bluuebunny/crossref_metadata_2025 huggingface dataset:
A corrected mixture law for B/A
Authors: Everbach E. Carr , Zhu Zhe-ming , Jiang Peng , Chu Boa Teh , Apfel Robert E.
Published: October 2005

A derivation is presented that corrects an expression for the effective acoustic nonlinearity parameter of a mixture of immiscible liquids. The derivation is based upon a mass fraction, rather than volume fraction, formulation.
A model for the propagation and scattering of ultrasound in tissue
Authors: Jensen Jo/rgen Arendt
Published: October 2005

An inhomogeneous wave equation is derived describing propagation and scattering of ultrasound in an inhomogeneous medium. The scattering term is a function of density and propagation velocity perturbations. The integral solution to the wave equation is combined with a general description of the field from typical transducers used in clinical ultrasound to yield a model for the received pulse-echo pressure field. Analytic expressions are found in the literature for a number of transducers, and any transducer excitation can be incorporated into the model. An example is given for a concave, nonapodized transducer in which the predicted pressure field is compared to a measured field.
Wave propagation in a piezoelectric human bone of arbitrary cross section with a circular cylindrical cavity
Authors: Paul H. S. , Venkatesan M.
Published: October 2005

A theoretical study of wave propagation in a piezoelectric cylinder of infinite length of arbitrary cross section with a circular cylindrical cavity of class 6 is investigated. The frequency equations are obtained by using the Fourier expansion collocation method and are analyzed numerically. The frequencies are evaluated for circular, elliptic, and cardioidal sections of bone and are tabulated. A plot of frequency spectrum is also presented for the cardioidal cross-section bar.
Temporal response of coupled one-dimensional dynamic systems
Authors: Dickey J. , Maidanik G.
Published: October 2005

A formalism is presented that describes the response of a complex of coupled one-dimensional dynamic systems to an impulse drive. The formalism is based on an impulse response operator that relates a drive applied to one point in the complex to the response at any point in the complex. The formalism is derived directly in the time domain and the impulsive drives which can be accommodated must be finite in time and applied at a spatial point. The constituent systems must be one-dimensional and possess a pulse propagation velocity that is not a function of position within the system. Systems interact through junctions that also define their spatial extents. The junctions are characterized by reflection and transmission coefficients that modulate the amplitude of reverberant components and by delays in the reflections and transmissions. Propagation in the systems is characterized by losses. Several simplistic examples are calculated and presented to illustrate the type of information that the formalism can provide.
Modeling of shape memory alloy hybrid composites for structural acoustic control
Authors: Rogers C. A. , Liang C. , Fuller C. R.
Published: October 2005

Experimental demonstration of active vibration and structural acoustic control using shape memory alloy (SMA) hybrid composites [C. A. Rogers, in Proceedings of the International Congress on Recent Developments in Air and Structure Borne Sound and Vibration (to be published)] has provided the motivation for investigating new control schemes and developing more accurate models. This paper will briefly describe newly developed constitutive models for shape memory alloy actuators and the hybrid material system. A general dynamical model for laminated SMA hybrid composite beams and plates will be presented with several theoretical results. A new structural acoustic model for laminated composite plates [Liang et al., J. Sound Vib. (to be published)] will be briefly described and the potential for active structural acoustic control using SMA hybrid composites demonstrated by numerical simulation.
Variability in the criterion for reporting annoyance in community noise surveys
Authors: Green David M. , Fidell Sanford
Published: October 2005

Independent estimates of the contributions of acoustic and nonacoustic factors to the prevalence of annoyance observed in 32 surveys of reactions to transportation noise are made by means of a previously described probabilistic model. The surveys show considerable variation in the level of noise exposure required to elicit self-reports of consequential degrees of annoyance. The distributions of the criteria for reporting annoyance with aircraft and with other noise sources overlap considerably, but the mean value of the criterion for reporting annoyance is about 5 dB more tolerant of nonaircraft exposure. Errors of estimates in quantifying noise exposure and human response in field studies are also assessed.
The influence of systematic primary-tone level variation L2−L1 on the acoustic distortion product emission 2f1−f2 in normal human ears
Authors: Hauser R. , Probst R.
Published: October 2005

