bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustical Factors in Jet Airport Design
Authors: Eldred Ken
Published: September 2005

With the advent of commercial jet airline operations, increased importance must be placed upon acoustical considerations in airport design. This paper reviews the relationships between the noise resulting from commercial jet and propeller airliner operations, including takeoff, taxi, and idle, for various projected traffic densities and various airport building functional design criteria. Presently used criteria are explained and new criteria are suggested to fill a gap in the over-all evaluation procedure for short time noises. Methods and examples are presented which expedite initial visualization of the major acoustical factors in an airport design situation, facilitate decisions for preliminary airport building layout, and enable evaluation of possible wall and roof structures.
Three-Dimensional Investigation of the Propagation of Waves in Hollow Circular Cylinders. I. Analytical Foundation
Authors: Gazis Denos C.
Published: September 2005

The propagation of free harmonic waves along a hollow circular cylinder of infinite extent is discussed within the framework of the linear theory of elasticity. A characteristic equation appropriate to the circular hollow cylinder is obtained by use of the Helmholtz potentials for arbitrary values of the physical parameters involved. Axially symmetric waves, the limiting modes of infinite wavelength, and a special family of equivoluminal modes are derived and discussed as degenerate cases of the general equations.
Calibration of Accelerometers in a Simulated Space Environment
Authors: Keast David N.
Published: September 2005

For the purpose of measuring the properties of cushioning materials under simulated space conditions, it has been necessary to calibrate accelerometers for use in this unusual environment. In this paper, calibrations over the temperature range from −320°F to +80°F, and at an atmospheric pressure of 5×10−5 mm Hg, are reported for several different types of barium titanate accelerometers. These calibrations were obtained at several frequencies between 20 cps and 100 cps by the optical viewing method.
On the Intensity of Ultrasonic Beams Diffracted by a Wire Grating
Authors: Sreekantath Gopala Menon , Verghese C. A.
Published: September 2005

A theoretical investigation of diffraction of plane waves by a transmission grating shows that the expressions for the intensity of a given order of diffracted beam are not the same for light and sound waves. The latter is cos2θ times the former, where θ is the angle of diffraction. This result has considerable effect on the relative distribution of intensity among the various orders in the two cases. The foregoing theoretical result is verified experimentally in the case of high-frequency sound waves in a liquid diffracted by a wire grating immersed in the liquid.
Problem of Elastic Bar with Mixed Time-Dependent End Conditions of General Form
Authors: DeVault G. P. , Curtis C. W.
Published: September 2005

A procedure is outlined for formulating an exact solution to any problem involving an elastic cylindrical bar with a free lateral surface and with mixed time-dependent end conditions. The method suggested is an extension to three dimensions of a transform method proposed previously for solving two-dimensional problems involving only longitudinal strain.
Nature of the Vocal Cord Wave
Authors: Miller R. L.
Published: September 2005

The shape of the vocal cord wave is an important parameter in a true analog representation of the vocal mechanism, since the final speech wave is a function of both the generator wave shape and the transfer impedance of the vocal tract. The shape of this wave has been determined by two independent methods: (1) by the derivation and use of a network having a characteristic which is the inverse of the first vocal resonance, and (2) by measuring the area of the vocal cord opening as a function of time through the use of motion picture studies. Harmonic analysis of some of the typical shapes obtained indicate that a uniform distribution of harmonic amplitudes is a rarity; instead there is a tendency for the distribution to have a cyclical variation of the form (sinkn/kn2). The results obtained through the use of the inverse network indicate that the main excitation of the higher resonances occurs at the point of vocal cord closure and that the magnitude of this excitation can be controlled by the talker over wide ranges.
Elastic Wave Propagation in Homogeneous and Inhomogeneous Media
Authors: Karal Frank C. , Keller Joseph B.
Published: September 2005

A general method is developed for the solution of the linearized equations of elasticity for both homogeneous and inhomogeneous media. This method yields solutions which describe propagating waves which may be pulses, rapidly changing wave forms, or periodic waves. It is not restricted by the usual considerations which depend upon separation of variables. The solution consists of a series of terms, the first of which describes the wave motion predicted by geometrical optics. Subsequent terms account for certain types of diffraction effects. The series is not necessarily convergent but is presumably asymptotic to the solution.
Sonically Induced Microstreaming Applied to a Surface Reaction
Authors: Nyborg W. L. , Gould R. K. , Jackson F. J. , Adams Carl E.
Published: September 2005

Special arrangements are used to produce small-scale eddying near surfaces at which reactions are taking place. Experiments in which the reaction involves a photographic emulsion acted upon by developer show that the development process is considerably accelerated in small areas where the near-surface flow is concentrated. Resonant gas bubbles appear to be by far the most efficient sources of sonically induced micro-eddying. When such a bubble rests on an emulsion surface the development reaction in its neighborhood is significantly affected, evidently because of the local “microstirring,” at ambient pressure amplitudes much less than are typically used in sonic and ultrasonic applications. Sonic microstreaming, especially as induced near resonant bubbles at boundaries, appears to be an important mechanism in accounting for certain well-known effects of ultrasound. Continued development may lead to means for applying microstreaming to surface processes in a controlled and specifiable manner.
Temporary Threshold Shift Produced by Intermittent Exposure to Noise
Authors: Ward W. Dixon , Glorig Aram , Sklar Diane L.
Published: September 2005

