bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound Absorption and Velocity Measurements in Oxygen
Authors: Shields F. D. , Lee Kun Pal
Published: September 2005

The tube method has been used to measure sound absorption and velocity in pure oxygen at 23.5°, 208.7°, and 301.3°C. At the elevated temperatures, the absorption was in excess of the classical value. This was attributed to thermal relaxation of the vibrational energy. At 208.7° and 301.3°C, the peak value of the relaxation-absorption curve is estimated to fall at 100 ±4 and 175 ±13 cps/atm, respectively. These values correspond to relaxation times of 1.71 × 10−3 and 1.01 × 10−3 sec and are considerably longer than would be expected by interpolation from previous data at higher and lower temperatures.
Note on the Effect of Dynamic Asymmetry on the Vibration of Cylindrical Shells
Authors: Koval L. R.
Published: September 2005

Photographs are presented showing the principal effect of dynamic asymmetries on shell vibrations: splitting of the natural frequencies into two nearby values, with each frequency having different locations for its nodes. The experimental procedure is briefly outlined.
Eddy Viscosity as a Possible Acoustic Absorption Mechanism in the Ocean
Authors: Schulkin Morris
Published: September 2005

Part of the attenuation observed in the propagation of acoustic energy at frequencies below 1 kcps through the deep ocean is attributed to a relaxation absorption by an eddy viscosity mechanism. A relaxation frequency of about 630 cps is estimated from the available data, and an absorption dependence on frequency of slightly more than the first power is estimated for the process near the relaxation frequency.
Absorption and Dispersion of Audio-Frequency Sound in Aerosols
Authors: Zink Jay W. , Delsasso L. P.
Published: September 2005

Experimental work is now being done on the transmission of sound through air containing solid particles. A pulse technique is used in which a sine burst containing about twenty complete waves is sent through the particle-filled air. Examination of the transmitted pulse with and without particles yields a measure of the absorption of the sound by the particles as well as the dispersion. The absorption can be determined to an accuracy of about ±0.01 db/ft, and the velocity changes to an accuracy of about ±0.2 ft/sec. The size and number of particles per cubic centimeter are determined by catching the particles that fall out of a known volume and examining them by means of photomicrographs. Results of these measurements will be presented and a comparison will be made between the theoretical absorption as calculated by Epstein and Carhart and the experimental absorption. The experimental arrangement will also be described. The work is being supported by the Sandia Corporation.
Quality of Organ Tones
Authors: Fletcher Harvey , Blackham E. Donnell , Christensen Douglas A.
Published: September 2005

The tones were produced by the pipe organ in the Smith Auditorium at Brigham Young University. They were picked up by a microphone placed at various positions in the auditorium and recorded on magnetic tape. The tape was taken into the laboratory where analyses of the tones were made. The structure of full organ tones becomes very complicated. For example, when the three keys for the major chord were depressed, there were 229 partials whose frequency and level were measured.

After the analysis of the tone was made, a synthetic tone was constructed by our synthesizer. Judgment tests were made by juries to see if synthetic tones could be distinguished from real tones. These juries were unable to distinguish between them. The paper discusses musical warmth. It shows that it is definitely related to the level variation of the partials. These variations are due to the frequencies of several partials being close together, causing beats.

Methods and apparatus were developed so that a tone could be warmed to any extent without using the large number partials produced in the pipe organ. A method of rating the warmth of organ tones is proposed and will be used in our future work on all musical tones.
The Violin as a Circuit
Authors: Schelleng John C.
Published: September 2005

The paper applies elementary circuit ideas to bowed-string instruments and their component parts. Parameters are defined and calculations based on simple circuit diagrams for the main resonance and the air resonance; curves describe their combined performance. The relative importance of circuit resistances—wood loss, radiation, and wall-surface loss—is discussed. Wall-surface loss is an important component of air decrement. No material improvement is to be expected from change in decrement or enclosure volume.

A theory for the wolfnote is given in terms of the beating of two equally forced oscillations, together with a criterion for its occurrence and a method for its elimination.

The paper analyzes principles of dimensional scaling between members of the violin family and shows why the cello and viola are more susceptible to wolftone than the violin.

A study of impedance requirements in wood shows that flexural similarity depends on the parameter c/ρ (compressional velocity over density); high values are in general favorable in the top plate. In the violin, cross-grain losses probably exceed those along the grain.
Measuring Techniques for Surface Noise, Absorption Coefficients, and Transmission Coefficients for Materials Exposed to Random Noise Fields in Small Enclosures
Authors: Colton Ernest
Published: September 2005

In order to reject ambient noise, surface microphones were developed by placing absorbent enclosures around nondirectional microphones. The advantages and errors of this method are discussed. A sound diffusing box is used to calibrate these microphone enclosures. The correction factors are qualitatively analyzed for a cylindrical enclosure. The sound diffusing box was used to measure the transmission loss of some materials. A directional (cardioid) microphone placed inside the sound diffusing box was used to measure directly the reflected sound energy of small samples of materials. A method for converting these measurements to absorption coefficients is described.
Photographic Method for Analysis of Fluid Motion
Authors: Hargrove Logan E. , Thurston George B.
Published: September 2005