The purpose of the present study was to determine the effect of primary-tone level variation, L2−L1, on the amplitude of distortion-product otoacoustic emissions (DPOAEs). The DPOAE at the frequency 2f1−f2 ( f2>f1) was measured in 20 ears of ten normally hearing subjects. Acoustic distortion products were generated by primaries f1 and f2 with geometric mean frequencies of 1, 2, and 4 kHz. The f2/f1 ratios were 1.25 (1 kHz), 1.23 (2 kHz), and 1.21 (4 kHz). The primary-tone level L1 was kept constant at either 65 or 75 dB SPL while the second primary-tone level L2 was varied between 20 and 90 dB SPL in 5-dB steps. The level differences L2−L1 generating maximal DPOAE amplitudes depended on L1 and on the geometric mean frequency of f1 and f2. There were large interindividual differences. Overall, the L2−L1 evoking maximal mean DPOAE amplitudes was −10 dB for geometric mean frequencies of 1 and 2 kHz with both L1=65 dB SPL and L1=75 dB SPL. For 4 kHz, L2−L1 was −5 dB with L1=65 dB SPL and 0 dB with L1=75 dB SPL. The mean slopes of the DPOAE growth functions in the initial linearly increasing portions were steeper at higher stimulus frequencies, increasing from 0.52 at 1 kHz to 0.72 at 4 kHz for L1=65 dB SPL and from 0.48 at 1 kHz to 0.72 at 4 kHz for L1=75 dB SPL.
Hydrodynamics of the excitation of the cupula in the fish canal lateral line
Authors: van Netten Sietse M.
Published: October 2005

Calculations on the dynamic behavior of the cupula in the fish lateral line canal are presented. The cupula is compared to a rigid half sphere that is sliding over an epithelium to which it is coupled elastically. The calculation of the hydrodynamic excitation of the cupula is based on a solution of the Navier-Stokes equation for a fluid flow past a vibrating sphere. No restrictions regarding the magnitude of the linear (ac) Reynolds number of the fluid flow are imposed on this solution. Cupular displacements calculated by the combination of hydrodynamics and mechanics of the cupula are compared to submicrometer displacements of the cupula of the ruff [Acerina cernua (L)], which have been measured interferometrically [van Netten and Kroese, Hear. Res. 29, 55–61 (1987); van Netten, J. Acoust. Soc. Am. 83, 1667–1674 (1988)]. A high degree of agreement is obtained between the calculations and the experimental data. By varying the relevant physical parameters of the model—cupular radius, the amount of elastic coupling, and viscosity of the fluid—their functional significance in lateral line transduction can be determined. From the theory, it appears that these physical parameters can be combined to only two independent dimensionless numbers, which completely determine the cupular frequency response. One number, the linear (ac) Reynolds number, is related to the hydrodynamics, whereas the second dimensionless number accounts for the interaction between hydrodynamics and mechanical properties of the organ.
Coupled ocean-acoustic model studies of sound propagation through a front
Authors: Heathershaw A. D. , Stretch C. E. , Maskell S. J.
Published: October 2005

A three-dimensional (3-D) numerical ocean model has been used to study sound propagation through an ocean front. The model has been used to provide environmental data for input to a range-dependent acoustic model to study the effect of eddies that form at the front on sound propagation characteristics. The model was set up in an idealized ocean domain but with the model physics and the temperature contrast across the front configured so as to represent the polar front east of Iceland. Acoustic ray tracing was carried out to illustrate the effect of frontal eddy features on sound propagation paths, and propagation loss calculations were performed to quantify their effect acoustically. It was found that dependent upon sound source/receiver depth combinations, the effect of the front and the eddies was to increase propagation loss by as much as 10–20 dB. This is comparable with the magnitude of the frontal effect that is seen in studies using analytical models of ocean fronts and with acoustic calculations that are based on measured environmental data. However, the results of this study have also shown that the acoustic predictions may be sensitive to the choice of ocean model parameter, in particular the horizontal eddy viscosity coefficient.
Effects of focusing on the nonlinear interaction between two collinear finite amplitude sound beams
Authors: Tjo/tta Jacqueline Naze , Tjo/tta Sigve , Vefring Erlend H.
Published: October 2005

