bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement and Analysis of Body Vibrations of a Violin
Authors: Luke Jon C.
Published: October 2005

Sinusoidal vibrations are induced in a violin by an electromechanical transducer. An optical sensor is used to measure the amplitude and phase of vibration at various locations on the body of the violin. Frequency-response curves for amplitude and phase are measured at 35 locations. These are fitted by a modified least-squares method to the theoretically expected response curves, which are expressible in terms of dissipative eigenmodes. Of the eight most prominent eigenmodes, as isolated numerically, seven show a nearly standing-wave character. For four of the seven, this standing-wave character is not clear in the unprocessed data.
Descriptions of the Speech of Patients with Cancer of the Vocal Folds. Part I: Measures of Fundamental Frequency
Authors: Hecker Michael H. L. , Kreul E. James
Published: October 2005

Speech samples of five patients with cancer of the vocal folds and five individually matched normal speakers were analyzed with respect to: (1) maximum rate of change of fundamental frequency, (2) fundamental-frequency perturbations related to specific consonants, (3) two perturbation factors, and (4) frequency distribution of fundamental frequency. It was found that most of these measures differentiated the pathological and normal speakers. The reliability and possible usefulness of each measure for detecting laryngeal cancer are discussed.
A Comparison of Preference Measurement Methods
Authors: Rothauser E. H. , Urbanek G. E. , Pachl W. P.
Published: October 2005

The present paper compares four methods for measuring the speech-quality parameter preference. The scales of the isopreference method, the category judgment method, the relative preference method, and the absolute preference judgment method (a proposed modification of the category judgment method) are related to a “preference unit” scale. Capabilities and performance of the methods are discussed and illustrated by evaluating a set of test signals with different types of degradation containing a subset of clearly discriminable signals. The paper tries to show how far preference results gained with one method allow prediction of corresponding results in terms of another method. Because of the quantitative limitations of subjective tests and especially since the four methods use different approaches and have different application ranges, it is not unexpected that the preference unit scale has been found to be more of scientific rather than of practical engineering interest. Listeners have been found capable of discriminating reliably, even without reference or anchor signals, more than the five quality steps provided by the category judgment method, and somehow also by the relative preference method. The proposed absolute preference judgment method recognizes this finding and, therefore, yields much better agreement with the isopreference method than the two other methods, which are apparently too strongly quantized.
Possible Transform on the Basilar Membrane
Authors: Zerlin Stanley
Published: October 2005

Cochlear models indicate that basilar membrane displacement in the basal region approximates a first-derivative transform of the input signal. Evidence regarding acoustic transients and their cochlear microphone equivalents in the guinea pig is cited to demonstrate this conversion and suggests the plausibility of the observations derived from models.
Vibration of a Stiff Bar Clamped at One End—Calculation of Tone-Quality Curves Using a Condenser-Microphone Pickup
Authors: Gancy A. B. , Bell R. O.
Published: October 2005

The characteristic tone of a stiff bar, clamped at one end and subjected to a strike impulse, has been calculated when the vibrations are detected by use of a condenser microphone. Such a geometry is used in percussion instruments which simulate the sound of a bell. As one consideration, it is necessary to include the position and length of the condenser plate as well as the position of the strike point to reproduce generally the relative voltage for each vibrational mode, as is experimentally observed.
On the Classification of Russian Fricatives in CV Syllables for Different Speakers
Authors: Lobanov B. M.
Published: October 2005

The sound spectra of the voiceless hard and soft Russian fricatives have been studied in various vowel contexts and with a population of five different speakers (three men, two women). The acoustic characteristics of the fricatives are described in terms of distributions in the FC, FL-plot, where FC is the frequency of the centroid of a short-time spectral section of the voiceless part of a fricative, and where FL is the frequency of the very beginning of the second formant transition from a fricative to a vowel. It is shown that the proper classification of the fricatives requires the self-normalization procedure, because of considerable differences which occur between the same fricatives spoken by different speakers. Results obtained from the study confirm the efficiency of the statistical method of self-normalization for the classification of the fricatives. The method was suggested earlier by the author for the classification of vowels.
Rise-Time Properties of Condenser Microphones
Authors: Homstöl Arnfinn , Gjaevenes Kjell
Published: October 2005

Some measurements performed to determine the rise times of two condenser microphones are described. The difficulties related to the measurements and their interpretation are explained. At peak levels of about 140 dB re 2×10−5 N/m2 the rise time of the B&K 4136 without protective grid and the B&K 4138 with protective grid are determined to 7±1 μsec.
Effect of Ultrasonic Vibration on Coefficient of Friction during Strip Drawing
Authors: Rozner A. G.
Published: October 2005

Effect of ultrasonic vibration on coefficient of friction between a rigid steel die and plastically deformed metal has been studied. The coefficient of friction was measured during a strip-drawing operation with and without application of ultrasonic vibration. The application of ultrasonic vibration during the drawing process substantially reduces the coefficient of friction and die stresses.
Noise Reduction by Applying Modulation Principles
Authors: Ewald Donald , Pavlovic Armin , Bollinger John G.
Published: October 2005

