bluuebunny/crossref_metadata_2025 huggingface dataset:
The mean-value method of predicting the dynamic response of complex vibrators
Authors: Skudrzyk Eugen
Published: October 2005

The mean-value theory predicts the mean line through the logarithmically recorded frequency-response curve of a complex vibrator, the height of the resonance peaks, and the height of the minima that occur between every two resonance peaks. It predicts the mean and the extremes in the frequency- response curve from the first resonance of the vibrator to very high frequencies. The computations are based on the mode masses and on the density of the resonances. They are simple and they give considerable insight into the dynamics of complex vibrators. Part I of this paper presents the basics of the mean-value theory. Part II deals with the variation of the vibration velocity with the distance from the driver and with the frequency. Part III is concerned with shells without and with stiffeners and with rib-stiffened plates. Because it is always the component of the characteristic velocity that is transmitted by discontinuities (as though the parts of the vibrator behind them were infinitely large) that determines the geometric mean values of the response, the effect of ribs and other appendages on the vibration can be predicted without much computation. As an example of the application of the theory, the vibration isolation that can be obtained by spring mounting a motor on a ring welded into a shell is computed in detail and the predictions for the ring excited shell are compared with the measurements.
Numerical integration method for reflected beam profiles near Rayleigh angle
Authors: Ngoc Tran D. K. , Mayer Walter G.
Published: October 2005

A numerical integration method is devoloped to calculate the intensity profile of an ultrasonic beam reflected from a liquid–solid interface. This numerical treatment is used to calculate nonspecular reflectivity at a range of angles of incidence near and at the Rayleigh angle. Calculations for a water–stainless steel interface are compared to a known approximate analysis for various beamwidths and frequencies. The theoretical predictions of the reflected beam profile near the Rayleigh angle of incidence are compared to experimental results.
Calculations of sound propagation through an eddy
Authors: Baer Ralph N.
Published: October 2005

By means of a corrected split-step parabolic-equation numerical algorithm, acoustic propagation through an ocean region characterized by a sound-speed distribution produced by an analytic model of an eddy is investigated. Parameter values for a moderate sized, cyclonic, Gulf Stream eddy are used. It is found that the presence of an eddy causes significant changes, both in nature and level, in the received acoustic field produced by an omnidirectional cw source. The eddy causes major changes in the arrival structure seen by a vertical array. The percentage of energy arriving at angles less than 5° from broadside increases from 5% to 50% in the presence of the eddy under consideration at 100 Hz. Greatly increased energy corresponding to horizontal arrival is noted. In addition, the effects of an eddy progressing through the region between an acoustic source and receiver is studied. The position of the eddy relative to the source causes changes in transmission loss of as much as 20 dB.
Horizontal directionality estimation considering array tilt and noise field vertical arrival structure
Authors: Wagstaff R. A.
Published: October 2005

A new approach to undersea ambient noise field horizontal directionality estimation from towed line array data is presented. This new technique includes the effects of the three-dimensional array response and the noise field vertical arrival structure during the estimation process. It is sufficiently general to include the angle of array tilt from the horizontal and does not require noise field stationarity as do most previous methods. The vertical dimension is included in the estimation process through a transformation of the noise field from a spherical coordinate system to a conical coordinate system of the array with an arbitrary tilt angle. The three-dimensional pseudostationary noise field estimate ? (ϑ,φ) which results is then integrated over the vertical (φ) to obtain the horizontal directionality estimate ? (ϑ). The results indicate significant improvement in ? (ϑ) when the array tilt and noise vertical arrival structure are accounted for.
Distribution of acoustic cues for stop consonant place of articulation in VCV syllables
Authors: Dorman M. F. , Raphael Lawrence J.
Published: October 2005

Most theoretical accounts of the identification of stop consonant place of articulation have focused on how bursts and formant transitions conspire to signal place in CV syllables. In the present series of experiments we have examined the identification of place in VCV syllables and have found that not only do the burst and opening transitions affect the judgement of place, but so also do the closing transitions and the duration of the closure interval. This outcome is consistent with the outcomes of many other experiments in showing that there are multiple acoustic events which bear on the identification of a given phone and that those acoustic events are distributed over time. Theoretical accounts of place identification based on data of this kind may prove more viable than theories based on data from the identification of place in the absolute, syllable-initial position.
Super-resolution acoustical passive imaging system using algebraic reconstruction
Authors: Sato Takuso , Uemura Kazuho , Sasaki Kimio
Published: October 2005

To obtain the fine structures of a wave field on a noise emitting object, a new super-resolution passive imaging system is constructed. The wave field detected by a hemispherically arranged microphone array corresponds directly to the wave field on the object by exploiting a priori information about the object’s physical structures. Thus resolution of one-tenth of a wavelength is realized. The principle, concrete construction, proposal of proper sound source models, and discussions on the effects of the measuring and additive noises are given, as well as several observed results.
Calibration data for the Telex 1470-A audiometric earphones
Authors: Michael Paul L. , Bienvenue Gordon R.
Published: October 2005

