bluuebunny/crossref_metadata_2025 huggingface dataset:
Consonance and dissonance of pairs of inharmonic sounds
Authors: Geary J. M.
Published: October 2005

The hypothesis that pairs of appropriate inharmonic sounds can evoke perceptions similar to conventional consonance and dissonance is examined. The inharmonicity considered is not the relatively small displacement of frequency components seen in conventional musical instruments (e.g., piano), but rather large, deliberate shifting of frequencies by a number of semitones. The hypothesis states that if there is a match between upper-frequency components of two such inharmonic sounds, consonance should be perceived. If near misses occur between upper-frequency components of the two sounds, causing audible beats, then dissonance should be perceived. The individual inharmonic sounds should have reasonably wide component spacing to avoid a noiselike timbre. This hypothesis was confirmed by experiments in which subjects chose which of two different inharmonic sound pairs was the more consonant. The sound pairs with matching frequency components were chosen more often than those with near misses. The difference was significant for the experimental subjects as a whole and was pronounced for subjects with musical experience. This last fact is important since the sound pairs with matching components were arranged to have conventionally dissonant relationships between their fundamentals, and vice versa for the pairs with near misses. It is speculated that the structures in music which have their origins in the harmonic series (intervals, chords, scales) may be alterable by electronically relocating the harmonics to inharmonic positions.
Parametric acoustic receiving array response to transducer vibration
Authors: Reeves C. Richard , Goldsberry Tommy G. , Rohde David F. , Maki Voldi E.
Published: October 2005

A parametric acoustic receiving array (PARRAY) uses nonlinear acoustic effects to achieve directional receiving array characteristics. The response of the PARRAY to transducer motion is significantly different from the response of conventional hydrophone arrays. In this paper, a theory relating motion of the tranducers to effects on the PARRAY output signal is developed and several models are derived. The models are useful both for evaluating the potential of the PARRAY for various applications and for specific PARRAY system design. Experiments with 5- and 340-m-long PARRAY’s are described and data which verify the models are presented. Electronic techniques of counteracting the effects of transducer motion are discussed.
Coupling of airborne sound into the earth: Frequency dependence
Authors: Bass H. E. , Bolen L. N. , Cress Daniel , Lundien Jerry , Flohr Mark
Published: October 2005

Simultaneous measurements have been made of sound pressure above the ground and seismic velocity below the ground surface resulting from a source suspended in the air a variable distance from the surface. The ratio of seismic velocity to acoustic sound pressure has been determined; there are peaks in the ratio in the vicinity of 45 and 90 Hz depending on the height of the speaker. The source–receiver distance was 10, 30, and 60 m; the source height was varied between 1 and 10 m. The frequency of maximum acoustic coupling was found to agree well with theory; the first and third shear modes appear to be excited. Results for vertical, horizontal, and radial motion indicate the coupled seismic signal is greatest for vertical, next greatest for radial, and least for transverse, though the difference between radial and vertical displacement velocities was not great and depended on the speaker altitude.
Dispersion of sound in a combustion duct by fuel droplets and soot particles
Authors: Miles Jeffrey H. , Raftopoulos D. D.
Published: October 2005

Dispersion and attenuation of acoustic plane-wave disturbances propagating in a ducted combustion system are studied. The dispersion and attenuation are caused by fuel droplets and soot emission from a jet engine combustor. The attenuation and dispersion are due to heat and mass transfer, and viscous drag forces between the emissions and the ambient gas. Theoretical calculations show sound propagation at speeds below the isentropic speed of sound at low frequencies. Experimental results are in good agreement with the theory.
Acoustic momentum and energy theorems for piecewise uniform ducts
Authors: Möhring W.
Published: October 2005

The problem of sound propagation in a constant-area duct with compliant walls is studied, including a uniform mean flow. The wall characteristics are assumed to be piecewise constant. Energy conservation leads to a unitary scattering matrix. A second relation of similar type is derived from momentum conservation which is, however, violated at the wall discontinuities, thereby introducing additional dyadic terms into this relation. The rank of the commutator of the scattering matrix and a wavenumber matrix is shown to be related to the number and type of the wall discontinuities. Explicit results are obtained if this rank is one. As an example, sound propagation in a duct with a semi-infinite splitter plate is discussed.
Propagation of waves in rectangular ducts with sinusoidal undulations
Authors: Nusayr Abdul-Majid
Published: October 2005

The method of multiple scales is employed to analyze the wave propagation in a rectangular hard-walled duct whose walls have weak periodic undulations. Interacting modes traveling in the same direction propagate unattenuated. The energy is continuously exchanged between the two modes. The modes that travel in opposite directions are attenuated and, there, may be cut off. This cutoff will depend upon the geometry of the cross section as well as the phase-angle differences between the undulations of the opposite walls.
Calculation of the strength and diffraction parameters in oceanic sound transmission
Authors: Esswein Robert , Flatté Stanley M.
Published: October 2005

