bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Sound Pulses for a Study of Circumferential Waves
Authors: Überall H. , Doolittle R. D. , McNicholas J. V.
Published: September 2005

In recent underwater experiments, multiple echoes that returned in the scattering of a single pulse have been tentatively analyzed in terms of creeping (or circumferential) waves appearing in the diffraction process. In other experiments, the presence of creeping waves has been inferred from steady-state interferences. It is suggested here that one should confirm the existence of circumferential waves by observing diffracted pulses in the near field around the scatterer, including the shadow region. A mathematical study of the creeping waves is performed, using the Sommerfeld-Watson transformation method of Franz and assuming that the initial plane sound wave possesses an arbitrary pulse shape. The expressions for the creeping pulses obtained on the surface of the scatterer include—but go beyond—previous results of Friedlander, found with a different method; we also considered geometrically reflected pulses and farfield expressions. The special example of an infinitely long, acoustically soft, circular cylinder is used, but an extension to other simple cases is possible. Some examples are discussed graphically.
Geometric Diffraction Loss in Longitudinal- and Shear-Wave Attenuation Measurements in an Isotropic Half-Space
Authors: Lord Arthur Edson
Published: September 2005

Polar diagrams of the asymptotic (large R) stresses in an isotropic half-space, due to point-normal and line-tangential harmonic forces applied to the surface, are given for Poisson's ratio of 0.20 and 0.45. A reciprocity-theorem calculation of these stresses helps to give insight into interesting features of the diagrams. An approximate theory of geometric diffraction loss based upon the asymptotic stresses, which neglects all phase fluctuations across the receiver and, hence, cannot be used in the Fresnel region, is derived for the following sources: (a) normal stress applied to a circular area of radius a; (b) infinitely long, narrow strip (of half-width a) of shear stress with displacement normal to the length; mid (c) torsional shear stress applied to a circular area of the half-space. In all cases, the receiver is of the same size, centered on and parallel to the source. The diffraction loss αD (to±0.50 dB) is: Case (a)—αD(dB) = 1.0(λ/a2)z, 3 < (zλ/a2) < 13, which agrees with the same source radiating into a fluid; Case (b)—αD(dB) = 0.40(λ/a2)z, 4 < (zλ/a2) < 15; Case (c)—αD(dB) = 9+1.60(λ/a2)z, 5 < (zλ/a2) < 14, where the diffraction loss in this region is considerably higher than in either Case (a) or (b). In the case of an infinitely long, narrow strip of shear stress with displacement parallel to the length, the entire radiation pattern can be obtained by numerical integration. Using Papadakis' results [.J. Acoust .Soc. Am. 36, 414–422 (1964)], a general diffraction correction of about 0.50 dB (a2/λ) is in order.
Transverse Vibrations of Cantilever Bars of Variable Cross Section
Authors: Gaines J. H. , Volterra E.
Published: September 2005

Approximate formulas are derived for upper and lower values of the three-lowest natural frequencies for transverse vibrations of cantilever bars of variable cross section. For cones, truncated cones, wedges, and truncated wedges, as well as bars of constant cross section, the effects of rotatory inertia and shear are taken into account also and compared with the results obtained by neglecting these effects according to the elementary Bernoulli-Euler's theory of bending of beams. Numerical results for the first three natural frequencies are presented in tabular form for different inertia characteristics.
A Spring with Time-Variable Stiffness
Authors: Rodgers P. W.
Published: September 2005

A linear electromagnetic spring of time-variable stiffness is described. Experimental data from such a spring tire given, showing linearity over a wide range of positive and negative stiffness. The operation and uses of the device are discussed.
Dispersion of Hypersonic Waves in Liquids
Authors: Fleury P. A. , Chiao R. Y.
Published: September 2005

The spectrum of light scattered from thermal sound waves has been studied to provide information about velocity and absorption of hypersonic waves in several liquids. Relaxation processes have been observed in CS2, CCl4, C6H12, C6H6, toluene, acetic acid, and nitrobenzene. In water at 6 Gc/sec, neither the Sound velocity nor its coefficient of temperature dependence differs from their values at 5 Mc/sec.
Surface Treatment of Quartz Crystals for Hypersonic Applications
Authors: Lamb J. , Seguin H.
Published: September 2005

Large variations in electromechanical conversion efficiency were observed in quartz crystals used for the generation of elastic waves by surface excitation at microwave frequencies. Significant improvements were effected by lightly etching all crystals when received in the polished condition and subsequently applying a fine polish to restore optical flatness of the surface. After such treatment, the measured electromechanical conversion efficiency was in good agreement with the calculated value and all crystals gave approximately the same response. Moreover, the measured attenuation at 3000 Mc/sec in disks 0.3 cm thick was considerably less than values in untreated crystals.
Propagation Modes of Infrasonic Waves in an Isothermal Atmosphere with Constant Winds
Authors: Pierce Allan D.
Published: September 2005