This paper presents techniques for determining nonperiodic spacing of events for the purpose of reshaping noise-frequency spectra. The object of the application is to provide reduced noise levels and the redistribution of the frequencies at which there is noise energy so as to generate fewer perceptible sounds. Three analytical techniques for predicting the noise spectrum resulting from nonuniform spacing are presented. Emphasis is focused on a semigraphical design technique using Bessel functions, which has proven to be of great value in the actual selection of modulated event spacing. Fourier analysis of an impulse approximation and a sinusoidal wave approximation are two other alternative techniques presented. The techniques outlined are applied to the problem of reshaping the noise spectrum of a 22-blade fan in a 5-hp induction motor. A comparison of predicted results provides an evaluation of the alternative approaches.
Sonic-Boom Analog for Investigating Indoor Acoustical Waves
Authors: Lin Sui
Published: October 2005

Acoustical waves induced by sonic booms in a room with an open window are investigated by using an electrical analog. The good agreement between the results from the electrical analog and those of Vaidya show that the electrical analog is a suitable device for investigating the room response to sonic booms.
Significant Audible Noise from Sodium-Water Reactions
Authors: Ying S. P. , Scott C. C.
Published: October 2005

The spectra of sound generated during sodium-water reactions have been observed at room temperature and 315°C. The audible sound radiated from hydrogen bubbles and the frying noise generated at the interface of sodium and water have peaks in the acoustic spectra at frequencies below 1.5 kHz and near 2 kHz, respectively. The experimental results of the oscillation frequency of a hydrogen bubble and its logarithmic decrement agree with theoretical predictions. The frying noise with peaks near 2 kHz results from a pressure that is generated owing to expansion caused by the heat liberated from the chemical reaction of water and sodium.
Multiple-Sensor Enhancement of Infrasonic Reception in the Atmosphere
Authors: Barnes T. G.
Published: October 2005

A series of field tests was conducted to determine the enhancement in reception of infrasonic signals in the atmosphere made possible by the use of a multiplicity of sensors. Firings of a 5-in. cannon were used as the source. The effect of the pattern and spacing of the sensors on signal-to-noise ratio was investigated until useful criteria were established. Multiplicities up to 224 active sensor elements were employed. The signal-to-noise enhancement was shown to be approximately equal to the square root of the number of sensors. Sensor multiplicity enabled the reception of signals at distances up to 47 miles upwind from the source.
Use of FM Pulses to Measure Acoustic Backscatter from Rough Plane Surfaces
Authors: Markson J. L. , Stern R.
Published: October 2005

Measurements of the backscatter of sound waves from three types of rough surfaces and a 6-in. stepdown were performed. Linearly frequency-modulated pulses were used in an effort to reduce fluctuations in the returned pulses caused by turbulence in the air. The use of FM pulses displayed the extreme frequency sensitivity of the backscatter from a very rough surface; however, the FM pulses allowed the returned signal to be averaged over a frequency interval determined by the degree of frequency modulation. Using this type of averaging, it was found that the mean-square backscatter from all surface types was only weakly dependent upon frequency; similarly, a relatively weak dependence on angle of incidence was found in the range of 0°–60°. The frequency range of the measurements was from 40 to 200 kHz; in this range the transmitted signal was linearly frequency modulated by 10, 20, and 40 kHz from initial frequencies of 40, 80, 120, and 160 kHz.
Reflection and Scattering from a Time-Varying Rough Surface—the Nearly Complete Lloyd's Mirror Effect
Authors: Parkins B. E.
Published: October 2005

The effect of a rough moving surface upon transmission between an omnidirectional source and receiver in an isovelocity medium is described for the case of a “slightly rough” surface using the method of physical optics. This is done by relating the spectral density of the received pressure to the spectral density of the source and the wave spectrum of the surface and also the geometry. The dependence of the received spectrum upon the interference between the direct and reradiated waves and the characteristics of the “frequency smearing” caused by scattering are described. A favorable comparison of the theory with the results of an experiment performed under nearly ideal conditions in a model tank is made.
Velocity Dispersion of the Lowest-Order Longitudinal Mode in Finite Rods of Circular Cross Section
Authors: Booker R. E. , Sagar F. H.
Published: October 2005

The velocity dispersion of the Young's modulus mode in a number of finite cylindrical fused silica, aluminum, steel, and brass rods was determined. Their velocity dispersion is shown to agree extremely well with that calculated from the Pochhammer-Chree theory for infinite rods of the same materials over the range of Ω values from 0 to 2.6, where Ω=ωa/cs, a is the bar radius, and cs is the shear-wave velocity. Small differences between the experimental and theoretical velocity dispersion occur when Ω exceeds 2.6; this is attributed to the occurrence of a phase shift when the L(0,1) mode is reflected from the endfaces of a rod. For every rod a few harmonics have been found to occur that do not lie on a smooth graph of frequency versus harmonic number. They may be displaced in frequency, or replaced by several resonances lying close together in frequency. This phenomenon occurs at specific values of Ω, which are associated with an end resonance and the higher-order symmetric modes.
Residual Potential and Approximate Methods for Three-Dimensional Fluid-Structure Interaction Problems
Authors: Geers Thomas L.
Published: October 2005

