bluuebunny/crossref_metadata_2025 huggingface dataset:
A methodological study on statistical evaluation of transmitted sound waves based on the system change of sound insulation
Authors: Iwashige H. , Ohta M. , Yamaguchi S.
Published: October 2005

The random noise fluctuation encountered in our living environment, such as street noise, road traffic noise, etc., exhibits various kinds of probability distribution forms apart from the usual Gaussian distribution due to the diversified causes of the fluctuations. From the practical viewpoint of control and regulation for such environmental noise, several statistics, such as median, L5 and L10 (in general, so-called Lα sound level), directly connected with the probability distribution form of random noise are very important for evaluation of the human response. Thus, it is essential to establish a systematic method for evaluating the effect of the system change of noise control on the widely used standard noise index such as Lα. In this paper, a general and fundamental consideration for statistical evaluation of transmitted sound waves has been theoretically proposed, when the system characteristic of the sound insulation is changed by the reinforcement work. The theoretical result is experimentally confirmed not only by the result by the digital simulation technique, but also by the actual observed data obtained using the reverberant room method. The results of the experiment are in good agreement with the theory.
A fiber optic lever for noncontact shock and vibration measurements
Authors: Cook Reginald O. , Hamm Charles W. , Akay Adnan
Published: October 2005

Frequency response of accelerometers used in shock and vibration measurements is usually limited by linearity considerations to one-third of the resonant frequency of the accelerometer. In addition, for highly sensitive measurements, the added mass of the accelerometer may alter the characteristics of the surface motion. And finally, to obtain displacement waveform measurements, the signal obtained through an accelerometer must be integrated twice with great loss of frequency response and dynamic range. The use of noncontacting fiber optic levers offers an attractive alternative in some shock and vibration problems, particularly where knowledge of displacement waveform characteristics is desirable. In this paper, displacement, velocity, and acceleration detection limits as well as frequency response and dynamic range of a fiber optic lever developed for shock and vibration measurements are presented and compared with corresponding published accelerometer specifications. Acceleration, velocity, and displacement waveform measurements from an impactively excited plate by a miniature shock accelerometer and a fiber optic lever are also compared.
AN/FQM-12(V) sonar test set. I: an automated acoustical measurement system
Authors: Truchard James J. , Ashby L. Wayne
Published: October 2005

In this paper we describe an automated acoustical measurement system. The system includes three minicomputers and a number of microprocessors for control and data handling. Multiprocessors are used to simultaneously handle all the processing functions. Interaction with the operator and overall timing and control for the system is handled by the central processor. Two peripheral processors are used for high speed data computation and processing. Several microprocessors provide intelligent control functions for the system. A sophisticated software operating system is used to integrate the hardware into a useable and flexible system. The user is offered a wide variety of options for display and output of measurement data. The software is designed to make implementation of any of these options as easy and convenient as possible for the user. [Work sponsored by NAVSEA 06H4D.]
Characterization of saccular nerve responses in the catfish
Authors: Moeng Robert S.
Published: October 2005

Extracellular single unit responses were recorded from saccular nerve fibers in unanesthetized catfish (lctalurus punctatus). Spontaneous activity and responses to tone pulse stimulation were examined. Interspike-interval (ISI) histograms indicated the presence of at least four types of spontaneous activity. Neurons having no auditory response capabilities had very regular spontaneous activity patterns while those having an auditory response generally showed bursting, irregular, or nonspontaneous patterns. ISI histograms clearly demonstrated phase locking in the nonspontaneous units and there was some evidence that phase locking also occurred in spontaneous units. Frequency response characteristics of the neurons, expressed as isointensity functions, revealed a continuous distribution of best frequency response from less than 200 Hz to over 1000 Hz. The high-frequency response found in some neurons in lctalurus are substantially higher than units found in any other teleost species and may correlate with data showing that this species can detect sounds to well over 4000 Hz [R. R. Fay and A. N. Popper, J. Exp. Biol. 62, 379–387 (1975)]. [Supported by NIH grant NS-09374.]
Effect of the rate of rise of tone burst on the tuning curve in the presence of peripheral inhibition
Authors: Ooyama H. , Yano J. , Sugai T. , Sawada S.
Published: October 2005

Unit spikes were recorded from the VIIIth nerve branch innervating the amphibian papilla of a urethane-anesthetized toad. Tonal stimuli were applied from an earphone through a coupling tube to the surface of the saccule. The tuning curve (TC) for fast rising tone bursts rose gradually toward both low and high frequencies (HF's) from the characteristic frequency (CF) of the unit. HF continuous tones had the effect of peripheral inhibition on the response to any test tones. As the rate of rise of tone bursts was decreased, the TC rose progressively at comparatively higher frequencies, while little change was seen near the CF and under. When the slow rising (90% rise per 20 ms and slower) test tone bursts were used, the rise of TC reached a saturation point, where HF cutoff of the TC was very steep. It seems that the sharp HF cutoff arises, because the thresholds are reached after the peripheral inhibition developed during the slow rising phase of the HF test tones themselves.
Masked underwater pure tone thresholds of the northern fur seal (Callorhinus ursinus)
Authors: Moore P. W. B. , Schusterman R. J.
Published: October 2005

