bluuebunny/crossref_metadata_2025 huggingface dataset:
Further Results on Binaural Unmasking and the EC Model. II. Noise Bandwidth and Interaural Phase
Authors: Metz P. J. , von Bismarck G. , Durlach N. I.
Published: September 2005

Data are presented on binaural unmasking of tones masked by noise as a function of the interaural phases of the tone and noise and the bandwidth of the noise. It is found that (1) for a tone of 250 Hz, the binaural unmasking increases by 10 dB as the bandwidth is reduced from 250 Hz to 4.2 Hz; (2) the functional form of the dependence on interaural phase is independent of bandwidth; (3) reducing the bandwidth increases the amount of unmasking at all frequencies; (4) previous versions of the EC model are inadequate for describing the results; and (5) the data can be described by assuming that the error factor k in the EC model depends on the bandwidth W and interaural phase θn of the noise according to a relation of the form k = 1 + K1(W)K2(φn).
Some Effects of Tonal Interactions as Seen in the Cochlear Microphonic
Authors: Nieder P. , Nieder I.
Published: September 2005

The microphonic response recorded from the round window of anesthetized cats with implanted electrodes was studied using stimuli consisting of two pure tones. Filtered or unfiltered responses were displayed oscillographically with sweeps phase locked to the low-frequency stimulus component. This permitted study of the amplitude modulation of the higher-frequency, components by the low-frequency stimulus. Complex modulation effects were found in all animals studied. Modulation envelopes could be either simple, with one maximum and one minimum per cycle of the low-frequency stimulus; or double, with two maxima and two minima per cycle. Simple modulation tended to be produced at lower SPL's of the low-frequency stimulus than double modulation. The phase of the modulation envelope relative to the low-frequency signal varied in some cases with the frequency and intensity of each stimulus component. For suitable frequency pairs, the phase angle of the low-frequency component of the cochlear response could be reduced by raising the SPL of the higher-frequency stimulus. When both stimuli were raised to high SPL's, the modulation pattern could shift by 180°. Results are qualitatively discussed in terms of a heuristic model involving stimulation of nonlinear “unit” generators by traveling waves.
Stimulated Brillouin Scattering: Effect of Sound Absorption on Hypersonic Velocity Measurements
Authors: Solovyev Victor A. , Goldblatt Norman R. , Montrose C. J.
Published: September 2005

The frequency spectrum of a sound wave generated by photon-phonon interactions is that of a damped harmonic oscillator with the shifted peak sharpened but not displaced by nonlinear amplification. Hence, the frequency of this line must differ from that given by the Mandelstam-Brillouin formula. The correction formula is given for a general case of a dispersive viscoelastic medium in terms of the frequency-dependent modulus and viscosity.
Distortion Compensating, Condenser-Earphone Driver for Physiological Studies
Authors: Molnar Charles E. , Loeffel Robert G. , Pfeiffer Russell R.
Published: September 2005

A design for a condenser earphone driver is given. The driver predistorts electrical input signals to counteract the inherent square-law operation of the condenser earphone. Thus, smaller-diameter earphones, with their wider bandwidth characteristics, can be used at stimulus levels of interest without appreciable harmonic distortion.
Elastic Plane-Strain Vibrations of a Hollow Cylinder Bonded to a Thin Shell
Authors: Anderson G.
Published: September 2005

Frequency equations for elastic plane-strain vibrations of an infinitely long hollow elastic cylinder bonded on the outer curved surface to a thin elastic casing are discussed and compared with similar equations appropriate for hollow cylinders with (i) traction-free surfaces and (ii) one traction-free and one clamped surface. The axisymmetric made uncouples into a shear mode and a radial-extensional mode. The effects of shell thickness, mass density, and elastic properties on the natural circular frequency, coefficients associated with the shear and extensional modes are discussed, and graphs of the natural circular frequency coefficients and of a displacement ratio are included.
Wide-Temperature-Range Free-Layer-Damping Treatment
Authors: Nashif A. D. , Cannon C. M.
Published: September 2005

The effectiveness of a specific multicomponent polymer blend as a wide temperature-range damping material is discussed. It is shown that such a blend promises to introduce significant damping over a wider temperature range than currently used materials in a free-layer damping treatment.
Simple Method for Calibrating Small Omnidirectional Hydrophones
Authors: Gould Robert K.
Published: September 2005

A small gas-filled bubble is suspended in a liquid by means of an acoustic standing-wave field. Equilibrium of the bubble is achieved by counter-balancing the buoyant force of gravity with a downward acoustic pressure-gradient force. The position and size of the bubble are measured, and it is replaced by a hydrophone in the same field. Measurement of the voltage output of the hydrophone at, immediately above, and immediately below the point of equilibrium leads to a determination of its sensitivity.
Characterization of Moving Acoustic Targets as Linear Time-Varying Filters
Authors: Moose Paul H.
Published: September 2005