A study of the propagation and interaction of two collinear finite amplitude sound beams, presented in a previous paper [Naze Tjo/tta et al., “Propagation and interaction of two collinear finite amplitude sound beams,” J. Acoust. Soc. Am. 88, 2859–2870 (1990)] is extended to include the effects of focusing. The validity of the parabolic equation when applied to strongly focused sound beams is discussed. Equations and algorithms based on a transformed parabolic equation are presented and used to compute the interaction between two collinear, focused sound beams, and between one plane wave and a focused sound beam. Numerical results are shown, with special emphasis on parametric generation and parametric reception of sound.
Expansion of integral equations arising in scattering theory
Authors: McDaniel Suzanne T. , Krauss Phyllis R.
Published: October 2005

Solutions to integral equations for the field on the boundary surface are obtained for the special case of scattering from a one-dimensional periodic pressure release surface. The results, which are expressed as an expansion in powers of hk, differ for different formulations of the boundary integral equation. Of the three integral equations considered, only one yields physically acceptable reflection coefficients, and these are identical to those obtained using the small waveheight approximation.
A two-dimensional Fourier transform method for the measurement of propagating multimode signals
Authors: Alleyne D. , Cawley P.
Published: October 2005

A technique for the analysis of propagating multimode signals is presented. The method involves a two-dimensional Fourier transformation of the time history of the waves received at a series of equally spaced positions along the propagation path. The technique has been used to measure the amplitudes and velocities of the Lamb waves propagating in a plate, the output of the transform being presented using an isometric projection which gives a three-dimensional view of the wave-number dispersion curves. The results of numerical and experimental studies to measure the dispersion curves of Lamb waves propagating in 0.5-, 2.0-, and 3.0-mm-thick steel plates are presented. The results are in good agreement with analytical predictions and show the effectiveness of using the two-dimensional Fourier transform (2-D FFT) method to identify and measure the amplitudes of individual Lamb modes.
Estimation of the parameters of the Rice distribution
Authors: Talukdar Kushal K. , Lawing William D.
Published: October 2005

This paper deals with the problem of estimating the parameters of the Rice distribution. The distribution has applications in sonar and radar signal processing and a proper estimation procedure with associated confidence intervals is important. Using the sample second moment as an estimate of the second moment of the distribution, two techniques, viz., methods of moments and maximum likelihood are applied to synthetic envelope data of known signal-to-noise ratios, in order to estimate the parameter from different sample sizes. It is concluded that the sample second moment is an unbiased estimate of the theoretical second moment and for the signal-to-noise ratio parameter both methods work without any significant bias and satisfy the criterion of maximum efficiency. However, the method of moments is simpler, easier to apply and therefore recommended as the method of choice.
Frequency resolution for diotic and dichotic listening conditions compared using the bandlimiting measure and a modified bandlimiting measure
Authors: Cokely Jeffrey A. , Hall Joseph W.
Published: October 2005

Two experiments were performed that examined the relation between frequency selectivity for diotic and dichotic stimuli. Subjects were eight normal-hearing listeners. In each experiment, a 500-Hz pure tone of 400-ms duration was presented in continuous noise. In the diotic listening conditions, a signal and noise were presented binaurally with no interaural differences (So and No, respectively). In the dichotic listening conditions, the signal or noise at one ear was 180° out-of-phase relative to the respective stimulus at the other ear (Sπ and Nπ, respectively). The first experiment examined frequency selectivity using the bandlimiting measure. Here, signal thresholds were determined as a function of masker bandwidth (50, 100, 250, 500, and 1000 Hz) for SoNo, SπNo, and SoNπ listening conditions. The second experiment used a modified bandlimiting measure. Here, signal thresholds (So and Sπ) were determined with a relatively narrow No band of masker energy (50 Hz wide) centered about the signal. Then, a second No narrow-band masker (30 Hz wide) was added at another frequency region, and signal thresholds were reestablished. The results of the two experiments indicated that listeners process a wider band of frequencies when resolving dichotic stimuli than when resolving diotic or monotic stimuli. The results also indicated that the bandlimiting measure may underestimate the spectral band processed upon dichotic stimulation. Results are interpreted in terms of an across-ear and across-frequency processing of waveform amplitude envelope.
Near-field transmitting and receiving properties of planar near-field calibration arrays
Authors: Van Buren Arnie L.
Published: October 2005