This method of showing fluid motion utilizes the optical interference patterns observed in a flow-birefringent fluid when viewed between crossed polarizing plates. The fluid used is an aqueous solution of milling yellow, a commercial dye product of National Aniline Division of Allied Chemical and Dye Corporation. The optical interference patterns are related to the stress distribution and streamline directions in the moving fluid. Motion pictures are made of the patterns. Fluid preparation, fluid properties, and photographic techniques will be discussed. Color motion pictures will be shown for low-frequency excitation for such elements as orifices and tubes. (This work was supported by the Office of Ordnance Research, Department of the Army, under Contract No. DA-23-072-ORD-583.)
Interrupted Speech and the Possibility of Increasing Communication Efficiency
Authors: Indiresan P. V.
Published: September 2005

It is known that speech remains intelligible when it is interrupted at a slow rate (about 50 cps). Such interruption reduces the time duration of transmission without increasing the bandwidth and, hence, can increase the effective utilization of a communication channel. The reasons for the intelligibility of interrupted speech are explained, and the theoretical limits to the interruption rate and sampling period are estimated. Interrupted speech, even if it does not reduce the information content appreciably, will still not be directly suitable for communication purposes because of switching noise. Three methods for overcoming this noise, namely, by reverberation, by integration, and by the reiteration of synchronized speech samples are described. It is shown that there is a possibility of increasing the efficiency of speech communication by a factor of at least two, perhaps, as much as ten times.
Impedance Seen by a Small Hydrophone in a Pipe
Authors: Fitzpatrick Hugh M.
Published: September 2005

An expression is given for the impedance seen by a small hydrophone suspended in a liquid-filled standpipe.
Propagation of Sound in Monatomic Gases
Authors: Greenspan Martin
Published: September 2005

The speed and attenuation of sound at 11 Mc were measured in He, Ne, A, Kr, and Xe at pressures ranging from atmospheric to a few mm Hg. The results in the nondispersive regime agree well with elementary theory. Those in the dispersive regime are compared with existing theories and with results previously obtained in He at 1 Mc.
On Sound Absorption in Liquids Having Rotational Isomerism
Authors: Nolle A. W. , Payne J. D.
Published: September 2005

Young and Petrauskas [Bull Am. Phys. Soc. Ser. II, 1, 122(A) (March, 1956), paper H8] have found relaxational sound absorption in certain liquids having rotational isomerism. We consider this phenomenon as a case of structural relaxation. The absorption parameter α/ρcν2 should be approximately proportional to (ρ/T2) exp [(F-PV)/RT], where F is a free energy difference and V has the dimensions of volume, and also to the square of ΔV, a volume difference between equilibrium states. Some new measurements are reported, in which the effects of pressure up to 1500 kg/cm2 on the velocity and absorption of ultrasonic waves in 2-methyl-butane are examined in the range −25 to +25°C. The theory gives a self-consistent, quantitative explanation of the experimental results if the quantity V is given a positive temperature coefficient. Approximately, V is 0.2 times the molar volume, and F is one kcal/mole. ΔV is several tenths of the molar volume. Static PVT measurements are also reported. The isothermal compressibility is much greater than the relaxational part of the ultrasonic adiabatic compressibility. (Supported by the Office of Naval Research.)
Diffraction of Ultrasound in Elastically Anisotropic NaCl and in Some Other Materials
Authors: Papadakis Emmanuel P.
Published: September 2005

Ultrasonic diffraction in NaCl and KCl single crystals, as well as in steel, has been studied by the pulse-echo method from 8–45 Mc/sec with 12-in. disk transducers. The diffraction is of the Fresnel type, so that the curves of loss due to diffraction can be plotted with a normalized abscissa S = z/(a2/λ), where z is the path length in the specimen, a the transducer radius, and λ, the ultrasonic wavelength. In general, the loss curve is not monotonic in S. The shape of the curve is dependent upon the specimen material, the crystallographic direction of ultrasonic propagation, and the transducer plating configuration. The position of the last local maximum in the loss curve is a function of the anisotropy of the specimen. In particular, its position in steel (isotropic case) agrees with the theoretical position for isotropic materials.
Acoustic Damping in Cavities with Mean Velocity and Thermal Boundary Layers
Authors: Cantrell R. H. , McClure F. T. , Hart R. W.
Published: September 2005

Viscous and thermal losses of acoustic energy at a metal wall are calculated for the condition in which there is a low Mach number flow sustaining a temperature difference between the gas and the wall. The acoustic loss is found to decrease as the walls are cooled below the temperature of the main body of the gas. The results of the study are relevant to experiments on acoustic amplification by solid rocket propellants and to at least some cases of liquid propellant rocket acoustic instability.
Shock and Vibration as a Branch of Acoustics
Authors: Batchelder Laurence
Published: September 2005

