bluuebunny/crossref_metadata_2025 huggingface dataset:
Phonetic Pattern Recognition Vocoder for Narrow-Band Speech Transmission
Authors: Dudley Homer
Published: September 2005

Syllabic spectral patterns of continuous speech have been classified into a finite alphabet through an automatic recognition process built into a “phonetic vocoder.” The classified spectra were then used to synthesize corresponding sounds approximating the original phonetic content, within broad limits. The principle of phonetic recognition can be applied to realize a maximally efficient coding of speech, considering only the phonetic content. The corresponding frequency band is about 50 cps, a 6-fold reduction over the frequency-band vocoder. Also, the recognition process assures that spoken words can be printed automatically as phonetic text.

Speech processed with the phonetic vocoder described here was obtained using an alphabet of only four consonants and six vowels. Nonetheless, limited vocabulary transmission was demonstrated over a band of about 100 cps indicating the feasibility of this coding method. Articulation figures of over 95% were measured using the spoken digits as test material. For a larger vocabulary of monosyllabic words, about 50% intelligibility was found in a limited test. Spectrograms of the vocoder input and output are compared.
Properties of Transducer Ceramics under Maintained Planar Stress
Authors: Brown R. F. , McMahon G. W.
Published: September 2005

In order to predict the performance of certain types of deeply submerged underwater transducers, measurements have been made of the properties of piezoelectric ceramics as a function of pressure, time, and electric field. Planar compressive stresses up to 35 000 psi were imposed on barium titanate and lead zirconate titanate ceramic by subjecting thin hollow spheres to uniform external pressure. With increasing stress, the dielectric constant, piezoelectric constant, coupling factor, and elastic compliance decreased by as much as 70%, part of the change being permanent but most of it reversible. The stability of the ceramic properties with duration and number of cycles of the imposed stress varied widely with ceramic composition. Large increases in high-field dielectric loss were observed at high stress in ceramics usually considered suitable for high-power projectors. The results indicate that transducers that utilize ceramic under planar stress may suffer significant degradation in performance when deeply submerged.
Segment Inventory for Speech Synthesis
Authors: Wang William S-Y. , Peterson Gordon E.
Published: September 2005

The inventory of segments required to synthesize an idiolect of American speech from recorded utterances has been partially investigated. A total of 43 phonetic units, including a unit of silence, is found essential. These units represent some of the major allophones of the phonemes of the idiolect. To obtain the segments, utterances are contructed with the desired sequence of the two phonetic units and with the proper intonation and stress environment. The utterances are recorded on magnetic tape, and the desired boundaries of the segments are determined by means of a technique employing a sound spectrograph. An attempt is made to match harmonics, formants, and amplitude envelopes between adjacent segments. To synthesize the idiolect it is estimated that an inventory of about 8500 segments is required. A sentence synthesized from over 40 such segments is demonstrated.
Jet Noise Reduction by Induced Flow
Authors: Dyer Ira , Franken Peter A. , Westervelt Peter J.
Published: September 2005

The effect on the generation of jet noise by the secondary air induction of a modified jet nozzle is analyzed. It is shown that the combination of the secondary air with the primary jet air creates a new jet stream of larger area, lower velocity, and lower noise generation. The decrease in noise radiation is found in terms of the area of the combined jet stream. Detailed check of the theory is not possible at present because measurements of the areas of the combined jet streams have not been generally made along with measurements of the noise. However, it is possible to estimate the upper limit of the appropriate jet stream area in order to obtain the upper limit on noise reduction. The upper limit on noise reduction obtained from the theory is consistent with existing measurements. Qualitative conclusions from the theory with respect to the spectrum and directivity of the noise radiated by jets with modified nozzles are in accord with measurements.
Reflections from Lossy Media
Authors: White J. E.
Published: September 2005

A simple analysis shows that, when a transient plane wave in an elastic medium is reflected at a plane boundary with a lossy medium, the transient waveform of the reflection is affected by the loss parameters of the second medium. If the attenuation in the second medium is small, and if the ρc products of the two media are matched, then the reflected waveform is the convolution of the incident waveform, with the integral of the Fourier transform of attenuation as a function of frequency. Thus, attenuation for a lossy solid or liquid can be obtained by this external-pulse technique. Where attenuation is some simple function of frequency, its Fourier transform is some recognized generalized function. Sample waveforms have been observed using airborne sound in specially prepared tubes; good qualitative agreement with predicted waveform was obtained.
Equivalent Electrical Network for the Transversely Vibrating Uniform Bar
Authors: Konno Masashi , Nakamura Hisashi
Published: September 2005

The equivalent network for the transversely vibrating uniform bars under various end conditions are given, the value of each element of the networks is determined, and graphs showing the frequency characteristics of each element in the matrices for the bars are given. Some considerations such as the effect of the neglect of the distributed mass are given. The analysis by the method of normalized functions is briefly explained by citing a few examples.
Long-Range Sound-Propagation Study in the Southern Ocean—Project Neptune
Authors: Kibblewhite A. C. , Denham R. N. , Barker P. H.
Published: September 2005