A formula is developed for the linear filter equivalent of a transmitter-target-receiver system for the case where all are moving. The impulse response of the system is in terms of the impulse response of the target. It is shown that even when the impulse response of the target is stationary, the system response is time varying.
Underwater Sound and Naval Acoustical Research and Applications before 1939
Authors: Klein Elias
Published: September 2005

This report describes some of the highlights of underwater sound and other naval acoustical technology in the United States during the period of World War I to World War II. A number of accomplishments in subaqueous acoustics of the Naval Research Laboratory are given, emphasizing sonar equipment research and development. Acoustic studies in air and ocean environments carried out at NRL are also described; and a general glimpse of the research climate in the early decades of NRL is portrayed.
Propagation of One-Dimensional Waves from a Source in Random Motion
Authors: Knowles J. K.
Published: September 2005

This paper is concerned with the transient problem of waves in an infinite one-dimensional medium owing to a monochromatic source whose position X(t) is a stochastic function of time. Asymptotic results for the farfield are given for the general class of stationary source motions and for the case in which X(t) is a Wiener process, corresponding to Brownian motion.
Analysis of Elastically Coupled Piezoelectric Resonators
Authors: Beaver W. D.
Published: September 2005

This paper presents an analysis of an elastically coupled piezoelectric resonator system consisting of a linear array of two or more counter electrode pairs placed on the major surfaces of a quartz crystal plate. Each pair of counter electrodes establishes resonator having a transverse thickness mode of motion. The equations describing this system are derived and applied to an array of n coupled resonators and specific numerical computations are made for the cases where n is equal to 2, 3, and 6. These results are plotted and show the dependence of the effective interresonator coupling on the dimensions of the electrode configuration.
Historical Background of the Haas and/or Precedence Effect
Authors: Gardner Mark B.
Published: September 2005

When two or more sound sources radiate identical or nearly identical complex signals, the listener hears a single image located at the nearer source, provided that the delay involved is between about 1 and 50 msec. This phenomenon (together with other closely associated aspects) is generally referred to as the “precedence effect” or “Haas effect.” Less frequently, the terms “law of the first wavefront,” “auditory-suppression effect,” “first-arrival effect,” and “threshold of extinction” have also been used in describing certain of these characteristics. Perhaps the earliest investigator to leave a clear record of his appreciation of the single-image aspect of the phenomenon was Joseph Henry who, in 1849, used the term limit of perceptibility in describing what he had observed. The present paper outlines the historical background of the effect from the standpoint of its investigation and its application in electroacoustical systems.
Rôle of Phase-Difference Cues in the Cutaneous Analog of Auditory Sound Localization
Authors: Gescheider George A.
Published: September 2005

The just noticeable difference in phase (ΔΘ) was measured for binaural stimulation and for stimulation of the ring and index fingertips of the same hand. At stimulus frequencies of 40, 60, 120, and 240 Hz, differences in phase up to 120° had no effect on cutaneous localization, while the values of binaural ΔΘ were only 3.6° and 3.3° for 120- and 240-Hz tones, respectively. When the vibration frequency was lowered to 20 Hz, a cutaneous ΔΘ of 47° was obtained. At this frequency, the locus of cutaneous stimulation was found to greatly influence ΔΘ. When the index fingertips of the two hands were stimulated, ΔΘ was 90°, and was 45° when the ring and index fingertips of the same hand were stimulated. A relatively low ΔΘ of 12° was obtained when both vibrator contactors were placed on the same fingertip. The results of this study fail to support von Békésy's hypothesis that the same time delays in stimulation are equally effective as cues in auditory localization and its cutaneous analog.
Factors That Influence the Localization of Sound in the Vertical Plane
Authors: Roffler Suzanne K. , Butler Robert A.
Published: September 2005

The ability of listeners to locate sound in the vertical plane was investigated. The results showed that for auditory stimuli to be located accurately (1) the stimulus must be complex, (2) it must include frequencies above 7000 cps, and, (3) the pinna must be present.
Frequency Distribution of Central Masking
Authors: Zwislocki J. J. , Buining E. , Glantz J.
Published: September 2005

Contralateral threshold shift has been investigated as a function of frequency difference between the masking and test tones. The obtained curves of frequency distribution indicate complex underlying processes. Both the masker intensity and the time delay from the masker onset affect the absolute amount as well as the frequency distribution of central masking. The frequency spread of masking appears consistent with the critical-band measures at medium masker levels but not at high and low levels.
Ultrasonic Buffer-Rod Technique for the High-Temperature Measurement of the Elastic Moduli of Short Specimens
Authors: Sather Allen
Published: September 2005

This paper describes a method of measuring the elastic moduli of short specimens to very high temperatures by the use of ultrasonics. A buffer-rod technique is used, but the sound is transmitted from the buffer rod to the short specimen across an interface without the use of a couplant. The specimen has a machined index region that extends into the uniform hot zone of a vacuum furnace. The required information is taken from the index region. The experimental technique used to achieve a mechanical bond between the buffer and the specimen that is sufficient to transmit a considerable quantity of ultrasound is detailed. This method has been successfully used to 1150°C, and has potential application up to 2500°C.
Symmetric Normal Modes in a Uniformly Rotating Fluid
Authors: Salant Richard F.
Published: September 2005