Severe vibration and mechanical shock are common by-products of modern technology and often produce enough stress to fracture a machine or an instrument. The techniques of mitigating these disturbances have become a new specialty of engineering. When prevention of structural failure is a primary objective, it is natural that most shock and vibration specialists should be drawn from the profession of mechanical engineers. But the new specialty transcends the mechanics of rigid bodies; it lies more in the realm of fundamental acoustics. Vibration is essentially the acoustics of solids. Shock is simply transient vibration. Most instruments in the shock and vibration laboratory are electroacoustic transducers, in principle if not in form. Even airborne sound is sometimes used to excite mechanical vibration. The acoustical engineer welcomes this new community of interest, for he is urgently concerned with controlling noise. Nearly all objectionable noise is of mechanical origin and must be reduced by the techniques of the shock and vibration specialist.
Use of Four-Pole Parameters in Vibration Calculations
Authors: Molloy C. T.
Published: September 2005

Linear elastic systems which have a single input point and a single output point can be characterized by a pair of simple linear equations, namely Finput=α11Foutput + α12Voutput,Vinput=α21Foutput + α22Voutput, where the F's are forces, the V's are velocities, and the α's are the four-pole parameters for the system. The use of four-pole parameters permits combinations of mechanical elements to be handled as a single entity, and, as the parameters belong only to the elastic system for which they are defined, they do not depend upon what precedes that particular system or follows it in a mechanical network. This permits the statement of results in a rather general form. These parameters have been used for many years in the analysis of electrical circuits, and it is the purpose of this paper to show their utility in the field of mechanical vibrations. In particular, the four-pole parameters for the basic mechanical elements mass, spring, and resistance will be obtained. Also, a description of mechanical sources will be given. The rules for the connection of four poles and a method of experimentally measuring four-pole parameters will be presented. A few specific problems illustrating the use of four poles will be set forth, namely: a generalized vibration isolation problem, the response of an elastically mounted mass on an electrodynamic shake table, shock excitation analysis, and some distributed parameter systems (i.e., helical springs and rubber in shear).
Shallow-Water Propagation in the Arctic Ocean
Authors: Hunkins Kenneth , Kutschale Henry
Published: September 2005

Dispersion characteristics of underwater sound on the Arctic continental shelf north of Alaska were investigated at ranges between 2 and 250 km and for frequencies between 3 and 250 cps. Explosive charges were used as sources, and geophones were used as detectors. Observations were interpreted in terms of normal-mode theory, and good agreement between theory and experiment was found for both phase and group velocity. Portions of the first and second modes were recognized at all ranges, and, at short ranges, “leaking modes,” associated with the ice layer, were also noted. For long ranges, the water wave amplitude varied as the −1.85 power of range.
Underwater Sound Propagation in the Arctic Ocean
Authors: Marsh H. W. , Mellen R. H.
Published: September 2005

Some results of a four-year experimental study of sound propagation in the Arctic are presented and interpreted. The duration, form, and intensity of waves received at distances up to 1400 km are explained using ray theory and modes, in which source characteristics, refraction, scattering at the ice surface, and bottom effects are important.
Some Sources of Characteristic Vocoder Quality
Authors: Cooper Franklin S. , Peterson Eugene , Fahringer Gerald S.
Published: September 2005

The voice quality typical of channel vocoders has been variously characterized, not always in complimentary terms. A preliminary study has isolated some of the factors which appear to contribute undesirable effects. One of these effects (referred to as roughness) is traceable to low frequency modulation or jitter of the pulses in the buzz signal employed in synthesizing voiced sounds. Another (referred to as reediness) appears to be caused by a general leveling of the instantaneous spectrum of the output speech. Other attributes, which become prominent when a vocoder is used as the synthesizing component of a bandwidth compression system, have been studied also. Experimental results and remedial measures will be discussed and illustrated by recordings. [This work was supported in part by the Carnegie Corporation of New York and in part by the Department of Defense in connection with Contract DA49-170-sc-1642.]
Compensatory and Pursuit Tracking of Pitch
Authors: Harris J. Donald , Pikler Andrew G. , Murphy Jerome E.
Published: September 2005

The present experiment explores, in a preliminary way, compensatory and pursuit frequency tracking of 250 cps, and of the musical interval middle C-middle E; delineates the individual differences among subjects; explores the effect of possession of absolute pitch; explores the effect of change in speed in the program over a range from 1.25 through 5 cps/sec; and indicates its possible usefulness in certain spheres such as in music psychology, in musical guidance programs, and in human engineering.
Hearing Theories and Complex Sounds
Authors: von Békésy Georg
Published: September 2005

Several auditory phenomena—pitch, tonal volume, tonal localization, and analogies between the ear and the skin—are discussed in the framework of the place and the periodicity theories of hearing.
Lower Limits of Auditory Periodicity Analysis
Authors: Guttman Newman , Julesz Bela
Published: September 2005

Tests utilizing an iterated, uninterrupted section of random noise disclose that periodicity (iteration) is easily detectable to about 1 cps and detectable with especial difficulty below 0.5 cps. Frequencies bounding regions of perception of pitch, motorboating, and whooshing are specified as 19, 4, and 1 cps, respectively.
Energy-Detection Model for Monaural Auditory Detection
Authors: Rowlands R. O.
Published: September 2005