An experiment to determine some characteristics of long-range underwater sound propagation was undertaken by the U.S. Naval Ordnance Laboratory in April 1964. In this experiment, Project Neptune, sound signals were dropped at various ranges from a listening station in Bermuda. To supplement this and other stations, one was established, by the New Zealand Naval Research Laboratory, off southern New Zealand to record the sound signals dropped on the final phase between Cape Town, South Africa, and Perth, Australia. The recorded energy was analyzed in 13-oct bands to determine the transmission-path characteristics for low frequencies. The signal envelopes were found to differ in shape from the usual solar case, and the attenuations were much larger than previously obtained for either RSR (refracted-surface reflected) or sofar propagation. These differences may be explained in terms of the different velocity structure of the Southern Ocean from that sound in the Atlantic or Pacific Oceans. In particular, the thermocline is not as pronounced as in temperate or tropical regions and is absent south of the Antarctic convergence. Thus, the energy was transmitted by a mixture of RSR and sofar modes, little sofar energy arriving from those shots whose tracks crossed the Antarctic convergence.
Deep-Ocean Sound Attenuation in the Sub- and Low-Kilocycle-per-Second Region
Authors: Thorp William H.
Published: September 2005

An experiment was conducted to provide an empirical evaluation of attenuation in sea water in the frequency range of 354–3540 cps. Recordings were made of solar shots detonated every 5 miles along a 500-mile track. The receiving elements were located near the axis of the sofar channel. An analysis is outlined both in terms of received energy spectrum and transmission loss as a function of range. The experimental data have been statistically fitted by least-squares methods to a mathematical model of the form NW = H0+10 log R+aR, where H0 represents the transmission loss in excess of inverse first-power spreading. These results have been combined with those from a subsequent experiment, conducted in the same geographical area, that extended the frequency coverage to 112 cps. The regression line fitting the joint set of coefficients to an upper limit of 1780 cps is given by a = 5.42×10−5 fkcps1.50 dB/yd. The present evaluation is compared with other results, and an apparent systematic anomaly is discussed.
Rating Scales and Two-State Threshold Models
Authors: Watson Charles S. , Bourbon Walter T.
Published: September 2005

The use of rating-scale isosensitivity data for testing discrete, two-state detection models is admitted to be inappropriate, unless additional assumptions are made. It is suggested that simple assumptions may, in fact, be made by which this model may maintain its basic description of sensory processes and yet make predictions about rating results. The predictions are shown to produce the same isosensitivity curves (ROC curves) as did the original, two-choice version of the model. These functions do not describe the results of rating experiments.
Ultrasonic Absorption and Velocity in Concentrated Aqueous Sulfuric Acid Solutions
Authors: Valleau J. P.
Published: September 2005

Sound absorption and velocity have been measured at 65 Mc/sec in aqueous sulfuric acid solutions at concentrations up to 13% oleum. The absorption goes through peaks at mole fractions of 0.5 and 1.0; the adiabatic compressibility has been calculated, and goes through a valley and a peak, respectively, at these two concentrations. No relaxation is observed. This behavior is discussed, but it has not been possible to distinguish very definitely between “structural” and “chemical” absorptions.
Radiated Field of a Rectangular Piston
Authors: Neubauer Werner G.
Published: September 2005

The radiated field of a rectangular piston in an infinite rigid baffle is expressed in terms of the complex Fresnel integral. The field, excluding that inside of the circumscribed hemisphere of the piston, compares favorably with the results of a numerical integration of the basic equation, even at points far from the axis of the piston. Agreement with a previous formulation of the same problem by Freedman is found near the piston axis.
Binaural Effects in Remote Masking
Authors: Hirsh Ira J. , Burgeat Michel
Published: September 2005

The dependence of binaural masked thresholds on the interaural phase relations of both the signal tone and the noise has been demonstrated in previous studies, and has been repeated here for a wide band of noise (200–4000 cps). A second experiment was carried out to test whether this dependence extended to the remote masking of low-frequency tones by a high-frequency band of noise (2000–4000 cps). The results indicate that a phase reversal of the tone at the two ears has the same effect in remote masking as in ordinary masking; but a phase reversal of the high-frequency band at the two ears produces changes in the masked threshold midway between those encountered in ordinary masking and no change at all. The results are interpreted as indicating that the interaural time relations between the remote-masking sources that result from a phase reversal of the high-frequency band involve a time shift of about one half-period of the band midfrequency and a decrease in the interaural correlation.
Comment on the Existence of the Fitzgerald Effect
Authors: Leonard R. W.
Published: September 2005

The author has given considerable thought to the problems involved in the audio-frequency resonances observed by Fitzgerald in crystalline solids [J. Acoust. Soc. Am. 36, 2086–2089 (1964)]. For reasons developed below, the existence of this effect seems extremely doubtful. It is the author's opinion that Professor Fitzgerald has measured the characteristics of the various apparati that he has used rather than those of the materials tested.
Studies of Observed and Predicted Values of Bottom Reflectivity as a Function of Incident Angle
Authors: Menotti F. R. , Santaniello S. R. , Schumacher W. R.
Published: September 2005