The strength and diffraction parameters, Φ and Λ, are of importance in understanding fluctuations in oceanic acoustic transmission. A method for calculating Φ and Λ is described. Floquet’s theorem is shown to be of use in the calculation of Λ for a range-independent sound-speed profile. The sensitivity of Λ and Φ to changes in the sound-speed profile and the buoyancy-frequency profile is investigated. It is shown that rays with large intensity tend to have small Φ and small Λ except very near caustics.
Effects of source motion on an acoustic signal in the frequency, time, and space domains
Authors: Flanagan R. P. , Weinberg N. L.
Published: October 2005

The effects of source motion on an acoustic signal received by an underwater sensor or array of sensors are examined using ray theory and time series analysis. The signal was modeled for the passage of a constant depth source over several kilometers in range to include propagation both inside an outside of a convergence zone. The effects of radial and skew (nonradial) source motions are determined and selective fading is observed when the reception of a narrow-band multiline signal of 200 ±1/2 Hz is investigated. The frequency, temporal and spatial coherences, and power spectra are calculated for the computed time series. Results show the effect of source placement in range and depth with a deeper source (450 m) having a broader spectrum and a much smaller coherence time than a shallower (100 m) source. Coherence bandwidths were only slightly affected by source position while spatial apertures were extremely large due to the simplified propagation model. Although the results for specific transducer separations are included, arguments based on multipath behavior with range generalize those results to the 500-to 700-km region.
Effects of source micromotion on an acoustic signal in the frequency, time, and space domains
Authors: Flanagan R. P. , Weinberg N. L.
Published: October 2005

The effects of periodic source micromotion on an acoustic signal are examined with micromotion in the vertical plane being emphasized. Single phone radial and skew source motions are investigated utilizing cw and narrow-band equispaced, equal amplitude, multitonal signals of 200 ±1/2 Hz. Brief comments on array reception are included. The study shows that source micromotion does not appreciably affect the coherence bandwidth of the received signal, but introduces a fluctuation having the period of the micromotion, Tmm, which can reduce coherence times appreciably. Spatial coherence lengths are extremely large due to the simplified ray model. Micromotion transfers power from the central peak of the power spectrum to side bands separated from that central peak by ±1/Tmm Hz. The power in the spectral side band of the received signal is dependent on the signal level and the magnitude of the source micromotion.
Sound propagation in a wedge-shaped ocean with a penetrable bottom
Authors: Jensen F. B. , Kuperman W. A.
Published: October 2005

Modal cutoff during up-slope propagation in a wedge-shaped ocean is studied using the parabolic equation model; theoretical results are compared with some model tank experiments.
Estimation of ocean-surface directional-frequency spectra: The inverse scattering problem
Authors: Labianca F. M.
Published: October 2005

This paper demonstrates, by theoretical means, that measured acoustic scattering data can be inverted to yield estimates of the ocean-surface directional-frequency spectrum. The inverse scattering technique developed is based on least-squares inversion through the generalized inverse for underdetermined linear systems of equations. The procedure is based on a recently developed acoustic scattering model which is capable of sampling all frequencies and directions of the gravity-wave field in a localized area of ocean surface. The technique is numerically tested on simulated data samples, constructed with the scattering model using pseudorandom numbers, for a Gaussian ocean surface. The estimation procedure is independent of the assumed form of the simulated directional-frequency spectrum, and the results obtained show that estimation agrees with that spectrum.
Low-frequency sound propagation off Mission Beach, California
Authors: Northrop John
Published: October 2005

Low-frequency (<50 Hz) sound transmission studies were conducted off Mission Beach, California. Sound from both explosive and cw sources, as received on bottomed geophones and hydrophones cable connected to the NOSC Oceanographic Tower, were used to determine the transmission paths and propagation loss. Sound speed and other parameters of the sub-bottom layers, as determined by divers, bore holes, and refraction shooting, were used as input to a FFP computer program to model the propagation loss. The computed propagation loss is less than that observed at short ranges (<2.5 Km) and greater than observed at longer ranges. The discrepancy is believed due to a slope reversal of the interface between the unconsolidated and the semiconsolidated layers. Propagation was best in the E–W direction, but the noise level was also higher. The buried hydrophones were quieter than the bottomed hydrophones and the S/N ratio of the E–W and vertical geophones was greater than on the hydrophones at 5 and 15 Hz. At these very low frequencies and short range the S/N ratio of the geophone recordings was greater than that on the hydrophone recordings.
Acoustic propagation in shallow water over a low-velocity bottom
Authors: Rubano Louis A.
Published: October 2005

The results of shallow-water acoustic experiments performed off the coast of Corpus Christi, Texas, are compared with theoretical computations. The measured results include vertical amplitude distributions in the water column, transmission loss in one-third octave bands, and dispersion analyses. Good agreement was obtained between the measured and theoretical results. Theoretical computations are based on a four-layer, fluid, normal-mode model.
The propagation of thunder through the atmosphere
Authors: Bass H. E.
Published: October 2005