An alternative model to the energy detector described in a previous paper is presented. The advantage of this new model is that the effect of varying the amplitude and phase of the pedestal may be deduced directly from the block diagram.
Binaural Interaction in the Lateral Lemniscus of the Cat
Authors: Rosenzweig Mark R. , Sutton Dwight
Published: September 2005

The search for the physiological bases of auditory localization has already revealed binaural interaction in the electrophysiological responses of the cerebral cortex and of the inferior colliculi. At the next lower station in the auditory pathway, the lateral lemniscus, Kemp and Robinson reported in 1937 that they did not find evidence of binaural interaction. We have recorded from the lateral lemniscus of the anesthetized cat with needle electrodes, stimulating the two ears with independently controlled clicks. Significant interaction was found when the time interval between the clicks at the two ears was less than about 3 msec. Eight animals were used. The curve of interaction versus time interval is similar to that of the initial part of the response of the inferior colliculus. The interaction may originate in the superior olivary complex where Stotler has found anatomical evidence for convergence of the ascending pathways from the two ears. (This work was aided by a grant from the National Science Foundation.)
Receiver Criterion and the Repetition of Messages in Noise
Authors: Carterette Edward C.
Published: September 2005

A source sends successively each of a set of messages over a noisy channel to a receiver who records them. After recording a message, the receiver decides whether or not he has correctly heard the message according to a criterion which he has adopted. Then, using a binary signal that is always heard by the source, he confirms or rejects the message. If it is confirmed by the receiver, the source sends the next message in the set, and, if it is rejected, the source repeats the rejected message until it is either confirmed or sent a fixed number of times. A simple probability model that describes this process with some accuracy was developed earlier at the Hearing and Communication Laboratory for the case of a source operating under a criterion. It is applied to the present situation, and experimental evidence obtained under several different criteria and noise conditions is presented. The constancy of the probability of a correct or incorrect confirmation of a message over successive presentations is discussed. (This research was carried out while the author was a National Science Foundation Fellow, and was supported in part by the U. S. Air Force under Contract No. AF 18(600)-571, monitored by the Operational Applications Laboratory, Air Research and Development Command, Bolling Air Force Base, Washington 25, D. C.)
Theoretical Studies of Sound Propagation in Shallow Water
Authors: Williams A. O.
Published: September 2005

The fundamental wave theory of sound propagation in shallow water was given years ago by Pekeris [“Propagation of sound in the ocean,” Geological Society of America, Memoir 27 (1948)] and others in terms of normal modes. It was also shown that theory and experiment had broad areas of agreement. The problem treated there is much idealized in comparison with situations of interest to geophysicists. Varying water depth, inhomogeneities, geological layering, and rough boundaries greatly complicate the analysis, altering the sound field and introducing attenuations other than that cylindrical spreading inherent in the two-dimensional problem. Some of these complications have been discussed in acoustical and geophysical journals, but no complete synthesis has emerged. Perhaps complete answers demand high-speed numerical analysis of specific cases, but there is need of additional analytical studies to join mathematical abstractions and geophysical applications, with the aim of finding fairly general and fairly reliable approximations covering classes of situations. Model experiments with accurately known parameters have been useful in specific cases of geophysical prospecting, and they should help to guide such analysis. Preliminary results of such an experiment, to be described, are encouraging.
Recent Field Measurements of the Absorption of Sound in Sea Water
Authors: Potter D. S. , Garrison G. R. , Murphy S. R.
Published: September 2005

The absorption coefficient of sound in sea water has been obtained by a series of direct transmission measurements at several moderately high frequencies in a sheltered, deep-water bay in Puget Sound. Advantage was taken of the essentially isothermal and isosaline properties existing during certain seasons of the year in this location. Utilization of fixed buoys, a radio link for range determination by acoustic travel time, and a method of space averaging minimized the fluctuations normally encountered in such a measurement. Values obtained, in decibels per kiloyard at 10°C and 30 parts per thousand salinity, are 14.4±0.7 at 60 kc, 36±1 at 142 kc, 57±2 at 272 kc, and 101±3 at 467 kc. Although the frequency dependence of the absorption coefficient given by these measurements follows the normal relaxation law, the magnitudes are lower than those given by Del Grosso (NRL Report 4279, Naval Research Laboratory, Washington, D. C., January 13, 1954) by 4 to 9 db/kyd. (This work supported by the Bureau of Ordnance, U. S. Navy, under Contract NOrd 12937.)
Forward Scattering in the Sea
Authors: Urick R. J. , Whitmarsh D. C. , Skudrzyk E.
Published: September 2005