The planar near-field calibration array (NFCA) was developed by Trott [W. J. Trott, Underwater Sound Ref. Rep. No. 55 (1961); also J. Acoust. Soc. Am. 36, 1557–1568 (1964)] for use in determining the far-field acoustic radiation from underwater transducers by measurements in the near field. As a projector, the NFCA produces a nearly uniform plane wave over a large volume in its near field and over a large frequency range. As a receiver the NFCA acts like a plane-wave filter for acoustic radiation (or target scattering) originating from within the plane-wave volume. Thus the NFCA can be used to determine the far-field performance of both receiving and projecting transducers. In addition, it can be used to insonify nearby targets with plane waves and determine the resulting scattered far-field pressure. Earlier papers concentrated on the geometrical design of NFCA’s and the computation of their relative element responses (or sensitivities) for a specified array configuration, near-field volume, and frequency range. This paper provides analytical expressions for the near-field transmitting voltage and current responses and near-field receiving voltage and current sensitivities of a planar NFCA. The paper also provides information to aid in the NFCA element selection process, especially with regard to shading of the NFCA.
A staircase model of tapered-thickness piezoelectric ceramics
Authors: Barthé Peter G. , Benkeser Paul J.
Published: October 2005

Tapered-thickness piezoelectric ceramics have been used in novel devices and imaging techniques, such as wideband transducers and frequency-controlled acoustic-beam translation. However, further application requires an adequate theoretical model of these tapered ceramics. In this work a staircase model is developed in which the thickness gradient is represented as discrete steps. Each step is modeled as an independent, constant-thickness section which contributes to the net response. The theoretical electric input impedance, spectral content, pulse, and continuous-wave pressure profile responses obtained with the model are shown to be in close agreement with the measured response of a tapered piezoelectric transducer.
Effect of a resonance of the frame on the surface impedance of glass wool of high density and stiffness
Authors: Allard Jean F. , Depollier Claude , Guignouard Philippe , Rebillard Pascal
Published: October 2005

A fast variation of the surface impedance of two layers of different thicknesses of the same material has been observed at low frequencies. These variations, which are predicted by the Biot theory, appear at the λ/4 resonance of the frame.
Regular polygonal arrays of resonant scatterers
Authors: Twersky Victor
Published: October 2005

Numerical results for the scattering cross section (S) of N=3–26 equally spaced monopole resonators on a circle (of radius b) indicate regularities in the values of the normalized diameter (2kb=4πb/λ=ρ with λ as the wavelength) corresponding to maximal scattering for symmetrical excitation. The peaks S∧(N) occur for ρ=ρ∧(N) between N and 2N, i.e., for circle circumference between Nλ/2 and Nλ. With increasing N, the values of ρ∧(N) in successive alternating sets (shells) of three or four values of N are close to ρm=2mπ−π/4; shell-1 consists of N=3–5, shell-2 of N=6–9, shell-3 of N=10–12, etc. The basis for the shell structure is delineated by a simple asymptotic approximation (for large ρ and N in the range ρ<2N) or a cylindrical wave representation for a sum of spherical waves. A simple approximation is also derived fo the shift in resonance frequency that occurs for ρ small enough for the array to respond as a collective monopole.
Arctic abyssal
T
phases: Coupling seismic energy to the ocean sound channel via under-ice scattering
Authors: Keenan Ruth Eta , Merriam Lynn Renee Lineback
Published: October 2005