Masked underwater pure tone thresholds were obtained for two female northern fur seals using an “up-down stair case” method and a “go/no-go” response procedure. Thresholds were determined at three continuous broadband masked noise levels at frequencies of 2, 4, 8, 16, and 32 kHz. The critical ratio (C. R.), defined as the ratio of signal power to spectrum level at masked threshold, were calculated for both animals. A psychometric function relating the pooled C. R.'s to frequency was plotted and found to be similar and showed parallel functions with C.R.'s of other marine and terrestrial mammals. These results support the contention that similar functions represent similar mechanisms that are related across species. [Work supported by ONR.]
Lingual vibrotactile testing: A Modified nonclamping procedure
Authors: Telage K. M. , Petrosino L. A.
Published: October 2005

Lingual vibrotactile thresholds were obtained from the anterior midline surface of the tongue for 20 subjects during test and retest conditions. Measurements were made at five frequencies (60, 100, 150, 200, and 250 Hz) using a new procedure which did not compress the lingual tissue. Modifications also included using a series of logic modules to program stimulus control and to track threshold sensitivity at frequency while simultaneously adding and subtracting attenutation in the manner of Bekesy audiometry. Procedures previously used by the author and his associates clamped the tongue and consistently obtained a summating response suggestive of frequency selective mechanoreceptors. Present test-retest results showed a flat configuration across frequency which agrees with the Duplex Theory of Mechanoreception [R. T. Verrillo, in The Skin Senses, edited by D. Kenshallo (Thomas, Springfield, 1968) pp. 139–159]. The authors conclude that previously using clamping techniques may have distorted lingual tissues so as to excite ventrally based frequency responsive mechanoreceptors.
Laryngeal adjustments in Japanese word accent
Authors: Yoshioka H. , Hirose H.
Published: October 2005

The role of the intrinsic laryngeal muscles in accomplishing various accent types in Japanese was studied. Specifically, the electromyographic activities of the posterior cricoarytenoid (PCA) and the thyroarytenoid (VOC) were investigated in comparison with that of the cricothyroid (CT). It was revealed that the PCA activity for the voiceless stops or affricates following the first mora with accent kernel was significantly smaller than that for those in the second mora not preceded by accent kernel, regardless of whether or not this second mora has accent kernel. The results were in good agreement with those of fiberoptic observation. The glottal width was always larger for the latter group. The VOC showed activity patterns similar to the CT, generally peaking for the accent kernel. However, the VOC activity tended to decline more rapidly than the CT after the peak. It was also suggested that VOC activity was related not only to the realization of accent but to various segmental features such as glottalization of the word initial vowel or voicelessness of the phonetic segment. [Work supported by NIH NS-13870.]
Sensorimotor integration just prior to Fo change
Authors: Miller A. , Hanson R. J. , Shulak C.
Published: October 2005

Pitch matching data gathered in a previous experiment [R. J. Hanson, Proc. IX Inter. Congr. Acoust. 1, 519 (1977)] were analyzed for reaction time to step changes in target frequency, for the accuracy and for the variability of pitch matching during reaction time. In the experimental task, subjects attempted to match the Fo of their own vowel production presented to one ear with a target sinusoid presented to the opposite ear, which changed randomly up or down by 5, 10, or 15 Hz in each trial. Subjects performed 48 trials in each of the two stimulus/ear configurations. Reaction time was determined using a recently developed two-state model of Fo control [R. J. Hanson, J. Acoust. Soc. Am. S64A]. Accuracy was measured using the percentage difference between the average Fo during reaction time and the target frequency. Variability was measured using the coefficient of variability of the pitch periods during reaction time. These three indeces were used to characterize sensorimotor integration during the dynamic processing period just prior to initiating an Fo change. The major results of this study are: (1) reaction time was shorter when the target was presented to the right ear and for larger changes in target frequency, but was equal for up and down changes in the target frequency; (2) accuracy and variability were not affected by the stimulus/ear configuration, the magnitude nor the direction of the target change. These findings corroborate and extend those of previous experiments regarding the processing advantage of the right ear/left hemisphere pathway for the target during reaction time.
The epiglottis in speech
Authors: Condax I. D. , Nartey Jonas
Published: October 2005

Based on dissections and on published X-ray tracings of the vocal tract we investigated the role of the epiglottis in the production of vowels. Our conclusion is that while the size and position of the epiglottis arc rather variable across subjects and across utterances, one pattern appears to be relatively stable: The angle of the epiglottis with respect to the adjacent portion of the tongue root appears to correlate well with the feature ADVANCED TONGUE ROOT. Since the cartilage of the epiglottis is sometimes more readily observed than is the tongue root itself, this correlation may be useful in some cases. Other patterns are less reliable. In order of decreasing reliability we present the following generalizations: (i) high vowels have a large space between the epiglottis and the tongue root, low vowels have little or none; (ii) back vowels have a relatively enclosed pocket between the epiglottis and the tongue root, front vowels have a relatively open pocket; (iii) vowel height has a marginally greater influence on epiglottis position as measured from the wall of the pharynx than does the feature TENSE. [Work supported by NIH.]
Tip of the tongue and slip of the ear: A comparative study
Authors: Browman C. P.
Published: October 2005