At small ranges and at high frequencies the scattering of sound in the sea is known to be the result of the focusing and defocusing action of the patches of inhomogeneity of the medium. The standard deviation of the transmitted amplitude should increase as the 3/2 power of the distance, and the amplitudes should be normally distributed. As the range increases, scattering passes over into an interference phenomenon because of the accumulating phase differences. The standard deviation of the amplitude should then increase as the square root of the range times the wave number, and the fluctuations should change from a normal distribution to a Rayleigh distribution with increasing range. Recent measurements at sea seem to confirm the more essential points of the theory. Although the behavior with range is generally verified, measured amplitudes tend to depart from theoretical expectations in the focusing and the transition range, where the shape of the patches of inhomogeneity seems to be essential, but approach the theoretical distribution when the interference fluctuations predominate. When the fluctuation of amplitude is greater than expected, the distribution curve usually shows several peaks, although the shape is between normal and Rayleigh when the fluctuation is more typical. Fluctuation measurements made at two frequencies enable the thermal and spacial size of the patches of inhomogeneity to be deduced. An estimate made in this way is in fair agreement with direct microthermal measurements in the sea.
Light Diffraction by Ultrasonic-Wave Visualization
Authors: Colbert H. M. , Zankel K. L.
Published: September 2005

The time dependence of the intensity of light in the Fresnel region diffracted by a progressive wave was investigated recently by H. M. Colbert and K. L. Zankel. The present study considers the time dependence of such light at the plane of visualization of the ultrasonic wave. The theory is presented for visualizing periodic ultrasonic wave of arbitrary form when it can be considered as a phase object. Experimental and theoretical results are compared and the usefulness of visualization in determining the shape of the ultrasonic wave is considered. It is concluded that the method would be useful in determining the relative magnitudes of the Fourier components, as well as relative phases among the components that arise in a dispersive medium.
Seismic properties of a Plane Lubricated Crack
Authors: Knopoff Leon
Published: September 2005

The nature of wave motions in the vicinity of discontinuities in the physical properties of materials depends upon the boundary conditions describing the discontinuities. These continuity conditions are established for a plane crack and are compared with the usual conditions selected for welded contacts. Several properties of wave motion under such conditions are explored. The reflection and refraction of plane compression and shear waves are investigated as type problems. Stoneley waves are demonstrably nonexistent. The dispersion of Rayleigh waves in a single layer overlying a half-space is calculated.
Short-Term Auditory Frequency Discrimination
Authors: Sekey Andrew
Published: September 2005

This study has been directed towards finding a quantitative relationship between the duration of a short tone and the distinctness of its pitch. The ability of listeners to detect slight changes of pitch is assessed by forced-choice binary judgment technique. Empirical error scores are compared with the predicted performance of a decision-theory model, which incorporates statistical receiver designed for estimating relative shifts between sound spectra. A satisfactory agreement is observed; it is subsequently argued that this provides preliminary evidence supporting the view that the auditory system is capable of adapting its parameters to stimuli of varying duration. The proposition for the establishment of an auditory “uncertainty principle” is critically reexamined, but conventional experimental techniques are considered inadequate for an unambiguous formulation. In its stead, the present approach offers a “trading relationship” |δf|T1.38 = const., between spectral shift and stimulus duration. Suggestions are also made for extending this type of investigation to more-general aspects of auditory perception in the time-frequency domain.
Temporal Summation for Tones in Narrow-Band Noise
Authors: Zwicker E. , Wright H. N.
Published: September 2005

Temporal summation was measured for tones within, above, and below a narrow-band noise centered at 1000 cps as a function of the time interval between the onset of the noise and the onset of the tones. The results show that the theory of temporal auditory summation is sufficient to predict the threshold of audibility for tones in a steady-state condition where there exists a threshold shift not caused by the physical presence of a masking stimulus. Variation of the time interval between the onset of the narrow-band noise and the tones did not produce results different from those found in the steady state.
Helium Tracing as a Tool for Aerodynamic Studies
Authors: Embleton T. F. W.
Published: September 2005

Helium has some advantages over other tracers for quantitative measurements of flow patterns in aerodynamic processes. It is shown to be feasible to inject helium upstream of the test section and to detect it downstream using a probe coupled to a mass-spectrometer type of leak detector. A typical diagram of helium concentration relating inlet and outlet points, is presented for a rotating impeller.
Directivity Index of a Three-Dimensional Array of Directional Sources
Authors: Arase T. , Arase E. M.
Published: September 2005

The directivity factor of a three-dimensional array of identical directional sources is derived. This calculation also gives the output power of an additive array of omnidirectional receivers in a directional noise field that is identical at each receiver.
Representation of the Mechanical Damping Possessed by Rubberlike Materials and Structures
Authors: Snowdon J. C.
Published: September 2005

Discussed in detail is the manner in which the damping possessed by rubberlike materials and structures experiencing sinusoidal vibration may be represented by the ratio of the imaginary to the real part of a complex elastic modulus. Examples are given of the way in which the damping possessed by low- and high-damping rubbers depends on frequency. Equations that predict the response to vibration of such distributed systems as damped rods and beams, and a simple structure comprised of two damped beams and a lumped element of mass are derived; and representative computation of input impedance and transmissibility are presented.
On the Noise Produced by Boundary-Layer Turbulence
Authors: Ffowcs Williams John E.
Published: September 2005