Earthquakes along the mid-arctic ridge radiate earthborne compressional and shear waves that couple into the waterborne arctic acoustic channel and propagate as T phases. The T-phase energy is transmitted above the epicenter through the seafloor at near-vertical angles. Scattering from the ice surface couples some of this energy into waterborne angles. At 5 Hz, the coupled energy is about 40 dB down from the incident levels, and at 15 Hz it is about 30 dB down. Scattering accounts for the characteristic spectral shape of the abyssal T phase that is more energetic at 15 Hz than 5 Hz. Several T-phase arrivals were recorded on hydrophones during the FRAM II experiment. From the measured acoustic levels, a transmission loss prediction between source and receiver, and the scattering conversion losses, the microearthquake acoustic source level in the water column is estimated to be about 250 dB re 1 μPa2-m/Hz at 5 Hz and 235 dB re 1 μPa2-m/Hz at 15 Hz. These levels lead to a crustal attenuation estimate of 0.52 dB/km at 5 Hz, which is consistent with FRAM II refraction measurements.
Finding the impedance of the organ of Corti
Authors: Zweig George
Published: October 2005

Measurements of the nonlinear response of the basilar membrane to a pure tone are shown to have a simple form for moderate membrane velocities:   V(x,f;Vu)/Vu≈[Ṽ(x,f)/Vu]ν(x,f), f⩽fc(x), where the response V is the velocity of the membrane at measurement position x, Vu is the umbo velocity, f is the frequency of the stimulus, and fc(x) is the local characteristic frequency. The frequency dependence of the functions ν(x,f) and Ṽ(x,f) is determined from the data, and ν(x,f) and ln Ṽ(x,f) are shown to be analytic functions in the lower half of the complex frequency plane, with Re{ν(x,f)} a monotonically increasing function of f at fixed x. The linear limit of basilar membrane motion is characterized by a transfer function T(x,f)=(Ṽ/V1)ν/(1−ν), estimated by extrapolating V(x,f;Vu)/Vu to a small membrane velocity V1. T(x,f) and ln T(x,f) are shown to be analytic functions in the lower half of the complex frequency plane. The inverse of the amplitude of the transfer function, which has both a deep dip at f≈fc(x) and a broad shoulder at lower frequencies, bears a striking resemblance to the neural threshold tuning curve. The functional form of T(x,f) is used to deduce the equation governing the motion of a section of the organ of Corti. Each section acts like a negatively damped harmonic oscillator stabilized at time t by a feedback force proportional to the velocity at the previous time t−τ. The time delay τ is proportional to the oscillator period [τ=1.75/fc(x)]. Like a laser, the organ of Corti pumps energy into harmonic traveling waves. Unlike the laser, the direction of energy flow abruptly reverses as the traveling wave approaches the point of maximum membrane velocity [fc(x)≈f]. All accumulated wave energy is then pumped back into a small section of the organ of Corti where transduction presumably occurs. Outer hair cells are conjectured to be active elements contributing to the negative damping and feedback of the cochlear amplifier.
Impact noise: The importance of level, duration, and repetition rate
Authors: Henderson Donald , Subramaniam Malini , Gratton Michael Anne , Saunders Samuel S.
Published: October 2005

The applicability of the equal energy hypothesis (EEH) to impact noise exposures was studied using chinchillas. Hearing thresholds were estimated by recording the evoked potentials from a chronic electrode implanted in the inferior colliculus. The animals were exposed to broadband impacts of 200-ms duration. The study was carried out in two parts. In experiment I, six exposure levels (107, 113, 119, 125, 131, and 137 dB SPL) and three repetition rates (4/s, 1/s and 1/4 s) were employed. In the second experiment, the total duration of the exposure as well as the total energy were kept constant by trading level and rate. Results indicate that hearing loss resulting from exposure to impact noise does not conform to the predictions of the EEH. The permanent threshold shift as well as the hair cell loss are more or less equal across the lower peak exposure levels. However, both the hearing loss and the hair cell damage increase for exposures with higher peak levels. Furthermore, hearing loss and cochlear damage are dependent upon the rate of exposure. Thus the amount of hearing loss and hair cell damage appears to depend on the interaction of several factors including peak level rate, and the susceptibility of the animal.
An ultrasonic Gaussian transducer with a curved back electrode
Authors: Du Gonghuan , Wu Junru , Ding Desheng , Gan Changming
Published: October 2005