Standard reference threshold levels for the Telex 1470-A audiometric earphones have been determined. The psychoacoustic evaluation of these earphones was completed by loudness balancing at threshold. The earphones were balanced to comparison standard earphones calibrated at the National Bureau of Standards. Coupler calibration was accomplished using the American National Standard Method. Objective (coupler) and subjective (psychoacoustic) data were combined and the resulting reference threshold sound pressure level data are reported herein. These data were compared to previous data for the 1470-type earphone. While good agreement with previous data was noted for low and mid frequencies, sizeable differences did occur at high frequencies. Possible sources of these discrepancies are discussed.
A cineradiographic study of chin marker positioning: Implications for the strain gauge transduction of jaw movement
Authors: Kuehn David P. , Reich Alan R. , Jordan James E.
Published: October 2005

Three normal adult subjects were filmed using lateral-view, high-speed cineradiography to measure the amount of movement of external skin points on the jaw relative to the underlying jaw bone. Metal markers were secured to the skin to simulate cantilever beam attachment points commonly utilized in the strain gauge transduction of jaw movements. Standard deviations of chin marker movement relative to the jaw ranged from 0.52 to 1.28 mm in an anterior–posterior direction and 0.67 to 2.31 mm in a superior–inferior direction. Lower lip and chin marker positions were highly correlated in the superior–inferior direction. Chin marker positions tended to be more superior and, in one subject, more anterior for labial than for nonlabial contexts. The degree of variability was not systematically different for the two different contexts.
Ultrasonic spectrum analysis using frequency-tracked gated rf pulses
Authors: Cantrell John H. , Heyman Joseph S.
Published: October 2005

A new method of ultrasonic frequency analysis is introduced which employs frequency-tracked gated rf drive pulses rather than shock-excited broadband spikes to generate the ultrasonic waveform. The new technique, a variation of the sampled-continuous wave technique, eliminates problems associated with finite pulse widths of conventional methods. It is shown to yield correct ultrasonic wave velocity measurements of the sample irrespective of receiver gate width or position provided any portions of two successive echoes are gated simultaneously into the spectrum analyzer. The experimental observations are substantiated by a theoretical model based on the time-frequency domain formulation of ultrasonic frequency analysis.
Long-time spectral and intensity characteristics of esophageal speech
Authors: Weinberg Bernd , Horii Yoshiyuki , Smith Bonnie E.
Published: October 2005

Long-time spectral characteristics and distributional properties of speech intensity produced by esophageal speakers were measured and compared with those of normal speakers. Substantial differences were observed in the distributional properties of speech intensity produced by normal and esophageal talkers. On the average, esophageal speech was about 10 dB less intense than normal speech. In addition, the average long-time spectrum for esophageal speech was characterized by a flattened spectral envelope. Other spectral differences between esophageal and normal speech were found and interpreted in terms of the known variations in voice and speech production of these two divergent forms of oral communication.
Increasing the intelligibility of sung vowels
Authors: Smith Lloyd A. , Scott Brian L.
Published: October 2005

The intelligibility of the front vowels (/i/, /I/, / /, and /F/) was investigated as sung in four different ways: (1) operatic, (2) in consonant–vowel–consonant (CVC) context, (3) with a raised larynx, and (4) with both raised larynx and in CVC context. All syllables were sung by a trained soprano at F4, A4, C♯5, F5, A5, and C♯6. Ten subjects listened and identified randomized sets of ten tokens of each vowel per condition (method of articulation) at each note. Results showed that, from C♯5 (nominal 554 Hz) to F5 (698 Hz), the intelligibility of operatic vowels (condition 1) fell from 56% to 16%. The mean intelligibility of the vowels at the three highest notes (F5, A5, C♯6) was 10% for condition 1, 64% for condition 2, 62% for condition 3, and 83% for condition 4. Results indicate that increased intelligibility across conditions is a function of increased energy in the higher harmonics and presence of consonantal transitions. The generally accepted notion that vowel sounds are largely unintelligible on higher notes pertains only to a restricted manner of production.
Resonant scattering of elastic waves from spherical solid inclusions
Authors: Flax Lawrence , Überall Herbert
Published: October 2005

Previous investigation concerning the scattering of elastic waves from solid spherical inclusions have furnished expressions for the scattering cross sections which, upon numerical evaluation, exhibited resonancelike features as a function of frequency. In the present work, we study these resonances in a fashion suggested by the resonance theory of acoustic scattering due to Flax, Dragonette, and Überall [J. Acoust. Soc. Am. 63, 723 (1978)]. The resonances of the solid inclusions, exemplified by iron or lucite spheres imbedded in an aluminum matrix, are found numerically in the individual normal-mode scattering amplitudes, and are interpreted in terms of phase-matched circumferential waves. Dispersion curves for the phase velocities of the latter are obtained, exhibiting two families of waves of different type. Finally, the connection of these waves with the Stonely waves on the boundary between two flat half-spaces is noted in high-frequency limit.
Relationship between solid nonlinearity parameters and thermodynamic Grüneisen parameters
Authors: Cantrell John H. , Breazeale M. A. , Nakamura Akira
Published: October 2005