This note is on the subject of sound radiated by rigid surfaces in turbulent flow. Some erroneous deductions made recently are discussed and a short survey of the relevant theories presented. It is pointed out that no fundamental errors exist in the basic theoretical work on this topic, and that some of the apparent inconsistencies are due to a misinterpretation of those theories.
Rotating Beam with Tip Mass Analyzed by a Variational Method
Authors: Craig Roy R.
Published: September 2005

Hamilton's principle is used in the determination of a variational principle, which is stated in forms making it suitable for the case of: (1) moderately large displacements of a beam which is initially stressfree, or (2) small displacements of a beam having initial stresses. In the latter form, the principle is applied to the problem of determining the effect of tip mass and rotational speed on the natural frequencies of a rotating beam carrying a concentrated tip mass. The variational principle stated here allows for an independent selection of displacement and moment coordinate functions in the manner suggested by Reissner. It thus imposes fewer constraints than would be imposed by the Rayleigh-Ritz method of assuming displacement coordinate functions only. The effect of tip mass is shown to be much greater on the frequency of the second mode than on the fundamental mode.
Vibrations of a Whirling Rayleigh Beam
Authors: Jones John P. , Bhuta Pravin G.
Published: September 2005

In this paper the vibrations of a whirling Rayleigh beam are studied. The vibrations are allowed to take place in the plane of rotation as well as in a direction perpendicular to the plane of rotation. Use has been made of undeformed coordinates resulting in the prediction of certain instabilities that have not been previously reported. The solutions of the frequency equations for a fixed-free beam and a simply supported beam are discussed.
Output Probability Distribution of a Correlation Detector with Signal-Plus-Noise Inputs
Authors: Jacobson Melvin J.
Published: September 2005

In this paper, a study is made of the problem of determining the probability density function of the output of a correlation detector whose two inputs consist of correlated signal corrupted by uncorrelated noise. The inputs are stationary and Gaussian, one having the characteristics of white noise and the other being RC-filtered white noise. The postmultiplier averager is also an RC filter. The general case of signal-plus-noise inputs is investigated, and the special cases of signal-only and noise-only inputs are also considered. Detailed results are presented when the ratio of the time constant of the postmultiplier filter to that of the premultiplier filter is 12 and also in the practical case when this ratio is large. With the probability distribution determined, a statistical theory of signal detection is applied, a major result being the determination of the relationship between detection probability and the classical detection measure, output signal-to-noise ratio.
Directivity of Spherical Receiving Arrays
Authors: Anderson Victor C. , Munson John C.
Published: September 2005

Beam pattern and directivity index are computed for spherical-volume and spherical-shell distributions of receiving elements. The limiting case of a continuous distribution of elements gives rise to simple closed-form expressions for the beam pattern. The side-lobe level of the beam pattern for the solid sphere is appreciably lower than that of the corresponding spherical shell. Comparison of the directivity index shows an increasingly superior performance for the solid sphere as the diameter to wavelength ratio D/λ becomes large.
Absorption of Diffuse Sound by a Strip or Rectangular Patch of Absorptive Material
Authors: Northwood T. D.
Published: September 2005

Previous calculations of the effective absorption coefficient of a rectangular patch of absorptive material have been extended in several respects. The new results are applicable to locally reacting materials for any size of patch and for a wide range of complex admittances. Specific use of the results is made in an examination of the reverberation-room method of measuring sound-absorption coefficients.
Responses of Cochlear Potentials to Changes in Hydrostatic Pressure
Authors: Butler Robert A. , Honrubia Vicente
Published: September 2005

Sustained and transient changes in hydrostatic pressure were transmitted directly to the perilymphatic space of guinea pigs. EP, as well as SP, CM, and AP, was measured before, during, and after pressure changes. Pressure applied to scala vestibuli led to an increase EP and SP, while pressure applied to scala tympani resulted in a decrease of these potentials. Comparable data were also obtained the anoxic cochlea. CM and AP failed to change when moderate amounts of pressure were applied. In guinea pigs whose organ of Corti was largely degenerated EP was normal, but it did not increase when pressure was applied to scala vestibuli, nor did it consistently decrease during pressure applications to scala tympani. These data were interpreted to mean that changes in EP normally occurring response to changes in hydrostatic pressure reflect variations in the output of dc generators located on the basilar membrane.
Periodicity Perception by Using Gated Noise
Authors: Harris Gerard G.
Published: September 2005