The TTS at 4 kc was measured 2 and 17 min after successive 12-min exposures to broad-band noise at 106 db SPL separated by 18 min of silence. The results indicate that the TTS existing at the beginning of a particular exposure can be treated as additional time of exposure. Thus, if the residual TTS has a value that would be produced by R min of exposure, then the total TTS at the end of an M-min exposure will be given by solving the equation for growth of TTS with exposure time set equal to M+R.
Development of Apparatus for the Analysis of Sound by the Sense of Touch
Authors: Guelke R. W. , Huyssen R. M. J.
Published: September 2005

An apparatus is described that applies the frequency components of speech, as spoken into a microphone, to the fingers of one hand with the purpose of enabling a deaf person to comprehend speech. Frequency is indicated by position along the fingers. The sense of touch is not called upon to make any direct frequency discrimination by distinguishing vibrational sensations of different frequencies as in previous attempts of this nature [R. H. Gault, J. Franklin Institute 204, 329–358 (1927)]. The frequency analysis is done partly electrically and partly mechanically. Small tuned steel reeds are used for the final frequency analysis. These steel reeds also serve as transducers by operating directly against the fingers.

The results of a short series of experiments on a deaf person are promising but the recognition of individual consonants is difficult.
Hot Wire Method for Visualizing Intense Stationary Sound Waves
Authors: Fand R. M. , Kaye J.
Published: September 2005

A simple method has been developed for visualizing intense stationary sound waves, using a thin electrically heated wire stretched in the direction of sound propagation. The nodes and antinodes of the sound waves appear as a series of alternate incandescent and dark areas on the wire. Photographs of the hot wire indicate the presence of hitherto unreported thermoacoustic phenomena.
Thermal Effects of Acoustic Streaming near a Cylindrical Obstacle
Authors: Walker C. T. , Adams C. E.
Published: September 2005

The cooling effect of acoustic streaming on a heated Thermistor imbedded in a cylinder placed in a sound field in air was studied and found to be in accord with theory.
Some Near- and Far-Field Noise Measurements for Rocket Engines Operating at Different Nozzle Pressure Ratios
Authors: Mayes William H.
Published: September 2005

Measurements of near- and far-field noise pressures are presented for a 1650-lb thrust engine and for 6000–7500-lb thrust engines for which the nozzle exit pressure was changed systematically in order to study its effects on the noise level and spectra. Near-field surveys indicated that the highest noise pressure occurred at about 20 exit diameters distance downstream of the nozzle near the transition from supersonic to subsonic flow. At a radial distance of three exit diameters, the noise pressure levels varied from about 145 db just upstream of the nozzle to about 170 db downstream of the nozzle, and no consistent trends were noted as a function of nozzle exit pressure. In general, the spectra at points downstream of the nozzle contained considerably more low-frequency noise than those measured upstream of the nozzle. It was noted that the maximum far-field noise was radiated in the downstream direction at angles of 30° to 45° from the jet axis. The acoustical power radiated from all nozzles averaged about 0.5% of the mechanical power of the exhaust stream, the least noise being radiated by the nozzle having an exit pressure less than atmospheric.
Distribution of Sound Sources in a Jet Stream
Authors: Dyer Ira
Published: September 2005

It is shown that the axial distribution of sound sources in a turbulent jet stream can be found simply in terms of (1) the spectrum of the total radiated power and (2) the frequency of the sources as a function of location along the jet axis. With the use of existing data on the sound power spectrum and recently reported but preliminary data on the frequency dependence of the most probable source location, an approximate axial distribution is derived. The derived distribution is in agreement with calculations by Sanders based on turbulence measurements, and with calculations by Ribner based on Lighthill's theory.
Effect of Sample Duration on the Articulation of Sounds in Normal and Clipped Speech
Authors: Ahmend Rais , Fatehchand Richard
Published: September 2005

Segments of vowels and consonants from nonsense syllables, accurately determined in position and width, are used for articulation measurements. The listening tests are performed on differentiated speech, and on differentiated speech subjected to severe clipping. Whether or not vowels are clipped, their segment lengths can be considerably reduced with little effect on articulation. This does not hold for consonants, with the exception of unclipped semivowels. The high articulation of interrupted speech is discussed, and some results are given.
Noise Generated by Two Interacting Air Jets
Authors: Ingard Uno , Maling George C.
Published: September 2005