The normal modes of a cylindrical cavity, containing a uniformly rotating, inviscid fluid, are examined. An approximate analysis, using the kernel-substitution technique, indicates that the fluid rotation increases the normal-mode frequencies.
Comparison of the Dynamic Response of a Complex Plastic Model with Its Prototype
Authors: Bannister Ronald L.
Published: September 2005

Experimental vibration characteristics of twin turbine-generator sets installed on a common bedplate (prototype system) were studied in the laboratory using a scale plastic model. Treating the major components of the machinery arrangement as rigid bodies, acceleration readings were recorded at many locations on the model and prototype while driving the system simultaneously with known sinusoidal forces. Symmetrical and antisymmetrical modes were separated by using two electrodynamic shakers at symmetrical locations. By comparing the response of the model and prototype, a detailed mode-shape comparison was established for the first nine major flexing modes. The results show that the natural frequencies and mode shapes of heavy machinery can be determined quite accurately from scaled plastic models.
Forced Thickness-Shear Vibrations of Discontinuously Plated Piezoelectric Plates
Authors: Bleustein J. L. , Tiersten H. F.
Published: September 2005

If the ratio of the length of an electrode strip to the thickness of a partially electroded infinite crystal plate is kept below a certain critical value known as Bechmann's number— which depends on certain geometric and material parameters then, for the crystal vibrating at frequencies in the neighborhood of its fundamental thickness-shear frequency, there are no anharmonic overtones of the thickness-shear motion. The concept of the discontinuously plated structure can be employed to design crystals with large values of Bechmann's number without decreasing the thickness of the electrode and consequently increasing the electrical resistance of the electrode. In this paper, by means of a special approximate theory, an explicit formula for the Bechmann's number of a discontinuously plated structure is obtained in terms of the dimensions and material properties of the insulating film, the electrode, and the crystal.
Resonant and Antiresonant Frequencies of Thick Disks and Thick Rods
Authors: Lucey George K.
Published: September 2005

Correction factors are derived that show the effect of thickness on the fundamental resonant-frequency equations for cylindrical disks and rods and an equation is given that defines a boundary between a thick disk and a thick rod. These corrections are verified for isotropic and planar isotropic materials using the published frequency data of Shaw and McMahon. Direct comparisons are made with the correction factors of Moseley, Rayleigh, Onoe and Tiersten, Bancroft, and Baerwald. Experimental evidence is provided to show that upon substitution of appropriate frequency constants the corrections apply to the antiresonant frequencies of thick disks and thick rods.
Power Flow and Energy Sharing in Random Vibration
Authors: Scharton Terry D. , Lyon Richard H.
Published: September 2005

The time-average power flow between two linearly coupled oscillators excited by independent white-noise sources is shown to be proportional to the difference in the time-average energies of the oscillators. This proportionality is independent of the strength of the coupling if the oscillator energies are correctly defined. Power balance and energy sharing in the two oscillator systems are investigated, and the power-flow energy-difference proportionality relation is extended to a group of N linear oscillators, all with the same natural frequencies and damping ratios and each coupled to all the others by identical springs and masses. The coupled-oscillator results are applied to a simple coupled-beam example, in which two almost identical Bernoulli-Euler Beams are lightly coupled together by stiffness terms. Experimental measurements for this system provide verification of the power-flow equations provided that the coupling loss factor be correctly computed.
Response of Plates to Random Load
Authors: Stanišić Milomir M.
Published: September 2005

By virtue of the mean-square calculus, a technique has been developed to determine the covariance and spectral-density functions for a plate of arbitrary boundary conditions subjected to loadings that are random in space and time. Also cross covariance and resulting spectral density functions are found. As an illustrative example, the theory developed here is applied to a simply supported plate subjected to both a point load and a line load that is random in time only. The solutions are presented in the form of infinite series that converge rapidly.
Influence of Beamwidth and Multiple Transmissions on Reverberation-Limited Sonars
Authors: Cole Bernard F. , Hanrahan John J.
Published: September 2005

Previous work on the discrimination of transducers against reverberation is extended to include the effects of dissimilar transmitting and receiving responses and multiple transmissions. The boundary reverberation index (analogous to the directivity index against noise) is expressed in terms of an ideal searchlight beamwidth that is defined as having a response of unity within the region bounded by its beam and a response of zero elsewhere. This ideal beamwidth is found by computing the total reverberation power associated with specific projector and receiver patterns. Both single and multiple transmissions are investigated. Various beamwidths for a single transmission are considered in order to determine the degradation in system performance when the transmitting and receiving beams have different dimensions. The sensitivity of these results to minor-lobe levels is demonstrated. The findings are then generalized by expressing the multiple transmission case in terms of an “equivalent” single transmission. The theoretical computations are compared with observed sea data and are shown to depend upon reverberation decay rate and hence upon water depth. Finally, the relationship between search rate, beamwidth, and system performance is developed.
Ray Transmissions in an Underwater Acoustic Duct with a Pseudorandom Bottom
Authors: Seifer A. D. , Jacobson M. J.
Published: September 2005