The status of current research into the relations between thunder and the lightning process is examined. Nonlinear effects near the discharge strongly influence the pressure waveform and hence the nearfield acoustic spectrum. At distances where measurements are typically made, propagation effects strongly influence the shape of the recorded spectrum. Since most measurements do not reliably determine propagation distances or the physical characteristics of the propagation path, they are of little value in deducing the nearfield pressure waveform. Even with these problems, the gross features of thunder can be explained qualitatively and there is hope that future experiments will provide information necessary to correct for propagation effects making the study of thunder a useful tool for testing theoretical models of lightning.
Torsional wave propagation in an infinite piezoelectric cylinder (622) crystal class
Authors: Srinivasamoorthy V. R. , Anandam C.
Published: October 2005

Torsional wave motion in an infinite right circular hollow piezoelectric cylinder belonging to (622) crystal class is investigated when the cylindrical surfaces are either traction-free or subjected to relative displacement. Open and short-circuit resonant frequency equations are formulated. Fundamental resonant frequency curves are given for traction-free cylinders. The theory is applied to the vibrations of annular accelerometers.
An underwater acoustic sound velocity data model
Authors: LeBlanc Lester R. , Middleton Foster H.
Published: October 2005

A computer model for generating world ocean sound velocity profile (SVP) information is presented. It employs a ’’least-squares’’ predictor to combine National Oceanographic Data Center (NODC) archival SVP data with any amount of available new sound velocity measurements that might be available. A technique is presented in the paper for the analysis of NODC World Ocean SVP data which is highly efficient. The technique is called empirical orthonormal function (EOF) analysis and it is capable of a very large compaction of the data set. This method provides a very compact presentation of the total statistical nature of the SVP data bank. The end result is a computer model which permits the optimum utilization of all archival data and any new data at a given place and time in world oceans to produce a new complete SVP. Of even greater significance is the fact that the form of the predicted SVP profile is such that it is easily employed in any propagation loss prediction model that is currently in use.
On the nature of two-tone aural nonlinearity
Authors: Humes Larry E.
Published: October 2005

The present manuscript begins with a review of the literature on two-tone nonlinearity and proceeds to the description of an ad hoc model of auditory nonlinearity which can account for several of the features of the psychophysical data on various two-tone nonlinearities, in particular, (f2−f1), (2f1−f2), and two-tone suppression. The two basic components of the model are (1) a nonlinearity which is a series combination of the classical power-series and compressive p-law nonlinearities and (2) an intensity-dependent (nonlinear) filtering scheme. The conceptual model proposed here not only describes the psychophysical data accurately, but also offers possible explanations for some of the apparent discrepancies between psychophysical and physiological data on two-tone nonlinearities.
Acoustic propagation in rigid three-dimensional waveguides
Authors: El-Raheb Michael
Published: October 2005

The linear acoustic propagation in finite rigid three-dimensional waveguides is determined analytically using an eigenfunction expansion of the Helmholtz equation. The geometry considered consists of straight and circular bends of rectangular cross section with continuous interfaces (branches and sharp corners are excluded). The phenomena of resonance shift and relocation are explained for a bend–straight duct combination.
Output of acoustical sources
Authors: Levine Harold
Published: October 2005

Acoustic radiation from a source, here viewed as an immobile point singularity with periodic strength and a given multipolar nature, is affected by the presence of nearly structural elements (e.g., rigid or impedance surfaces) as well as that of a background flow in the medium. An alternative to the conventional manner of calculating the net source output by integrating the energy flux over a distant control surface is described; this involves a direct evaluation of the secondary wavefunction at the position of the primary source and obviates the need for a (prospectively difficult) flux integration. Various full and half-planar surface configurations with an adjacent source are analyzed in detail, and the explicit result obtained, in particular, for the power factor of a dipole brings out a substantial rise in its output as the source nears the sharp edge of a half-plane.
Farfield angular radiation pattern generated from arrayed piezoelectric transducers
Authors: Sato J. , Fukukita H. , Kawabuchi M. , Fukumoto A.
Published: October 2005

Farfield angular radiation patterns generated from plank-shaped and arrayed piezoelectric transducers are obtained by using a finite element analysis method. The calculation and experimental results are obtained for piezoelectric ceramic transducers with typical width W to thickness T ratio of 0.6 and 2.0. At W/T=0.6 the radiation pattern is that of diffraction from a plane aperture, while at W/T=2.0 the pattern is significantly different from the plane aperture theory. This is mainly due to the coupling between the thickness and other modes of vibrations in the piezoelectric transducer.
Resonances in sound scattering from water droplets in air
Authors: George Jacob
Published: October 2005