Lexical retrieval errors (tip of the tongue) and perceptual errors (slip of the ear) occurring in casual conversation were collected and analyzed. The distribution of the errors with respect to the position within the word, position within the syllable, and level of stress was determined. Both lexical and perceptual errors occurred less frequently on the final syllable of the word and on stressed syllables. Lexical errors occurred less frequently on initial syllables of the word, while perceptual errors occurred more frequently on initial syllables of the word. Implications for processing models will be discussed [Work supported by NIH and the UCLA Phonetics Laboratory .]
Frequency, amplitude, and load effects on the dynamic properties of elastomers
Authors: Cole John E.
Published: October 2005

The dynamical-mechanical properties of elastomer materials, which are widely used in devices such as antivibration mounts, are known to depend upon the nature of the loading of the material. While many aspects of the dependence of the dynamic properties on frequency and temperature are well known and customarily accounted for, these properties are also known to vary significantly with other aspects of the loading such as strain amplitude and static load. Furthermore, not all of these aspects of the loading appear to act independently. In this paper we discuss the dependence of the dynamic properties of elastomers on frequency, dynamic strain amplitude, and static loading. While the effects of frequency and strain amplitude appear to be separable, it does not appear to be as easy to deal with the effects of static loading. The implications of these effects on designs using elastomers is discussed. [Sponsored by USN Office of Naval Research—Structural Mechanics Program.]
Improved lower bounds for fundamental frequencies of beams
Authors: Hanna S. , Michalopoulos C. D.
Published: October 2005

Lower bounds for buckling loads and fundamental frequencies of elastic bodies have been developed recently from energy considerations. In general, these bounds are very simple to calculate but they lack the accuracy of upper bounds. In this paper, an improved lower bound is obtained. Numerical results are presented to demonstrate the improvement on existing lower bounds. The method is specifically applied to determine a lower bound to the fundamental frequency of nonuniformly compressed beams. Comparison is made of these results with those obtained by other methods. [Work supported in part by NASA.]
Dynamic stability of nonuniformly compressed beams
Authors: Hanna S. , Michalopoulos C. D.
Published: October 2005

The boundaries of the principal region of instability and upper bounds of natural frequencies of a nonuniformly compressed beam are determined approximately using the free-vibration eigenfunctions of the uncompressed beam with the same boundary conditions. Specifically, beams under distributed compression, such as the beam's weight, and beams subjected to multiple concentrated loads are considered. Numerical results are given for beams having hinged-hinged, fixed-hinged, free-free, and fixed-free end conditions. [Work supported in part by NASA.]
Effect of a random ocean current on acoustic propagation
Authors: Newhall B. K. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

The effects of a random current on the fluctuations of an underwater sound transmission are considered for a horizontal isospeed channel. The current is assumed to have a constant unperturbed part, plus small depth-dependent random variations in magnitude and direction. Using ray theory the current influence on ray geometry, travel time, spreading loss, and boundary effects is investigated. Then consistent approximations to total-field phase and amplitude at a fixed receiver are obtained. Acoustically pertinent statistics, including the mean and variance of total-field phase, are found as functions of the statistics of the current fluctuations. Conversely, it is shown how statistics of the assumed current structure can be described in terms of the total-field phase statistics. This initial study provides a basis for future investigations which will utilize more elaborate current and sound-speed models. [Work supported by ONR.]
Evidence of Doppler frequency shift between direct and bottom-reflected ray families
Authors: Sehn G. J.
Published: October 2005

An underwater acoustics experiment was performed in July 1975 in 14 000 ft water near Bermuda. A cw projector (100–400 Hz) was towed at a depth of 300 ft out to 20 NM from a near-bottom hydrophone along various tracks. Rapidly varying periodic interference phenomena producing amplitude fades as great as 20 dB were a significant feature of the received cw time history. Subsequent ray trace analysis showed the periodicity of the cw signal modulation to correspond to the differences in Doppler frequency shift between the families of direct path rays and the first bottom-reflected rays.
Ray displacements and time delays in the ray-mode analogy
Authors: Murphy E. L.
Published: October 2005