The principles of geometrical optics are applied to a study of ray acoustics in an isovelocity sound channel bounded by a lossy, pseudorandom (facet) bottom below and a free, planar surface above. A point source and receiving point are fixed and in a plane normal to the bottom so that all rays between them are coplanar. At each point of ray reflection, the bottom is assumed locally linear with sufficient length so that almost all of the reflected radiation takes the locally specular direction. At a point of ray reflection, the bottom is assumed to have a small random slope about a zero mean and a small random depth deviation about a constant mean value. Effects of boundary loss and phase shift, geometrical spreading loss, and travel time are included; and bottom-reflected arrivals are shown to be almost constant in amplitude but incoherent in phase. Multipath interference of all arrivals is treated by a random-walk theory. Graphs are presented giving the mean and standard deviations of the sound-field intensity for various source and receiving point geometries.
Reprogramming of the Sonic Output of the Dolphin: Sonic Burst Count Matching
Authors: Lilly John C. , Miller Alice M. , Truby Henry M.
Published: September 2005

The sound-producing mechanisms in the bottlenose dolphin (Tursiops truncatus) operate naturally underwater with a closed blowhole. In these experiments, Tt's reprogrammability in the vocal airborne mode and in vocal-acoustic interlock with another species is demonstrated. Human-speech (Hs) output programs were constructed from randomized vowel-consonant (VC) and consonant-vowel (CV) lists and simple English words and phrases. The analysis of the dolphin's sonic vocal output in response to these Hs vocal programs demonstrates Tt's reprogramming: in matching number of and trains of bursts, interburst silences, and latencies; ability to differentiate between Hs stimuli and other Hs comments or corrections, and ability to program from natural delphinic sounds to “humanoid” emissions.
Statistical Properties of Reverberant Sound Fields
Authors: Waterhouse Richard V.
Published: September 2005

Reverberant sound fields are used in several standard acoustical measurements, in which the sound field is sampled at different points. Here, the distributions of such sampled values are considered for the reverberant sound fields derived from different types of signal. It is shown that the values approach equality only where the field contains many frequency components simultaneously. For finite numbers of components, exact expressions in closed form are found for the distributions. For the field derived from a single frequency component, the values of mean-squared pressure follow a gamma distribution. For two or more frequency components of different mean amplitude, the distribution is related to a gamma distribution, and some computed values of it are given for the case of two components. Some experimental data are given. The results bear on the accuracy to be expected in reverberant field measurements.
Fourier Series for Intensity of a Small Gaussian Light Beam Modulated by a Progressive Ultrasonic Wave
Authors: Hargrove L. E.
Published: September 2005

Equations are obtained for the Fourier components of the time variation of light intensity in the farfield of a Gaussian light beam that has passed through a thin progressive ultrasonic wave located at the light beam waist. Some results of calculations of central intensity are shown for Gaussian beam waist diameter equal to and less than the ultrasonic wavelength.
A Further Note on the Reflection and Transmission of Sound Waves by a Moving Fluid Layer
Authors: Yeh C.
Published: September 2005

The reflection and transmission of sound waves by a moving fluid layer are treated theoretically using the more proper boundary conditions, and the reflection and transmission coefficients are determined. A specific numerical example is also given.
Excitation of Linear Systems by Gaussian Random Processes
Authors: Langseth R. E.
Published: September 2005

Theoretical analysis of linear, time-invariant systems excited by Gaussian random processes is a highly developed subject. A recent paper by Chen [“Response of a Linear System to Nonstationary Shot Noise.” J. Acoust. Soc. Am. 41, Pt. 1, 822–826 (1967)] tends to be rather abstruse, mainly because the analysis overlooks the general utility of the superposition principle. which. basically. is the defining characteristic of linear systems. Cognizance of this essential characteristic renders computation of the response probability distributions quite straightforward for this class of problems. An alternative approach to Chen's problem is sketched herein, using the perspective contained in well-known textbook methods.
Quick Method to Determine Phase of Reflection
Authors: Donato R. J.
Published: September 2005

A rapid technique is described for discriminating between acoustically hard and soft underwater sediments using an intensity-modulated display. The recorder used was capable of responding to either positive or negative excursions of the pressure waveform; and by observing the time displacement of the reflected wave when the mode of recording is changed, we may determine the sign of the acoustical impedance contrast.
Proposed Nondimensional Form for Turbulent-Boundary-Layer Pressure Fluctuations
Authors: Gardner S.
Published: September 2005