Resonances in the scattering of acoustic plane waves from water droplets in air are studied. A simple equation to locate the resonances is presented and 12 of the low-frequency resonances are plotted.
Multipath interference nulls in long-range, low-frequency, acoustic propagation by normal modes
Authors: Gordon David F.
Published: October 2005

Several aspects of multipath interference beats are here investigated by analyzing long-range propagation losses computed by normal mode theory. Three typical deep water sound-speed profiles are used at frequencies of 100 Hz and below. The phase shifts which accompany the nulls of interference beats are shown to be organized into patterns resembling certain patterns in the phase of ocean tides. The average distance between nulls of a specified depth is determined by counting and is found to differ widely over the three profiles. These differences arise from the convergence zone structure, which in each of the three profiles is different and leads to different multipath combinations. Plots of interference length between adjacent modes versus mode phase velocity are shown to give a result similar to ray theory loop length and are useful in determining which multipaths are present at a given point. Certain features of the mode theory results can be identified with ray theory caustics, but at sufficiently low frequencies these features disappear. When they are not present, the propagation loss can display a series of surface interference images in depth with alternating bands of high and low loss. The distance between nulls can often be predicted from the phase velocities of the two strongest sets of arrivals.
Volume scattering strengths and zooplankton distributions at acoustic frequencies between 0.5 and 3 MHz
Authors: Holliday D. V. , Pieper R. E.
Published: October 2005

Measurements of ultra-high-frequency acoustic volume scattering strengths in California current waters revealed a complex structure of thin scattering layers in the upper 100 m. These scattering strength profiles are illustrated along with size distributions of zooplankton collected at the same time and depth as the acoustic measurements. Within the uncertainties in the biological measurements and the assumed physical properties of the animals collected, the principal features of the acoustic profiles can be explained by the zooplankton distributions.
On the radiated noise due to boundary-layer transition
Authors: Lauchle Gerald C.
Published: October 2005

A theory is presented for the noise radiated by the incompressible boundary-layer transition that occurs on an infinite, rigid flat plate. It is hypothesized that it is the intermittency of the boundary-layer flow within the transition zone that is dominant in noise production. Using Lighthill’s analogy, it is shown that dipole, quadrupole, and octupole sources are generated. The dipole sources are attributable to the shear stress fluctuations that occur in transitional flow while the others are due to fluctuating Reynolds stresses and their images. Under the assumption that dipole sources are more efficient than quadrupoles or octupoles when the Mach number is very small, the power spectrum of the radiated noise due to the dipole contribution is derived. The spectral level rises at 6 dB/octave, peaks at a frequency corresponding to the time it takes for a turbulence burst to convect through the transition region, and then drops off again at 6 dB/octave. The radiation efficiency is analyzed and found to be quite low; it is only 20% of that for a fully developed turbulent boundary-layer flow.
Φ and Λ computations for real and canonical oceans
Authors: Leung R. , DeFerrari H. A.
Published: October 2005

Numerical methods are developed for the computation of Φ, the strength parameter, and Λ, the diffraction parameter, for arbitrary vertical sound-speed and Brunt–Väisälä frequency profiles. Normal mode solutions to the internal wave equation are obtained numerically. Conventional ray tracing using segments of constant sound-speed gradient determines the ray paths. The ray tube method [S. Flatte et al., Sound Transmission through a Fluctuating Ocean (Cambridge U.P., Cambridge, England, 1979)] is developed and solved numerically to give the phase curvature A (x) and, in turn, used to compute Λ. Model computations examine the relationship between the parameters and source–receiver range and depth for canonical profile and profiles typical of the mid-latitudes in the North Atlantic and Pacific Oceans. Results are compared with the approximate forms of Φ and Λ given by Flatté. We find good agreement with the approximate forms for the canonical profile, but significant differences for the real profiles.
Mode interactions in an isovelocity ocean of uniformly varying depth
Authors: Williams A. O.
Published: October 2005

Pierce’s treatment of normal-mode propagation for an ocean in which physical parameters vary slowly with range is used to calculate mode interactions for isovelocity water of depth varying linearly with range. Simplifying assumptions are (a) two dimensions only, depth and range, and (b) a pressure-release bottom interface (reasonably valid for all but the highest modes). After general procedures are established, an explicit result is derived for the interaction contribution of mode 2 to mode 1 (the lowest mode), for down-slope propagation with several allowed modes. Changes, mainly only of signs and phases, are derived to cover up-slope propagation as well as the contributions of mode 1 to mode 2. Each interaction yields a forward-scattered component and a considerably weaker back-scattered one. Each is proportional to the bottom slope. The forward component is also proportional to the ratio depth to acoustic wavelength; the back component follows the inverse ratio. When normalized to the unperturbed outgoing mode functions, the interaction contributions are essentially of equal magnitudes, as would be expected in the absence of loss mechanisms.
Noise in relation to annoyance, performance, and mental health
Authors: Broadbent Donald E.
Published: October 2005