A method developed previously for an analysis of the two-dimensional excitation of an elastic cylindrical shell by a transverse, transient acoustic wave is extended to three-dimensional applicability. In addition, some fluid-structure interaction approximations are presented that follow naturally from the rigorous development. Application to finite element analysis of the transient response of submerged structures is discussed.
Dispersion of Axially Symmetric Waves in Three-Layered Elastic Shells
Authors: Keck Henry E. , Armenàkas Anthony E.
Published: October 2005

The frequency equation for trains of axisymmetric harmonic waves traveling in infinitely long three-layered circular cylindrical shells and rods is established on the basis of the three-dimensional theory of elasticity. The shells or rods are assumed to be made of three concentric cylinders, each of different isotropic material, bonded perfectly at their interfaces. The frequency equation has been evaluated numerically on an IBM 7044/7094 DCS system, and the effect of the geometric and physical parameters of the three-layered shells on the frequency of the first few modes is illustrated. The limits that the phase velocities of the various modes of propagation approach asymptotically at large wavenumbers are established analytically and verified by the numerical results.
Dynamics of Magnetostrictive Ring Transducers
Authors: Wilkinson J. P. D.
Published: October 2005

This paper presents a numerical approach to calculating the dynamic behavior of magnetostrictive transducers in the shape of a shell of revolution (for example, a cylindrical ring). The method accounts for the effects of saturation and loss, which are important in magnetostrictive devices. It is applicable to either biased or unbiased transducers. Since most transducers of this type are of a scroll construction, the effects of the alternating layers of magnetostrictive material and epoxy bond are included.
Application of Weighted-Gaussian-Quadrature Methods to Convergence-Zone Phenomena
Authors: Floyd Edward R.
Published: October 2005

Weighted-Gaussian-quadrature methods are applied to convergence-zone range integrals without any severe caustic or multipath anomalies. Both flat and curved earth cases are examined. It is shown that in the convergence zone the curved-earth effects are of the same order of magnitude as the thermocline effects and should be included for a meaningful calculation. Weighted-Gaussian-quadrature methods are compared to contemporary methods that approximate the sound-velocity profile with a piecewise analytic segmented profile. Gaussian-quadrature methods avoid the class of anomalies that are due to discontinuous derivatives of some finite order at the junction of two segments of the approximated profile. Illustrative numerical examples are included.
Focusing Properties of a Cylindrical Liquid-Filled Compound Acoustic Lens
Authors: Folds D. L.
Published: October 2005

A compound lens exhibiting low spherical aberration over a wide field of view is described. The results of aberration analyses based on the wavefront deviation technique are presented and computed diffraction patterns are shown. The fabrication of a compound lens is described and experimental and theoretical results are compared at 700, 800, and 900 kHz.
Target Strength of Focused Liquid-Filled Spherical Reflectors
Authors: Folds D. L.
Published: October 2005

The target-strength characteristics of thin-walled spheres filled with low-sound-velocity fluids have been investigated in the frequency range 100–225 kHz. Theoretical and experimental observations show that the target strength of fluid-filled spheres is independent of orientation, can be optimized with proper choices of materials, and can be frequency independent. Comparisons of target strength are made with other well-known passive reflectors.
Perturbation Calculations of Propagation Loss in the Deep Ocean
Authors: Nicholas Nicholas C.
Published: October 2005

Propagation loss expressions were derived by means of perturbation theory corrections to the normal-mode series solution to the acoustical wave equation with parabolic sound-speed profile and sinusoidal point source. A fourth-order power series was used to approximate nonparabolic speed profiles with coefficients determined by a least-squares fit. Perturbation corrections were made to second order for the wave functions and to third order for the eigenvalues. Calculations were made for two realistic speed profiles and an idealized nonparabolic speed profile. Local focusing of sound in a parabolic speed profile had been reported in previous papers [H. Überall and N. C. Nicholas, J. Acoust. Soc. Amer. 44, 1259–1261 (1968); and N. C. Nicholas and H. Überall, J. Acoust. Soc. Amer. 48, 745–753 (1970)], but no local focusing was found for the nonparabolic cases computed. Numerical results showed good agreement with the few available measurements and ray-acoustics estimates of propagation loss.
Amplification and Attenuation of Acoustic Waves in Nonhomogeneous Steady Flows
Authors: Salant Richard F. , Toong Tau-Yi
Published: October 2005

An investigation of the interactions between waves and steady flow fields was stimulated by the problem of combustion instability in rocket engines. A one-dimensional analysis of traveling acoustic waves in flows of an inviscid nonconducting perfect gas, containing mass and heat sources, reveals the existence of a coupling between acoustic waves and nonhomogeneous steady flow fields. This coupling results in either amplification or attenuation of the waves, depending on the gradients of the steady flow variables, phase relationships between oscillations in mass/heat sources and flow field, and injection conditions. A portion of this amplification or attenuation is a result of energy transport between the waves and the flow field, while the remainder is a result of variations in group velocity and impedance. In addition higher-order effects, such as the generation of backward-moving acoustic waves and entropy waves by forward-moving acoustic waves, can occur. Results of experiments with nonuniform velocity fields are in agreement with theoretical predictions. In particular, an air jet discharging into a straight organ pipe and a converging air flow through a tapered pipe are found to attenuate acoustic waves propagating through the pipes.
Frequencies of a Hanging Chain Supporting an End Mass
Authors: Woodward J. H.
Published: October 2005