It has been observed that the excess noise generated as a result of the interaction or mixing of two small air jets is considerably greater than the noise produced by the individual jets. The “interaction noise” produced by jets that lie in the same plane has been measured for jet intersection angles between 0 and 180°. Similar measurements have been made as a function of jet separation by using two jets that intersect at a 90° angle but do not lie in the same plane.
Simple Examples of Magnetomechanical Wave Motion
Authors: Ingard Uno
Published: September 2005

The phase velocity on a periodic line consisting of coupled mass elements (coils) in a magnetic field is shown to be analogous to the phase velocity of a transverse Alfvén wave in a conducting, incompressible fluid. As another example of the magnetomechanics of a simple “distributed” system, the motion of a conducting string in a magnetic field is discussed.
Acoustical Problems in Two Round Churches
Authors: Mikeska E. E. , Lane R. N.
Published: September 2005

Acoustical measurements and design considerations are discussed for two churches with circular floor plans. One was carefully planned with the acoustics in mind and has proved successful. The other was built with a parabolic concrete dome; a thin sprayed absorbent lining inside the dome was counted on to eliminate sound focusing effects. Echograms taken at several positions inside the church illustrate the resulting severe echo problems.
Acoustoelectronic Auditorium
Authors: Olson Harry F.
Published: September 2005

The term “acoustoelectronic auditorium” is used to designate an auditorium complex incorporating an integrated design of the room acoustics with the sound reinforcing apparatus. Under these conditions, the acoustic characteristics of the electronic sound system are coordinated and correlated with the acoustics of the enclosure. The features of the acoustoelectronic auditorium are as follows: an enclosure providing a large stage, a low ceiling and a seating capacity of 300; sound reinforcing apparatus consisting of the following features: concealed and fixed stage microphones, concealed and fixed auditorium loudspeakers, and a delay system.
Diffraction of a Plane Sound Wave by a Semi-Infinite Thin Elastic Plate
Authors: Lamb George L.
Published: September 2005

The diffraction of a plane small amplitude sound wave incident upon a semi-infinite thin elastic plate is investigated theoretically. The problem is formulated in terms of an integral equation relating the discontinuity in pressure across the diffracting plate to its flexural displacement and the usual fourth order thin plate differential equation governing the flexural motion of the plate when driven by the pressure discontinuity. This pair of coupled equations is then shown to be amenable to solution by the Wiener-Hopf method. A perturbation procedure, valid in the limit of increasing plate stiffness, is employed to obtain expressions for the sound fields radiated by and transmitted through the plate as well as for the diffracted sound field.
Vibration of Uniform Square Plates Bounded by Flexible Beams
Authors: Cox Hugh L. , Benfield Wilcomb A.
Published: September 2005

The fundamental frequencies of flexural vibration are determined for uniform isotropic square plates that have pinpoint supports at the four corners and flexible beams along the edges. The flexible beams are pinned to the plate so that the beams resist only deflection of the plate boundaries. Finite difference solutions, which simplify the treatment of the boundary conditions for definite values of Poisson's ratio, are used to obtain the approximate solutions.
Some Measurements on the Effects of Interchannel Intensity and Time Differences in Two Channel Sound Systems
Authors: Leakey D. M.
Published: September 2005

The results of some practical measurements on the effects of interchannel intensity and time differences in two channel (stereophonic) sound systems are presented. The effects of alterations in the listener position are also covered. The test signals used ranged from single component tones to wide and narrow band noise and included running speech. A theory based on the assumption that the brain is sensitive to interaural time difference and its variation with head movement is developed and is shown to be in reasonable agreement with the practical findings.
Psychophysical Estimate of the Velocity of the Traveling Wave
Authors: Schubert Earl D. , Elpern Barry S.
Published: September 2005

An extension of a method originally employed by Békésy in 1933 was used to estimate the velocity of the traveling wave along the cochlear partition. The method consists of masking a different length of the basilar membrane at each of the two ears so that the wave produced by a simultaneous click at the ears emerges from the shorter masked portion of one ear sooner than from the other. As a result the click lateralizes toward the side where the wave emerges sooner. The time interval by which the click to the “earlier” side must be delayed to center the subjective click is an estimate of the original difference in time of emerging from the masking and hence of the time taken to travel the portion of the membrane represented by the difference in cutoff frequency of the two masking noises. Measurements were taken for 14 overlapping half-octave segments of the basilar membrane on 7 subjects. Measurement was not possible below 1000 cycles with the instrumentation used. The velocity estimates range from 55 m/sec near the stapes to approximately 30 m/sec at a point some 20 mm away.
Reflection and Refraction of Elastic Waves at the Interface of Two Moving Semi-Infinite Plane Media
Authors: Samuels J. Clifton
Published: September 2005

The problem of the reflection and refraction of elastic waves at an interface of relative motion is solved. Total reflection of dilatational and rotational waves can occur for certain ranges of angles of incidence depending on the relative speed of the media. For very high relative speeds, resonance of the reflected and refracted waves occurs for certain angles of incidence, called angles of resonance. For a Poisson material and identical moving media, the relationship of the angle of resonance to the relative Mach number (based on the dilatational wave speed) is worked out and presented in the form of a curve.
Steady-State Behavior of the Dynamic Absorber
Authors: Snowdon J. C.
Published: September 2005