The relationship between the ultrasonic nonlinearity parameter for solids and the acoustic Grüneisen number has been derived for longitudinal ultrasonic wave propagation in the pure mode directions of cubic crystals and isotropic solids. Agreement between the acoustic Grüneisen number and the thermodynamic Grüneisen parameter is best for ultrasonic harmonic generation measurements along the [100] direction of a cubic crystal. Comparison of the temperature curves of the acoustic Grüneisen number of copper shows that the acoustic Grüneisen number generally follows the temperature dependence of the lattice contribution to the thermodynamic Grüneisen parameter.
An experimental study of parametric acoustic arrays with intermediate directivity in water
Authors: Huckabay John M.
Published: October 2005

Intermediate difference frequency directivity for the parametric acoustic array is identified with the transition from narrowbeam (Rutherford scattering) directivity to broadbeam (primary product pattern) directivity. Experimental data are presented in which parametric arrays with intermediate difference frequency directivity were formed for several primary frequency bands, step-down ratios, primary source configurations, and directivity ratios. The experimental results compare well with theoretical predictions. The difference frequency half-power beamwidth with intermediate directivity was observed to always be greater than the computed narrowbeam and broadbeam results; and low sidelobes, which are characteristic of intermediate and broadbeam directivity, were observed in the difference frequency beam patterns. Parametric acoustic source performance with intermediate directivity was demonstrated in the nearfield of the parametric array with a modest decrease in directivity and apparent source level as compared to farfield conditions.
A theoretical vertical and lateral model for the analysis of acoustic subbottom data through simulation
Authors: Bolus R. , Sivaprasad K. , Frost A.
Published: October 2005

A high vertical/lateral resolution subbottom survey using a 3-m paraboloidal reflector operating at 12 kHz in a 1/2-ms pulsed mode was taken at the University of New Hampshire Ocean Modeling Facility at Lake Winnepeasaukee, New Hampshire. Echograms show a vertical time series composed of several low amplitude single pulsed width signals and several high amplitude unresolvable interacting pulses. The low amplitude pulses are assumed to be reflections from discrete boundaries and the high amplitude unresolvable signal is assumed to indicate a continuous impedance function over depth. A combined discrete and continuous vertical impedance model has been used to simulate the experimental vertical time series. Facsimile graphs taken with the narrow beam show semirandomly positioned reflectors in the sediment column with high definition of subbottom features, while those taken simultaneously over the same cruise track with a wide beam show layers and loss of images. A lateral diffraction model was used to demonstrate that the narrow beam indication of semirandomly positioned reflectors is consistent with the wide beam indication of layers.
Classical geometric construction of multipaths
Authors: Floyd Edward R.
Published: October 2005

Geometric construction by straight edge and compass of the multipaths is developed for the symmetric (i.e., both source and receiver at the same depth) first-convergence-zone case for a given range with a bilinear sound-velocity profile.
The Helmholtz resonator as a high-power deep-submergence source for frequencies below 500 Hz
Authors: Henriquez T. A. , Young A. M.
Published: October 2005

The use of the Helmholtz resonator in low-frequency underwater acoustic applications is discussed. Specific design parameters and their effect on acoustic performance are addressed. A design example is used in the analysis.
New measurements of compressional wave attenuation in deep ocean sediments
Authors: Mitchell Stephen K. , Focke Karl C.
Published: October 2005

In many situations of low frequency acoustic propagation in the ocean, the acoustic properties of the bottom are an important factor. One quantity of which few measurements have been made or reported is the compressional wave attenuation profile. This paper reports attenuation measurements based upon measurements from explosive sources which encountered the ocean bottom several times. It was found that compressional wave attenuation coefficients at 100 m depth are approximately 0.015 dB/m-kHz in terrigenous turbidite sediments and 0.03 dB/m-kHz in calcareous sediments. These values are as low as, and lower than, the smallest previously reported estimates.
Contralateral cueing effects in forward masking
Authors: Pastore Richard E. , Freda Jon S.
Published: October 2005

Previous research has shown that monaural simultaneous masking is reduced by contralateral cues which are identical in frequency (and phase locked) to the signal, while backward masking is reduced by cues which provide precise timing information about the signal. This letter summarizes a series of experiments which investigated contralateral cueing effects in forward masking. No cues were found to be effective in reducing forward masking; not even cues effective in reducing backward or simultaneous masking for the same practiced subjects
Excess attenuation in echosonde signals
Authors: Clifford S. F. , Brown E. H.
Published: October 2005

The scattering of sound by turbulence redistributes the acoustic energy flow in space. For sound propagation with a given geometry, such a redistribution can appear as an energy loss in the received part of a beam. Such a loss now is called excess attenuation. The following analysis determines the amount of excess attenuation in the signal obtained in the configuration of a typical monostatic echosonde. Such estimates of excess attenuation are of great importance for accurate quantitative acoustic remote sensing of atmospheric parameters.
Spatial correlation of surface generated noise in a stratified ocean
Authors: Kuperman W. A. , Ingenito F.
Published: October 2005