An ultrasonic Gaussian transducer with a curved back electrode has been designed and fabricated. A theoretical principle of the design based on electromagnetic theory is developed. The experimental results show that the sound fields generated by the Gaussian transducers fabricated based on the design agree well with the theoretical predictions.
A note on acoustic pulse distortion in liquids exhibiting a continuous distribution of Maxwell relaxation processes
Authors: Leander Johan L.
Published: October 2005

Acoustic pulse distortion in liquids exhibiting a continuous distribution of Maxwell relaxation processes is analyzed by means of linear systems theory. The causality condition for the phenomenological model is noted. Distortion quantities relating the pulse shape to the absorption and dispersion are presented. It is shown that these quantities can be expressed in terms of moments of the relaxation time spectrum.
Spatial response profiles of posteroventral cochlear nucleus neurons and auditory-nerve fibers in unanesthetized decerebrate cats: Response to pure tones
Authors: Kim D. O. , Parham K. , Sirianni J. G. , Chang S. O.
Published: October 2005

Encoding of 1- and 5-kHz pure tones by auditory-nerve (AN) fibers and choppers of the posteroventral cochlear nucleus (PVCN) was investigated. Neuronal responses were analyzed as the discharge rate, rate change, and the mean and standard deviation (or σ) of spike counts. The major findings are: (1) Sideband inhibitory areas were observed in spatial profiles of rate changes of PVCN choppers whereas they were absent in those of AN fibers; (2) spatial profiles of rate changes and mean discharge rates of PVCN choppers were sharper than those of high spontaneous-rate (HSR) AN fibers and were comparable to those of low and medium SR (LMSR) AN fibers for 1 kHz at 50 and 70 dB SPL re: 20 μPa; (3) to 5 kHz, 30 dB SPL, PVCN choppers were strongly driven comparable to HSR AN fibers whereas LMSR AN fibers were weakly driven (implying higher thresholds); (4) PVCN choppers exhibited higher maximum discharge rates (300–600 spikes/s) than either LMSR AN fibers (200–250 spikes/s) or HSR AN fibers (150–250 spikes/s); (5) mean-to-σ ratios of PVCN choppers, particularly at 70 dB SPL, were much higher than those of LMSR or HSR AN fibers; (6) rate-change profiles of LMSR AN fibers were distinct from those of HSR AN fibers, more conspicuously for 1 kHz than for 5 kHz; (7) the neural response profiles to 5 kHz were sharper than those to 1 kHz; and (8) 45% of PVCN choppers in the present study exhibited SR>20 spikes/s whereas only 11%–12% of AVCN choppers in previous studies of anesthetized cats exhibited the same SR, which may represent an effect of anesthesia. The observations support a hypothesis that the transformation of the discharge-rate signal from AN fibers to PVCN choppers leads to an amplification of the mean discharge-rate signal with an increase in the signal-to-noise ratio. The observations suggest that PVCN choppers can encode pure-tone frequency in a spatial profile more accurately than HSR or LMSR AN fibers. The present data on AN and PVCN spatial profiles should be valuable to CN modeling studies by providing the input to the CN and the output of a class of physiologically characterized CN neurons for an identical set of stimuli.
Oblique reflection of a nonlinear P wave from the boundary of an elastic half-space
Authors: Shu K. T. , Ginsberg Jerry H.
Published: October 2005