The “ray-mode” analogy is useful for qualitatively anticipating the gross features of underwater acoustic modal propagation. With each acoustical mode, it associates a cycle distance and cycle time (related to modal group velocity) along the analogous “ray-paths.” In this paper, it is demonstrated that the phenomenon of ray displacements as proposed in modified ray theory and a corresponding cycle travel time modification can account for quantitative discrepancies between ray and modal cycle distances and group velocities [see, K.M. Guthrie, J. Sound Vib. 32, 289–293 (1974)]. The purpose of this demonstration is twofold. On one hand, the cycle distance and travel time modifications, as a physical explanation for the discrepancies, are shown to be local, near-boundary phenomena. On the other hand, the quantitative success of beam and time displacements as a correction to bring modified cycle distance and travel times into agreement with the more exact modal results, serves as a test of the approximations used to develop modified ray theory.
Sound propagation in a temporally varying ocean
Authors: Ahluwalia D. S. , Reiss E. L.
Published: October 2005

As a result of internal and surface tides, diurnal heating and cooling, and other phenomena, there is a slow temporal variation in the sound velocity in the ocean. The sound propagation from a periodic point source in an ocean with a temporally, slowly varying, sound velocity is analyzed by using a combination of the methods of, normal modes, two times, and stationary phase. We find that for a class of sound velocities, the order of magnitude of the pressure amplitude changes suddenly at a sequence of times, from large to small, and conversely. These “fades” are accompanied by phase shifts.
Three-dimensional propagation modeling using the parabolic approximation
Authors: Baer R. N. , Moseley W. B.
Published: October 2005

An algorithm has been developed for the propagation of sound in a three-dimensionally varying ocean region. We start with the Helmholtz equation in cylindrical coordinates and apply the parabolic approximation in range (retaining variation in horizontal angle). The method involves the split-step Fourier algorithm in depth and angle. In addition, an analytic continuation procedure in angle is used to facilitate implementation on a computer with finite memory. Initial computer results show identical answers compared to the two-dimensional split-step parabolic program when all angular variation is absent, and excellent agreement to an exact solution of the parabolic equation that contains an initial field that varies with angle. The numerical results of these calculations will be discussed.
Construction of a new source function for the parabolic equation algorithm
Authors: Garon H. M. , Hanna J. S. , Rost P. V.
Published: October 2005

Present means for initializing the parabolic equation (PE) field include: (1) using a coherent sum of modes (or rays) or (2) representing the farfield of the source in terms of a Gaussian. Approaches based upon the first turn out to be far too complex, overwhelming the simple elegance of the PE algorithm. The use of a Gaussian, while simple to implement, is inefficient in terms of the distribution of energy in the vertical-wavenumber (kz) domain. We propose, instead, a new source function which appears as a low-pass filter in the kz domain, designed using existing digital filter construction techniques. As a result of this much more efficient energy distribution, a fourfold reduction in required transform size for comparable cases is obtained. The benefits also derived from this approach include: (1) a simple procedure for implementing aperture-limited sources, (2) the ability to run much higher frequencies compared to the Gaussian source for a fixed transform size, and (3) ease in normalizing the source energy distribution. A description of the algorithm as well as numerical examples will be provided.
Corrections to the parabolic approximation in propagation modeling
Authors: DeSanto J. A. , Perkins J. S. , Baer R. N.
Published: October 2005

An exact integral relation between the solutions of the Helmholtz and parabolic equations and its stationary phase evaluation has been previously reported [J. A. DeSanto, J. Acoust. Soc. Am. 60, S33 (A) (1976)]. The procedure yields corrections to the parabolic solution (P) which (among others) involve the second range derivative of P. We have programmed this latter correction using the (range-independent) AESD profiles and make a quantitative comparison (rms error as a function of range) between the exact normal mode (NM) result and P, on the one hand, and between NM and the corrected parabolic (CP) on the other. The improvement is dramatic. The rms errors (both including and excluding phase) of the NMCP comparison are at least a factor of 3 less than the NM-P errors. We illustrate the conclusions with extensive numerical results. To summarize: (a) the correction is functionally simple, (b) it's easy to program, and (e) it yields significantly improved results. Finally we remark that the quantitative comparison between propgation models is far better than the canonical eyeball method.
Statistics of normal mode amplitudes in a random ocean
Authors: Dozier L. B. , Tappert F. D.
Published: October 2005

Acoustic waves in a random ocean have been studied by means of coupled mode equations, a system of stochastic ordinary differential equations for the acoustic normal mode amplitudes as a function of range. The random coupling coefficients represent scattering from internal wave normal modes. Deterministic master equations, which predict the average power in each mode as a function of range, can be derived from the coupled mode equations by using certain approximations. Monte Carlo simulations, numerically solving many realizations of the coupled mode equations, have been carried out in order to establish the validity of the master equations as a function of range and acoustic frequency. In addition, fluctuations of the power about the average value are predicted by yet another system of equations, but whose coefficients are linear combinations of those appearing in the master equations. The Monte Carlo results also establish the region of validity of these fluctuation predictions. [Work supported by ONR.]
Amplitude fluctuation statistics of narrow-band signals and noise in the sea
Authors: Urick R. J.
Published: October 2005