A theoretical model of the ocean bottom has been developed for studies of bottom reflectivity. The model consists of many absorbing liquid, plane parallel layers over one semiinfinite solid. Using this model, computations of reflection coefficients as a function of incident angle were performed. Measurements of the acoustic reflectivity of an area of Atlantic Ocean bottom, using a deep streamed projector and two deep-fixed receiving hydrophones, were made at a frequency of 1000 cps and for two pulse lengths. The experimentally derived reflection coefficients are analyzed on the basis of pulse length, for each hydrophone, and comparison is made with the predicted coefficients obtained from the theoretical model.
Effect of Masking on the Pitch of Periodic Pulses
Authors: Rosenberg Aaron E.
Published: September 2005

The pulse-train pitch-matching experiments of Flanagan and Guttman have been extended to investigate the effect of selective masking on the pitch of these stimuli. For unmasked stimuli, at pulse repetition rates below approximately 150 pps, a pitch mode correlated with the pulse repetition rate is generally obtained; at fundamental frequencies higher than approximately 150 cps (and below 800 cps), a pitch mode correlated with the fundamental frequency is generally obtained even if the fundamental component has been rejected from the challenge stimulus by filtering. There is a transition region of repetition rates of the challenge stimulus in which the cues for both pitch modes are strongly competing. Present results indicate that if, to challenge stimuli in or near the transition region, high-pass noise (1000-cps cutoff) is added the “buzz” quality associated with the pulse-rate mode can be masked and a fundamental-frequency pitch judgment elicited. Conversely, low-pass noise (1000-cps cutoff) can mask the “tonal” quality associated with the fundamental-frequency mode and elicit pulse-rate pitch judgments. Narrow bands of noise or sinusoids are equally effective as maskers. Fundamental-frequency pitch judgments and pulse-rate pitch judgments are suppressed by narrow bands of noise or sinusoids centered at about 500 and 5000 cps, respectively. It is concluded that, for pulse-train stimuli with repetition rates in or near the transition region, fundamental-frequency and pulse-rate pitch modes are associated with distinct auditory channels below 1000 and above 1000 cps, respectively, with special prominence to the regions near 500 and 5000 cps, respectively. It is further suggested that these results tend to support periodicity mechanisms for mediating these modes of pitch perception.
Resonance-Absorption Cross Section of a Pipe Organ
Authors: Benade A. H.
Published: September 2005

Each chromatic rank of pipes in gu organ provides a set of resonant absorbers for reverberant sound. The averaged internal absorption of pipes resonating near angular frequency ω is ρ̄ = (2π2/0.06) (c2/ω3) (Γr/Γ) (Γ − Γr). The resonance width Γ is the sum of the widths Γr, Γw, Γm, arising from radiation, wall losses, and viscosity in the mouth region. The velocity of sound is c. Organ pipes (radius a and length L) are scaled so that a∼Lβ, so that absorption by a pipe that resonates at ω in its nth mode is expressible via the properties of a pipe whose fundamental is ω, with radius a, radiating area S, and mouth end correction E. Many pipes in rank absorb strongly at any given frequency. The major contribution comes from the largest pipes excited in their higher modes. A 73-pipe rank centered at middle C can give a total resonance absorption as high as 0.5 m2 at 62 cps, down to about 0.028 m2 at 2000 cps. Absorption by external pipe surfaces (calculated elsewhere) is negligible, except at the highest frequencies.
Transition Régime for Acoustic Fluctuations in a Randomly Inhomogeneous Medium
Authors: Stone R. G. , Mintzer D.
Published: September 2005

Further experiments have been made relating the acoustic fluctuations, resulting from transmission through water whose refractive index varies randomly in space and time, to the range from source to receiver, the acoustic frequency, and the parameters of the scattering medium. Both the wave-theory and ray-theory regions are explored, and good agreement with theory found.
Power Spectral Density of the Response of a Nonlinear System to Random Excitation
Authors: Khabbaz Ghassan R.
Published: September 2005

The damping and spring forces acting on a single-mode oscillator are considered as a power series in velocity and displacement, respectively. The power spectral density of the response of such a system is derived through a perturbation procedure. Moreover, the mean-square response is calculated when the excitation is an ideal white Gaussian process. The influences of both nonlinear damping and stiffness forces on the behavior of the system are discussed.
Equivalent Circuits of Solid Horns Undergoing Longitudinal Vibrations
Authors: Mohammed A.
Published: September 2005

Equivalent circuits of sections of solid horns undergoing longitudinal vibrations are derived. The Bessel and hyperbolic families of horns are used as illustrations of the application of the general expressions for the derivation of equivalent circuits; the familiar T- and π-equivalent circuits are presented. Formulas for the special cases of parabolic, conical, catenoidal, hyperbolic, and exponential horns are given.
Series Solutions for Structural Mobility
Authors: Neubert V. H.
Published: September 2005