The frequency equation is derived for a uniform chain fixed at the upper end and carrying a concentrated mass at the free end. The first five natural frequencies are determined for a wide range of end mass to chain mass ratios. It is shown that for mass ratios exceeding eight, simplified relations may be used to approximate the natural frequencies.
Approach to the Multiple-Surface-Reflection Problem in a Linear-Gradient Medium
Authors: Raphael David T.
Published: October 2005

The approach to the multiple-surface-reflection problem in a linear-gradient medium presented by D. T. Raphael [J. Acoust. Soc. Amer. 47, 1437–1439 (1970)] is a new approach and different from the one developed by M. J. Jacobson [J. Acoust. Soc. Amer. 36, 2298–2305 (1964)]; the former exploits an acquiring-ray angle solution for a linear-gradient medium in order to solve the problem, whereas the latter involves Snell's law substitutions and can be used to accomplish the same.
Large Nearfield Calibration Array
Authors: Pida George
Published: October 2005

Farfield transmitting response, free-field sensitivity, and directivity patterns of both small and large (up to 18 ft in one dimension) underwater audiofrequency transducers have been obtained by direct measurement made in the nearfield with a special hydrophone, the NRL 33-ft ×33-ft nearfield calibration array (NFCA). Some of the measured results are compared to the results determined by the classical farfield measurements, except where only computed results were feasible. The calibrating array hydrophone consists of 2500 acoustic sensors in a square array of 8-in. spacings. These acoustic sensors were amplitude shaded according to the distribution advanced by Mr. W. James Trott [J. Acoust. Soc. Amer. 36, 1557–1568 (1964)]. Applicable theory and fabrication design data for the special hydrophone are briefly noted.
Rational Design of Matched Absorbing Terminations for Tubes
Authors: Burns Stephen H.
Published: October 2005

The density-dependent impedance and propagation constants of a lossy material are combined to yield a measure of the demerit of a given design. For absorbing sound of a single frequency, an ideal reflection-free termination can be designed. This design yields acceptable results for all higher frequencies. The theory is compared with some experiments in which steel-wool terminations (only 114 cm long) absorbed sounds of frequency 480 Hz and higher.
Numerical Study of the Gain Pattern of a Shielded Acoustic Antenna
Authors: Strand Otto Neall
Published: October 2005

The farfield gain pattern of a shielded acoustic antenna is studied numerically by the use of Kirchhoff's integral. Circular symmetry and perfectly absorbing walls are assumed. Results are reported for a frequency of 2 kHz.
Apparatus Used in Pulse-Type Ultrasonic Flaw Detection
Authors: Yamamoto Eiji
Published: October 2005

In pulse-type ultrasonic testing, the size of the defect or flaw in a specimen is estimated by the size of the echo reflected by the defect of flaw. By this method, the acceptability of the specimen is determined. In today's ultrasonic flaw detecting, the reflection coefficient of flaws, the characteristics of the acoustic field, the echoes from flaws in specimens, etc., are handled as those of continuous waves. However, in order to improve the resolving power, which is one of the flaw-detecting capabilities of the ultrasonic flaw-detecting method, it is necessary to minimize the number of waves contained in the pulses, and because of this the frequency distribution becomes wide. Under a condition such as this, it is not possible to determine the quantitativeness of echo from a flaw. With respect to the above problem, the author conducted a study especially on the probe, transmitter, receiver amplifier, etc., of the apparatus used in pulse-type ultrasonic testing, mainly in order to obtain the quantitativeness of the echoes reflected by flaws.
Sound Radiation from a Reciprocating Compressor Orifice without Valve
Authors: Trella Thomas J. , Soedel Werner
Published: October 2005

As a first step toward the acoustic radiation modeling of a reciprocating air compressor, the suction and exhaust valves were removed and the compressor was made to cycle air through a single circular orifice. The theoretical model incorporates the aharmonic and large piston motion by thermodynamically modeling the flow in the cylinder. The flow through the orifice was modeled as compressible. Contraction coefficients on an ON-OFF basis were used to account for streamline effects in the orifice section. The farfield acoustic spectrum was predicted by treating the orifice as a monopole source radiating into an infinite halfspace. Agreement between theoretical prediction and experimental measurements was encouraging. A small rise in both the predicted and measured frequency spectrum was hypothesized to be a Helmholtz resonator effect, since it occurred in the expected frequency band. The theoretical calculations were carried out using both a conservation of mass and momentum approach and a conservation of mass and energy approach. Small differences in the results of these two approaches were observed. Finally, with a desire to simplify future models, influences of individual terms in the equations on instantaneous mass flow rates were evaluated.
EVALUATION OF THE GUNDEFENDER EARPLUG: TEMPORARY THRESHOLD SHIFT AND SPEECH INTELLIGIBILITY
Authors: Mosko J. D. , Fletcher John L.
Published: October 2005