A dispersion relation for low-frequency disturbances in an isothermal atmosphere with constant horizontal winds is derived. It relates the three components of the wave-propagation vector k to the angular frequency ω and depends on the sound speed, the wind velocity v, and the acceleration of gravity g. The relation is obtainable from that for propagation in an isothermal atmosphere without winds if ω is replaced by ω−k⋅v. The dispersion relation is studied with reference to the problem of the propagation of waves from a stationary source of limited spatial extent viewed by a stationary observer. The topology of the propagation surface in k space is examined. Propagation modes are defined as corresponding to disjoint portions of the surface in k space for fixed ω. The criteria for a given mode existing for given wind speed and frequency are derived and the group velocity of each type of mode is studied. The theory predicts the existence of two wind modes that, at sufficiently high frequencies, have group velocities nearly identical to the wind velocity. Phase velocities of the wind modes also tend to equal the wind velocity. In the latter portion of the paper, the trajectories of fluid particles are studied for each type of wave-propagation mode. It is shown that, in terms of particle motions, the wind modes are physically indistinguishable from the gravity mode predicted for an isothermal atmosphere at rest when viewed by an observer moving with the wind.
Steady-State Responses of One-Dimensional Periodic Flexural Systems
Authors: Ungar Eric E.
Published: September 2005

Expressions are derived that describe the steady-state behavior of infinitely long beams with uniformly spaced attached impedances and that permit damping and fluid loading to be taken into account readily. The case where the attached impedances produce only lateral forces is treated on the basis of classical beam-flexure theory. Relations governing the segment-to-segment propagation constant and the impedance the system presents to a force acting at an impedance attachment point are derived; the response to forces acting at all impedance attachment points, with a constant phase difference between adjacent forces, is also deduced. Additional results, applicable only in the region outside the near fields of the impedance attachment points, in cases where the interval between attached impedances encompasses many flexural wavelengths, are formulated in terms of the reflection and transmission coefficients that are effective at the impedance attachment points, and thus apply for impedances of any degree of complexity. A corresponding expression for the propagation constant is obtained, and a method (which is suitable also for numerical analysis of a wide variety of complex one-dimensional systems) is developed for determining the steady-state oscillations resulting from a given wave or waves injected at a given location.
Transient Response of Thin Elastic Shells
Authors: Wilkinson J. P.
Published: September 2005

A solution for the transient response of a thin elastic shell that rests on a viscoelastic foundation is found by means of the mode-acceleration method. For a uniform load, this solution is compared with a similar solution obtained by means of the mode displacement method. A numerical example for a hemispherical shell illustrates that the mode acceleration method converges slightly more rapidly that the mode-displacement method during the time of application of the transient pulse.
Long-Range Deep-Sea Attenuation Measurement
Authors: Urick R. J.
Published: September 2005

A series of standard U. S. Navy explosive charges was dropped by an aircraft en route from Bermuda to Brazil, and recordings were made at various hydrophone locations of the missile impact locating system in the Atlantic. Data from the Bermuda station have yielded attenuation coefficients between 10 and 480 cps for deep-sea propagation over a total pathlength of 2600 miles. The results are compared with the compilation made by Thorp [J. Acoust. Soc. Am. 38, 648–654 (1965)]. The data suggest a low-frequency relaxation process as one of a number of possible attenuation processes of sound transmission in the deep sea.
Reflection of Plane Viscoelastic Waves from Plane Boundaries
Authors: Cooper, Jr. Henry F. , Reiss Edward L.
Published: September 2005

The reflection of time-harmonic plane dilatational or shear waves from the rigid or stressfree boundary of an “arbitrary” linearly viscoelastic half-space is studied. Properties of general plane waves—i.e., plane waves whose amplitudes vary across their wavefronts—are used to determine the reflected dilatational and shear waves. In general, the reflected waves are general plane waves and there is a phase shift at the boundary. When certain specified conditions prevail, the reflected waves are attenuated only in their direction of propagation. Necessary and sufficient conditions on the material properties are derived for the existence of surface waves. It is shown that no surface waves can exist for certain viscoelastic materials. In general, surface waves are possible only for discrete incidence angles. However, for a special class of viscoelastic materials, which we call elasticlike, reflected surface waves may exist for a range of incidence angles greater than a specific critical angle. For the elasticlike materials, the phase shift at the boundary is the same as in the analogous elastic problem. In general, the phase velocities and reflected angles are functions of the incidence angle, the frequency, and material properties.
Medium- and Far-Field Expressions for Velocity Potential of Circular Plane Piston
Authors: Williams A. O.
Published: September 2005

Equations developed by L. V. King [Can. J. Res. 11, 135–155 (1934)] can lead to useful expressions for the velocity potential of a circular plane piston, in an infinite rigid baffle, radiating into a dissipationless fluid. An exact series is derived, in negative powers of distance from the center of the piston face to the field point, with specific formulas for all coefficients. The first term is the Fraunhofer approximation. It is then shown that a much simpler series, with the same first term and with explicit coefficients, closely approximates the exact one, provided that the piston radius is at least a few acoustic wavelengths in size and that the field point, as viewed from the source, is at only a small angle from the beam axis. This approximate series always converges, and rapidly so for distances from just outside the near field to the remote regions governed accurately by the Fraunhofer expression. At any distance outside the near field, the angular range of validity includes almost all of the power radiated in the beam.
Forced Motions of an Encased Cylinder of Decreasing Thickness
Authors: Achenbach Jan D. , Herrmann G.
Published: September 2005