The resonant vibration of machinery and resiliently mounted equipment can be reduced with a dynamic absorber of suitable design. The necessary analytical and graphical information for an optimum design is presented in this paper. It is assumed that the absorber mass is attached resiliently to the vibrating item with a rubber-like material, and not with a spring and dashpot in parallel as considered in the classical theory of Ormondroyd and Den Hartog. The dynamic absorber utilizing a material with a stiffness proportional to frequency and a constant damping factor can reduce the resonant vibration of machinery and equipment items considerably. Its performance is superior to that of the classical dynamic absorber.
Residual Masking at Low Frequencies
Authors: Harris Cyril M.
Published: September 2005

Short duration auditory fatigue, i.e., the temporary shift in the threshold of hearing following the cessation of a masking source, may be termed “residual masking.” In this study, curves of residual masking vs frequency have been obtained in a free-field in the low-frequency range, for 250-cps masking tones at sound pressure levels of 90 and 110 db, following the method of Munson and Gardner. These masking patterns were obtained 150 and 200 msec after the cessation of the masking tone. In addition, residual masking at 250 cps was measured as a function of the mel-band intensity level of a “white noise” masking source. Plots of loudness density vs frequency were computed from residual masking patterns, and the loudness of the pure-tone masking source was evaluated.
Experiments on the Bone-Conduction Threshold in a Free Sound Field
Authors: Nixon C. W. , von Gierke H. E.
Published: September 2005

Earlier investigators of the free-field bone-conduction threshold occluded the auditory meatus with plugs and muffs and reasoned by various arguments that the real-ear attenuation obtained was less than the attenuation provided for air-conducted sound. The conclusion was that the sound perceived reaches the auditory system via bone conduction. The present experiments are a check on these conclusions for the frequencies from 1000 to 8000 cps. With the auditory canal occluded by plugs and muffs the whole skull, or sections of it, was covered with a 2-in. layer of absorbent cotton. The muffs were not covered. A higher free-field threshold with the cotton indicated that without cotton the sound was reaching the ear via bone. [The sound pressure level (SPL) at the surface of the muffs was not altered by the surrounding cotton.] Cotton over the entire head raised the bone-conduction threshold by 10 to 18 db from 2000 to 8000 cps (8 subjects). Bone-conduction thresholds determined previously were confirmed from 1000 to 8000 cps. The front and back of the head were approximately of equal sensitivity with respect to bone conduction. Covering only the side of the head facing the sound source raised the threshold more than covering the “shadow” side alone. The results suggest a possible method for improving the effectiveness of special noise-attenuating devices.
Scattering of Impulsive Elastic Waves by a Rigid Cylinder
Authors: Gilbert Freeman , Knopoff Leon
Published: September 2005

The exact solution to the problem of the scattering of compressional elastic waves from a line source by a rigid, infinitely dense cylinder imbedded in an isotropic, homogeneous, perfectly elastic medium is obtained in integral form. The integrals are evaluated asymptotically obtain the motions on the wave fronts. In the illuminated zone the saddle point method of integration yields the geometrical optics approximation to the reflected field. In the shadow zone the diffracted field is obtained by evaluating the integrals by the method of Dougall and Watson. In the case of an incident P wave the observed events in the illuminated zone are (1) direct P, (2) reflected P, and (3) reflected S. In the shadow zone the observed events are (1) diffracted P and (2) diffracted S. Both diffracted wave fronts travel around the cylinder with the velocity of P waves.
Neural Funneling along the Skin and between the Inner and Outer Hair Cells of the Cochlea
Authors: von Békésy Georg
Published: September 2005

An attempt has been made to show that (1) the rotating tones in hearing, (2) the rotating vibrations on the skin, (3) the difference limen for the smallest perceptible distance on the skin, and (4) Mach's law of contrast are all a consequence of the same funneling action of the nervous system. In many situations the role of the funneling action can be better understood if a neural funneling unit is proposed, taking into account that a local stimulus produces both an area of activity and, around it, an area of decreased sensitivity. Since the inner and outer hair cells in the cochlea show a difference in sensitivity, the funneling action between these areas of different sensitivity has been investigated. It has been found that, between such areas, the locus of the sensation is continuously displaced as the intensity of the stimulus is increased. This suggests that along the organ of Corti there is a longitudinal displacement produced by variations in frequency, and a radial displacement between the outer and inner hair cells produced by variations in sound pressure. Thus there seems to be a pitch-loudness coordinate system in the ear. The cochlear model (described earlier) with nerve supply was therefore further developed into a cochlear model with more and less sensitive nerve supplies, in order to represent the outer and inner hair cells in the organ of Corti.
Masking by Tones vs Noise Bands
Authors: Ehmer Richard H.
Published: September 2005