The sound from a steady distant sinusoidal source in the sea fluctuates in amplitude because of multipath interferences, surface motion, internal waves, microstructure, and other propagation effects. Such fluctuations are found to follow a Rician or modified-Rayleigh distribution having as parameter the fraction of random power in the received signal. At the output of a conventional sonar processor—namely, a narrow-band filter, a squarer, and an integrator—the fluctuation statistics are accordingly determined by the propagation processes occurring in the sea between source and receiver. On the other hand, ambient sea noise is found, from analyses of field recordings, to have fluctuation statistics determined by the processor itself; ambient noise samples at the processor output obey a chi-square distribution having a number of degrees of freedom equal to twice the BT product of the processor, as would be expected from a Gaussian input. The two distributions—Rician-power for signals and chi-square for noise—while formally different, have remarkable similarities in the limits. In short, the output fluctuations statistics of narrow-band signals and Gaussian ambient noise can apparently be predicted from estimates of the degree of randomness introduced by the prevailing propagation conditions, and from a knowledge of the processor, respectively, provided these statistics remain stationary during the analysis period. [Work supported by the Navy ASW Systems Project Office, Code ASW-13.]
Blade rate radiation from cavitation volume modulation on merchant vessels
Authors: Gray L. M. , Greeley D. S.
Published: October 2005

The radiation of acoustic energy from merchant vessels at blade rate frequency is dominated by the mechanism of propeller cavitation modulation. These modulations are generated by the response of the propeller blade to the spatially nonuniform vessel wake. Since these blade rate lines and their harmonics are a major contributor to low-frequency ocean ambient noise, the prediction and measurement of these merchant ship spectra have recently been the subject of considerable interest. This paper briefly reviews the results of an ongoing effort to predict the cavity volume time history for a given merchant ship propeller. These results show interesting limits for the unsteady propeller cavity volume which imply a limit for the maximum blade rate radiation from a given propeller. These limiting volumes are compared to volumes measured on merchant ship propellers using stereo photography, yielding relationships for typical cavitation on merchant vessels. The acoustic radiation from this volume source is reviewed and the developed relationships for unsteady propeller cavity volumes are compared to volumes inferred from recently measured levels of blade rate lines from three merchant ships.
Low-frequency sound absorption in the ocean
Authors: Schulkin M. , Marsh H. W.
Published: October 2005

Recent work on low-frequency sound absorption in the ocean and laboratory has been examined with regard to temperature dependence, pH dependence, and boron concentration in an effort to arrive at a practical expression consistent with existing knowledge for use in sonar prediction and design applications. It is found that the maximum absorption per wavelength, which is proportional to the chemical compressibility, is related to the pH at the sound channel axis depth. Furthermore, the relaxation frequency dependence on temperature as found by Simmons is examined in terms of the macroscopic viscosity of seawater, as suggested by Glotov for the magnesium sulphate relaxation at higher frequencies.
Sound absorption in sea water by a third chemical relaxation
Authors: Fisher F. H.
Published: October 2005

Evidence is presented for a third chemical relaxation producing sound absorption in the ocean. After accounting for sound absorption in the Atlantic and Pacific due to boric acid, magnesium sulfate, and water, there appears to be a third relaxation at 3 kHz (possibly higher) with αλmax = 0.28 × 10−5 at 4°. The existence of this relaxation was determined by using the Fisher—Simmons equation for sound absorption based on Simmons' laboratory work. For the Pacific data, the boric acid contribution was reduced to 0.4 that of the Atlantic. The third relaxation was deduced from Thorp's data in the Atlantic and Lovett's data in the Pacific. The new relaxation may be the one predicted by Garland, Patel, and Atkinson for MgHCO3 for which αλmax = 0.58 × 10−6 at 9 kHz at 25°. [Work supported by the Office of Naval Research.]
Seismic signal processing using an inverse diffraction technique
Authors: Salisbury John I. , LeBlanc Lester
Published: October 2005

A seismic processing technique is presented for determining the average interval velocity and layer thickness of a multilayered ocean floor. The processor operates on the seismic data recorded by an array of hydrophones located on the ocean surface. The computer algorithm making up the processor is based on Kirchoff diffraction integral and an iterative solution is obtained using the Fourier transform (FFT). Since the processor is not limited by any restrictions imposed by the use of approximations, high resolution can be obtained in shallow water by using a large receiving array. At present, the evaluation of the seismic processor has been accomplished by using synthetic seismic data. This insures that the actual parameters being solved for are known, thus the accuracy and resolution of the processor can be ascertained.
Earth surface displacement generated by propagation of acoustic plane waves within a gas-filled buried pipe (theoretical)
Authors: Jette A. N. , Parker J. G.
Published: October 2005