A hollow cylinder is encased in a thin elastic shell and subjected to a time harmonic pressure at the inner surface of the cylinder. Plane strain and axial symmetry are assumed. The material of the cylinder is incompressible in bulk and both elastic and viscoelastic behavior in shear are considered. The inner radius of the cylinder increases monotonically with time. The influence of loss of mass and stiffness on the forced motion of the system is considered. The oscillatory motion consists of the superposition of a maintained vibration and a transient term. The maintained vibration takes into account the loss of mass and stiffness in a quasistatic manner. For an encased viscoelastic cylinder, the transient term is damped rapidly. A bounded resonance effect occurs when the instantaneous frequency of the system passes through the value of the external forcing frequency.
Statistical Description of Noise under Shore-Fast Sea Ice in Winter
Authors: Milne A. R.
Published: September 2005

Ambient noise under short-fast sea ice in midwinter is generated at the surface of the ice by wind action as well as by mechanical cracking caused by declining air temperatures. An attempt has been made to relate field measurements of underwater noise to the sources of the noise by means of a geometrical model of the environment. The statistical properties and the spectra of the under ice noise can be related to the surface density and the waveform of the source pressure pulses by means of the model.
Measurements of Reaction Time in Intelligibility Tests
Authors: Hecker Michael H. L. , Stevens Kenneth N. , Williams Carl E.
Published: September 2005

The possible advantages of including measurements of reaction time in speech-intelligibility tests are discussed. Such procedures are likely to provide independent measures of the performance of speech-communication systems and to increase the sensitivity of conventional intelligibility tests. A preliminary experiment employing an automated version of a multiple-choice test is used to illustrate this approach.
Judgments of the Relative and Absolute Acceptability of Aircraft Noise
Authors: Bishop Dwight E.
Published: September 2005

Subjects selected from airport neighborhoods judged the acceptability of noise produced by actual aircraft flyovers and by recorded flyover signals on both a relative and absolute (category) basis. Judgments were compared with the maximum perceived-noise level occurring during the flyovers. For a given perceived-noise level, little difference between ratings of takeoff and approach noise or live and recorded noise signals was observed. In the relative-judgment tests, a larger change in perceived-noise levels (16 PNdB) was required for a doubling, or halving, of the acceptability rating than the 10 PNdB originally assumed in developing the perceived-noise-level scale. In making category judgments of noise acceptability, a distinct shift between outdoor and indoor judgments occurred. Comparison with previous judgments of aircraft noise, employing different category scales, suggests relatively good agreement as to the noise levels at which a significant degree of dissatisfaction with the noise environment is expressed.
Acoustical Description of Syllabic Nuclei: An Interpretation in Terms of a Dynamic Model of Articulation
Authors: Stevens Kenneth N. , House Arthur S. , Paul Allan P.
Published: September 2005

Measurements of formant frequencies throughout the vocalic portions of a number of phonemically symmetric consonant-vowel-consonant utterances have been performed using spectrum-matching techniques implemented on a digital computer. The contours representing the first two formants as a function of time are described in terms of several parameters, including initial and final frequencies, midpoint frequencies, durations, and measures of curvature. The data illustrate the manner in which each of these parameters is influenced by the features of the vowel and by place of articulation of the adjacent consonants. The results provide evidence that diffuse tense vowels in English are characterized by diphthongal asymmetric articulatory motions, whereas nondiffuse vowels are not, and that the influence of the consonantal environment on the articulation of the vowel is greater for lax vowels than for tense vowels. Some general statements are made concerning the extent to which contiguous vowels and consonants influence each other's production.
Pulse Technique for Measuring the Scattering of Sound from Turbulence
Authors: Baerg William , Schwarz W. H.
Published: September 2005

A technique was developed for measuring the scattering of ultrasonic waves (25–65 kc/sec) from turbulence. The transmitter and receiver were of the solid-dielectric, condenser type. The scattered signal was separated from the direct and reflected signals by means of pulses, and was measured at angles from 21.5° to 165°. Readings of the root mean square of the scattered wave were obtained, which were 10−6 times the incident signal.
Ultrasonic-Pulse Propagation through Films, Foils, Fibers, and Whiskers
Authors: Gelles I. L.
Published: September 2005

Ultrasonic-pulse techniques are extended to very thin samples in the forms of films, foils, thin plates, whiskers, fibers, and fine wires. Details of the experimental techniques are described. Separate sample and transducer supports are used with independent micrometer screw adjustments to bring sample and transducers into alignment and nondestructive contact. The sample behaves like an elastic waveguide that propagates in the lowest-order modes. Major emphasis is on the lowest compressional and horizontal shear modes in isotropic planar samples and lowest compressional and torsional modes in isotropic cylindrical samples. Propagation in the 10 Mc/sec region was achieved through planar samples ranging down to 1000 Å, in thickness and through cylindrical samples ranging down to a few microns in diameter. The thinnest samples require the use of buffer plates. Representative measurements of velocity and elastic constant are presented for metal, semiconducting, and insulating materials. Applications and limitations of the described techniques are discussed.
Problem in Dynamic Thermoelasticity
Authors: Tsui Y. T.
Published: September 2005