There are many psychological factors which cause differences of human response to the same level of sound energy. Nevertheless, experiments have allowed these factors to be understood, at least to the extent where policy decisions can be made. The results show that increasing levels of noise increase annoyance, probably increasing the general arousal or excitability of the nervous system. This gives changes in performance which are sometimes detrimental, but not by any means always. Annoyance is associated with psychiatric ill-health, but increases in noise do not appear to increase the proportion of people with such illness.
Thoughts on the future of acoustics
Authors: Rosenblith Walter A. , Barger James E. , Elliott Lois L. , Embleton Tony F. W. , Apfel Robert A.
Published: October 2005

This is a brief report of the final Plenary Session of the anniversary meeting of the Acoustical Society of America in Cambridge, Massachusetts in June 1979. It summarizes briefly conjectures about the future of acoustics with special reference to interdisciplinary technology, hearing problems, noise, and physical acoustics.
An analytical model for the nearfield of a baffled piston transducer
Authors: Tjo/tta Jacqueline Naze , Tjo/tta Sigve
Published: October 2005

The linearized sound field of a baffled piston source (radius a, wavenumber k) in a dissipative fluid is considered. A simplified parabolic equation is derived for ka≫1 and then solved analytically. The solution matches a plane collimated beam in the vicinity of the source and has the Bessel function directivity in the farfield. The nearfield–farfield transition is studied. The range of validity of the parabolic equation is discussed. Its exact solution is shown to be the first term of an expansion in powers of (ka)−2 for the solution of the Helmholtz equation. The higher-order terms are secular at distances of order a(ka)1/3 from the piston.
A characteristic function equation for two-interval forced-choice experiments
Authors: Hartmann W. M.
Published: October 2005

The percent correct responses in a two-interval forced-choice detection experiment can be calculated from the probability density functions for the excitation on the two intervals. This letter introduces an equation which relates the percent correct responses to the characteristic functions of the probability densities. The equation can result in considerable mathematical simplification in the prediction of detection performance in cases of multiple sources of signal or noise.
Time average holography of the tympanic membrane
Authors: Khanna S. M. , Tonndorf J.
Published: October 2005

This Letter presents evidence for the fact that substantial parts of the Ph.D. thesis of one of us (SMK) and some of our joint papers have been plagiarized by a group of Indian scientists.
Thermoviscous regions for the principal and higher sound propagation modes in tubes
Authors: Weston D. E.
Published: October 2005

The different thermoviscous attenuation regions for the principal mode of sound propagation in a gas-filled tube may be defined in a simple diagram, with boundaries based on discriminants containing dimensionless combinations of radius, wavelength, and mean free path. The additional condition for propagation of higher-order modes may be placed on the same diagram. The condition is always satisfied in the ’’very wide tube’’ region, which makes experimental investigations of the principal mode more difficult in this region.
A new method to acquire impulse responses in concert halls
Authors: Berkhout A. J. , de Vries D. , Boone M. M.
Published: October 2005

A new method is proposed to acquire impulse responses in concert halls with large signal-to-noise ratios and with a high resolution. In our proposal an omnidirectional loudspeaker is used which is driven by an amplified sweep: a signal containing all frequencies of interest smeared out in time. By using a deconvolution technique, an almost perfect pulse is obtained with a high peak pressure and a short effective duration. Measurements were made in two different concert halls to illustrate the practical implications of the new technique.
Acoustics in human communication: Evolving ideas about the nature of speech
Authors: Cooper Franklin S.
Published: October 2005

This paper discusses changes in attitude toward the nature of speech during the past half century. After reviewing early views on the subject, it considers the role of speech spectrograms, speech articulation, speech perception, messages and computers, and the nature of fluent speech.
Effect of the surface correlation on the average scattered pressure in Eckart’s formulation
Authors: Bruno Daniel R. , Novarini Jorge C. , Vara César D.
Published: October 2005

Eckart’s formulation of acoustic wave scattering from a randomly rough surface expresses the average pressure as the Fourier transform of the probability density function [C. Eckart, J. Acoust. Soc. Am. 25, 566–570 (1953)]. This implies a complete independence from the correlation function of the surface, a rather surprising result which does not follow from Eckart’s only assumption of statistical homogeneity. A more detailed derivation which takes into account surface correlation is given here.
Bubble swarm acoustics: Insertion loss of a layer on a plate
Authors: Junger Miguel C. , Cole John E.
Published: October 2005

The farfield pressure radiated by a force-excited, extensive plate, separated from an ambient liquid by an air bubble swarm, is expressed in closed form in terms of bubble swarm and plate parameters, frequency, and the spherical angle ϑ from the normal to the plate. Comparing the pressure field with that of the plate in the absence of the bubble swarm, a ϑ-dependent insertion loss is computed. The wavenumber and impedance of the bubble swarm being highly dispersive, simple asymptotic expressions giving the insertion loss are formulated for various frequency ranges.
Maximum likelihood detection and estimation for harmonic sets
Authors: Eddy T. W.
Published: October 2005