The theory of surface displacements caused by acoustic plane progressive wave propagating at frequencies of 200–2000 Hz in the gas within a pipe buried in the earth is presented. It is shown that in order to satisfy the boundary conditions at the pipe—earth interface both shear and compressional waves must be excited and that these waves interfere with each other at the surface of the earth, giving a series of maxima and minima separated by about 275 Hz. This interference is a consequence of the large difference between velocities of propagation of compressional and shear waves in the earth medium. Dependence of the magnitude and character of radiation from the pipe walls into the earth medium on these velocities will be discussed. [Work supported by the American Gas Association.]
Earth surface displacement generated by propagation of acoustic plane waves within a gas-filled buried pipe (experimental)
Authors: Morris M. S. , Parker J. G.
Published: October 2005

An abandoned water line, 1000 ft in length, consisting of 2-in.-i.d. steel pipe buried a depth of approximately 3 ft, has been used to investigate the magnitude of earth surface accelerations generated by propagation of plane acoustic waves in the gas contained within the pipe. Measurements have been made of the attenuation of the acoustic waves, of the radial and longitudinal acceleration of the walls of the pipe, and of the acceleration at the earth's surface over a frequency range of 200–2000 Hz at a point 120 ft from the acoustic source. Results of this investigation have indicated that, in general, radiation from the pipe walls is large compared to that calculated from theory for a small hole in the pipe. A general description of the facility and experimental measurements will be presented. [Work supported by the American Gas Association.]
Effects of diffraction on pressure impulse propagation
Authors: Layton M. R. , Carome E. F.
Published: October 2005

Investigations are being made of the effect of diffraction on the propagation of acoustic impulses in water. Gaussian-shaped pressure pulses are obtained by applying 0.1 μsec wide voltage pulses to thick piezoelectric plates that act as piston sources. Acoustic probe techniques are being used to examine in detail the resulting pressure pulses. These are strongly affected by diffraction phenomena and, because of the transient nature of the process, special care must be taken in interpreting the observed data. Comparisons between experimental and theoretical time and space pressure profiles are presented. [Supported in part by the Office of Naval Research.]
Interaction of sound with noise
Authors: Stanton T. , Beyer R. T.
Published: October 2005

A continuous 2.3-MHz signal of amplitude 0.09 atm was generated in water by a ceramic transducer. After passage through distances up to 0.7 m, the signal was detected by a second transducer and fed to a spectrum analyzer. The noise in the medium was provided by a mechanical noisemaker striking the metallic wall of the water-filled tank. The noise spectrum lay between 2–8 kHz, with component amplitudes up to 0.01 atm. The analyzed spectrum of the perturbed signal contained sidebands, shifted from the original signal frequency by 2–8 kHz, down approximately 70 dB from the primary signal level. Steps were taken to avoid interference from direct pickup of the audio noise signal by the transducer, by inserting a high-pass filter between the receiving transducer and the spectrum analyzer. Measurements of the sideband level were made as a function of the length of the interaction region, and an increase in the level was noted with increase in the path length. [Work supported by ONR.]
Analysis of experiments on diffraction of sound by rigid screens
Authors: Hadden W. James , Pierce Allan D. , Vidimos Robin A.
Published: October 2005

Measurements made in an anechoic chamber at NASA Langley Research Center of the sound from a point source diffracted around a rigid screen are presented. Two cases of interest are discussed, the first concerns sound propagating in still air, the second involves low-Mach-number ambient flow past the screen with the trailing edge as the diffracting edge. The results of these measurements are compared with calculations based on (i) an analysis of diffraction by rigid screens by one of the authors, (ii) an extension of Candel's theory of plane wave diffraction in a moving medium to the point source case, and (iii) a recently developed numerical technique for obtaining the diffracted pressure field when the source and receiver are not necessarily far from the diffracting surface.
Comments on the energy and momentum of sound waves
Authors: Garrett Steven , Putterman Seth
Published: October 2005

The energy and momentum and sound waves is discussed for waves with (a) no net mass fluctuation and (b) no net jump in velocity potential. These two cases are mutually exclusive and in neither case is the ratio of energy to momentum given by the speed of sound, in agreement with Rayleigh 1905. It is shown that in the procedure for quantizing hydrodynamics the simultaneous implementation of (a), (b) leads to incorrect (but commonly accepted) results for the momentum of sound waves.
Measurement of ultrasonic dispersion by phase comparison of continuous harmonic waves
Authors: Ting C. S. , Sachse Wolfgang
Published: October 2005

The method of phase comparison of continuous waves is applied to determine the dispersion relation, phase velocity, and group velocity as a function of frequency in dispersive materials. A combination of the variable frequency method and the variable path-length method is found necessary to eliminate any uncertainty in the dispersion relation determination. Experiments are performed on specimens of various thicknesses. A constraint equation is derived from the assumption that the dispersion relation is unique and independent of the specimen thickness. This equation provides a procedure for determining the absolute number of wavelengths in the specimen. A transducer self-compensation procedure is also used to reduce the errors in analyzing the test results among the specimens. Measurements in unidirectional, fiber-reinforced Boron-Epoxy specimens show good agreement with results reported previously in the literature. [Supported by AFOSR Grant 76-299.2.]
On the acoustics of coupled cavities
Authors: Thompson C.
Published: October 2005