This paper deals with the dynamic treatment of a transient thermoelastic problem for an elastic half-space that is exposed to step temperature and velocity on its entire plane boundary and is constrained against transverse displacements. The stress distribution pertaining to this problem, whose plane boundary is subjected to step- and/or ramp-type temperature only, was previously treated by V. I. Danilovskaya [Prikl. Mat. i Mekhan. 14, 316–318 (1950)], T. Mura [Proc. Japan Natl. Congr. Appl. Mech., 2nd, pp. 9–13 (1952)], and E. Sternberg and J. G. Chakravorty [J. Appl. Mech. 26, 503–509 (1959)]. In physical reality, when the boundary experiences temperature variations, it often also experiences velocity variations. A comparison of present results with previous results reveals that the stress distributions are changed considerably once the velocity variation on the boundary is considered.
Correlation of Ambient Sea Noise
Authors: Arase Elizabeth M. , Arase T.
Published: September 2005

Space-time correlations of ambient sea noise were measured with vertical pairs of hydrophones in the frequency range of 125–1131 cps and with horizontal pairs in the range of 22–63 cps at various sea states (SS) in the deep ocean. The experimental results are compared with those obtained from theoretical models of a uniform distribution of surface-noise sources, radiating with an intensity pattern of cos2nα, where α is the angle from the vertical. At SS5 and frequencies above 400 cps, a good fit to the experimental spatial correlations as well as to the principal peak of the space-time correlation is obtained for n = 1. At the same sea state, the 250-cps data correspond to n = 12. In the low-frequency range, omnidirectional noise sources explain the experimental data up to and including SS5. The model does not give a sufficient explanation for the space-time correlations at SS3 in the range 400–1131 cps.
Lateralization of a Weak Signal Presented with Correlated and with Uncorrelated Noise
Authors: Egan James P. , Benson William
Published: September 2005

When a strong signal is presented monaurally, listeners can easily lateralize the sound. However, if noise is added to both ears, there may be uncertainty as to which ear received the signal. This uncertainty was measured over a range of signal energies with perfectly correlated noise (N0) and with uncorrelated noise (NU). In the main experiment, the monaural signal occurred on each trial, and this signal was presented to either the right or the left ear by random determination during the single observation interval. Listeners responded “right” or “left.” Measures of signal detection were also secured with the monaural signal under release from masking (N0) and without such release (NU). With uncorrelated noise (NU), the listener requires only slightly greater signal energy (1–2 dB) in order to lateralize as well as he can detect. With correlated noise (N0), the psychometric function for lateralization is not only displaced considerably toward higher signal energies, relative to those required for detection, but the slope of the function for lateralization is smaller than that for detection. When a monaural signal is easily detected in uncorrelated noise, it is also easily lateralized. However, when the signal is strong enough to be readily detected with correlated noise, it is still poorly lateralized.
Standing Sound Waves of Finite Amplitude
Authors: Weiner Stephen
Published: September 2005

A technique is presented for estimating finite-amplitude effects for standing acoustic waves. The method consists of equating the nonlinear energy loss from the fundamental mode of oscillation to the work done on this mode by its higher harmonics. The higher harmonics are determined by the assumption that the wave-form is a sawtooth. Results are obtained for the limiting amplitude of oscillation, which are in qualitative agreement with previous results where these are available. The problems considered are (1) propagation of simple waves; (2) sound produced by a piston in a closed tube; (3) sound resulting from acoustic instability in a closed tube; (4) sound produced by a piston in a closed tube with the even harmonics strongly damped; and (5) sound resulting from acoustic instability in a closed tube with the even harmonics strongly damped.
Attaining Consonance in Arbitrary Scales
Authors: Pierce J. R.
Published: September 2005

A digital computer was used to synthesize a scale of tones with fundamentals 18 oct apart; each tone had nonharmonic partials separated by 18 oct or multiples thereof. When sounded together, two tones separated by an even number of 18-oct intervals were more consonant than two tones separated by an odd number of 18-oct intervals. The scale synthesized is one example of many possible unconventional scales that can exhibit consonance and dissonance.
Acoustic Response of a Rectangular Receiver to a Rectangular Source
Authors: Fujii Yahei , Yamada Kazunari
Published: September 2005

This Letter considers an approximation for the acoustic response of a rectangular receiving aperture to a similarly aligned coaxial rectangular source. Graphical results for the response versus aperture separation are given for two cases.
Some Factors Affecting the Perception of Continuity in Alternately Sounded Tone and Noise Signals
Authors: Elfner Lloyd , Homick Jerry L.
Published: September 2005

Three experiments are reported that employed 78 normally hearing college students who demonstrated an ability to concentrate on an interrupted white noise that alternated with a tonal burst. The purpose of these experiments was to investigate the effects of the duration of the white noise and the frequency of the tonal burst on the perception of continuity under monaural and dichotic presentation. The effect of the number of noise pulses in the stimulus interval was also investigated. The results showed that under monaural presentation the perception of continuity was affected by both the duration of the noise and the frequency of the tone. Only the duration variable was significant under dichotic presentation. The number of noise pulses in the stimulus interval significantly affected the perception of continuity.
Input-Output Characteristics of the Lateral-Line Sense Organs of Xenopus laevis
Authors: Harris G. G. , Milne D. C.
Published: September 2005