In a previous study it was proposed that tonal masking arose mainly from the cochlear activity pattern of the masking tone, modified by the formation of beats between the signal and masking tones. The present study casts further light on these proposed mechanisms by comparing the masking effects of pure tones of 500, 1000, 2000, and 4000 cps at 60 and 80 db SL with 13 octave bands of noise of equal intensities and centered at the same frequencies. The results show that the noise bands produce about the same amount of extended masking despite the absence of any possible aural harmonic distortion, but greater direct masking due to the elimination of beats. Furthermore, the noise-masking curves join the tone-masking curves at the second peak in the latter, providing strong additional support for the proposed mechanisms of auditory masking.
Listener Reaction to Stereophonic Reproduction by Reflected Sound
Authors: Levy Sidney E. , Sioles George W. , Brociner Victor , Carlisle Richard W.
Published: September 2005

Comparisons were made by numerous observers of the stereophonic perception of direct versus reflected sound. For conventional direct sound, two loudspeakers having wide frequency response were used at spacings of from six to fifteen feet, directed towards the listeners. For reflected sound, equivalent dual sound sources were used placed back-to-back near the walls of a room in which it was desired to establish a stereophonic sound field. The frequency response of the latter system was equalized to have the same apparent response as the conventional system.

Many of the tests were conducted behind a sound permeable screen. Listeners were mixed in their ability to identify the reflective system and in their preference for one system over the other, although they reacted favorably to both systems.
Auditory Detection of a Noise Signal
Authors: Green David M.
Published: September 2005

Measurements of the detectability of a noise signal in noise are reported in this paper. Parameters of the noise signal such as the band width, duration, and center frequency are investigated. The results are compared with an optimum-detection model. For some constant detectability the equation generated by the model and one constant, an attenuation factor, closely fit the experimental data over the major range of the experimental parameters. The major area of discrepancy between model and data is the shape of the psycho-physical function. Implications of the data for the critical-band mechanism are also discussed.
Lateralization of High-Frequency Tones
Authors: Mills A. W.
Published: September 2005

Thresholds for interaural difference between the intensities of dichotic tone pulses were measured on five subjects by the method of constant stimuli, at frequencies between 250 and 10 000 cps and at a sensation level of 50 db. The just noticeable dichotic difference in intensity is about 1 db at 1000 cps, a little smaller at lower frequencies, and still smaller (0.5 db) at higher frequencies. This function is compared with the interaural difference in intensity produced by the just noticeable deviation from the median plane of an actual source of tone pulses. At low frequencies, where phase or time differences are generally considered more important than intensity differences for auditory localization, these two functions differ greatly. At frequencies between 1500 and 6000 cps, the threshold for a dichotic difference in intensity matches the interaural difference in intensity that is produced by the just noticeable deviation from the median plane of an actual source. The relation between the discrimination of dichotic differences in phase and intensity and the discrimination of actual direction is shown in a graphical summary.
Acoustic Radiation Force on a Uniformly Moving Smooth Body, to the First Order in the Velocity
Authors: Lothe Jens
Published: September 2005

It is shown that the acoustic radiation force on a uniformly moving smooth body is given correctly to the third order by simple first-order theory, in agreement with a calculation by Nabarro [Phil. Mag. 41, 1276 (1950)].
Toward a Model for Speech Recognition
Authors: Stevens Kenneth N.
Published: September 2005

An approach to the design of a machine for the recognition and synthesis of speech is proposed, with particular emphasis on problems of acoustical analysis. As a recognizer, the proposed machine accepts a speech wave at its input and generates a sequence of phonetic symbols at its output; as a synthesizer it accepts a sequence of symbols at its input and generates speech wave. Coupling between the acoustical speech signal and the machine is achieved through two peripheral units: one an analog filter set or equivalent, and the other a model of the vocal tract. Between the analog filters and the phonetic output the signal undergoes an intermediate form of representation that is related to vocal-tract configurations and excitations but is not necessarily described specifically in these terms. Each stage of analysis is performed by synthesis of a number of alternative signals or patterns according to rules stored within the machine and by comparison of the synthesized patterns with the input signals that are under analysis. Possible advantages of the proposed method of analysis are discussed. An experimental study based on the general analysis approach is described in an Appendix. In this study a method for the determination of the frequencies of vocal-tract resonances from the speech wave is simulated on a digital computer.
Spatial and Temporal Absorption in a Viscous Medium
Authors: Mintzer David , Tanenbaum B. Samuel
Published: September 2005

The relation between spatial and temporal absorption for acoustic waves in a viscous medium is discussed by considering the problem of a viscous-liquid filled tube with a piston at one end and a reflecting termination. The solution of the problem is found in terms of traveling waves from image sources, and standing waves in a tube. The phase velocity and attenuation of the steady-state terms for both solutions are the same. The transient part of the standing wave solution gives rise to the usually plotted velocity and temporal attenuation; it is shown that these do not have the same meaning as in the spatial absorption case, since they depend upon the allowed wave numbers of the system, that is, upon the geometry and boundary condition.
Experimental Investigation of the Noise Generated by the Turbulent Flow Around a Rotating Cylinder
Authors: Wilson L. N.
Published: September 2005