A model is developed for the calculation of the spatial properties of the noise field produced in a stratified ocean by the action of wind at the surface. The random noise sources are represented by correlated monopoles distributed over an infinite plane located an arbitrary depth below the surface. Wave-theoretical methods are applied to derive expressions for the intensity and spatial correlation of the noise field. A normal-mode representation of the noise field is used to reduce these expressions to forms which allow physical interpretation and are suitable for numerical computation. Examples are given of intensity profiles and spatial correlation in the vertical for three generic sound-speed profiles. The results show that the sound-speed profile and the presence of the bottom can be important in determining the spatial properties of the noise field. An example is given of a calculation of the horizontal spatial correlation using the fast field program (FFP).
Effect of a class of random currents on acoustic transmission in an ocean with linear sound speed
Authors: Newhall B. K. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

The effects of random fluctuations in an ocean current on underwater cw sound transmission between a bottomed source and receiver are determined for an ocean channel with a linear, depth-dependent sound speed. A horizontal, depth-dependent current is considered whose components are random processes. Effects of such a current on ray geometry are determined and six basic current-induced ray states are found. Under certain conditions, including the assumption that the sound-speed gradient is larger than current-component gradients, only one ray state may arise. The geometry of this state is expressed explicitly in terms of the current. Approximations for travel times, total-field intensity, and their first and second moments are obtained. These moments depend significantly on properties of the source–receiver current component. Intensity moments are predicted using ocean-current data. For selected parameter values, a difference between relative mean intensity and relative intensity without current of as much as 9 dB and a standard deviation of relative intensity as large as 3 dB are found. These moments are rapidly varying with transmission range; however, useful bounds are derived which are slowly varying and which display an unusual behavior near certain critical ranges.
The use of quantitative criteria for the optimum design of concert halls
Authors: Baxa Donald E. , Seireg A.
Published: October 2005

This paper describes a set of eight quantitative merit criteria for the design of concert halls, used in a developed automated computer optimization procedure based on a modified method of images. Idealized optimum hall configurations and surface absorption coefficients are determined based on each criterion. The acoustical merits of the optimum designs for a hall with given floor and stage areas are evaluated and compared to those of an existing hall with acclaimed acoustical quality. They are also compared to those calculated when the total sum of all the eight merit criteria is used as the optimizing objective function. The study represents a first attempt at optimizing acoustic space based on quantitative figures of merit. The developed technique can be invaluable in giving insight into the effect of improving a particular design objective on the configuration and absorption coefficients, as well as how the improvement of one merit criterion can affect the other criteria.
The tempered Fourier transform
Authors: Teaney Dale T. , Moruzzi Victor L. , Mintzer Frederick C.
Published: October 2005

A constant-Q digital spectral analysis scheme is described which exploits the ’’perfect fifth’’ symmetry of the 12-tone musical scale.
A method of calculating average array signal response in a two-path medium
Authors: Worley R. D.
Published: October 2005

A method is described for calculating average signal array gain for cw acoustic signals in a multipath medium. The two-path case is considered; the extension to many paths is straightforward but tedious. Only phase fluctuations are treated; the signals arriving along the two paths may have different amplitudes, but these amplitudes are assumed constant in time and uniform across the array aperture. It is suggested that for beam formation by delay and sum the array signal gain for single path represents the upper limit of performance for multipath. The calculation of gain requires a knowledge of the signal correlation across the array aperture for each path, as well as the signal correlation between the first arrival at one hydrophone and the second arrival at another as a function of hydrophone spacing.
Importance of the swimbladder in acoustic scattering by fish: A comparison of gadoid and mackerel target strengths
Authors: Foote Kenneth G.
Published: October 2005

Previous determinations of the swimbladder contribution to the fish backscattering cross section have been hindered by ignorance of the acoustic boundary conditions at the swimbladder wall. The present study circumvents this problem by direct comparison of target strengths of three gadoid species and mackerel — anatomically comparable fusiform fish which respectively possess and lack a swimbladder. The relative swimbladder contribution to both maximum and averaged dorsal aspect backscattering cross sections is shown to be approximately 90% to 95%, which is higher than most other estimates. The new results were established for fish of 29- to 42-cm length and acoustic frequencies of 38 and 120 kHz.
Acoustics of gas-bearing sediments I. Background
Authors: Anderson Aubrey L. , Hampton Loyd D.
Published: October 2005