In the toad Xenopus laevis, the lateral line system may be considered as a single organ, containing about 30 000 hair cells, which is used to detect moving objects. It is organized in groups of neuromasts, called stitches, which are directionally sensitive to water velocity. Each stitch is innervated by two large (∼8 μ) myelinated fibers. Electrophysiological recordings made from the nerve to a piece of skin in vitro show that these two fibers are spontaneously active and are sensitive to water velocities in opposite directions. The spontaneous activity in one fiber may have a slight positive correlation with the spontaneous activity in the other. This indicates that the origin of the spontaneous activity should not be Brownian motion of the cupula. Its origin is probably in the portion of the nerve between the hair cells and the start of myelination. Interval histograms of spontaneous activity show an exponential tail for long intervals and few small intervals. There is a characteristic absence of intervals less than about 10 msec. Evoked responses are repetitive, with rate, number of spikes, and latency, dependent on stimulus intensity. These results indicate that both place and pulse position coding could be used to convey the information necessary for the perception proper to this organ.
Model of Loudness Summation Applied to Impaired Ears
Authors: Scharf Bertram , Hellman Rhona P.
Published: September 2005

The loudness of complex sounds composed of three or four pure tones was measured as a function of the over-all spacing ΔF between the lowest and highest components. The measured relation between loudness and ΔF was compared to calculations from Zwicker's model of loudness summation. In eight ears with a conductive impairment, loudness summated normally and as predicted by the model; loudness remained approximately constant as a function of ΔF near threshold and increased with ΔF beyond the critical band at higher sensation levels. In eight ears with a cochlear impairment, loudness did not change with ΔF at any tested sensation level. This invariance of loudness was not predicted by tire model nor was it found in six normal ears tested in the presence of a 90-dB uniform masking noise intended to simulate the cochlear impairment. Under masking, loudness summated as predicted. The unexpected results in cochlear pathology were ascribed, tentatively, to a possible widening of the critical band.
Resonance and Sounding Frequencies of the Flute
Authors: Coltman John W.
Published: September 2005

The passive resonance frequencies of the flute were measured with high precision and compared with the frequencies obtained by blowing. The differences, which vary from +20 to −25 cents over the scale, are wholly accounted for by air temperature and composition and by variation of coverage of the mouth hole. No frequency pulling due to the blowing mechanism was observed. Measurements of frequency and radiated power using an artificial blowing mechanism provide an explanation for the variations in lip configuration observed in photographs. The tapered head joint provides a partial compensation for lip-coverage variation, but irregularities in the resonant column give marked departures from calculated frequencies based on a smooth tube.
Ultrasonic and Hypersonic Studies of Vibrational Relaxation in Benzene
Authors: Hunter Joseph L. , Carome E. F. , Dardy Henry D. , Bucaro J. A.
Published: September 2005

Ultrasonic absorption measurements have been made in benzene over the frequency range from 7 to 570 Mc/sec at 6° and 25° C. Velocity measurements at both ultrasonic and hypersonic frequencies also were made in the temperature range 6°–60°C. The observed relaxation effects may be interpreted in terms of double relaxation of the vibrational specific heat. Analysis of the absorption data indicates that the vibrational specific heat associated with all but the lowest vibrational mode relaxes in the ultrasonic range, with the measured relaxation frequency varying from 510 Mc/sec at 6°C to 560 Mc/sec at 25°C. Correlation of the ultrasonic and hypersonic data also indicates a second relaxation frequency (associated with the lowest vibrational mode) of the order of 10 Gc/sec.
Vibration of a Spherical Shell in an Acoustic Medium
Authors: Hayek Sabih
Published: September 2005

The basic equations for axisymmetric, nontorsional vibration of a spherical shell in an acoustic medium are obtained by the use of Lagrange's equations. Dynamic displacements and the pressure in the fluid were obtained for the case of forced motion of the shell under a harmonic, concentrated force.
Free Vibrations of a Slender Bar with Nonuniform Characteristics
Authors: Mok Chi-Hung , Murray E. A.
Published: September 2005

The free vibrations of a slender bar with characteristics slightly different from those of a uniform one are discussed. A simple approximate solution to this problem is presented. Results from experiments conducted with a bar of variable cross section in free-free flexural vibrations indicate that the theory adequately predicts resonant frequencies and nodal locations.
Reverberation under Arctic Sea-Ice
Authors: Brown J. R. , Brown D. W.
Published: September 2005

Reverberation from explosive sounds detonated beneath uniform young summer sea-ice were recorded in September 1964 in the Arctic Archipelago. Backscattering strengths were obtained for three octave bands between 1.28 and 10.24 kcps, and for grazing angles between 10° and 70°. The reverberation measured is significantly lower than that measured under well-rotted polar pack ice in September 1963 [J. R. Brown, J. Acoust. Soc. Am. 36, 601–603 (L) (1964)], and a great deal lower than the results obtained by Milne in April [A. R. Milne, J. Acoust. Soc. Am. 36, 1551–1556 (1964)], under pressure-packed one-year ice. A strong dependence of under ice backscattering on surface roughness is thus indicated.
Reverberation from Deep Scattering Layers in the Western North Atlantic
Authors: Chapman R. P. , Marshall J. R.
Published: September 2005