Starting from first principles, the optimum receiver for the detection of a harmonic set embedded in white Gaussian noise is derived. The receiver obtained also provides the maximum likelihood estimate of the fundamental frequency of the harmonic set. Three signal conditions are studied: (1) the harmonic amplitudes are known exactly, (2) the harmonic amplitudes are unknown, but have known, independent probability distributions, and (3) the harmonic amplitudes are unknown and have unknown, independent probability distributions. For cases (1) and (2) the optimum receivers are derived. For case (3) the receiver obtained cannot be claimed to be optimum; however, it does have intuitive appeal. In each case the receiver cross correlates the (transformed) spectral estimates with a periodic impulse train whose period corresponds to each possible fundamental frequency of the harmonic set. The receiver for case (3) has an additional interesting property in that it discards all spectral estimates less than a certain value. Some extensions to these results are discussed for situations where (a) the spectral estimates are obtained from data lengths much shorter than the observation interval, and (b) multiple similar harmonic sets may be present.
Analysis of acoustical effects of relative receiver-source motion at intermediate ranges in a deep ocean
Authors: Kays J. L. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

The effects of receiver and source motion are examined for a cw signal transmitted through a deep ocean at ranges of tens to hundreds of km. Ray theory is used to develop results for multipath signals consisting of a wide variety of combinations of SRBR and RSR ray arrivals. A bilinear sound-speed profile is assumed for which bottom and surface sound speeds need not be equal, and receiver and source are chosen to move on the surface. Numerical results are presented using time-dependent total-field expressions, valid for suitably limited time intervals. Analytical expressions are developed which closely approximate numerical results and which provide general conclusions regarding acoustical effects of receiver–source motion at different ranges. When only SRBR rays can occur, total fields are shown to have significantly different characteristics depending on range, in contrast to the virtually range-independent total fields which contain RSR rays. When total-field phase is interpreted in terms of an approximate Doppler shift, the frequency change shows relatively wide variations with both range and total-field composition. Thus, a given frequency shift at the receiver may be the result of considerably different receiver–source directions and speeds.
Bubble oscillations of large amplitude
Authors: Keller Joseph B. , Miksis Michael
Published: October 2005

A new equation is derived for large amplitude forced radial oscillations of a bubble in an incident sound field. It includes the effects of acoustic radiation, as in Keller and Kolodner’s equation, and the effects of viscosity and surface tension, as in the modified Rayleigh equation due to Plesset, Noltingk and Neppiras, and Poritsky. The free and forced periodic solutions are computed numerically. For large bubbles, such as underwater explosion bubbles, the free oscillations agree with those obtained by Keller and Kolodner. For small bubbles, such as cavitation bubbles, with small or intermediate forcing amplitudes, the results agree with those calculated by Lauterborn from the modified Rayleigh equation of Plesset et al. For large forcing amplitudes that equation yielded unsatisfactory results whereas the new equation yields quite satisfactory ones.
The effect of sediment rigidity on bottom reflection loss in a typical deep sea sediment
Authors: Vidmar Paul J.
Published: October 2005

The effect of sediment rigidity on bottom reflection loss, RL=−20 log10‖R‖, where R is the plane-wave reflection coefficient, is studied using a computational model. A single inhomogeneous turbidite layer overlying a homogeneous substrate is treated with an emphasis on low frequencies (10 to 200 Hz) and low grazing angles (0 ° to 45 °). We find that sediment rigidity can be neglected for thick layers (∠500 m) while it can produce significant increases in RL for thin layers (∠36 m). The frequency dependence of RL for thin layers has a low-frequency regime characterized by large peaks (∠25 dB) recurring at short (∠2 Hz) intervals. At high frequencies there remains a persistent increase in RL (∠4 dB). The most important mechanism for sediment S-wave excitation is found to be compressional wave conversion at the sediment–substrate interface.
Filled rubber materials system: Application to echo absorption in waterfilled tanks
Authors: Corsaro R. D. , Klunder J. D. , Jarzynski J.
Published: October 2005