This paper describes mode conversion effects and subsequent waveform distortion arising when a finite amplitude dilatational (P) wave that has already experienced nonlinear distortion is obliquely incident on a stress-free boundary of an isotropic elastic half-space. A two-term perturbation expansion is first employed to identify the dominant nonlinear effects. The understanding of wave interactions obtained from the perturbation analysis is then exploited to derive a successful solution using the method of characteristics for two-dimensional wave. It is shown that the incident and reflected P waves undergo nonlinear amplitude dispersion along their ray paths. The orientation of the rays for the reflected waves are time dependent, being governed by a modified form of Snell’s law, in which the phase speed incorporates the nonlinear correction for the association particle velocity. The reflection coefficients are shown to resemble those of linear theory, except for the dependence on the variable angles of reflection. The nonlinear propagation and reflection laws are solved to determine temporal waveforms for the reflected P and SV (vertically polarized shear) waves. This requires an iterative procedure in order to trace rays arriving at a specified field point at an arbitrary instant back to their source.
Generating eigenray tubes from two solutions of the wave equation
Authors: Bowlin James B.
Published: October 2005

A method is presented for calculating the paths taken by sound between a source and receiver. These paths, which are called eigenray tubes, are obtained from two solutions of the wave equation at finite frequency, one propagated from the source and the other propagated from the receiver. The results are not restricted to the high-frequency limit as is the case with classical ray traces. This generalization of classical ray tracing could be an important new tool in acoustic tomography. A numerical example is included with plots of 11 eigenray tubes.
A new algorithm for sound speed in seawater
Authors: Spiesberger John L. , Metzger Kurt
Published: October 2005

Travel times of acoustic pulses across a 3000-km section in the northeast Pacific are used to estimate an algorithm for the speed of sound in seawater. This algorithm, derived from tomographic techniques, is inconsistent both with the international standard algorithm derived by Chen and Millero [J. Acoust. Soc. Am. 62, 1129–1135 (1977)] and with the algorithm of Del Grosso [J. Acoust. Soc. Am. 56, 1084–1091 (1974)]. Both previous algorithms were derived from laboratory experiments. The additive correction, δc (m s−1), to Del Grosso’s sound speeds between 0- and 4-km depth is δc(p)=−0.104 189 813 8×10−2p+0.210 143 906 0×10−4p2−0.141 411 578 8×10−6p3+0.317 812 236 0×10−9p4−0.217 806 024 3×10−12p5 with p being pressure-gauge units in kg cm−2. The rms error of δc is about 0.05 m s−1 and 0.1 m s−1 between the intervals of 0 to 2 km and 2 to 4 km, respectively. At about 3-km depth, sound speeds predicted by Chen and Millero and Del Grosso are about 0.7 m s−1 and 0.2 m s−1 too fast, respectively. An accurate algorithm for sound speed is of fundamental importance in acoustics and in tomographic measures of ocean temperature.
Ultrasonic velocities in pure hydrocarbons and mixtures
Authors: Wang Zhijing , Nur Amos
Published: October 2005

Ultrasonic velocities were measured in hydrocarbons of n-alkanes, 1-alkenes, and naphthenes as a function of temperature, using the ultrasonic pulse transmission method. The velocities of all the hydrocarbons measured decrease with increasing temperature approximately linearly, although the rate of decrease is different for different hydrocarbons. The data also show that hydrocarbons of the same homologous series with higher carbon content have higher bulk moduli (or lower compressibilities) and the measured velocities V in mixtures of these pure hydrocarbons obey a simple physical mixing law V=Σi=1nXiVi, where Xi is the volume fraction and Vi is the velocity, respectively, of the ith component.
The elastic moduli of a thick composite as measured by ultrasonic bulk wave pulse velocity
Authors: Papadakis Emmanuel P. , Patton Thadd , Tsai Yu-Min , Thompson Donald O. , Thompson R. Bruce
Published: October 2005

One thick filament-wound composite in the form of a large thick-walled cylinder with locally orthorhombic symmetry has been measured by ultrasonic velocity to calculate its elastic moduli. The basic assumption was that small sections of the composite could be treated as a homogeneous body analogous to a crystal for ultrasonic propagation. The experimental work and the results as best expressing homogeneous body theory are presented. Because of the high anisotropy with the normal to the layers (the three-direction) much different from the axial and hoop directions, it was necessary to calculate slowness surfaces with approximate values of c13 and c23 in order to find the directions of the Poynting vectors to use in making actual measurements on c12 and c13.
Sound exposures and hearing thresholds of symphony orchestra musicians
Authors: Royster Julia Doswell , Royster Larry H. , Killion Mead C.
Published: October 2005