A new nondimensional form for turbulent-boundary-layer surface pressure fluctuations is proposed on the basis of recent experiments. This form should be applicable to measurements made with transducers of different resolving power.
Sea Lion Echo Ranging
Authors: Shaver H. N. , Poulter T. C.
Published: September 2005

References suggested in a comment on our paper “Sea Lion Echo Ranging” have been reviewed. The research described in these references is discussed here with regard to its bearing on the question of whether the California sea lion can be assumed to use active sonar. None of these references seem to justify a conclusion contrary to our premise, and some of them seem to be irrelevant to the question.
The Fitzpatrick Method
Authors: Collins Francis
Published: September 2005

The dimensional method recently described by Fitzpatrick is used to obtain simple relations between two common units of angular measure and between two common units of length.
Angular Velocity
Authors: Copley Lawrence G.
Published: September 2005

Two remarks are made concerning recent Letters on units and terminology for frequencies.
Experiment on Sound Propagation in Shallow Water with Velocity Structure
Authors: Kibblewhite A. C. , Denham R. N.
Published: September 2005

An investigation into the propagation of sound in shallow, isovelocity water was carried out previously using an extensive area of the continental shelf off the west coast of New Zealand. This area has been re-examined when a negative velocity gradient was present in the water layer. The results obtained show that this area provides a classic example of normal-mode propagation in shallow water under conditions of both constant sound velocity and a negative gradient. The values of attenuation obtained are on the whole greater when a negative gradient occurs, but their general behavior with frequency is similar in both cases. In addition, the attenuations are comparable with those obtained in other shallow-water areas and are consistent with the predictions of normal-mode theory.
Uniform Spherical Radiation through Thick Shells
Authors: Molloy Charles T. , Yeh Gordon C. K.
Published: September 2005

Wave propagation from a spherical transducer through a fluid medium and a concentric viscoelastic spherical shell (not necessarily thin) to a fluid medium of infinite extent has been analyzed. Formulas for the acoustic field when the transducer is driven with constant-amplitude sinusoidal radial velocity, have been derived. Numerical results show that the insertion loss due to the presence of the shell is an oscillatory function of frequency, indicating the existence of regions of favorable and unfavorable transmission, which are primarily controlled by the transducer-shell spacing. The magnitudes of the maxima and minima of the insertion loss are determined primarily by the mass per unit area of the shell. The insertion-loss function does not depend strongly upon the elastic constants or the material dissipation of the shell. A simple model consisting of a fluid-filled tube with a piston and a spring-supported “masslike” wall exposed to ambient fluid has been found to be a useful tool for interpreting the results. The analysis has been extended to the case of uniform radiation in the presence of a multilayered viscoelastic spherical shell. Numerical results show that by properly choosing the parameters, a low-pass filter effect can be obtained.
On the Detection of a Known Signal in a Non-Gaussian Noise Process
Authors: Spooner Ronald L.
Published: September 2005

In this paper, three receiver designs for the detection of a known signal in an additive non-Gaussian noise process are considered. The noise process consists of white Gaussian noise modulated by a random-spectrum level. The first receiver considered is an optimum (likelihood) processor and the remaining two receivers are suboptimum designs consisting of a cross correlator and a likelihood correlator. The basic processing operations of the three receivers are investigated and compared on the basis of their effects in observation space. The performance of each receiver is evaluated and presented in terms of ROC curves. A comparison of the performance curves indicates a loss in optimum performance as compared to the Gaussian noise case and a significant loss in performance of the suboptimum receivers relative to the optimum receiver.
Use of Articulation Tests in Auditorium Studies
Authors: Nordlund Bertil , Kihlman Tor , Lindblad Sven
Published: September 2005

A method for studying the correlation between the acoustic features and the articulation or intelligibility score of an auditorium has been developed. An artificial speaker is placed in the speaker position. Nonsense monosyllables are reproduced via this speaker. In different listener positions, stereophonic recordings are made via an artificial head with microphones in the ears. These recordings are later reproduced via earphones to a test group. The method enables the listening conditions to be kept equal, and only the acoustic character of the room will influence the results. Pilot studies have been made under laboratory conditions and have shown that the method is sensitive and reveals effectively the acoustic features of a room. These studies have been made, and certain introductory data are given. This method will be applied in different auditoriums and also tested under laboratory conditions to study the optimal value of reverberation time, definition (after Meyer), etc.
Comparisons of Training Techniques for Complex Sound Identification
Authors: Corcoran D. W. J. , Carpenter A. , Webster J. C. , Woodhead M. M.
Published: September 2005

Fourteen different synthetic engine sounds were mixed with five different synthetic cavitation sounds at realistically difficult signal-to noise ratios. Eighty one Royal Navy ratings, divided into eight training groups, were asked to identify the 14 engine sounds. Training procedures were varied among groups to answer some questions pertinent for programming a teaching machine. It was found that (1) verbal descriptions of the actual physical characteristics of the sounds give better results than those supplied by experienced listeners, (2) the order in which training items are presented is important. The most useful order involved changing one relevant quality per item, (3) “good” high engine-to-cavitation ratio) recordings may be an advantage if alternated with realistically “bad” ones, (4) feedback (knowledge-of-results) procedures should be concentrated more at the end of a training program and recordings should be extended temporally to overlap with the feedback, (5) a large population of engine noises is desirable for but probably not essential to, a good program.
Sine and Cosine Masking
Authors: Green David M.
Published: September 2005