In investigating the behavior of subcomponents of a structural system, attention is often given to the matching of mobility or impedance at mounting or junction points. Thus, if the mobility at a point in a certain frequency range is of interest, the structure supporting that point might be a black box containing a structural model designed to duplicate the desired mobility. The paper discusses methods for arriving at models based on various forms of series solutions for mobility of linear systems. Models are presented for a particular example: a uniform, thin bar with free ends. Although it is well known that a model with a very large number of discrete elements would adequately represent a uniform bar, the purpose of the present study is to investigate the possibility of furnishing a model containing only a few elements. The mobility of combinations of the simple models is also presented. Improving accuracy of mobility results in better prediction of transient response. An example is included to show that a properly devised system with only a few degrees of freedom can be superior to systems having many degrees of freedom.
Vibrations of Transversely Isotropic Cylindrical Shells of Finite Length
Authors: Prasad C. , Jain R. K.
Published: September 2005

Flexural, axisymmetric, and torsional vibrations of a transversely isotropic, simply supported, cylindrical shell of finite length are considered. Comparatively simple forms of the equations of motion have been obtained by introducing three auxiliary variables. The solution of these equations is given in terms of Bessel functions. Applying suitable boundary conditions, the frequency equations have been derived. Three-dimensional theory of elasticity is used in the analysis.
Learning to Identify Complex Sounds: Prompting versus Confirmation
Authors: Sidley Norman A. , Winograd Eugene , Bedarf Erwin W.
Published: September 2005

Three groups of subjects were taught to identify, by label, complex sounds. With temporal overlap controlled, confirmation and prompting training procedures were compared. Despite recent emphasis on the superiority of prompting procedures, no significant difference in the efficacy of the two methods was observed.
Release from Masking for Speech
Authors: Weston Peter B. , Miller James D. , Hirsh Ira J.
Published: September 2005

Intelligibility scores were obtained from 12 listeners for monosyllabic words presented monaurally with noises at one or both ears. Release from masking previously reported by Licklider [J. Acoust. Soc. Am. 20, 150–159(1948)] was confirmed, but sizable differences between right and left ears in the amount of release were not found. However, one listener consistently had about 5% more release for speech at the right than the left ear.
Effect of Filter Type on Energy-Detection Models for Auditory Signal Detection
Authors: Mathews M. V. , Pfafflin Sheila M.
Published: September 2005

Two different assumptions about the shape of the filter in energy-detection models for auditory signal detection are investigated. It is shown that, when the mean square output of the filters is equated, the variance calculated for the model whose filter consists of a single resonant circuit is half that of a model whose filter has a rectangular passband. Some implications of this result are discussed.
Acoustic Bridge for the Measurement of Liquid Quantity
Authors: Ward Thomas L.
Published: September 2005

Liquid quantity measurement in aerospace vehicles during free fall is complicated by the fact that liquid in a partially emptied tank will cluster in globules distributed through the tank. The liquid quantity can be determined indirectly by measuring the volume of a gas occupying the “empty” volume of the tank. The volume flow from a low-frequency acoustic source is divided by two fixed acoustic resistances. A portion flows into the unknown volume and a portion flows into a reference volume. The differential pressure between these volumes can be used as a measure of the unknown volume.
Evaluation of New Couplers for Circumaural Earphones
Authors: Charan K. K. , Cox J. R. , Niemoeller Arthur F.
Published: September 2005

An experimental investigation of three couplers, suitable for testing circumaural earphones, was made to determine the limitations on their use. Two of these couplers were modified forms of standard U.S. couplers, the ASA-type 1 and the NBS-9A, while the third was a simple flat plate with a hole in which the test microphone is flush mounted. Results presented are based on tests made using the Telephonics TDH-39 earphone with NAF-48490-1 cushion and the Philips model HA-10 circumaural earphones. Below 2000 Hz, all three couplers are reliable and useful for measuring the responses of circumaural earphones. Above 2000 Hz, small variations in the electroacoustic system, defined by the earphone, cushion, coupler, and measurement microphone, cause large variations in the measured response. Variations in earphone responses are shown to be caused by variations in (1) earphones of a particular type, (2) cushions of a particular type, (3) applied force on the earphone, and (4) placement of the earphone on the coupler. These variations are in addition to the expected variations in the measured responses of different types of earphones when used with different types of cushions and when measured on different types of couplers.
Electropneumatic Acoustic Generator
Authors: Fiala Walter T. , Hilliard J. K. , Renkus J. A. , Van Houten John J.
Published: September 2005

Research and development leading to an electropneumatic acoustic generator capable of producing in excess of 6 KW of acoustic power is reviewed. The modulation of pneumatic power through an electrodynamically controlled valve provides a transducer capable of producing either random or complex periodic signals. The development of this valve required considerable investigation of materials to establish the necessary compliance and optimized moving valve structure to obtain a reliable sound generator. The efficiency of this generator with respect to the pneumatic power supply is as high as 17%. The evaluation of the power spectrum, amplitude distribution, and nonlinear characteristics of the transducer is performed in a progressive-wave tube. Current developments include units that produce considerably more acoustic power or extend the useful frequency range of the sound generator.
Free-Molecule Propagation in Rarefied Gases
Authors: Sessler G. M.
Published: September 2005