Acoustical properties of water saturated and gassy sediments are observed to be significantly different. The present state of knowledge of the acoustical properties of saturated sediments, gassy water, and gassy sediments is reviewed. The dynamics of bubbles in water and in various solid materials, including sediments, are experimentally examined in a companion paper. Pulsation resonance is exhibited by the bubbles in all materials examined. Predictions of bubble resonance frequency and damping are shown to agree with the measurements. Equations for sound speed and attenuation, based on the model of resonating gas bubbles, are shown to agree with published measurements in gassy sediments. Parameters required for predicting gassy sediment acoustical properties are identified. Ranges of values of these parameters for various sediments are discussed.
Mode selective transfer of energy from sound propagating inside circular pipes to pipe wall vibration
Authors: Kerschen E. J. , Johnston J. P.
Published: October 2005

Experimental results are presented which show a mode selective transfer of energy from sound propagating inside a circular pipe to pipe wall vibration. The experiments utilize broadband noise generated by flow through a restriction in the plastic (PVC) pipe. For each higher acoustic duct mode, the energy transfer occurs in a narrow frequency band located slightly above the higher-mode cut-on frequency. A match in axial phase velocity between the higher acoustic duct mode and a compatible pipe wall vibrational mode is proposed as the mechanism for the energy transfer. Theoretical predictions for the frequency at which the axial phase velocity match occurs show good agreement with the experimental results.
NSMRL calibration of microphones at depth in dry hyperbaric chambers
Authors: Harris J. Donald
Published: October 2005

A history is given of the primary calibration of microphones in the NSMRL hyperbaric chamber. A Western Electric 640-AA 1-in. condenser microphone was first calibrated by White [NSMRL Report 261 (1955)] using, in a reciprocity technique, a 4-in. and an 8-in. loudspeaker from 125–8000 Hz in air compressed in 50-ft steps to 250 ft simulated sea water (fsw). Most recently Miller calibrated a Bruel and Kjaer (BK) 4144 1-in. microphone in compressed air at 33-ft steps to 132 fsw, using an electrostatic actuator. Data are comparable for these and for three intervening NSMRL studies. They are further comparable to data in the literature for the BK 4132 1-in. condenser microphone collected at a selection of depths to 1023 fsw in compressed air using an electrostatic actuator and for the BK 4144 unit in a helium–oxygen mixture at a selection of depths from 250–870 fsw. It was found that depths to perhaps 400–500 fsw yield a fairly regular linear loss in sensitivity at frequencies to 2 kHz, amounting to 5–9 dB at 200 fsw, and that nonlinearities and resonances occur depending on the microphone used, the depth, and the gas at higher frequencies. Differences among units are such that for careful studies of acoustic noise in such chambers, the calibration of earphones or other transducers, or for the recording of speech in hyperbaric conditions, a facility should arrange for a calibration of its microphone (s) in the gas/depth conditions of interest.
Geographic variation of low-frequency sound absorption in the Atlantic, Indian, and Pacific Oceans
Authors: Lovett Jack R.
Published: October 2005

A new contour chart of the Atlantic and Indian Oceans depicts the variation in the boric acid sound absorption term as controlled by the pH value at the SOFAR axis. The recently published Russian World Ocean Atlas, Volume 2: Atlantic and Indian Oceans, provides the new pH values. These new pH values for the Atlantic require revisions of the previously presented sound absorption versus pH equation and Pacific contour chart [J. R. Lovett, J. Acoust. Soc. Am. 65, 253–254(L) (1979)].
Low-frequency sound absorption in sea water: A borate-complex relaxation
Authors: Mellen R. H. , Simmons V. P. , Browning D. G.
Published: October 2005

Resonator measurements of sound absorption in borate solutions show that magnesium, calcium, and carbonate are also involved in the low-frequency absorption in sea water.
A review of deep ocean sound attenuation data at very low frequencies
Authors: Kibblewhite A. C. , Hampton L. D.
Published: October 2005

The behavior of the attenuation coefficient at very low frequencies (below 200 Hz) has been clouded by the unexplained scatter in experimental data. Recent experiments have indicated that some of this scatter reflects a regional dependence. An attempt is made here to review all the relevant data and to achieve some rational grouping in terms of such regional effects.
Effective area to be used in diffraction corrections
Authors: Chivers R. C. , Bosselaar L. , Filmore P. R.
Published: October 2005

Measurements of ultrasonic velocity and attenuation require ’’diffraction corrections’’ for the finite size of the source and receiver. These diffraction corrections depend on the area of the source which is usually taken as the physical area of the piezoelectric element of the the transducer. Measurements are reported which indicate that the effective area of a disk-shaped element may vary with the exciting frequency and may differ by 40% from the physical area of the disk. The method reported may be of value in the selection of transducers, in accurate diffraction correction calculations, and in the field of ultrasonic exposimetry.
Compilation of empirical ultrasonic properties of mammalian tissues. II
Authors: Goss S. A. , Johnston R. L. , Dunn F.
Published: October 2005

The compilation of the literature on ultrasonic propagation properties of mammalian tissues [J. Acoust. Soc. Am. 64, 423 (1978)] is continued with the addition of 45 papers yielding over 700 lines of parametric data.
Acoustical research in the physical sciences: Superconductivity and superfluidity
Authors: Rudnick I.
Published: October 2005