Results of the masking of one sinusoid by brief pulses of another sinusoid are reported as a function of the phase of the masking pulse. In one case, the brief (10-msec) masker is presented as a sine pulse; in the other case, the masker is presented as a sine pulse. The sine pulse produces more masking than the cosine pulse at frequencies below the frequency of the masker and less masking at frequencies above the frequency of the masker. This inversion is explained on the basis of the power spectra of the two pulses. Details of the results are compared with a simple filter model and indicate that the ear's filter is at least a second-order system with a greater rate of attenuation above the center frequency of the filter than below.
Mathematical and Electrical Models of Auditory Detection
Authors: Jeffress Lloyd A.
Published: September 2005

McGill's generalization of Marill's formula for the probability of a correct response in a two-alternative, forced-choice experiment is obtained from a special case of the noncentral chi-square distribution. The present paper shows that a special case of the noncentral chi distribution is more appropriate than the noncentral chi square for monaural detection of a tonal signal in a continuous background of Gaussian noise. The special noncentral chi function fits distributions obtained from an electrical model, and yields psychometric functions appropriate both to it and to human observers. Estimates of bandwidth and of integration time derived from the distribution functions lie within the range of values often assumed from human subjects.
Establishment of Objective Criteria Reflecting Subjective Response to Roller-Bearing Noise
Authors: Lucht R. F. , Scanlan R. H.
Published: September 2005

In recent years, the question of noise generated by rolling-element bearings has been given considerable attention. That a certain irreducible “minimum” noise is created by a properly functioning bearing has been pointed out in earlier work. Acceptable roller-bearing noise levels above this minimum are regarded in this paper as being, of necessity, set by subjective standards. The paper addresses itself first to the validity or consistency of certain subjective evaluations of bearing noise made by a group of observers in representative circumstances. Next, the question is examined as to what quantitative objective measurements are to be made in order to reflect accurately the character of the subjective evaluations. Finally, correlations between objective and subjective data are shown to be good. A representative method is thus defined for providing objective criteria that reflect subjective appraisal in this type of problem.
Masking-Level Differences Determined with and without Interaural Disparities in Masker Intensity
Authors: McFadden Dennis
Published: September 2005

Psychometric functions were obtained for three listeners for the interaural conditions Nm-Sm and N0-Sπ using seven different noise spectrum levels. In addition, data were collected on the N0-Sπ condition with the spectrum level in one ear smaller than that in the other ear. In these N0′-Sπ′ conditions, the signal-to-noise ratio was kept equal in the two ears. The masking-level differences (MLD's) for the N0-Sπ conditions declined gradually as the level of the noise was reduced, and for small spectrum levels, they were essentially the same as the MLD obtained when the masker was turned off. The MLD's declined more rapidly for the N0′-Sπ′ conditions, but a small MLD was obtained even when the spectrum level in one ear was 60 dB smaller than that in the other ear. For the Nm-Sm conditions, masking increased linearly with increases in spectrum level, but for N0-Sπ, the relation was not linear—a further indication that the basis for detection is different in MLD and non-MLD conditions. The results are discussed in terms of “internal noise,” the effect of which is to alter the effective interaural correlation as the masker level is reduced. Signal: 400 cps, 250 msec; masker: continuous, wide-band noise; method: two-interval forced choice.
Measurement of Perstimulatory Loudness Adaptation
Authors: Stokinger Thomas E. , Studebaker Gerald A.
Published: September 2005

Experiments were conducted to investigate two of the variables encountered in the measurement of perstimulatory loudness adaptation. The first of these variables is the instruction to the observer for comparing the sensations in the test and control ears; i.e., equality based on equal loudness versus that based on a midline localization of the sound image. The second is the time of presentation of the comparison tone; i.e., simultaneous presentation with a portion of the adapting tone versus a delayed presentation mode in which the comparison tone occurs after the termination of the adapting tone. The results reveal (1) that adaptation measured by localization balances exceeds that measured by loudness balances and (2) that the simultaneous loudness-balance method shows more apparent adaptation than the delayed balance method. Hypotheses are presented in an attempt to explain these results.
Azimuth and Elevation Errors Inherent in Sound-Ranging Calculations
Authors: Austin Michael E. , Gomez Richard B.
Published: September 2005

A square army of four microphones can be used to detect acoustic signals propagated through the atmosphere. Use of such an array allows the determination of the azimuth and elevation angle of the acoustic wave. Possible errors in these angles and the means of determining their respective values are considered in this paper. By making use of the known arrival times of the signals of each microphone, expressions for the error in azimuth and elevation angle are derived.
Use of an Average Response Computer to Provide Reproducible Bursts of Noise
Authors: Raab David H. , Leshowitz Barry
Published: September 2005