A temporary-threshold-shift reduction protocol and a speech intelligibility in noise procedure were used to evaluate the Gundefender earplug. Test results indicate the comparability of the Gundefender to the V.51R for temporary-threshold-shift reduction. Improved speech intelligibility scores in low-noise and no-noise conditions were obtained for the Gundefender.
Acoustic Level and Vocal Effort as Cues for the Loudness of Speech
Authors: Allen George D.
Published: October 2005

A review of previous studies of speech loudness shows great variability in the derived psychophysical functions relating loudness to speech power [i.e., sound-pressure level (SPL)] and other physical and psychological measures, such as subglottal pressure (SGP) and vocal effort. This paper argues that, because of the complex nature of speech production and perception, traditional scaling procedures that yield exponential relations between loudness and some other measure should be replaced by multidimensional techniques. Two experiments on speech loudness scaling using partial correlation analysis demonstrate that loudness judgments depend upon both acoustic cues, as measured by peak SPL, and vocal effort cues, as measured by peak SGP in one experiment and subjective effort in the other. The relative dependencies upon these cues are different for different listeners and are at least somewhat resistant to distortion via signal attenuation and/or masking with white noise. These differences between listeners might be exploited in the search for relationships between speaking and listening.
Voice Spectrograms as a Function of Age, Voice Disguise, and Voice Imitation
Authors: Endres W. , Bambach W. , Flösser G.
Published: October 2005

In order to determine if speech spectrograms can be used to identify human beings, two questions must be studied: (1) does the formant structure of phonemes uttered by a certain speaker change over a long interval of time, and (2) can the formant structure be changed by disguise, or is it even possible to imitate the formant structure of another speaker? Spectrograms of utterances produced by seven speakers and recorded over periods of up to 29 years showed that the frequency position of formants and pitch of voiced sounds shift to lower frequencies with increasing age of test persons. Speech spectrograms of texts spoken in a normal and a disguised voice revealed strong variations in formant structure. Speech spectrograms of utterances of well-known people have been compared with those of imitators. The imitators succeeded in varying the formant structure and fundamental frequency of their voices, but they were not able to adapt these parameters to match or even be similar to those of imitated persons.
The Laterality Effect in Lingual-Auditory Tracking
Authors: Sussman Harvey M.
Published: October 2005

This study investigated binaural sensory processing when continuous nonspeech tonal stimuli were dichotically presented. The experimental task consisted of auditory (frequency) pursuit tracking, and consequently there was no influence of selective attention or competition on the listening task. The target sound was externally controlled, whereas the cursor sound was generated and controlled by the transduced movements of either the subject's tongue or hand. A significant laterality effect was found only when the source of motor control over the acoustic signal was the speech-related movements of the tongue. The theoretical implications of these results towards a feedback regulatory theory of speech production are discussed.
Behavioral Measurements of Absolute and Frequency-Difference Thresholds in Guinea Pig
Authors: Heffner Rickye , Heffner Henry , Masterton Bruce
Published: October 2005

Absolute and frequency-difference thresholds were determined by the conditioned-suppression technique. The results show that the average frequency range of audibility at +50 dB sound-pressure level extends from 86 Hz to 46.5 kHz, with a best frequency near 8 kHz. Individual differences in sensitivity are related to body weight and, probably, age. The average frequency-difference limen is 3.5% from 125 Hz to 42 kHz. Compared to other mammals, the auditory capacities of guinea pig are within one standard deviation of the mammalian mean on each of six dimensions: high-frequency and low-frequency cutoff, lowest intensity, best frequency, area of the audible field, and frequency discrimination.
A Study of the Influence of the Olivocochlear Bundle on the N1 Responses to Repeated Tone Pulses
Authors: Daigneault E. A. , Stopp P. E.
Published: October 2005

The amplitude of the N1 responses (guinea pig) to successive members of a train of brief tone pulses falls progressively over the first few members. The effect lessens as the interpulse interval is increased (10–50 msec). Central section of the olivocochlear bundle does not influence this phenomenon.
Some Suggestions Concerning Basilar-Membrane Displacement and Signal Audibility
Authors: Zerlin Stanley
Published: October 2005

Movements of the basilar membrane and associated cochlear structures give rise to changes in the amount of neural activity measured in first-order neurons. “Upward” displacements result in increased activity and “downward” displacements in reduced activity. Such changes should be reflected in listening performance as the cochlear duct is moved in the two opposing directions. A detection study designed to investigate differences in audibility resulting from membrane displacement (Deatherage and Henderson, J. Acoust. Soc. Amer. 42, 438–440 (1967)] gave results that appeared contrary to these general principles of peripheral transduction. The idea of a 90° phase shift on the basilar membrane and of a time lag between traveling waves are here suggested. These considerations make the psychoacoustic results more compatible with present notions concerning membrane displacement and neural activity.
Acoustic Force on a Liquid Droplet in an Acoustic Stationary Wave
Authors: Crum Lawrence A.
Published: October 2005