The near- and far-field noise from the turbulent boundary layer developed on a rotating cylinder has been studied; both smooth and artificially roughened surfaces were employed. The cylinder walls were sufficiently thick to inhibit appreciable boundary-layer-excited vibration noise. The mean square pressure followed a U4 law in the near field, and the total acoustic power radiated to the far field followed a higher exponent law: approximately U6. The necessity to excise spurious peaks at harmonics of the cylinder speed from the measured far-field spectrum introduced inaccuracy in the computed power law, bringing some doubt to bear on the accuracy of the exponent. The U6 law, unless it is a fortuitous average of laws of lower and higher power, suggests that the dominant radiators are of a dipole type. Drag calculations from hot-wire measurements allowed an estimate of the efficiency (acoustic power/mechanical power) of the far-field radiation, resulting in an efficiency of the order of 30 times that for the quadrupole radiation from a jet at a Mach number of 0.228. Even so, the measured noise power from the boundary layer over a rigid wall appears to be relatively small in any practical application to the noise in aircraft. This is in contradistinction to the noise radiated by boundary-layer-induced vibrations of a flexible wall or panel which can exceed the former by some orders of magnitude.
Determination of Ultrasonic Velocities by Measurement of Angles of Total Reflection
Authors: Mayer Walter G.
Published: September 2005

A simple method, based on the total reflection of a sound beam from a liquid-solid boundary at the critical angles, is described. With this method, it is possible to measure the velocity of longitudinal and shear waves in the solid by locating the angles of maximum reflection in the liquid.
Sonically-Induced Microstreaming near a Plane Boundary. I. The Sonic Generator and Associated Acoustic Field
Authors: Jackson Francis J. , Nyborg Wesley L.
Published: September 2005

An experimental arrangement is described which permits controllable generation of small-scale acoustic streaming, i.e., “microstreaming” near a plane boundary S. This arrangement, which consists essentially of a cylindrical bar oscillating longitudinally above the boundary S in question, has been used in studies of sonically-produced effects at a fluid-solid interface. The present paper deals with first-order pressure and velocity fields in the thin layer of fluid between S and the vibrating face of the bar. Theoretical expressions are developed, based on a simple model in which incompressible flow is assumed. Experimental determination of the pressure field was accomplished by means of a special hydrophone arrangement described herein, which measures the pressure at points along the plane boundary. The first order theory agrees well with experiment, and is thus judged satisfactory as basis for a detailed treatment of the microstreaming flow, to be given in a subsequent paper. A byproduct of the work is a method for calibration of small hydrophones.
Intense Stress Field Produced in a Semi-Infinite Elastic Solid by a Bomb Blast at the Surface
Authors: Serbin Hyman
Published: September 2005

The response of a solid subjected to intense blast pressures depends on the ratio of the applied pressures to the stresses (yield stress, etc.) characteristic of the material of the solid. When this ratio is small, the solid can be expected to respond elastically. The paper develops the elastic theory of a semi-infinite solid exposed to a blast initiated at a point on the surface, assumed to be in air at sea level. The results are explicit expressions for the displacements and stresses for early time, small radial distances, and shallow depths. Application to the case where the solid represents the earth is discussed.
Propagation of Intense Shock Waves into the Earth
Authors: Serbin Hyman
Published: September 2005

An earlier paper by the author considered the behavior of a semi-infinite solid reacting elastically to a point-initiated blast wave at the surface. When the applied pressures are sufficiently high, the solid will experience inelastic behavior characteristic of the material. The earth is here regarded as a medium made up of solid matter, water, and air voids. It is assumed that the principal effect of high normal stresses is to close up the air voids and that thereafter the medium acts like an elastic solid. The calculation of the peak pressure vs depth is compared with experimental data derived from nuclear bomb tests and shows reasonable agreement considering the wide scatter of test points.
Bubble Transducer for Radiating High-Power Low-Frequency Sound in Water
Authors: Sims Claude C.
Published: September 2005

The bubble transducer consists of a conventional low-impedance electrodynamic driver with an air-filled rubber membrane, or “bubble,” of adjustable volume over the diaphragm. The system at resonance produces large volume displacement of the water with small linear diaphragm displacement at frequencies below 200 cps. For constant diaphragm volume velocity, the addition of the resonating bubble increases the power output by a factor of approximately 1000.
Pitch of Periodic Pulses without Fundamental Component
Authors: Flanagan James L. , Guttman Newman
Published: September 2005