An average response computer can be used to store samples of noise. Since waveforms are easily recorded, reproduced and erased, the two noise bursts in an auditory discrimination trial can be either identical in waveform or randomly different. These two conditions are compared in a preliminary study of intensity discrimination.
Effect of Shear and Rotatory Inertia on Flexural Vibrations of Rib-Stiffened Plates
Authors: Laura P. A.
Published: September 2005

The response of a damped, simply supported rib-stiffened plate subjected to sinusoidal and random excitation is determined analytically. The effects of shear and rotatory inertia are discussed. The expressions derived in this study indicate that consideration of rotatory inertia does not present any difficulties and that the mean-squared value of the displacement is reduced considerably (a) at high frequencies, and (b) with deeper height of the stiffening ribs.
High-Frequency Plate Damping Due to Gas Pumping in Riveted Joints
Authors: Ungar Eric E. , Maidanik Gideon
Published: September 2005

Previously derived expressions for the damping associated with gas pumping at riveted and other multipoint-fastened joints are restated and discussed. Quantitative predictions based on the theory, which considers the pressure dependence of gas viscosity on the basis of gas kinetics, are shown to be in reasonable agreement with data obtained with three different gases over a wide range of pressures.
Underwater Acoustic Wavefront Variations and Internal Waves
Authors: Beckerle J. C. , Wagar J. L. , Worley R. D.
Published: September 2005

Variations in the measurement of the direction of acoustic wavefronts were obtained in a deep ocean experiment for a fixed source and hydrophone configuration. The nature of the fluctuations are interpreted as resulting from internal ocean waves.
Steered Beam Analysis Using a Shaded Linear Array
Authors: Hughes W. J.
Published: September 2005

A parameter that permits easy calculation of a steered beam of an unshaded line array of N equally spaced elements has been developed by Doolittle. This Letter extends the principle to a line array shaded by the Dolph-Chebyshev method.
Relation of the Exact Transient Solution for a Line Source near an Interface between Two Fluids to Geometrical Acoustics
Authors: Pierce Allan D.
Published: September 2005

The exact transient solution obtained by the Lamb-Cagniard-Smirnov-Sobolev-Pekeris method is summarized for waves from a line source of arbitrary time dependence near an interface between two fluids of different sound speeds and densities. The solution is used to give an alternate derivation of the pressure (or dp/dt for the refracted arrival wave) increments at times of onset of the reflected, refracted arrival, and transmitted waves originally obtained by the geometrical acoustics theory of Friedrichs and Keller for incident weak shocks. The exact theory shows that the Friedrichs-Keller results (rigorously valid at onset times) may be extended to give an asymptotic approximation for waveforms following onset times. The strength of the logarithmic singularity accompanying the refracted arrival wave when the incident pressure is discontinuous is also derived from the exact theory.
Improved Integral Formulation for Acoustic Radiation Problems
Authors: Schenck Harry A.
Published: September 2005

Three different integral formulations have been used as a basis for obtaining approximate solutions of the exterior steady-state acoustic radiation problem for an arbitrary surface whose normal velocity is specified: (1) the simple-source formulation, adapted from potential theory; (2) the surface Helmholtz integral formulation, based on the integral expression for pressure in the field in terms of surface pressure and normal velocity; and (3) the interior Helmholtz integral formulation, in which the surface pressure is determined by making a certain integral vanish for all points interior to the radiating surface. For certain characteristic wavenumbers, it is shown that no solution of the simple-source formulation exists in general and that there is no unique solution of the surface Helmholtz integral formulation. The interior Helmholtz integral formulation is subject to similar difficulties and has undesirable computational characteristics. A Combined Helmholtz Integral Equation Formulation (CHIEF) that overcomes the deficiencies of the first two methods and the undesirable computational characteristics of the third, is described. The significant improvement over the previous three methods, which is accomplished through the use of CHIEF, is illustrated by numerical examples involving spheres, finite cylinders, cubes, and a steerable array mounted in two different boxlike structures.
Pulse Shapes of Spherical Waves Reflected and Refracted at a Plane Interface Separating Two Homogeneous Fluids
Authors: Towne Dudley H.
Published: September 2005