This is a brief survey of the role of physical acoustics in exploring the superconducting and more particularly the superfluid state. The nature of 1st, 2nd, 3rd, 4th, and 5th sound, and ways in which they are used to measure superfluid properties are described.
Correlation of the phase and amplitude fluctuations between direct and ground-reflected sound
Authors: Daigle G. A.
Published: October 2005

Recent attention to the effects of atmospheric turbulence on the interference of sound waves above both hard and soft boundaries has provided a spherical wave theory that allows for partial covariance between direct and ground-reflected sound. Measurements of the interference spectrum at distances up to 45 m over a flat asphalt surface as well as measurements of jet noise over grass to a distance of 1100 m were shown previously to be in satisfactory agreement with the theory. The covariance between the two sound paths was estimated with one adjustable parameter by considering the transverse autocorrelation of the phase and amplitude fluctuations. The theory has now been further extended by considering explicitly, in addition to the transverse autocorrelation, the longitudinal autocorrelation of the phase and amplitude fluctuations along each path. At shorter distances of propagation it is found that the longitudinal autocorrelation, being close to unity, is necessary to estimate the partial covariance between the direct and reflected sound. At larger distances of propagation the longitudinal autocorrelation of both the phase and amplitude fluctuations goes to zero, contrary to the transverse autocorrelation which remains if the path separation is still of the same order as the correlation length of the medium. The new theory is compared with previous experimental results and yields essentially identical agreement as before but no longer requires an adjustable parameter.
The detection of the temperature structure coefficient of the atmospheric boundary layer by acoustic radar
Authors: Zhou Ming-yu , Lu Nai-ping , Chen Yan-juan
Published: October 2005

The magnitude of the temperature structure coefficient is computed from echosonde data. The results clearly show that the magnitude of CT2 fluctuates with time. The fluctuation has a positive bias and fits the logarithmic normal distribution. The analysis of the spectra of CT2 shows that the spectrum Pf(CT2) usually follows the f−3 rule in both stable and unstable stratifications. There is a peak range of energy in the frequency range 10−3 to 3×10−3 s−1. The analysis of time-height cross sections of CT2 indicates that the distribution has a horizontally stratified structure in stable conditions, and follows the rule CT2∝ z−4/3 in unstable conditions. In addition, the variation of CT2 during a cold front passing the station and the relation between the weather system and boundary layer structure are analyzed.
Diffraction of a plane pulse by thin arbitrarily shaped obstacles
Authors: Buchen P. W. , Haddon R. A. W.
Published: October 2005

Kirchhoff’s time-dependent solution of the wave equation is transformed into a convolution in the time domain, by means of a simple but effective parametrization of a plane-wave front. It is shown how this representation can be applied to the diffraction of a plane pulse by thin arbitrarily shaped obstacles. The diffracted pulse is shown to depend almost entirely on a single function which can be easily determined from the specified geometry. The general method is then applied to two classical problems: diffraction by a half-plane and circular screen. The solutions obtained are expressed in terms of elementary functions and are demonstrated to be uniformly valid across shadow boundaries. The method is ideally suited to numerical computation in the case of complicated geometries.
Forward sound scattering by small nylon cylinders in water
Authors: Hunter Lloyd P. , Lee Paul P. K. , Waag Robert C.
Published: October 2005

A finestructure has been observed in the 5° to 30° angular range of forward scattering patterns of single nylon filaments and a pair of parallel filaments in water. The observations agree with the calculations of the total radiation pattern resulting from the interference of the radiation from those parts of the ultrasonic beam remaining after the removal of the radiation incident upon the scattering object by absorption.
Use of noise signals for multi-mode operation of phased arrays
Authors: Lee B. B. , Furgason E. S.
Published: October 2005

A technique is described with which it is possible to simultaneously transmit and receive in different modes (directivity radiation patterns) of an array utilizing correlation detection and the unique properties of statistically independent noise signals. The feasibility of a particular application—phased arrays which scan simultaneously in more than one direction—is demonstrated by using a simple ultrasonic three transducer linear array and a random signal ultrasonic correlation system. Theory and experimental results are presented which evaluate the effects of clutter and variations in the system parameters on the system signal-to-noise ratio. Results show that multi-mode (multiple scan direction, multiple focal point, etc.) operation can improve phased array performance by decreasing the scanning time necessary to cover a desired volume of space even though extra correlation time may be needed in some cases to reduce the small amount of interference noise which exists between modes.
Diffraction by a rectangular aperture
Authors: Otsuki Takuro
Published: October 2005

The diffraction of an acoustic wave by a rectangular aperture in a soft plane screen is examined by a method which uses orthogonal functions and Fourier transformations. Numerical results of the plane-wave transmission coefficients for normal incidence are given for b/a=1∠8 and ka=0∠2, where 2a and 2b are the side lengths of the aperture and k is the wavenumber.
Backscattering from a plate with a thickness discontinuity
Authors: Woolley Barry Lee
Published: October 2005