Reverberation from deep scattering layers was measured at 37 sites in the western North Atlantic. Resonant scatterers, presumably the swimbladders of bathypelagic fish, were responsible for the bulk of the observed reverberation. Three scattering layers, each populated with a characteristic size of scatterer, were found to persist over distances of several hundred kilometers. During the day, these layers were at depths between 300 and 900 m. A migration towards the sea surface of scatterers from the shallowest layer at sunset appeared to be responsible for most of the low frequency reverberation observed at night. The majority of the scatterers from the deepest of the layers did not experience a daily migration in depth. Two of the layers studied showed pronounced decreases in depth with increasing latitude. No seasonal variations in scattering strengths were observed.
Acoustical Measurements in Philharmonic Hall (New York)
Authors: Schroeder M. R. , Atal B. S. , Sessler G. M. , West J. E.
Published: September 2005

The acoustics of Philharmonic Hall in New York were evaluated by a new method utilizing a digital computer. Measurements were made before, during, and after a four-phase alteration program of the Hall. The following quantities were studied: (1) reverberation times based on the earlier and later portions of the decay, (2) energies of the direct sound and of reflections from the suspended ceiling, (3) “early” energies (energies arriving within 50 msec of the direct sound) and “reverberant” energies (arriving after 50 msec), (4) directional distributions of the early energies, (5) ratios of early-to-reverberant energies, (6) intensities of reflections from the rear wall, and (7) the over all ambient noise level of the Hall. Reverberation times in the octave band 500–1000 Hz, for the main floor, based on the earlier and later portions of the decay, were found to be 1.9 and 2.1 sec, respectively, for the Hall in its original state. In the present state of the Hall, the main floor has a reverberation time of approximately 1.8 sec for both early and later portions of the decay, thus indicating a more exponential decay process. The early and early-plus-reverberant energies on the main floor showed a deficiency at low frequencies before the alterations; now, they have a relatively flat spectrum. For an early state of the Hall, the directional distribution of the early energy was close to that expected for a diffuse sound field on the second terrace, but deficient in lateral reflections on the main floor. For the present state of the Hall, the directional distribution of the early energy is less dependent on position, but there are still relatively more lateral reflections on the second terrace than on the main floor in the midfrequency range (250–1000 Hz).
Noise Localization after Unilateral Attenuation
Authors: Bauer Robert W. , Matuzsa John L. , Blackmer Raymond F. , Glucksberg Sam
Published: September 2005

Partial hearing loss was simulated by insertion of V51-R plastic earplugs. Subjects wore plugs continuously for periods ranging from 6 h to 3 days. Predictable shifts in localization errors were observed when the stimulus was a broad-band and noise made up of frequencies above 3000 cps. Reorientation in azimuth localizazation with earplugs inserted required three days or more unless accelerated by specific training.
Peripheral Origin of Auditory Responses Recorded from the Eighth Nerve of the Bullfrog
Authors: Frishkopf Lawrence S. , Geisler C. Daniel
Published: September 2005

Single-unit recordings have been obtained from the posterior branch of the bullfrog's eighth nerve at points peripheral to the ganglion. These units can be fitted into the three classes (viz., simple, complex, and non-auditory) that were established by Frishkopf and Goldstein in a previous study [J. Acoust. Soc. Am. 35, 1219–1228 (1963)]. The sequence in which units of different classes were encountered on any one electrode pass supports the hypothesis that the complex units originate in the amphibian papilla and the simple units originate in the basilar papilla.
Aural Pulse Compression by Bats and Humans
Authors: McCue J. J. G.
Published: September 2005

Some misconceptions about pulse compression, current in the literature, are described and corrected. The discussion centers on the possible use of pulse compression by bats, but includes some calculations on dispersion in the Peterson-Bogert model of the human cochlea. Recent findings on the resistance of bats to jamming are noted.
Effects of Calcium on Sound-Evoked Cochlear Potentials in the Guinea Pig
Authors: Moscovitch David H. , Gannon R. Patrick
Published: September 2005

Scala tympani in guinea-pigs were perfused with artificial perilymph solutions containing calcium in ionic concentrations from 2.7 to 80 mequiv/liter. Cochlear-potential responses to 7000-cps tone pips at 80 dB re 0.0002 dyn/cm2 were recorded from the first turn, using differential electrodes. The cochlear-microphonic (CM) and negative summating potential (SP) amplitudes recovered immediately following perfusion and were augmented relative to control values for several minutes thereafter. The N1 component of the action potential (AP) recovered within 2 min or less after perfusion with solutions containing normal concentrations of calcium, but was depressed for longer periods with increasing concentrations. Depression of the AP was qualitatively related to the increase in calcium concentration. Augmentation of the CM and SP and depression of the AP associated with increased calcium concentrations in scala tympani are discussed in relation to the generation of these potentials and the action of the olivo-cochlear bundle.
Integration of Acoustic Power at Threshold by Normal Hearers
Authors: Olsen Wayne O. , Carhart Raymond
Published: September 2005