This paper considers the time-averaged acoustic force exerted on a spherical liquid droplet in an acoustic stationary wave. Experimental and theoretical values are presented for the minimum acoustic pressure amplitudes required to trap small individual droplets of various liquids near the pressure antinodes of a stationary sound field in a cylinder filled with water. The liquids used were paraldehyde, hexane, benzene, toluene, chlorobenzene, and carbon tetrachloride. Droplet radii ranged from 400 to 800 μ, and acoustic-pressure amplitudes required to trap the droplets ranged from 1 to 15 bars. Calculated and observed values for the acoustic force are in substantial agreement, provided the compressibility of the liquid droplets is considered.
Potentials for Elastic Displacement in Spherically Symmetric Media
Authors: Richards Paul G.
Published: October 2005

The choice of P and S designations is somewhat arbitrary in heterogeneous elastic media, but becomes precise in the high-frequency limit of ray theory. This fact is used in a radially heterogeneous isotropic medium to establish three potentials (P,S,T) with the following properties: (1) every displacement solution is represented by some (P,S,T); (2) T(r,t) is decoupled from P and S, is a potential for SH motion, and satisfies second-order wave equation; and (3) the coupling of P and SV is represented by coupled equations in potentials P and S. At high frequencies these equations decouple (for an important class of sources) into separate second-order wave equations for P and S. An important role, in this decoupled case, is played by the variable density. Several possibilities suggested by the general P and SV equations are also outlined.
Free Vibrations of Generally Orthotropic Plates
Authors: Mohan D. , Kingsbury H. B.
Published: October 2005

An analytical study of the natural frequencies and mode shapes of anisotropic thin plates is presented. The plates are considered to be constructed from an orthotropic material such that the principal elastic axes of the materials are not parallel to the plate edges. By use of Galerkin's method, the change in natural frequencies and mode shapes are investigated as the material elastic axes are rotated with respect to the natural geometric coordinates. Three sets of edge conditions are considered: (1) all edges simply supported; (2) one pair of opposite edges fixed with the other pair free; and (3) one edge fixed with remaining edges free. The results of this investigation show that the plate mode shapes are strongly affected by the orientation of the elastic axes and that they cannot be predicted on the basis of conventional isotropic- or orthotropic-plate analysis.
An Investigation of a Double Family of Normal Modes in an Isovelocity Underwater Acoustic Surface Duct
Authors: Au Whitlow W. L.
Published: October 2005

This article treats an underwater isovelocity surface duct overlying a negative velocity gradient layer that requires two distinct families of normal modes to represent the acoustic field in the image-interference region. Each family contains an infinite number of modes. The significance of the two families of modes at short ranges is demonstrated by comparing numerical results obtained from ray theory with results from normal-mode theory. The contribution to the total normal-mode solution by the second family of modes is a complicated function of the gradient below the surface channel, the range, and the receiver depth. Within the image-interference region, the second family of modes becomes increasingly important as the range and gradient decrease and the receiver depth increases. However, beyond the image-interference region, the second family of modes may be neglected without appreciable error. The properties of the various modal elements are investigated and some generalizations concerning the second family are derived.
Acoustic Attenuation in Composite Materials
Authors: Higgs R. W. , Eriksson L. J.
Published: October 2005

An experimental study of sound attenuation in lead-wool-polyurethane composites and nickel-Cerrobend composites was conducted for different compositions, frequencies, and pressures. At specific compositions, the attenuation reached a maximum considerably higher than the attenuation of the components. The maximum attenuation occurred where the compressional modulus is changing most rapidly with composition; at this composition, the attenuation is most unstable with pressure.
Invariance of Geometric Spreading Loss with Changes in Ray Parametrization
Authors: Warfield J. T. , Jacobson M. J.
Published: October 2005

In the ray theory of acoustics, there has been some confusion regarding the variables to be held constant in the evaluation of partial derivatives of the ray position vector in the calculation of geometric spreading loss. It is shown that the general formula for spreading loss remains unchanged when the parameter along a ray is changed from travel time to a new parameter, provided any variable that occurs in the expression for the position vector is regarded as a function of the new parameter and the initial ray angles.
Effect of Four-Quantum Vibrational-Vibrational Coupling on Sound Absorption and Dispersion Curves
Authors: Shields F. D. , Bass H. E.
Published: October 2005

Previous measurements of sound absorption due to vibrational relaxation in CO2/D2S mixtures indicate a vibrational-vibrational (v-v) coupling between the bending mode of CO2 and the stretching modes of D2S. A theory by Tanczos was used to analyze the results, but this theory did not allow for quantum changes greater than two in either one of the colliding molecules. Theoretical curves were calculated, therefore, for a v-v coupling in which a two-for-one quantum exchange took place between the bending mode in CO2 and the stretching modes in D2S. The theory has now been extended to treat cases where the v-v coupling involves a three-for-one quantum exchange between modes. Using this theory, there is a slight improvement in the theoretical fit to the experimental absorption data on CO2/D2S mixtures. This is to be expected because of the near resonance between the 0310 level of CO2 and the 100 and 001 levels of D2S.
The Effect of Interaural Signal-Frequency Disparity on Signal Detectability
Authors: Robinson Donald E.
Published: October 2005