This paper describes a materials system for forming rubber composites with selectable acoustic properties. It is particularly suitable for laboratory use in molding small articles with longitudinal sound speeds and impedances less than (or not much greater than) those of water, and with sound absorption coefficients which may be varied over a wide range. The composites are formed using a common silicone rubber resin (RTV-602) to which various fillers may be added in controlled amounts. In this study, we measured the sound speed, density, and attenuation coefficient for more than 100 samples containing various concentrations and types of these fillers. These data were then reduced to determine the best-fit coefficients in a set of descriptive equations. Thereafter these equations could be used to calculate the filler concentrations needed to form composites with specific required properties. To demonstrate the usefulness and predictability of these materials in an application of general interest, these composites are used to construct several broadband anechoic coatings which reduce tank wall reflections by 20–35 dB at frequencies from 400 kHz to greater than 7 MHz. One- and two-layer coatings were designed using equations derived from Brekhovskikh’s treatment of sound propagation in multilayer media. These coatings were then molded as tiles, and their actual performance is compared with that theoretically predicted. When applied to the inside walls of ultrasonic testing tanks, these tiles significantly reduce the tank size needed for various laboratory and biomedical applications.
Acoustic wave scattering by a finite elastic cylinder in water
Authors: Su Jen-Houne , Varadan Vasundara V. , Varadan Vijay K. , Flax Lawrence
Published: October 2005

Numerical results are obtained for a finite circular elastic cylinder with spherical end caps using Waterman’s T-matrix method. In addition to the important practical applications that this geometry has in underwater acoustics, for the first time this method is applied to elastic scatterers that have a discontinuity in the first derivative of the normal to the surface. This makes the problem numerically difficult and is a good test of the effectiveness of the T-matrix method. The frequency dependence of the backscattering cross section is presented for a cylinder whose overall length is twice its diameter. Our results are compared with experiments showing excellent agreement.
Reflection from a corrugated surface
Authors: Wirgin A.
Published: October 2005

The action of a plane wave upon a sinusoidal pressure-release surface covering an impenetrable medium is studied by means of the Rayleigh and Waterman theories. It is demonstrated that solutions computed from the Rayleigh theory are obtained in about half the time necessary for the obtention of Waterman theory solutions having the same precision. Furthermore, it is possible to obtain solutions from the Rayleigh theory, at quite reasonable cost, that are at least as precise as those obtained from the integral equation method by Uretsky in connection with the experiments of La Casce and Tamarkin. This proves, contrary to prevailing opinion, that the Rayleigh theory is fully capable of describing the scattering phenomena produced by a wide class of corrugated surfaces, including those whose roughness is rather large. The minimal width of this class is shown herein to be 0<h/d<0.34, 0<kh<4.1, −π/2<ϑi<π/2, with h and d the amplitude and period of the grating, and k and ϑi the wavenumber and angle of incidence of the impinging wave.
Method for measuring acoustic radiation fields
Authors: Weinreich Gabriel , Arnold Eric B.
Published: October 2005

An acoustic field which varies sinusoidally in time is completely determined by the complex values of its pressure on two concentric spheres. We have developed an experimental procedure which carries out such a measurement. If the source of sound is located inside the inner sphere, we experimentally obtain an expansion in spherical waves whose outgoing and incoming (that is, reflected) components are independently determined. This paper describes both the apparatus and the underlying theory, and presents illustrative results on the wave reflected from the wall of an anechoic chamber.
Parametric coding of speech spectra
Authors: Flanagan J. L.
Published: October 2005

We suggest that a class of speech coders can be designed from criteria that are perception-specific. Such a class represents a middle ground between ’’waveform’’ coders and speech-specific ’’source’’ coders. We argue that, within perceptually acceptable limits, a bandpass portion of a speech signal can be represented by its short-time spectral amplitude ‖ Sn ‖ and its phase derivative ?n. Both parameters are evaluated at the center frequency ωn of the passband whose spectral width is Wn rad/s. We show that the short-time spectral amplitude is identical to the Hilbert envelope An of the passband waveform. As a by-product, we show that the bandwidth occupied by both An2 and An2 ?n is the same as that for their parent bandpass signal, but their spectra are translated to the range 0 to Wn. No comparable statements can be adduced for An and ?n, but on practical grounds, we conjecture that useful low-pass limits of less than Wn/2 can be applied to both. Finally, we outline techniques to utilize the passband parameters An, ?n, An2 and An2 ?n in digital voice coding.
Computer studies on parametric coding of speech spectra
Authors: Flanagan J. L. , Christensen S. W.
Published: October 2005

We report a series of computer experiments aimed to increase our understanding about the sufficiency of the short-time amplitude spectrum for speech coding, and to examine how bandpass segments of the speech spectrum might be represented parametrically. For this purpose we utilize the absolute value of the short-time Fourier transform and the time-derivative of the short-time phase, evaluated at frequency intervals chosen according to auditory criteria. We analyze and digitally encode these parameters. We find that a frequency resolution corresponding to contiguous 1/6-octave bands, spanning the range 200 to 3200 Hz, is a perceptually satisfactory design, and permits digital coding of respectable quality at transmission rates in the range 20 to 16 K bits/s. We also find that a combination of subband coding and short-time spectrum coding leads to comparable results and provides added economy in processing.
Poststimulatory pitch shifts for pure tones
Authors: Rakowski Andrzej , Hirsh Ira J.
Published: October 2005