Threshold responses for seven durations of 250 , 1000 , and 4000-cps and white noise were determined for 32 normal-hearing persons. The time parameters and spectral characteristics of the stimuli were carefully specified. The following results were obtained. (1) There was no significant difference between the male or female groups employed here with regard to their threshold response to short-duration acoustic stimuli. (2) The decrease in intensity required for threshold response as a function of stimulus length was a real difference when the stimulus was systematically doubled in length from 10 to 500 msec. (3) Changes in the intensity necessary for threshold response resulting from changes of signal length were highly similar for 250-, 1000-, and 4000-cps and white-noise stimuli of more than 50 msec in length, but there was an excessive increase in intensity needed for response when 250-cps stimuli were made shorter than 50 msec in duration. (4) Test-retest reliability of threshold response to short-duration acoustic stimuli was excellent. (5) The model proposed by Garner and Miller [J. Exptl. Psychol. 37, 293–303 (1947)] accurately described the mean threshold data obtained in this investigation.
Analysis of Speech in a Helium-Oxygen Mixture under Pressure
Authors: MacLean D. J.
Published: September 2005

Tape recordings made in the helium-oxygen atmosphere of the U. S. Navy Sealab II have been analyzed by spectrographic techniques. The divers breathing this gas mixture have an unusual voice quality often characterized as “Donald Duck” speech. The Sealab experiment permitted speech analysis of divers living in such an atmosphere for several days. A study of the recorded data has led to the following observations: (1) formant shifts are responsible for the unusual quality of the helium-oxygen speech; (2) the formant shifts are nonlinear—the first-formant shift being greater than the higher ones; (3) energy associated with fricative sounds has also been observed to shift upward; (4) pitch or fundamental frequency changes are usually not significant; (5) after several days in the preponderantly helium atmosphere of Sealab, changes occurred in the speech quality that made it sound more natural.
Crosslanguage Study of Perceptual Confusion of Plosive Phonemes in Two Conditions of Distortion
Authors: Singh Sadanand
Published: September 2005

The intelligibility of /p t k b d g/ as spoken and heard by native speakers and listeners of Hindi and English and the relationship of this intelligibility to the transitions of consonants to vowels in CV monosyllables were investigated. Phoneme boundaries were determined. A measure of intelligibility was obtained in terms of information transmitted per stimulus for four and two separate channels and a composite channel. The separate channels represented distinctive linguistic features. Redundancy was quantified through a comparison of the information transmitted by these systems. There was uniformity among the four speaking-listening groups in information transmitted at six points of temporal segmentation and in 20 different bandwidths, as well as similarity in the importance of channels. Models of linearity were set to assess information as a function of (1) time, (2) width of the frequency band, and (3) lower frequency of the frequency band. Multiple correlations of 0.83 in the case of (1), (2), and (3), of 0.83 in the case of (1) and (2), and of 0.77 in the case of (1) and (3) were found.
Brillouin Scattering and Thermal Relaxation in Benzene
Authors: O'Connor C. Leonard , Schlupf Joseph P.
Published: September 2005

Measurements of Brillouin scattering in benzene were made over a temperature range of 10°–50°C, using a 75-mW gas laser operating at 6328 Å. The scattered radiation was analyzed by a Fabry-Perot étalon with a finesse of 60 in conjunction with a pressure scanning system that was linear to one part in a thousand. The experimental results of benzene, together with those of different liquids studied by other authors, are compared with a recent theoretical study by R. D. Mountain. The experimental data indicate that in benzene and carbon disulfide the internal vibrational degrees of freedom are weakly coupled to the translational degrees of freedom in the fluids. In such cases, thermal relaxation of vibrational degrees of freedom can be described by a single relaxation time. It appears that for carbon tetrachloride a single relaxation mechanism does not apply. There is not good agreement between relaxation times determined from velocity-dispersion measurements at ultrahigh frequencies and relaxation times calculated from excess sound absorption in ultrasonic measurements.
Reference Pressure for Sound-Pressure Level
Authors: Young Robert W.
Published: September 2005

Dissatisfaction with 0.0002 μbar as a reference pressure for sound-pressure level is not really widespread; a broad view of the benefit to be derived from general use of a single small reference pressure has led to proposed standardization on 0.0002 μbar for all media.
Elastic Constants of Magnesium Aluminate Spinel
Authors: Lewis M. F.
Published: September 2005

The elastic constants of magnesium aluminate spinel have been measured by an ultrasonic pulse-echo technique. The results are C11 = 2.79 ± 2%, C44 = 1.53 ± 2%, C12 = 1.53 ± 4% in units of 1012 dyn/cm2.
Existence of Longitudinal Waves in Anisotropic Media
Authors: Kolodner I. I.
Published: September 2005