The problem of determining the pressure distribution in two rigid cavities coupled by a rectangular waveguide is formulated in terms of integral equations. Development of analytical techniques for evaluating the perturbation in terms of eigenvalues and damping constants will be obtained. Experimental verification of the proposed technique will also be presented.
Arrival times of scattered ultrasonic signals from a solid inclusion in an elastic solid
Authors: Rhodes Deborah J. , Sachse Wolfgang
Published: October 2005

Measurements are reported of the arrival times of broadband ultrasonic pulses scattered by a circular, cylindrical, solid inclusion imbedded in a matrix whose longitudinal wave speed is lower than that of the cylinder. The wavenumber-inclusion radius product, ka, ranged from approximately 1 to 15. The matrix materials were water, acrylic, and brass and the inclusion materials were copper, quartz, stainless steel, and tungsten. A strong, scattered pulse, corresponding to a circumferential wave on the cylinder is observed for cs > cl, where cs is the shear wave speed of the inclusion material and cl is the longitudinal wave speed of the matrix material. These observations are in agreement with published results. The experiments also show that the pulse corresponding to the circumferential wave is not observed for cs < cl. It is shown how the approximate diameter and longitudinal wave speed of the inclusion can be determined from the arrival times of the scattered pulses. [Supported by NSF Grant ENG75-13703.]
Spectral analysis of elastic pulses scattered from two cylindrical cavities in a solid
Authors: Sancar Selcuk , Pao Yih-Hsing , Sachse Wolfgang
Published: October 2005

A solution for the scattering of plane harmonic waves from two traction-free, cylindrical cavities in an elastic solid is obtained in terms of cylindrical wave functions. The scattered waves are expressed as an infinite sum of orders of scattering, the first order being the usual single scattering approximation and each successive order being expressed in terms of single cylinder scattering coefficients. The exact eigenfunction solution is numerically evaluated for incident plane waves of frequency ranging from 0 to 10 MHz and the power spectrum of the backscattered radial stress amplitudes resulting from a delta-function incident pulse is calculated for various combinations of cavity radii and separations. Approximate high-frequency, farfield solutions are derived and compared with the exact solution. Experimental backscattering spectra with broadband ultrasonic pulses are obtained in specimens of aluminum containing two side-drilled, parallel holes. The experimental results are compared with both the exact and the approximate solutions. The approximate high-frequency solution is exploited in an attempt to derive simple expressions which explain the major details of the spectra and which can be used for quantitative flaw characterization in ultrasonic nondestructive testing. [Supported by NSF Grant ENG75-13703.]
Measurement of power from a planar ultrasonic transducer; experimental consistency study
Authors: Cook B. D. , Cavanagh E.
Published: October 2005

In a previous paper [“Precision acousto-optic calibration of ultrasonic transducers,” B. D. Cook, Paper C3, J. Acoust. Soc. Am. 59, S7 (A) (1976)] a method of accounting for the nearfield in acousto-optic power measurements was discussed. This paper describes the successes and difficulties encountered in implementing such a theory.
Analysis and design of wave interference directional microphones
Authors: Carnes Ted N. , Reynolds Douglas D.
Published: October 2005

Analytical models of a wave interference directional microphone were developed for use on a digital computer. Many microphone design parameters were analyzed in detail, Wave interference directional microphones consist of cylindrical tubes with sound pressure receiving ports spaced along their length. Electroacoustical transducers are placed near one end. Both ends are terminated by acoustical impedance elements. The microphone is classified as an end-fire receiving array for air use. Variations of this type of microphone have existed for many years; however, a detailed analytical model was never developed and verified. The microphone was modeled using acoustical transmission line theory. Various microphone configurations were evaluated for frequency response and directivity. The most important effects on performance, tests proved, are caused by internal sound wave propagation, and these effects can alter performance drastically from that predicted by geometric line array theory. The models were verified by comparison of measured and predicted frequency response and directivity of actual microphones. Many design parameters of the directional microphone were analyzed, utilizing the theoretical models. This information will be presented.
Piezoelectric polymer receiving arrays for ultrasonic applications
Authors: DeReggi A. S. , Edelman S. , Roth S. , Warner H. , Wynn J.
Published: October 2005

Broadband ultrasonic detector elements each approximately 2 mm in diameter and multielement linear arrays have been constructed using commercially available polyvinylidene fluoride sheet 25 μm thick. Electrode and electrical lead patterns were deposited on both surfaces by vacuum evaporation. Poling was achieved by applying ∼2000 V across the electroded parts of the sheet while the temperature was cycled from room temperature to ∼120°C over a period of ∼1 h. The open-circuit responsivity of the samples to ultrasound was measured in the frequency range of 300 kHz to 1 MHz with the samples freely immersed in water, with the array backed by a steel ref1ector plate, and with the array a distance away from the reflector plate. The measurements were performed with the elements connected to a preamplifier by means of a 50 Ω coaxial tube about 30 cm long. Since the capacitance of an element is about 8 pF, the measured responsivity of about −230 dB re 1 V/μPa was degraded considerably by the cable capacitance. The results are consistent with a piezoelectric response mechanism where ultrasonic pressure fluctuations induce thickness compression of the polymer. Reflector plates provide up to 6 dB boost in the pressure sensed and a corresponding increase in response. Ease of fabrication, low cross-talk between adjacent elements of an array, flat response over a wide range of frequency and low cost suggest usefulness in ultrasonic imaging systems.
First sound in superfluid helium
Authors: Maris H. J.
Published: October 2005