Gated white noise was used as a stimulus in a psychophysical experiment to determine the temporal resolution of the ear. Although exhibiting temporal periodicity of the envelope, gated while noise has a uniform power spectrum that possesses no information for a place mechanism of the ear. Four subjects varied the gating frequency to match this stimulus to a 0.1-msec click whose repetition frequency was set by the experimenter. All stimuli were 40 dB SL. Ungated noise was added to the gated noise to mask any switching transients. Fraction of time noise was gated on and filter conditions were set by the experimenter. For an on time fraction of 0.2 and 0.5, time information in the gated noise (all pass and 2400 cps high pass) could be utilized to match to a click frequency up to 750 cps. With 4800 cps high-pass gated noise, a weak timing signal was probably perceived up to 2000 cps. In a second part of the experiment, subjects attempted to lateralize gated, binaurally incoherent noise. A lateralized image could be formed up to a frequency of about 600 cps. The timing signal present in gated noise is not necessarily related to the percept of pitch, especially for high pass stimuli.
In Situ Measurements of the Attenuation of High-Frequency Sonar Pulses in Sea Water
Authors: McLeroy E. G.
Published: September 2005

Measurements have been made of the attenuation coefficient in sea water (in situ) of pulses in the frequency band 160 to 2100 kc/sec. A technique employing multiple reflection of the pulse eliminates relative motion of the transmitting and receiving transducers, and restricts the extent of water transmission path to 10 ft. The results are found to agree well with the viscous-relaxation theory of absorption except at certain times when anomalously high values of attenuation are measured.
Low-Frequency Sound Attenuation in the Deep Ocean
Authors: Urick R. J.
Published: September 2005

Signals received from Sofar bombs dropped from an aircraft eastward from Bermuda have been studied quantitatively. The energy density of the signals received at Bermuda, measured in various bands between 20 and 1600 cps, can be accounted for by cylindrical spreading beyond a “transition range” predicted approximately by simple considerations, plus an attenuation coefficient in dB per megayard given by the linear expression 1.5+8.2 f, where f is the frequency in kc/sec. At frequencies below 1 kc/sec, this attenuation is far in excess of that which would be produced by absorption alone. At very low frequencies the excess attenuation is postulated to be due to the failure of the Sofar sound channel to act as an acoustic trap. At frequencies from about 50 to 500 cps, quantitative evidence is presented to indicate that the dominant attenuation process is scattering by index-of-refraction inhomogeneities deep in the sea. Other characteristics of Sofar-transmitted signals are described.
Radiation Impedance of Membranes and Plates: Their Acoustic Coupling with the Propagating Medium
Authors: Lowenthal S. , Tournois P.
Published: September 2005

The radiation impedance of membranes and plates of finite width, carrying traveling wave, is calculated. The method used leads to a relatively simple analytic expression. The problem of acoustic coupling of these strips with the fluid propagating medium is then examined.
Application of a “Relative” Procedure to a Problem in Binaural-Beat Perception
Authors: Tobias Jerry V.
Published: September 2005

The existence of binaural beats has long been considered an indication of binaural interaction for timing and for periodicity information. In the past, bilaterally matched sound-pressure or sensation levels have been used in the investigation of these beats, and the measuring technique was one that may be termed “absolute.” However, the present study, in investigating with a “relative” technique the limits of dichotic intensity which permit binaural beats, shows that listeners respond to the presence of beats whenever the tones to both ears are above threshold. It is suggested that this new result fits more neatly into current theoretical formulations. The frequencies investigated ranged from 100 to 2000 cps. As other authors have previously reported, the best performance occurred in the 400- to 600-cps range. The present findings strengthen the case for an auditory nervous system with timing channels independent of other transmission lines and, thereby, also have implications for pitch theory.
Effect of Small Additions of Cobalt on the Dynamic Magnetostrictive Properties of Nickel Ferrous Ferrite
Authors: Davis C. M. , Ferebee S. F.
Published: September 2005

The dynamic magnetostrictive properties of nickel ferrous ferrite were investigated to determine its suitability for use in electromechanical transducers. A previous investigation [C. van der Burgt, J. Acoust. Soc. Am. 28, 1020–1032 (1956)] showed that small additions of cobalt increase the value of the electromechanical coupling coefficient. Recent work by the authors showed that the improvement resulting from cobalt additions is much larger when 3% to 6% of the NiO is replaced by FeO and the specimens are quenched from above 1100°C to room temperature. In this manner a reproducible material having values of electromechanical coupling coefficient equal to or greater than that of nickel is obtained. The maximum value of the coefficient (0.36) occurred for (NiO)0.913(CoO)0.027 × (FeO)0.06(Fe2O3) sintered at 1400°C and quenched to room temperature.
Design and Performance of a New Reverberation Room at Armour Research Foundation, Chicago, Illinois
Authors: McAuliffe D. R.
Published: September 2005

During the last six months the ART Acoustics Section has been moved to new quarters. In these new facilities a reverberation room has been built for use in the acoustic research of that group. The room has a volume of approximately 3000 cu ft and a reverberation time of about 5 seconds. The four walls and ceiling of the room have been splayed. Measurements indicate that the room has a relatively uniform reverberation with respect to frequency. Data will be presented to show the ambient noise level in the room, the steady-state sound energy distribution within the room, and the reverberation time as a function of frequency and location within the room.
Reflection and Transmission Coefficients for Stress Waves in Bars
Authors: Plunkett R. , Doolen R. B.
Published: September 2005