Recent papers demonstrated the existence of longitudinal waves in a linear, homogeneous, anisotropic elastic medium (in two distinct directions), and that the same argument applies to materials having “positive longitudinal elasticity.” Here, we give another proof of the same fact, and establish a bit more: there exist at least three distinct directions along which longitudinal waves will propagate.
Natural Frequencies of Closed Spherical Sandwich Shells
Authors: Wilkinson J. P. D.
Published: September 2005

Solutions for the axially symmetric motion of an elastic spherical sandwich shell are obtained from a theory of shells that includes the effects of transverse shear deformation, transverse normal stress, and rotatory inertia. Frequency equations and mode shapes are derived for the free vibrations of a closed spherical shell. It is shown that three branches appear in the spectrum of torsionless modes, and two branches appear in the spectrum of torsional modes.
Signal-Detection Analysis of Equalization and Cancellation Model
Authors: Green David M.
Published: September 2005

An analysis of the equalization and cancellation model from a signal-detection standpoint is presented. At low frequencies, say 250 cps, one can neglect the time-error parameter because any slight phase error is small as compared with the period of a sinusoid and all the error in the binaural mechanism can be treated as small-amplitude error. Using this assumption, it is possible to derive the equations presented in the text. Three main conclusions can be drawn from this analysis. (1) The signal-detection analysis generates the same equations as Durlach's signal-to-noise-ratio approach, except for a multiplicative factor that reflects the accuracy of the monaural energy measurement. (2) The parameter associated with the amplitude error, because of the multiplicative factor, is different from Durlach's by a factor of 5. (3) The new analysis predicts that shortening the signal duration or decreasing the noise bandwidth will increase the size of the masking-level difference. Both effects have been observed.
Reliability of TTS from Impulse-Noise Exposure
Authors: Hodge David C. , McCommons R. Bruce
Published: September 2005

A comprehensive damage-risk criterion (DRC) for impulse-noise exposure is needed, and it is desirable to state the DRC in terms of allowable TTS (temporary threshold shift), since TTS is both a valid and convenient measure of noise effects on hearing. This is possible only if TTS is also a reliable measure. Four TTS-reliability studies are reported. The following conclusions are reached. (1) Individual subject's TTS's are not sufficiently reliable to permit generalization of impulse-noise effects. (2) Group mean TTS varies only slightly across a series of exposures and is considered to be a reliable (consistent, repeatable) measure. This is true for the exposure of normal-hearing subjects to different impulse-noise conditions, for the TTS's of subnormal-hearing subjects, and for frequencies representative of the whole range of human hearing. (3) The formulation of an impulse-noise DRC should be based on group data (means, quartiles, etc.). Samples should be as large as possible and should be representative of the population to which generalization of results is desired.
Ultrasonic Diffraction Loss and Phase Change in Anisotropic Materials
Authors: Papadakis Emmanuel P.
Published: September 2005

The loss and phase change in progressive longitudinal waves from a finite circular piston source radiating into certain anisotropic media are calculated in this paper. Three-dimensional calculations are presented for propagation along 3-, 4-, and 6-fold symmetry axes. Relationships sufficient to permit the performance of the calculation for 2-fold axes are derived. The anisotropy is introduced as a term in the spatial part of the phase in the integral for the pressure in the field of the piston. Geometry proper for pulse-echo measurements was assumed in the calculation. The diffraction loss fluctuates with S = zλ/a2 (z is the distance into crystal, λ, is the wavelength, a is the transducer radius) before becoming monotonic increasing as the logarithm of S. The positions of the peaks in the loss are functions of the anisotropy of the medium. The phase change, on the other hand, increases monotonically to a limit of π/2 from S-0 to infinity. However, the phase has plateaus where the loss has peaks. Both new and previously published experimental data on diffraction loss along 3-, 4-, and 6-fold axes in crystals agree quantitatively with theory. Some data on 2-fold axes are also presented. The methods for correcting attenuation and velocity measurements for diffraction are given.
Propagation of Waves from a Spherical Surface of Time-Dependent Radius
Authors: Achenbach Jan D. , Sun C. T.
Published: September 2005

The dynamic response of an infinite elastic medium to a time-dependent pressure in a spherical cavity is investigated. For a finite length of time, the wall of the cavity is subjected to an ablation process and the radius of the cavity increases monotonically from the initial value a0 to the permanent value b. Polar symmetry is assumed throughout the analysis. Explicit expressions are derived for the radial and the tangential stresses. The analysis is valid for arbitrary ablation rates and cavity pressures. For a constant ablation rate and a constant cavity pressure, the solutions are compared with the corresponding quasistatic results.
Scattering and Reflection by Elliptically Striated Surfaces
Authors: Burke J. E. , Twersky V.
Published: September 2005

Closed-form approximations for the power-reflection coefficient, for the phase of the coherently reflected wave, and for the differential-scattering cross section per unit area, are given for random distributions of semielliptic protuberances on free or rigid base planes. For low frequencies, the real and imaginary parts of the required scattering amplitude (f) of an isolated protuberance are given explicitly to the eighth and sixth power of the frequency, respectively; for high frequencies, we use an approximation for f consisting of the geometrically reflected term plus a Fraunhofer diffracted term. Illustrative numerical examples are given for semiellipses ranging from perpendicular strips, through semicircles, to the near-limiting case of nearly flat strips.