A description of those properties of superfluid helium which make it of special interest to acousticians will be given. Two areas of recent research will then be treated in detail. The first of these is the study of the scattering of sound by thermal waves in liquid helium. This work has led to a better understanding of the dispersion of the thermal waves. The second topic is the transmission of first sound across interfaces between solids and liquid helium. Despite much work, both theoretical and experimental, a full understanding of this problem has not yet been achieved. [Work supported by the NSF through the Materials Research Laboratory at Brown University and through Grant No. DMR75-14761.]
New approaches to analog music synthesis
Authors: Hutchins B. A.
Published: October 2005

Analog, voltage-controlled electronic music synthesizers have been developed over a period of about ten years into a fairly standard commercial product. While these synthesizers are unquestionably useful for certain types of music, they are also limited in many ways. A number of fairly simple “new modules” involving conventional circuitry and conventional electronic components can be developed and added to the conventional set of synthesizer modules. New types of excitation sources for driving processing type modules are also possible. Beyond these, new developments in electronics make possible entirely new synthesis devices and suggest new approaches to older unsolved problems. As one example, digital control of analog synthesis based on a microprocessor approach makes it possible to realize musical structures and developments of a greater complexity than is possible with manual control alone. As a second example, charge-transfer analog shift registers provide, analog delay in a compact and inexpensive form, thus making possible new approaches to special musical effects, reverberation, and pitch extraction, to name a few.
Electronic synthesis models of acoustic instruments
Authors: Luce D. A.
Published: October 2005

Combining correlative analysis of acoustic musical instrument sounds with basic physical properties leads to functional models for electronic synthesis. Determination of the number of degrees of freedom and their ranges associated with psychoacoustically important parameters is crucial for efficient models. Derivation of three models for the trumpet, violin, and French horn and simulative synthesis examples will be presented.
Hybrid sound synthesis
Authors: Mathews M. V.
Published: October 2005

Most general purpose digital computers are not fast enough to directly compute musically sophisticated sound waves in real time. A hybrid system in which a computer controls an analog synthesizer can generate interesting sounds in real time. The computer supplies three main services. It senses the gestures of the performer. It provides a memory for storing these gestures as time functions. It computes the time functions which control the synthesizer as a complex combination of the real time gestures of the performer and the time functions in memory. The hybrid system is a good instrument with which to study the real time interactions between a performer, his instrument, and the sound he is producing. At present, the precision, quality, and range of timbres which can be obtained from a hybrid system are limited by the analog synthesizer. Shortly these limitations will be removed by replacing the analog device by a special purpose digital synthesizer.
Attenuation and dispersion of first sound in pressurized liquid He4 near Tλ
Authors: Carey R. , Buchal Chr. , Pobell F.
Published: October 2005

High precision measurements of the velocity u, the attenuation α, and dispersion D of first sound have been made along the lambda line in He4 for frequencies up to 1 MHz and for temperatures |T − Tλ| ⩽1 mK. Our data can be understood in terms of order-parameter relaxation and order-parameter fluctuations. We find that the time τ characterizing the relaxation process below Tλ and the time τ characterizing the fluctuations both above and below Tλ have the same temperature and pressure dependence; that is, only one time scale is important very near the phase transition. The analysis of the attenuation due to fluctuations above Tλ allows us to determine a simple scaling law for all our data, valid over four decades in ωτ, α(T > Tλ)/α(T = Tλ) = ωτ/(c + ωτ), where c ≃ 0.5. A similar relation for the dispersion at T > Tλ was also determined.
Investigation of ultrasonic cavitation in liquid helium in the Megahertz frequency range
Authors: Carey R. F. , Roeney J. A. , Smith C. W.
Published: October 2005

Considerable evidence, both theoretical and experimental, indicates that the lowest-energy state of an excess electron in liquid helium consists of the electron bound in a helium-free spherical cavity of about 1.7 nm radius. This state has become known as the electron-bubble. Investigators have suggested that these electron-bubbles may serve as nuclei for ultrasonic cavitation. To examine this possibility, acoustic spectra in liquid helium were studied using quartz transducers whose resonant frequencies were in the low megahertz range. These spectra were measured as a function of displacement amplitude both above and below the lambda point. In addition, these spectra were obtained in the presence and absence of a source of electron-bubbles. Results will be compared with similar studies at lower frequencies and the role of the electron-bubble as a nucleus for cavitation will be discussed. [This work was supported in part by the Air Force Office of Scientific Research.]