Acoustic-wave propagation in gases is studied for the case where the ratio of the transmitter-receiver separation s to the mean free path Λ of the gas molecules is sufficiently small so that the propagation constant is independent of Λ (free-molecule propagation). Experimental results, obtained in air and in argon, are found to be in agreement with the existing theories. Free-molecule propagation is distinguished from ordinary sound propagation that takes place if s/Λ is sufficiently large in order that the propagation constant is independent of s. The ranges of free-molecule propagation and sound propagation are found to be approximately s/Λ < 1 and s/Λ > 5, respectively.
Transient Vibration of Thin Elastic Shells
Authors: Kraus H. , Kalnins A.
Published: September 2005

A complete solution for the response of an arbitrary shell subjected to time-dependent surface loads is derived by means of the classical method of spectral representation. The solution is expanded in terms of the modes of free vibration, and their orthogonality is proved for an arbitrary shell. As an example, the response of a spherical shell to a suddenly applied uniform normal load is calculated in detail.
Masking of Speech by Aircraft Noise
Authors: Kryter K. D. , Williams Carl E.
Published: September 2005

Word-intelligibility tests at various intensity levels were administered to a crew of trained listeners in the presence of recorded noise from jet and propeller-driven aircraft. The noise was that which would be present outdoors and in a house as the result of engine runup operations and if aircraft were flying overhead shortly after takeoff and prior to landing. According to visual inspection of the data, methods of measuring or evaluating aircraft noise predict the results of the speech tests in the following order of merit, from best to worst: (1) articulation index (AI), (2) perceived noise level in PNdB, (3) speech-interference level (SIL), (4) noise criteria (NC), (5) over-all sound-pressure level (SPL A scale), and (6) over-all SPL C scale. The differences among PNdB, SIL, NC, and dB (A), in this regard, are probably not significant according to these tests.
Forced Vibrations of a Two-Degree-of-Freedom System with Combined Coulomb and Viscous Damping
Authors: Yeh Gordon C. K.
Published: September 2005

An exact solution for steady forced vibrations of a two-degree-of-freedom system with two viscous dampers and one Coulomb damper subjected to a simple, harmonic ground excitation is presented. The solution is valid for motions without standstill. The results are expressed in terms of nondimensional parameters that allow evaluations of response amplitudes and phase angles for various frequency ratios, mass ratios, and amounts of viscous and Coulomb damping. In the limits, the resulting expressions agree properly with those for a system without the Coulomb damper and with Den Hartog's [J. P. Den Hartog, “Forced Vibrations with Combined Viscous and Coulomb Damping,” Phil. Mag. 9, 801–817 (1930); “Forced Vibrations with Combined Coulomb and Viscous Friction,” Trans. ASME 53, APM 107–115 (1931).] expressions for a single-degree-of-freedom system with a Coulomb damper. Formulations for the special case of a two-degree-of-freedom system with a Coulomb damper (without viscous dampers) are also obtained. One numerical example of the general formulation is presented and the results are compared with those based on the approximate method of equivalent viscous damping. In Appendix A, numerical results are presented to compare the exact and approximate solutions for a single-degree-of-freedom system with combined Coulomb and viscous damping. The exact solution obtained in this paper can be used to estimate the accuracy of approximate methods for analyzing more-complex systems containing Coulomb damping.
Solid Erosion in Low-Amplitude Sound Fields
Authors: Howkins S. D.
Published: September 2005

The behavior of a bubble of air trapped underwater in a hole, 1 mm in diameter and 1 mm deep, and exposed to a 20-kc/sec sound field was investigated as the applied sound amplitude was slowly increased. It was found that, in degassed water, the bubble could sometimes cause erosion to occur on a nearby polished brass surface at much lower sound amplitudes than when the bubble is absent. Further experiments showed that this was probably due to collapse or transient cavitation occurring in locally enhanced sound-pressure fields in the vicinity of resonant bubbles. This would tend to show that the threshold for collapse cavitation can be affected by bubbles or air pockets present in the liquid.
Adaptive Technique to Discriminate against Coherent Noise in a Narrow-Band System
Authors: Shor S. W. W.
Published: September 2005

It is shown how to use the mathematical method of steep descent to adjust the time delays and shading of an arbitrary array of hydrophones to increase the signal-to-noise ratio and to discriminate against coherent interference. Since the method requires only about 4M correlations at each step for each beam to which it is applied, where M is the number of hydrophones, it can probably be realized in real time in those narrow-band systems to which it is suited. The results of a computer modeling of the method are presented in which, by filtering the output of the hydrophones of a 23-element array, it is found possible to eliminate the effect of an interfering signal 40 dB stronger than the desired signal and offset by 15° from it in bearing.
Free Vibrations of Thin Isotropic Oblate-Spheroidal Shells
Authors: Penzes Leslie E. , Burgin George
Published: September 2005