The pitch of a periodic pulse train is matched to that of another train whose fundamental component of frequency is rejected. Three modes of pitch perception are found. The first obtains for pulse rates less than 100 pps. Here, in a manner similar to that found previously for unfiltered stimuli, the pitches are matched to equate pulse rate, regardless of the polarity patterns of the trains. The second mode occurs for fundamental frequencies in the approximate range 200–500 cps. Here there is a decided tendency to equate fundamental frequencies. The third mode is manifested for fundamental frequencies of the order of 1000 cps and higher. In this range subjects tend to equate the fundamental of the matching tone to the lowest spectral component present in the matched stimulus. Between the modes, transition regions exist in which the pitch assignment generally is difficult and uncertain. The stimuli are studied with an electrical analog of the basilar membrane. Waveforms of membrane displacement and first spatial derivative of displacement are obtained from the analog. The three (psychophysical) pitch modes are found to be manifested in these mechanical functions of the basilar membrane.
Binaural Summation of Loudness
Authors: Reynolds George S. , Stevens S. S.
Published: September 2005

A stimulus of a given sound pressure sounds louder when it is heard with two ears than when it is heard with only one ear. This fact is demonstrated by a series of experiments designed to quantify the ratio of binaural to monaural loudness at various stimulus levels. The methods used included magnitude estimation, magnitude production, one-vs-two-ear ratio production, monaural-binaural loudness matching, and the cross-modality matching of loudness to the apparent intensity of a vibration.

The results indicate that (1) monaural loudness grows as a power function of sound pressure with an exponent of about 0.54, whereas binaural loudness grows with an exponent of 0.6, and (2) the ratio between binaural and monaural loudness increases as a power function of sound pressure with an exponent of about 0.066. This ratio is 2:1 at about 90 db SPL. At lower levels the ratio is smaller, and at higher levels it is larger.
Response of Cochlear Models to Aperiodic Signals and to Random Noises
Authors: Tonndorf Juergen
Published: September 2005

Traveling bulges along the cochlear partition were recorded in response to gradual step-function signals (the simplest form of a transient). Such a bulge resembles a train of waves decaying both in time and in space. Since each half-wave grows longer in duration with its rank order, it forms its own individual envelope, including the location of maximal displacement. The latter location depends upon the time constant in essentially the same manner as that in response to steady-state signals upon inverse frequency. The point of over-all maximal displacement (usually due to the first half wave) varies with the time constant of the applied signal but also with the signal shape. At any given point along the partition, the propagation velocity of each half-wave varies with the initial amplitude and its inverse time constant while its deceleration with distance depends upon the inverse time constant only. This is signified by the fact that the velocity-distance curves of various portions of each bulge tend to approach a common point which is frequently located beyond the helicotrema. The response to random noise (and to bands thereof) is a superposition, in time and in space, of responses to single transients in random distribution.
Sonically Induced Microstreaming near a Plane Boundary. II. Acoustic Streaming Field
Authors: Jackson Francis J.
Published: September 2005

In a previous article, the author described an experimental arrangement suitable for generating small-scale near-boundary acoustic streaming, i.e., “microstreaming,” in a precise and controllable manner. Such microstreaming is of particular interest insofar as it can have considerable influence on processes taking place at a solid-liquid interface. In the present paper, results of a comprehensive study of the microstreaming flow field associated with the aforementioned experimental system are discussed in some detail. Photographs are shown of the various flow configurations, and data are presented on streaming speeds as a function of significant experimental parameters. Theoretical expressions are developed along lines of conventional acoustic streaming theory to describe various features of the flow. The correlation between theory and experimental results is found to be good when certain criteria, described herein, are fulfilled.
Thrust on a Piston Driven Half-Open Tube
Authors: Hudson George E.
Published: September 2005

The motion of the gas in and near a tube open at one end and closed at the other by a piston driven in nearly sinusoidal motion is investigated. Experiments disclose that when the frequency of the piston motion is near the fundamental acoustic resonance frequency of the gas column an intermittent air jet associated with a system of vortex rings is expelled from the tube's open end. This results in an appreciable average thrust on the tube which, however, is much less than might be expected from purely acoustic considerations. A theoretical analysis has been made which takes account of the intermittent vortex and jet formation, as well as of the acoustic radiation field. The analysis leads to formulas for the average thrust and power dissipation and to a relation between the driving frequency and the amplitude of the gas motion at the open end. An empirical parameter κ which represents the fraction of energy dissipated in vortex motion appears in these formulas. It is found possible to evaluate this parameter in terms of the observed thrust at resonance. From this datum the curve of thrust versus driving frequency is calculated and is found to agree well with experiment.
Low-Frequency Motion of Bodies in an Elastic Wave Field
Authors: Miles John W.
Published: September 2005

The mean translation and rotation of a body having elastic constants and a density that differ only slightly from those of an otherwise homogeneous medium in which it is imbedded and having dimensions that are small compared with the wavelength are calculated for an arbitrary incident wave field. The problem is reduced to the evaluation of two integrals in potential theory, and explicit evaluations of these integrals are given for an ellipsoid. The results are applied to the motion of a sphere and a prolate spheroid under the influence of plane P and S waves.
On Thermally Induced Sound Fields
Authors: Trilling Leon
Published: September 2005