The general theory of backscattering from the impedance discontinuity presented by a plate made up of two semi-infinite sections of different thicknesses is given along with some illustrative calculated results.
Acoustic elliptic lenses: An historical note
Authors: Dunn F. , Fry F. J.
Published: October 2005

The early employment of acoustic elliptic lenses in the low megahertz frequency region is recounted briefly.
Lucubrations on ’’Optimum turbulent boundary layer induced noise suppression with suboptimal realizations’’ [J. Acoust. Soc. Am. 66, 1404–1411 (1979)]
Authors: Bordelon Derrill J.
Published: October 2005

Owsley’s and Fay’s analysis of a collinear clustered array of sensors has been extended to the case of an arbitrary number of sensors in each cluster inasmuch as the representation of Gohberg and Semencul (GS) has been employed to provide a convenient and numerically efficient method of computing the minimum variance distortionless look (MVDL) beamformer and array gain for the array. The formalism is also unconstrained by any assumption regarding the strength of turbulent boundary layer (TBL) induced noise relative to the strength of additive uncorrelated sensor noise.
Maximum a p
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i estimation of narrow-band signal parameters
Authors: Wolcin Joseph J.
Published: October 2005

Maximum a posteriori (MAP) techniques are applied to the problem of estimating the unknown parameters of a frequency modulated narrow-band signal in additive white Gaussian noise. Signals are assumed to have unknown amplitude, initial phase, and frequency versus time history, although a priori information concerning the frequency trajectory may be available. In addition, it is assumed that the signal frequency trajectory can be adequately modeled by a continuous piecewise linear function of time. It is shown that the MAP estimator maximizes a linear combination of (1) coherent match of signal induced outputs to received observations, and (2) a term dependent only upon a priori knowledge. This second term reduces to a measure of trajectory smoothness in the special case of a Gauss–Markov a priori frequency model. Lastly, a MAP detection scheme is suggested for cases in which the presence of such signals is an issue.
Eigenmode analysis of the interference patterns in reverberant sound fields
Authors: Chu W. T.
Published: October 2005

Results for the interference pattern in a reverberant sound field have been derived by means of an eigenmode analysis and compared with results obtained from the free-wave model. It is found that the incoherent or random nature of the sound field assumed in the free-wave model can only be achieved if the room is excited by random noise. For single frequency excitation an equivalent incoherent field can be approached by additional averages of results over many different source locations. The analytical solutions are supported by a computer study based on the eigenmode model. A detailed discussion about the correction factor due to boundary interferences in relation to sound power measurement is also given.
Transient response of thin elastic spherical shells
Authors: Singh Anand V.
Published: October 2005

This paper presents the development of a finite element for the analysis of spherical shells. The derivation of stiffness and mass matrices is based on the improved shell theory which takes into account the effects of rotary inertia and shear deformation. This finite element is then used to determine the natural frequencies and mode shapes for the free axisymmetric vibration case for free, hinged, and fixed boundary conditions. The transient response in the radial direction at the apex of the shell is calculated for shells subjected to time-dependent internal radial pressures.
The ASA*50 Papers. A record of the plenary sessions celebrating the fiftieth anniversary of the Acoustical Society of America
Authors: Bolt Richard H.
Published: October 2005

An introduction to the papers presented at the Plenary Sessions of the 50th anniversary meeting of the Acoustical Society of America, Cambridge, Massachusetts, 11–15 June 1979.
Resonant tube for measurement of sound absorption in gases at low frequency/pressure ratios
Authors: Zuckerwar Allan J. , Griffin William A.
Published: October 2005

A resonant tube has been developed to measure sound absorption in gases, with specific emphasis on the vibrational relaxation peak of N2, over a range of frequency/pressure ratios from 0.1 to 2500 Hz/atm. The experimental background losses, measured in argon, show good agreement with the theoretical wall losses except at a few isolated frequencies. Measures to minimize spurious contributions to the background losses include the use of rigid cavity terminations, external excitation, and a differential technique of background evaluation. Room temperature measurements of sound absorption in binary mixtures of N2–CO2, in which both components are excitable, yield the following results for the locations of the respective vibrational relaxation peaks in Hz/atm: (f/P)max=0.063 + 123m for the N2 peak, m=mole percent of added CO2; (f/P)max =34 500−268m for the CO2 peak, m=mole percent of added N2. The figure 0.063 is an upper bound due to the presence of 2.5 ppm H2O.
Acoustics in human communications: Room acoustics, music, and speech
Authors: Schroeder Manfred R.
Published: October 2005

This paper reviews acoustics in human communications in terms of room acoustics, music, and speech.
Velocity inversion in a stratified medium with separated source and receiver
Authors: Gray Samuel H. , Cohen Jack K. , Bleistein Norman
Published: October 2005

An inverse method for determining the velocity in a stratified medium is described here. The method allows the source and receiver used to probe the medium to be separated both horizontally and vertically. An integral equation for the velocity variation is derived under the assumption of small variations from a known reference velocity. A closed form solution to the integral equation is derived for the case in which the reference velocity is constant. The method is tested on synthetic data.
Functional model of a simplified clarinet
Authors: Stewart Stephen E. , Strong William J.
Published: October 2005