The problem of the free vibration of a thin isotropic, oblate spheroidal shell has been solved by Galerkin's method. Membrane theory and harmonic axisymmetric motion have been assumed in order to derive the differential equations of motion. This derivation leads to two ordinary differential equations with variable coefficients that can be reduced to one ordinary second-order differential equation with variable coefficients. The resulting eigenvalue problem is solved by Galerkin's method. It is shown that Galerkin's solution for the oblate spheroid yields the exact solution for the sphere as the eccentricity of the oblate spheroid goes to zero. It is also shown that two sets of frequencies exist for the oblate spheroidal shell. After the frequencies are determined, the tangential displacements are obtained as solutions of a homogeneous system of equations.
Expressions for the Electromechanical Coupling Factor in Terms of Critical Frequencies
Authors: Mohammed A.
Published: September 2005

Many expressions for the coupling factor in terms of the fundamental resonant and antiresonant frequencies have been developed. The applicability of many of these is limited, either because they have been obtained from simplified equivalent circuits, or because they apply to particular electromechanical configurations. Approaching the problem by way of the wave equation and mechanical analysis raises difficulties that can only be resolved for relatively simple cases. An approach through a generalized equivalent circuit is used to determine more-general expressions for the coupling factor in terms of the resonant and antiresonant frequencies at the fundamental and overtone modes of vibration. Theoretical and practical applications of these expressions are presented.
Acoustic Interaction Effects in Arrays of Small Spheres
Authors: Weston D. E.
Published: September 2005

Multiple acoustic scattering in line and plane arrays of spheres can sometimes reduce the acoustic pressure on the sphere surface to well below the free-field value, especially for gas-filled spheres in water. However, under certain conditions, there can be an enhancement. The resonance phenomenon is much sharper for a single spherical bubble than for a cylindrical bubble or a cylindrical vortex. The line array of small spheres behaves just like the cylindrical bubble: the sharp sphere resonance is suppressed and a broader resonance at a lower frequency appears. A plane array of such spheres behaves just like a plane screen of gas—there is no resonance at all. The reduction in phase velocity is calculated from scattering considerations for a composite medium having a low concentration of below-resonance spheres.
Frequency Discrimination of Random-Amplitude Tones
Authors: Henning G. Bruce
Published: September 2005

The ability of human observers to discriminate frequencies of tones between 1000–15 000 cps was measured in a temporal two-alternative forced-choice discrimination experiment. On each trial, one of the test tones, selected at random, was attenuated by a random amount ranging from 8 to 20 dB in 2-dB steps. Comparison of the results of this experiment with those of previous experiments in which fixed-amplitude tones were used, indicates little difference between the observers' abilities to discriminate frequencies of fixed- and random-amplitude tones at 1000 cps. Discrimination with random-amplitude tones becomes relatively poorer, however, as frequency is increased. For example, the classical data show a frequency just-noticeable difference (jnd) of 40 cps at 10 000 cps; in the present experiment, with random-amplitude signals, the observers were unable to achieve 75% correct responses until ΔF was 300 cps.
Detection of Auditory Signals in Reproducible Noise
Authors: Pfafflin Sheila M. , Mathews M. V.
Published: September 2005

Twelve reproducible noises were used as stimuli in a two-interval forced-choice signal-detection experiment. The noises were stored numerically in a PB250 computer that converted them to sound during the experiment by means of a digital-to-analog converter. The 240 numbers specifying a noise were sampled at a rate of 2500 numbers/sec, generating a 96-msec stimulus. A sinusoidal signal with a period of 8 samples/cycle was added to one noise on half the trials. Spectral analyses were computed for all stimuli. On nonsignal trials, biases to particular noises were found that could be explained in part, but not entirely, by differences between the noise pairs in energy around the signal frequency. Performance on signal trials was related to the energy difference between the stimuli in the region near the signal frequency, but was not entirely accounted for by this variable. Special characteristics of certain noises appear to affect the subject's response when these noises appear in either signal or nonsignal trials. Additional experiments further defined various aspects of these findings, but did not establish the origin of the biases.
Finite-Difference Method for the Investigation of the Vibrations of Solids and the Evaluation of the Equivalent-Circuit Characteristics of Piezoelectric Resonators. I
Authors: Lloyd P. , Redwood M.
Published: September 2005

The differential equations of motion and boundary conditions of a piezoelectric resonator are first described in general terms, and then developed in a form suitable for the analysis of the free or forced vibrations of contour modes of a thin rectangular plate. Simplifications made possible by elastic and piezoelectric constants of certain symmetries are discussed. A finite-difference representation of these equations is then developed, particular attention being given to the difficulties of dealing with the boundary conditions at the corners. The paper then deals with methods of handling the resulting set of simultaneous equations so as to determine the resonant frequencies, particle displacements, vibrational nodes, and equivalent-circuit characteristics of various modes of vibration.
Effect of Filter Bandwidth and Attenuation Characteristic on Sound-Transmission-Loss Measurements
Authors: Sepmeyer L. W. , Oliphant K. S.
Published: September 2005