A review is given of Cagniard's method for determining the shapes of the reflected and transmitted waves resulting from a point source of spherical waves of arbitrary waveform located in one of two homogeneous fluids separated by a plane interface. Symmetry relations enable the basic Cagniard solutions for reflection to be obtained from those or transmission, and a reciprocity relation shows that the formulas for transmission when the source is located in one of the two fluids can easily be obtained from the formulas for transmission when the source is located in the other fluid. An Appendix lists explicit solutions for all cases (reflection or transmission with the source located in the fluid of higher or lower sound velocity). The propagation of jump discontinuities the Cagniard solution is shown to be in agreement with geometrical ray theory. Impulse reflection and transmission coefficients are obtained from the asymptotic values of the basic Cagniard solutions. It is then demonstrated that these same coefficients can be deduced from a solution to Laplace's equation.
Influence of Nonlinearities on the Degenerate Vibration Modes of a Square Plate
Authors: Evensen D. A.
Published: September 2005

von Karman's nonlinear plate equations are used to investigate the effects of nonlinearities on the degenerate vibration modes of a square plate. Galerkin's procedure is used to reduce the problem to two coupled nonlinear differential equations, and approximate solutions are obtained by the method of harmonic balance. For linear vibrations, the degenerate modes can be superimposed to form an infinite variety of nodal patterns. However, the nonlinear analysis shows that for finite amplitude vibrations the modes combine to give only four distinct nodal patterns. These nodal patterns are oriented along the lines of symmetry of the plate.
Diffraction of Antiplane Shear Waves by a Finite Crack
Authors: Loeber J. F. , Sih G. C.
Published: September 2005

The scattering of polarized harmonic shear waves by a sharp crack of finite length under antiplane strain is considered. Use is made of integral transforms, which reduce the problem to the evaluation of a system of coupled integral equations. Special emphasis is placed on obtaining the detailed structure of the crack-front stress and displacement fields, which control the instability behavior of cracks in brittle materials. While the dynamic stresses around the singular crack point are found to be qualitatively the same as those encountered under statical loading, they differ quantitatively in that the intensity of the dynamical stress field, which may be regarded as a measure of the force tending to cause crack propagation, depends on the incident wavelength. At certain wavelengths, this intensification is shown to be larger than the static case. The method of solution in this paper applies equally well to boundary value problems in electromagnetic and acoustic theory.
Detection of Noiselike Sounds in Telephone Speech
Authors: Drucker Harris
Published: September 2005

A method of separating noiselike sounds from vowel/vowellike sounds where the speech is of telephone quality is presented. This procedure involves the use of the χ2 nonparametric test, which analyzes the fluctuations of the time waveform and separates the speech into two classes depending on the randomness of the waveform. Initial computer simulations show the feasibility of the method, but since the recognition networks must operate in real time and the χ2 test is nonlinear, a linear model to the χ2 test is constructed that can be easily implemented, operate in real time, and obtain an efficiency close to that of the χ2 test. The false-alarm and false-recognition rates obtained using the linear model on a test sentence of 45 phonemes and 6-sec duration are in the order of 12% and 85%, respectively.
Elastic Waves Propagation in Circular Cylinders Having Hexagonal Crystal Symmetry
Authors: Eliot Frank C. , Mott G.
Published: September 2005

The exact solution to the problem of an axially-invariant elastic wave propagating in an infinitely long cylinder of isotropic material having a traction-free curved surface was first given by Pochhammer in 1876. The solution has been extended by Redwood and others to include axially variant waves. In the present work, we have derived expressions for the propagation of waves in an infinite circular cylinder of material having hexagonal crystal symmetry, where the axis of the cylinder coincides with the crystallographic c axis. Normalized plots of phase velocity vs frequency are shown for representative isotropic and hexagonal materials. The plots have been extended to sufficiently high order that the form of all higher modes can be extrapolated. For materials of hexagonal crystal symmetry, we have found that the phase velocity plots do not change in form from those of isotropic materials, but are displaced by small amounts dependent upon the particular elastic constants chosen.
Ultrasonic Examination of Liquid-Solid Boundaries Using a Right-Angle Reflector Technique
Authors: Rollins Fred R.
Published: September 2005

A motor-driven ultrasonic goniometer is described consisting of a single transducer and a 90° reflector. This relatively simple device facilitates rapid investigation and automatic recording of reflection data. The reflectivity curves are interpreted in terms of reflector geometry and the physical properties of the specimen. Among other things, the technique has been used to determine surface-wave velocities in the Y-Z plane of quartz, and the results are shown to be in reasonable agreement with both theoretical and other experimental data.
Wave Propagation in a Viscous Incompressible Fluid Contained in Flexible Viscoelastic Tubes
Authors: Chow Joseph C. F. , Apter Julia T.
Published: September 2005

The dispersion attenuation of waves in viscoelastic tubes filled with a viscous incompressible fluid are analyzed, with special attention to two cases: where the constitutive relation of the wall is that (1) of a Voigt material, and (2) of a standard linear solid. Explicit expressions show the dependence of the phase-velocity and damping factor on the various parameters characterizing the fluid and the viscoelastic tube. In comparison with elastic tubes, viscoelastic tubes have a higher phase velocity and attenuation coefficient. Also, as the ratio of the relaxation time of the viscoelastic material to the period of the oscillation increases, there is a marked difference between the behavior of the waves for the two types of materials considered. The frequency equation for a stretched elastic tube is also derived. The analysis is restricted to waves whose amplitude is infinitesimal with the wavelength large and the wall thickness small as compared with the radius of the tube.