Previous experimental work has raised a question about the validity of one-dimensional wave theory for predicting the reflection of compression pulses in elastic bars. The measurements reported here are in much better agreement with these predictions than those previously reported.
Ambient Noise in a Coastal Lagoon
Authors: Painter Daniel W.
Published: September 2005

The results of a four-day underwater ambient-noise investigation conducted in a Mexican shallow-water lagoon are shown by pressure spectra in the frequency range 40 cps to 20 kc/sec. The pressure spectra are differentiated on the basis of noise generated by wind, tidal currents, and biological activity.
Measurement of Residual Masking in a Free-Field at Low Frequencies
Authors: Harris Cyril M. , Grundy Albert B.
Published: September 2005

Measurements have been made of residual masking in a “free-field,” produced by a 250 cps pure tone. Data have been obtained for the shift in threshold, 150 and 200 milliseconds following the cessation of the masking tone, employing the ABX Technique described by W. A. Munson and M. B. Gardner [J. Acoust. Soc. Am. 22, 177 (1950)]. Such data have been obtained at sound pressure levels of 110 and 90 db. The threshold shift at 250 cps produced by thermal noise has been measured as a function of the mel band intensity level of the noise. From these data so-called “loudness density patterns” for the 250-cps masking tone have been computed. These are plots of the loudness contribution in millisones per mel vs frequency 200 milliseconds following exposure to the masking tone. [This work has been supported under U. S. Air Force Contract AF 33(616)2454.]
On the Relationship between Temporary Hearing Loss and Masking
Authors: Miller James D.
Published: September 2005

This experiment was designed to test the hypothesis that differences in the effective noise level from one critical band to the next can account for the typical audiogram showing the temporary hearing loss which results from an exposure to noise of uniform spectrum level. For equal masking, or (B+K−QAT), the greatest losses were found at the highest frequencies and the smallest losses at the lowest frequencies. However, the hypothesis implied that for equal masking all frequencies would show equal losses. Further analysis revealed that when the data for temporary hearing loss were plotted against the quantity (B+2.7K−QAT), the points for all test-tone frequencies fell on a common curve. [This research was supported by the U. S. Air Force under Contract No. AF 18(600)-571.]
Measurements on a Vibrating Conductor in a Magnetic Field
Authors: Kelley Joseph G.
Published: September 2005

A taut wire, vibrating freely in a magnetic field, generates an emf. If current is allowed to flow as a result, it damps the vibratory motion. On the other hand, vibration can be caused by an applied ac current. Then, large changes in the imaginary component of the complex impedance are noted when the frequency approaches an odd harmonic of the wife's mechanical resonance. These effects have been measured and found in agreement with a recently proposed theory.
Technique for the Measurement of Blocked Impedance
Authors: Sahin G. A.
Published: September 2005

The blocked impedance of an electroacoustic underwater sound transducer is measured by using a pulsing technique. It is thus possible to measure the blocked impedance under free-field acoustic loading conditions without resorting to some means of clamping the transducer or to the usual interpolation method. Both theory and measurements will be discussed. A means of readily identifying the natural resonance frequency from either an impedance or an admittance plot is also demonstrated.
Electromechanical Filters
Authors: Lal Sharma Roshan
Published: September 2005

Some recent studies on electromechanical filters which make use of axially symmetric flexural vibrations of thick circular plates, are discussed. Resonant mechanical elements, nonresonant coupling elements, and magnetostriction transducers, which comprise such a filter, are considered individually. (1) Dependence of an extended frequency spectrum of a finite disk as derived from an improved theory, on Poisson's ratio, is discussed. In addition, employing an energy approach an equivalent circuit of such a disk is defined. Graphical data showing the results for some practical cases are also presented. (2) In spite of the fact that the coupling elements are not amenable to exact theoretical analysis, some interesting empirical and experimental data have been obtained. Some possible modes of wave propagation are considered. Influence of coupling elements on the free vibrations of circular disks is also discussed. (3) Making use of a space vector, very useful equivalent circuits of magnetostriction transducers are derived for various boundary conditions. Also discussed is a practical design whereby the useful frequency range of magnetostriction transducers is extended well beyond 450 × 103 cps.
Electronic Music Maker
Authors: Kent Earl L.
Published: September 2005

Great latitude is possible in several aspects of music production through the use of an electromechanical control of electronic tone generators. Exact control of tone production yields precision, greatly exceeding that possible through manual control. In addition, the scope of musical effects is extended beyond the physical limitations of the player. Additional smoothness in glissandos, and greater complexity of melodic lines, harmonies, and rhythms become feasible. Also, the limitations of the even tempered scale need no longer exist. The quarter-tone scales desired by some modern composers, as well as other scales, become quite feasible. The total effect is limited only by the imagination of the composer and the tonal resources of the music reproducing medium which is being controlled. This technique could be adapted for converting the output of a composing computer directly into music. A short tape recording will be used to demonstrate the potential of this device for expanding musical horizons.
Siren Experiments with Noncircular Holes and with a Noncircular Nozzle
Authors: Meyer Max F.
Published: September 2005

New siren experiments confirm the inadequacy of Ohm's tone definition.