To check the effect of both filter bandwidth and attenuation characteristics on sound-transmission-loss measurements, two partitions were measured with the following filters: 12-oct (n = 3) Butterworth characteristic, 13-oct (n = 3) Butterworth characteristic, and 13 oct (n = 2) Butterworth characteristic. No significant difference was found between the noise reduction of a plaster wall obtained with the 12-oct (n = 3) filter or the 13-oct (n = 3) filter. However, on both walls a significant difference, ranging from 0 to 4 dB between 100 and 4000 Hz, was obtained between the noise-reduction characteristics measured with the two 13-oct filters having different attenuation characteristics.
Compliance of Mechanical Contacts and Its Significance for Ultrasonic Hardness Testing and for Vibration-Amplitude Measurements
Authors: Kleesattel Claus
Published: September 2005

The contact between two elastic bodies, pressed against one another by a steady force, has the properties of a spring whose compliance depends primarily on the elastic moduli and on the area of real contact. If the bodies in contact are mechanical resonators, then the magnitude of the contact compliance can be derived from the shifts that the resonance frequencies undergo when the contact is made. The bigger the area of contact, the bigger are the resulting frequency shifts. Thus, it becomes possible to measure hardness. When measuring vibration amplitudes with a pointed sensor, the contact compliance produces an error that can be corrected by measuring the frequency shift of the sensor rod and inserting it into a correction formula.
Measurement of Perceived Acoustic Quality of Sound-Reproducing Systems by Means of Factor Analysis
Authors: Eisler Hannes
Published: September 2005

The factor analytic model, as here applied, conceives of a numerical quality judgment of a certain program played by a given reproducing device as a weighted sum of a measure of the quality of the different reproducing properties (e.g., purity of transients, full treble) possessed by the device in question. The weights constitute measures of the requirements made by the particular program on these properties. Factor analysis splits a raw-data matrix—consisting of, e.g., quality judgments for a number of combinations of program-loudspeaker systems—into two matrices: a factor loading matrix consisting of the weights and a factor-score matrix consisting of the quality of the reproducing properties. The rank of these matrices (number of factors) reflects the number of dimensions (properties) that implicitly enter into the listener's judgments. Four listeners judged, on a 7-point scale, the quality of 24 programs (music, speech, traffic noise, etc.) played on 10 sound reproducing systems of highly different general quality. The data were factor analyzed (component analysis of covariances), and factor loadings for the programs and factor scores for the loudspeaker systems were computed. Nine factors were extracted and rotated, and 7 of them tentatively interpreted (sound level, purity of transients, environmental information, bass boost, full-treble reproduction, high-treble relative midrange, disturbing directional effects). An attempt at validation showed good agreement between factor scores (reproducing properties) for the 4 listeners in spite of variation of preferences between listeners reflected in the factor loadings. Despite technical imperfections, it is concluded that factor analysis is a useful instrument for the assessment of acoustical properties.
Relaxations in Polyethylene: Orientation of the Lamellar Crystals
Authors: Eby R. K. , Colson J. P.
Published: September 2005

A torsion pendulum has been used to make mechanical measurements on linear polyethylene between −175° and +110°C at about 1 Hz. Samples in which orientation had been induced by crystallization in a temperature gradient were measured together with unoriented but otherwise comparable samples. The data are analyzed to show that the a relaxation in polyethylene is sensitive to the orientation of the deformation with respect to the structural and morphological symmetry. For shearing in the a-c face of the unit cell and lamella boundaries the relaxation average over all directions is different from the average for shearing in all possible planes in the cell and boundaries. The γ relaxation does not exhibit this difference. Various viscoelastic parameters such as the real part of the modulus and the magnitude of the relaxations do not correlate with lamella thickness in the present samples.
Edgetones and Nappe Oscillation
Authors: Schwartz H. Ivan
Published: September 2005

Similarities between the mechanisms of edgetones and nappe oscillation (a phenomenon in which a thin sheet of water discharging freely from an overspill weir oscillates violently) are discussed. Attention is drawn to the fact that, for a water nappe subject to harmonically varying transverse air pressures, the elements that deviate farthest from the equilibrium trajectory are not, as might be supposed, those that depart when the pressure reaches its peak value but, in fact, those that depart when the pressure is zero. Important implications of this curious finding are discussed, and it is suggested that the motion of an oscillating nappe system is governed by a differential-difference equation that accounts for instability and hysteretic characteristics and allows for a rational explanation of the transfer of energy from the jet to the vibratory motion. Similar considerations may apply to the instability characteristics of jet-edge systems.
Space-Time Correlation Functions for Surface-Noise Model
Authors: Lytle Dean W. , Moose P. H.
Published: September 2005

A general form of the space-time correlation coefficient for a surface-generated sea-noise model is derived. Specific results are cited for the cases or vertically displaced point receivers with single-frequency, low-pass, and bandpass white uncorrelated radiators, and these results are compared with those of previous investigators.
Development of a Viscoelastic Composition having Superior Vibration-Damping Capability
Authors: Ball George L. , Salyer Ival O.
Published: September 2005