The function relating interaural signal-frequency difference (Δf) to masking-level difference (MLD) was obtained using a two-alternative forced-choice procedure. The masking noise was presented diotically (N0) at a spectral level of 45 dB. The signals to the two ears were gated simultaneously and each was 1 sec in duration. For all Δf conditions, the signal to one ear was 400 Hz. In separate sessions, signal frequencies of 406, 420, 440, 460, 500, 550, 600, and 700 Hz were presented to the other ear. The MLD was found to decrease from about 10 dB at Δf = 6 Hz to about 7 dB at Δf = 150, 200, and 300 Hz. This limiting value of the MLD is also the MLD for the 400-Hz signal presented monaurally (N0-SM).
Jaw Movements under Delayed Auditory Feedback
Authors: Sussman Harvey M. , Smith Karl U.
Published: October 2005

The spatial and temporal movement characteristics of the jaw while subjects spoke under delayed auditory feedback was investigated. An analog-digital-analog computer system was used to instrument the delayed speech signal and a strain-gauge transducer was used to monitor the movements of the jaw. The speech sample consisted of the high, middle, and low front vowels /i/, /ɛ/, and /æ/ embedded in the carrier phrase: “That's a CVC a month.” Measurements were made of maximal jaw opening distances during the vowel segment, jaw activity duration throughout the utterance, and jaw velocity during the opening and closing phases of the vowel gesture. The disruptive effects caused by the temporally delayed speech signal were found to be specific to the: (1) magnitude of the delay interval; (2) vowel context; and (3) space-time dependent variable being measured. Increased jaw-opening excursions were found, depending upon the vowel context, and a positional target overshoot was noted at the 0.3-sec delay interval, especially for the midvowel /ɛ/. The time period of active jaw articulation was considerably lengthened at the 0.1-sec delay interval, especially for the high vowel /i/. The jaw velocity measures showed increased movement rates for both opening and closing vowel gestures as a function of vowel openness.
What Does the Lemur Really Hear?
Authors: Mitchell Curt , Vernon Jack , Herman Paul
Published: October 2005

Behavioral audiograms of five ringtail lemurs, determined by a single-lever shock avoidance method, are reported. The frequency range, 0.1–40 kHz, is compared with data from a previous study. Increased sensitivity in the middle frequencies are reported by this method.
Implications of Fresnel Corrections in a Non-Gaussian Surface Scatter Channel
Authors: McDonald John F. , Spindel Robert C.
Published: October 2005

An investigation is made of the effect of the beam pattern of a source exciting an acoustic surface scatter channel using the Fresnel corrected physical optics approximation. Results are presented for monochromatic and impulsive excitation using both deterministic and random boundaries. In the random case, non-Gaussian statistics are permitted for the surface deformations. This study concentrates on the limits of very narrow and very broad frequency-invariant beam patterns and specular geometry at moderate grazing angles. The results for the broad beam pattern are found to be simpler than the corresponding ones for narrow and intermediate beam patterns. The theory is applied towards the calculation of impulse response convolutions and bifrequency spreading functions. An attempt is made to relate current and past physical results in a nomenclature suitable for application in signal processing and communication theory.
Time-Smear and Frequency-Smear Studies on the BIFI Range
Authors: Sussman Bernard , Kanabis William G.
Published: October 2005

The BIFI range is a shallow-water acoustic range in Long Island Sound, about 19 miles long and 110 ft deep. Results of time-smear and frequency-smear studies made on this range are presented. It is shown how these results may be used to predict signal fluctuation. In time-smear studies, the received signal is divided into a front, a main arrival, and a tail. The relative energies of the three sections of the signal are computed, and these results are used to predict the range of signal fluctuations. The above analysis and computation are easily carried out on a digital computer using, as input, data automatically punched on cards. Frequency smear is the Doppler shift undergone by a signal as a result of being reflected from a moving surface. Many frequency-smear spectra were obtained for varying sea states, and, from these, dispersion as a function of sea state was calculated. The dispersion increased with sea state, in agreement with theory.
Acoustic Horns with Spatially Varying Density or Elasticity
Authors: Shaw E. A. G.
Published: October 2005

The transformation of acoustic impedance can be accomplished either by a controlled variation of wavefront area as the wave progresses, or by transmission of the waves through a medium in which there is a gradient of density or elasticity. The second concept does not seem to have been exploited despite the fact that the effective density of a fluid medium can be increased by introducing suitable arrays of obstacles, and the bulk modulus of a liquid decreased by compliant inclusions. The present analysis shows that for plane waves a medium in which density varies as (B + mx)−2 or elastic modulus as (B − mx)2, where x is distance and B and m are constants, is analogous to the familiar exponential horn. Simple analytical solutions are also found for radial variations of density or elasticity which transform the behavior of sectoral and conical horns into the acoustic equivalents of exponential horns. Since the wave equation is separable in both cylindrical and spherical coordinates, these solutions are exact. Three examples of artificial fluid structure are given and the relationships between array size, bandwidth, and damping are discussed.
Waveforms and Frequency Spectra of Acoustic Emissions
Authors: Stephens R. W. B. , Pollock A. A.
Published: October 2005

