with results for sinusoidal excitation. A fatigue curve for random excitation is computed on the assumptions that strain peaks are distributed as in Rayleigh's distribution curve, and that Miner's non-interacting law of damage accumulation is valid. The predicted lifetimes for bare 2024 Al are larger than those measured; the differences are suggestive of a nonlinear damage-accumulation law, attributable to interactions between strain peaks of different levels. The results for Alclad 2024 do not suggest a nonlinear law.
Thickness Vibrations of Piezoelectric Plates
Authors: Tiersten H. F.
Published: September 2005

The thickness vibrations of an infinite anisotropic plate with electrodes coated on both surfaces are investigated using the linear piezoelectric equations. In general, the three fundamental solutions of the differential equations are found to couple at the traction-free surfaces of the plate. The solution reduces to the well-known uncoupled solution for the purely elastic case when the piezoelectric constants are zero. The transcendental equation which determines the resonant frequencies is derived. The theory is applied to a ferroelectric ceramic in two special cases; one with the plate polarized in the thickness direction, and the other with the plate polarized in its plane. The theory is also applied to a rotated Y-cut quartz plate. In all of these special cases the three solutions of the differential equations uncouple. Two of these solutions are identical with the purely elastic solutions and cannot be excited electrically, whereas the third differs from the purely elastic solution and can be excited electrically. The frequency equation obtained from this piezoelectric solution shows that the resonant frequencies are not integral multiples of the fundamental.
Nonacoustical Method for Measuring Sensitivity of a Piezoelectric Hydrophone
Authors: Raymond Fred W.
Published: September 2005

An equation describing the sensitivity of a piezoelectric hydrophone is derived. It is shown how the parameters of this equation can be easily measured, thus providing a simple method for determining the basic response of the hydrophone.
Design of Vibrating Disks for Mechanical Radiation
Authors: Williams Philip H.
Published: September 2005

Some experimentally determined properties of free-edge, clamped-edge, and simply supported-edge vibrating flexure disks are summarized. Sources of nonradiative dissipative losses are discussed in connection with electroacoustic efficiency. Constants for use in predicting the natural frequency of the gravest mode in each case are presented, together with a remark concerning a satisfactory construction technique for sandwiching quartz or ceramic with metal to make up an electrically excitable composite disk.
On Noise Produced by Boundary-Layer Turbulence
Authors: Meecham William C.
Published: September 2005

The question of possible sound produced by stresses at a rigid surface is discussed. It has been previously pointed out that these stresses won't produce sound. The error in the original analysis is shown to be a confusion between hydrodynamic pressure and sound-field pressure.
Mechanical Impedance and Transmissibility of Simply Supported Beams
Authors: Snowdon J. C.
Published: September 2005

The response to vibration of simply supported damped beams has been determined theoretically. Expressions have been derived for the transmissibility and input impedance and, in one case, the transfer impedance of such beams vibrating in their transverse modes, and for the transmissibility of one- and two-stage systems of beams loaded by lumped elements of mass. The effect of varying beam damping is considered in detail.
Wave Propagation in an Infinite Piezoelectric Plate
Authors: Tiersten H. F.
Published: September 2005

The problem of wave propagation in an infinite piezoelectric plate belonging to crystallographic class C6v, situated between shorted electrodes, is rigorously analyzed for two special orientations of the sixfold axis. The solution is derived using the linear piezoelectric equations. The analysis shows that for a given frequency and wave number in the propagation direction there are three independent solutions of the differential equations, and, furthermore, that these three solutions couple at the traction-free boundaries of the plate. The dispersion curves can be calculated from the resulting transcendental equations. It has previously been shown that the resonant frequencies at infinite wavelength of a plate, in which the electromechanical coupling factors are high, deviate considerably from those of the purely elastic solution. Thus the dispersion spectrum calculated from this analysis will deviate considerably from that of the purely elastic analysis. It is shown in an appendix that the solution for the plate of infinite width is also applicable in the case of the plate of infinitesimal width.