A functional model of a simplified clarinet has been developed and implemented on a digital computer. The simplified clarinet consists of a standard clarinet mouthpiece and reed attached to a straight cylindrical tube. In the model, the tube and mouthpiece are represented by a lumped element approximation to a transmission line and the reed is represented as a nonuniform bar, clamped at one end. Differential equations for the system are solved numerically on a digital computer to obtain pressures and volume velocities of the air in the tube and mouthpiece, and positions of the reed at successive time increments. The model exhibits self-sustained oscillations, threshold blowing pressures, frequency shifts, and spectra of mouthpiece and radiated pressures which are similar to those of an actual simplified clarinet. A previously unreported dependence of volume velocity in the reed aperture on the initial or rest opening of the aperture was also found.
Ultrasonic measurement of larynx height and vocal fold vibratory pattern
Authors: Hamlet Sandra L.
Published: October 2005

This paper describes the modification and extension of an ultrasonic through-transmission technique for examining vocal fold activity. The purpose was to achieve improved lateral resolution in the cranio-caudal dimension. A transducer was specially designed to produce an eliptical beam, so that a measurable signal might be received through the extreme upper and lower edges of the vibrating vocal folds. An interpretation of amplitude variation within the ultrasonic waveform is offered, with illustrative data shown for a single subject.
A note on eigenvector decomposition of correlation matrices
Authors: McDonough R. N.
Published: October 2005

Any Hermitian matrix, such as the spatial correlation matrix of measured data from an array of sensors at some frequency, can be represented as the sum of the dyads formed from its eigenvectors, weighted by the corresponding eigenvalues (the spectral decomposition of the matrix). Each term of this sum is of the form of the spatial correlation matrix due to a single source, received at the array with random amplitude, but fixed wave front (not necessarily planar). The spectral decomposition can thus be interpreted as analysis of the actual correlation matrix into components due to a number of (perhaps hypothetical) uncorrelated sources, with the appropriate complex delay factors and average powers displayed explicitly. In this note, we discuss this briefly, and illustrate with an example.
Surface acoustic waves of finite amplitude excited by a monochromatic line source
Authors: Kalyanasundaram N. , Anand G. V.
Published: October 2005

A technique for obtaining a uniformly valid solution to the problem of nonlinear propagation of surface acoustic waves excited by a monochromatic line source is presented. The method of solution is an extension of the method of strained coordinates wherein both the dependent and independent variables are expanded in perturbation series. A special transformation is proposed for the independent variables so as to make the expansions uniformly valid and also to satisfy all the boundary conditions. This perturbation procedure, carried out to the second order, yields a solution containing a second harmonic surface wave whose amplitude and phase exhibit an oscillatory variation along the direction of propagation. In addition, the solution also contains a second harmonic bulk wave of constant amplitude but varying phase propagating into the medium.
Analysis of the broadband parametric array with Gaussian primary directivity patterns
Authors: Rolleigh Richard L.
Published: October 2005

The three-dimensional integral solution for the secondary sound produced by a parametric array is formulated in a manner useful for the consideration of broadband or transient primary signals. It is shown that when the primary pressure field can be modeled as spherically spreading from the origin, the low-frequency secondary sound can be expressed as the convolution of the ’’input’’ to the parametric array with the ’’impulse response’’ of the parametric array. By modeling the primary directivity functions as Gaussian, the impulse response is reduced to a single integral. The ’’frequency response’’ of the parametric array is derived and shown to be the Fourier transform of the impulse response. For the special case of an observer on the axis of symmetry, an exact analytic result for the frequency response is obtained and is compared with previous theories and with experiment.
Two-tone unmasking in the forward-masking procedure: suppression or perceptual cueing?
Authors: Lutfi Robert A. , Yost William A.
Published: October 2005

Unmasking in the forward-masking procedure was investigated in two experiments. In the first, signal frequency (fs) was held equal to the frequency of the primary masker component (f1) while the frequency of a secondary masker component f2 (where f2≳f1) was varied. In the second experiment, f1 and f2 were held constant while signal frequency varied. The results are discussed in terms of the effects potential perceptual cues may have on unmasking in the forward-masking procedure.
Masker interaction in pure-tone forward masking
Authors: Widin Gregory P. , Viemeister Neal F.
Published: October 2005

Forward masking of a 1-kHz, 20-ms probe was examined using two temporally distinct 1-kHz, 20-ms maskers, separated by 6.5 ms. The interval between the second masker and the probe was the same as the interval between the first and second masker. Masking functions were obtained for each masker separately, and for varying levels of one masker with a fixed level of the other. The presence of the first masker at a fixed level raised the probe threshold over that obtained with the second masker alone: this elevation was approximately constant, independent of the level of the second masker. The results indicate that masking effects of the two maskers are not independent, i.e., the maskers interact. Several models of masker interaction are discussed.