Illustrations are given of information carried in the waveforms and frequency spectra of acoustic emissions. The effects of multiple reflections and resonances are discussed. A model of the acoustic-emission source wave is developed, and arguments are given why this wave should be a pulselike function, rather than an oscillatory function of stress. Further use of this model may allow more quantitative treatment of emission amplitudes, energies, and spectra. Experimental results show the use of two instruments for the evaluation of emission spectra. The feasibility of using frequency analysis to obtain information about source events is demonstrated.
The Acoustical and Mechanical Properties of Sonite
Authors: Higgs R. W. , D'Amico P. M. , Speerschneider C. J.
Published: October 2005

Sonite is a material used for acoustic decoupling in deep-ocean sonar transducers. Its density, bulk modulus, sound velocity, and attenuation constant have been measured as a function of precompression and ambient pressure. The sound velocity and attenuation constant were measured at 40 kHz and 12°C, utilizing a water-filled impedance tube. By using a delay line technique at 1 MHz, the material was found to exhibit transverse isotropy. Sample preparation and measurement techniques are described.
An Intensity Differential Equation in Ray Acoustics
Authors: Solomon L. P. , Armijo L.
Published: October 2005

A desired goal of either ray acoustics or normal-mode analysis in underwater sound propagation problems is the prediction of the intensity at some field point. The ray-bundle approach in ray acoustics is a technique which has been employed to predict intensity. By formulating the ray-path problem in terms of a differential equation, rather than in terms of a range integral, a second differential equation can be obtained which describes the continuous variation of intensity along the ray. An extension of the calculation of intensity to allow for variation of the speed of sound with range as well as depth is easily accomplished. It is shown that, for the intensity function to be continuous, a sufficient condition on the velocity function is that it be twice continuously differentiable except at caustics where the theory breaks down.
Impact Noise Isolation of Composite Floors
Authors: Vér István L.
Published: October 2005

This paper describes a procedure for calculating the impact-noise level of a bare stiff structural floor when excited with a standard tapping machine. Calculations are also given for the improvement in impact noise isolation achieved by adding to the structural floor (a) an elastic surface layer, (b) a locally reacting floating floor, and (c) a resonantly reacting floating floor.
Comments on “Solution of Acoustical-Radiation Problems by Boundary Collocation” [J. L. Butler, J. Acoust. Soc. Amer. 48, 325–336 (1970)]
Authors: Laura Patricio A.
Published: October 2005

The purpose of the present letter is twofold: first to list some additional references dealing with recent applications of the boundary collocation technique and second to add some comments regarding the convergence of the method.
Monaural Detection with Contralateral Cue (MDCC). IV. Psychometric Functions with Sinusoidal Signals
Authors: Taylor M. M. , Smith S. M. , Clarke D. P. J.
Published: October 2005

Detection performance in the monaural detection with contralateral cue (MDCC) task was measured for sinusoidal signals over a range of signal-masker levels at several cue intensities and phases. In the first experiment, the effect of cue intensity was measured at two phases, one giving good performance and the other leading to poor performance. With good phase, cue intensity had little effect except that performance declined with a very loud or very soft cue. With bad phase, increasing the cue intensity made performance worse. Over a considerable range of cue intensity and signal-masker level, bad-phase performance was well below chance. In the second experiment, the effect of cue phase was determined at a single cue intensity. Performance was an asymmetrical function of cue phase. The slopes of the derived psychometric functions were also a function of phase, approximating the slope of an ideal detector for signal known exactly (SKE) when phase was good, and approximating that of the simple monaural detection psychometric function when the phase was bad. The data lend support to the idea that binaural interaction involves at least two independent mechanisms.
A Correlation Model of Binaural Masking Level Differences
Authors: Osman Eli
Published: October 2005

This paper presents a quantitative functional model, called the correlation model, to be used for interpreting empirical results on binaural masking level differences (BMLDs), which are obtained experiments on the detection of sinusoidal signals embedded in binaural noise. The receiver is presumed to behave as if it computes a statistical decision variable equivalent to a linear combination of three quantities, the energy levels at the channels deriving from the two ears and the interchannel cross correlation, where the coefficients are dependent on the interaural noise cross correlation and the interaural amplitude ratio for noise but are completely independent of signal parameters. Additive internal noise is assumed. Equations for BMLDs are derived with the restriction of equal noise levels at the two ears. Predictions derived from the model are compared with empirical results from several studies. These show BMLDs for antiphasic, homophasic, and monoaural input configurations at different frequencies of tonal signal, and BMLDs for varying interaural correlations of signal and of noise, where the noise correlation is statistical or deterministic. Similarities and differences between the correlation model and another model, the equalization cancellation model, are discussed in detail.