An intensive investigation of polymers, plasticizers, and fillers was conducted with the resulting development of a viscoelastic material that effectively damps 38-in. steel plating. This vibration damping material exhibits greater than 3% critical damping over two decades of frequency, and a 45°F temperature range, at a one-third plate-weight application. At the temperature of maximum efficiency, the material exhibits greater than 9% critical damping over a decade of frequency. The viscoelastic damping material consists of a self-extinguishing vinyl chloride/vinyl acetate copolymer, and is capable of withstanding both saline water and JP-4 jet fuel. The application of this material in spaced and constrained damping systems results in the effective damping of steel plate up to 1.75 in. thick. The investigation also demonstrated that three types of fillers are useful in increasing the damping effectiveness of the polymer system: (1) flake, (2) granular, and (3) low-density granular. The flake filler (e.g., graphite) has the effect of both increasing damping and broadening the operable temperature and frequency range of the damping system. The granular filler (e.g., carbon black) reinforces the polymer network and thereby promotes energy loss. The low-density granular filler (e.g., wood flour) decreases the bulk density of the system without proportional reduction in damping effectiveness.
Power-Group Transformations under Glare, Masking, and Recruitment
Authors: Stevens S. S.
Published: September 2005

A masking stimulus, either visual or auditory, raises the exponent of the psychophysical function relating sensation to stimulus. This power transformation applies only to the part of the function that is influenced by the masking stimulus. Since a given masking noise affects only weaker stimuli, the result is a discontinuous loudness function, which resembles the discontinuous brightness function produced by a glare. The loudness functions for low-frequency stimuli resemble those obtained under masking, as do also the recruitment functions in hard-of-hearing ears.
Comments on “Effects of Waveform Correlation and Signal Duration on Detection of Noise Bursts in Continuous Noise” [D. H. Raab, E. Osman, and E. Rich, J. Acoust. Soc. Am. 35, 1942–1946 (1963)]
Authors: Green David M.
Published: September 2005

Raab, Osman, and Rich [J. Acoust. Soc. Am. 35, 1942–1946 (1963)], in a recent paper, have presented data on the detection of a noise signal added to a background noise. These data are said to lend support to the hypothesis that the human observer is an energy detector. This hypothesis is applied, in their discussion, to experiments involving the detection of an increment in a sinusoidal signal. The writers suggest that a particular result obtained with the sinusoidal signal, termed negative masking, is the result of an improper definition of the effective stimulus. Finally, they contend that, whatever stimulus transformation is actually used by the observer's detection system, it cannot possibly be rectification. This letter attempts to make three points. First, the data of Raab et al. do not lend support for the energy-detection hypothesis—although, admittedly, there are data supporting this hypothesis [D. M. Green, J. Acoust. Soc. Am. 32, 121–131 (1960); D. M. Green and S. T. Sewall, ibid. 34, 1207–1216 (1962)]. Second, it is pointed out that the hypothesis of full-wave rectification will predict exactly the effect that it is said not to predict. Finally, the terms “pedestal effect” and “negative masking” are discussed.
Comment on “Vibrational-Energy Transmission in a Three-Element Structure” [Richard H. Lyon and Terry D. Scharton, J. Acoust. Soc. Am. 38, 253–261 (1965)]
Authors: Newland D. E.
Published: September 2005

The definition and use of coupling-loss factors in the calculation of power flow between randomly excited systems is discussed, with particular reference to the paper cited.
Low-Frequency Scattering by Soft Spheroids
Authors: Burke James E.
Published: September 2005

The exact series solution for the scattering of a plane wave by a soft spheroid is used to obtain explicit long-wavelength approximations. The farfield scattering amplitude is given to the sixth power of the frequency and the near field is given to the second power. The results are valid for prolate and oblate spheroids and arbitrary angles of incidence and observation.
Particle Waves and Audiofrequency Modes in Crystals
Authors: Fitzgerald Edwin R.
Published: September 2005

Starting with the idea that wave mechanics should be useful in dealing with mechanical properties of solids, a connection between particle waves and deformation in crystals is developed. The connection is one in which Planck's constant h plays a prominent part. According to the view described, nonelastic deformation in crystals arises through the propagation of internally generated particle momentum waves with the de Broglie wavelength λ = h/mvi. Here, m and vi are the mass and velocity, respectively, of certain, initially field-free atoms that exist because of lattice defects in the crystal. The particle waves in question are not the probability waves of contemporary, orthodox quantum theory which satisfy the Schrödinger equation. Instead, real-property waves governed by a new differential equation are proposed. Solutions to this equation for both finite and infinite lattices lead to frequency-wave vector conditions from which a number of interesting results follow. These include the occurrence of characteristic frequencies or modes associated with nonelastic deformation, and, in particular, the existence of discrete audiofrequency modes whose frequencies depend on Planck's constant, atomic mass, and lattice segment length. The particle-wave view thus leads directly to predictions of nonelastic audiofrequency resonances in vibration experiments and to expectations of acoustic emission during unidirectional plastic deformation. Applications of these same ideas to other aspects of mechanical behavior are also described briefly.