The sound fields induced in a real gas by boundary temperature variations are examined to illustrate how the pressure, temperature, and vorticity modes of motion interact. The pressure mode describes the irrotational propagation of longitudinal disturbances, the temperature mode, convective heat diffusion, and the vorticity mode, the diffusion of vorticity introduced at boundaries by the no-slip condition (boundary layer). The plane sound wave due to an instantaneous wall temperature rise is a sharp pulse, traveling at sonic speed and proportional to the inverse fourth root of the acoustic Reynolds number based on distance traveled; its thickness grows as the square root of elapsed time. Along a wall, it generates a boundary layer whose friction coefficient is proportional to the inverse square root of the acoustic Reynolds number based on distance from the front. The resulting effective wall slope induces a secondary circular pressure pulse generated by the foot of the plane wave; because this source moves at sonic speed, a pressure singularity appears there, due to the contributions piled up since the beginning of the motion.
On the Statistical Mechanics of an Adiabatically Compressible Fluid
Authors: Kraichnan Robert H.
Published: September 2005

The extension of classical statistical mechanical methods to non-Hamiltonian systems is discussed. The statistical equilibrium of a confined adiabatically compressible fluid is examined on the basis of a generalized phase space representation, and it is found that there exists a tendency toward equipartition of energy between compressive and vorticity modes which is modified by the viscous dissipation forces. The application of the method to determining nonequilibrium energy transfers between acoustic modes and vorticity modes is discussed.
Radiation Resistance of Magnetostrictive-Stack Transducer in Presence of Second Transducer at Air-Water Surface
Authors: Stumpf F. B. , Lukman F. J.
Published: September 2005

The radiation resistance of a nickel magnetostrictive-stack transducer in the presence of an identical in-phase transducer at an air-water surface was obtained. The transducers are resonant at 20 kc and their radiating surfaces are squares whose sides are 0.38 of the wavelength in water. Curves were obtained for the radiation resistance vs separation distance for electrical driving forces of the interacting transducer which were 1.0, 2.0, and 3.9 times the electrical driving force of the reference transducer. It was found that for a given driving force ratio, the radiation resistance with interaction oscillated about the value for the radiation resistance of the transducer with no interaction and that these oscillations decreased in amplitude as the separation distance was increased. Near 2λ, the interaction effect became negligible. Furthermore, it was found that the interaction increased with increasing electrical driving force of the interacting transducer. Qualitative agreement is found with treatments of the interaction radiation resistance of other physical situations, but an adequate analytical study of this case is needed.
Determination of the Velocity of Sound in Distilled Water
Authors: Brooks Richard
Published: September 2005

The velocity of sound is determined in distilled water over the temperature range from 22 to 25°C. The method used consists of measuring the transit time of two sound paths of different lengths traveling between the crystal faces of two barium-titanate transducers. With an accurate measure of the length, the velocity is determined from the quotient of ΔI/Δt. It is believed that the accuracy of the measurements is within ±1 ft/sec.
Acoustical Behavior of Some Engine Test Cell Structures
Authors: Watters B. G. , Labate S. , Beranek L. L.
Published: September 2005

This paper presents some recent data on the acoustical behavior of certain components of engine test cell structures. These data include information on (a) the directivity patterns of vertical stacks and (b) the noise reduction provided by some water-spray systems, (c) the Soundstream absorber, and (d) a 90° vertical bend.
Pitch Discrimination of Two-Frequency Complexes
Authors: Schodder G. R. , David E. E.
Published: September 2005

Apparently the pitch difference limen (DL) for a single high-frequency sinusoid can be smaller in the presence of a nearby constant frequency component than in isolation. It is demonstrated that this effect arises from the time-envelope properties of the two-frequency complex. This result is consonant with those of Flanagan and Saslow who found that the pitch DL of a periodic vowel sound is smaller than the DL of a sinusoid at the fundamental frequency.
Thermoelectric Microphone for Modulated Ultrasonic Waves
Authors: Hanel Rudolf A.
Published: September 2005

Conventional thermal microphones record the temperature increase generated by the absorption of acoustical energy. The microphone described in this paper measures the periodic change of the temperature that is generated by an amplitude-modulated sound wave. This microphone is small, omnidirectional, free of drift, and extremely sensitive. Temperature variations in the order of 3×10 5 C have been recorded by means of a narrow-band amplifier tuned to the modulation frequency. The temperature distribution in a thermocouple enclosed in a sound-absorbing material, and the optimum modulation frequency are calculated. A relaxation function is introduced to help interpret the results physically. Also, the electronic input circuit is discussed in detail.
Semiplastic Earplugs
Authors: Zwislocki J.
Published: September 2005

Description of the development of an earplug with soft elastic walls and a viscous core malleable at body temperature. The problems of suitable material, shape, and size are considered as well as the shape and size adaptability. People have found these earplugs sufficiently comfortable to sleep with, and they ensure a sound attenuation equal to or better than any known earplug. One size fitted 90 percent of the ears of the 25 people tested sufficiently well.