Changes in the pitch of a short tone pulse (25 msec, 1000 Hz), following a leading tone, were measured at various leading-tone frequencies and for various time intervals between the leading tone and the tone pulse. The results show that poststimulatory pitch shifts away from the pitch of the leading tone are significant and reproducible. It is suggested that poststimulatory pitch shifts may influence the results of various psychoacoustic experiments on pitch perception.
A serial phase shift beamformer using charge transfer devices
Authors: Brady J. J.
Published: October 2005

This paper describes the design and measured performance of a serial phase shift beamformer which uses a charge transfer device (CTD) for storing the element samples from a cylindrical array. By using a serial structure the amount of hardware needed for multiple beams can be reduced markedly from that needed in conventional parallel preformed beams. Since one beamformer produces all beams, the beams have the same spatial characteristics. To demonstrate the potential cost and space benefits of the new architecture, an experimental version was built and tested to confirm the operational characteristics. The array used for the test was an existing AN/WQS-1 cylindrical array. The beam pattern of the CTD was measured in the ARL:UT test tank. As an aid to performance evaluation, a time delay beamformer was also housed in the AN/WQS-1 cylinder. The beam patterns of the two show close agreement in main lobe and sidelobe structure.
Further examination of synthetic-aaperture sonar in a turbulent medium
Authors: Ikeda Osamu , Sato Takuso
Published: October 2005

Images obtained using synthetic aperture sonar systems are often degraded by the effects of multiplicative and additive noises resulting from turbulence of the medium, random vibrations of the transmitter and receiver system, and various noise sources. In this paper, first, a unified evaluation of the effects of multiplicative and additive noises on the reconstructed image is proposed. In this method, the coefficient of variation of the image is used as the measure. Then, the correlation technique, which has been proposed in a previous paper to reduce the effects of turbulence, is evaluated using this measure. To show the plausibility of the theoretical discussions, several experimental results, which were obtained using a specially arranged synthetic aperture sonar system to evaluate the effects, are presented. The relation between the number of sampling points and the quality of reconstructed images is shown, and the effect of the correlation technique is examined under the condition that large turbulences of the medium exist. These results show the effectiveness of the proposed method.
Higher order mode effects in circular ducts and expansion chambers
Authors: Eriksson L. J.
Published: October 2005

The theory of higher order modes in circular ducts is reviewed and applied to expansion chambers. Numerous schemes have been proposed for use in labeling the various higher order modes in a circular duct. This has led to confusion and, in at least one case, to erroneous descriptions of the higher order modes. In an attempt to solve this problem, a specific approach, analogous to that used in rectangular ducts, is recommended that has geometric clarity and elegance. The cutoff frequencies for these various modes are discussed with respect to propagation in an expansion chamber. Incomplete and misleading statements in the literature concerning the calculation of cutoff frequencies are reviewed. Higher order mode propagation through an expansion chamber is analyzed for various inlet and outlet locations, and experimental results presented. The interaction between plane wave and higher order mode effects is discussed.
Coupled acoustic–optic modes in deformable ferroelectrics
Authors: Pouget J. , Maugin G. A.
Published: October 2005

Based on a fully Galilean electrodynamics of ferroelectric dielectric deformable bodies and the equations for weak fields linearized about an initial rigid-body ferroelectric state with hexagonal symmetry deduced in a previous paper (in which a symmetry breaking was exhibited), a rather complete study of coupled, dispersive, and attenuated bulk wave-propagation modes is presented. Apart from usual optic modes, resonance couplings and repulsion of branches for acoustic modes and polaritons are exhibited for various directions of propagation (longitudinal, orthogonal, and arbitrary settings of the bias polarization field). A birefringence effect for polaritons and an acoustical activity are placed in evidence. In addition to the analytical study which leans on the use of small coupling parameters in order to allow for a manageable discussion of the dispersion behavior for both nondissipative and dissipative processes, and to illustrate these theoretical results, numerical estimates and plots of the most interesting coupling effects are given for a test material such as ferroelectric barium titanate.
A technique for measuring the plane-wave reflection coefficient of the ocean bottom
Authors: Frisk George V. , Oppenheim Alan V. , Martinez David R.
Published: October 2005

A new technique for the measurement of the plane-wave reflection coefficient of a horizontally stratified ocean bottom is described. It is based on the exact Hankel transform relationship between the reflection coefficient and the bottom reflected field due to a point source. The method employs a new algorithm for the numerical evaluation of the Hankel transform which is based on the ’’projection-slice’’ theorem for the two-dimensional Fourier transform. The details of the algorithm are described in the companion paper. Although the algorithm is applied to the case of an isovelocity ocean, the general theory for measuring the plane-wave reflection coefficient in a refracting ocean is developed. The technique provides information about the reflection coefficient, not only for real incident angles, but also for complex angles, thus potentially providing substantial additional structural information about the bottom. The method is shown to yield excellent results with synthetically generated data for the cases of a hard bottom and slow isovelocity bottom.