To assess the risk of noise-induced hearing loss among musicians in the Chicago Symphony Orchestra, personal dosimeters set to the 3-dB exchange rate were used to obtain 68 noise exposure measurements during rehearsals and concerts. The musicians’ Leq values ranged from 79–99 dB A-weighted sound pressure level [dB(A)], with a mean of 89.9 dB(A). Based on 15 h of on-the-job exposure per week, the corresponding 8-h daily Leq (excluding off-the-job practice and playing) ranged from 75–95 dB(A) with a mean of 85.5 dB(A). Mean hearing threshold levels (HTLs) for 59 musicians were better than those for an unscreened nonindustrial noise-exposed population (NINEP), and only slightly worse than the 0.50 fractile data for the ISO 7029 (1984) screened presbycusis population. However, 52.5% of individual musicians showed notched audiograms consistent with noise-induced hearing damage. Violinists and violists showed significantly poorer thresholds at 3–6 kHz in the left ear than in the right ear, consistent with the left ear’s greater exposure from their instruments. After HTLs were corrected for age and sex, HTLs were found to be significantly better for both ears of musicians playing bass, cello, harp, or piano and for the right ears of violinists and violists than for their left ears or for both ears of other musicians. For 32 musicians for whom both HTLs and Leq were obtained, HTLs at 3–6 kHz were found to be correlated with the Leq measured.
Electrophysiological evidence of nonlinear distortion products to two-tone stimuli
Authors: Rickman Maureen D. , Chertoff Mark E. , Hecox Kurt E.
Published: October 2005

Spectral analysis of auditory-evoked potential recordings from ten normal-hearing subjects to two-tone signals revealed energy at difference tone (DT=f2−f1) and cubic difference (CDT=2f1−f2) frequencies that was not present in the acoustic signal. Control experiments and calibrations provided substantial evidence supportive of the biological nature of these auditory nonlinearities, suggesting that they are not the result of electromagnetic, acoustic, or analytic artifact. Amplitudes of DT- and CDT-evoked responses were evaluated for rarefaction and condensation signals with f1=510 and 800 Hz across frequency ratios (f2/f1) of 1.16, 1.26, 1.36, and 1.46. Additionally, time-domain summation and subtraction of separately collected evoked responses to rarefaction and condensation signals were performed to demonstrate that these electrophysiological DT and CDT responses reflect their expected quadratic and cubic nature. Suggestions for development of clinical applications of assessing auditory nonlinearities using this methodology are provided.
Virtual pitch and phase sensitivity of a computer model of the auditory periphery. II: Phase sensitivity
Authors: Meddis Ray , Hewitt Michael J.
Published: October 2005

In a companion article [Meddis and Hewitt, J. Acoust. Soc. Am. 89, 2866–2882 (1991)] it was shown that a computational model of the auditory periphery followed by a system of autocorrelation analyses was able to account for a wide range of human virtual pitch perception phenomena. In this article it is shown that the same model, with no substantial modification, can predict a number of results concerning human sensitivity to phase relationships among harmonic components of tone complexes. The model is successfully evaluated using (a) amplitude-modulated and quasifrequency-modulated stimuli, (b) harmonic complexes with alternating phase change and monotonic phase change across harmonic components, and (c) mistuned harmonics. The model is contrasted with phase-insensitive theories of low-level auditory processing and offered as further evidence in favor of the value of analysing time intervals among spikes in the auditory nerve when explaining psychophysical phenomena.
Modeling the effects of extraneous sounds on the perceptual estimation of first-formant frequency in vowels
Authors: Roberts Brian , Moore Brian C. J.
Published: October 2005

Adding either a narrow-band noise or a pair of tones in the F1 region of a voiced vowel can influence its perceived vowel quality. These effects were measured as a change in the position of the phoneme boundary on a continuum of vowels, perceived as changing from /ɪ/ to /ɛ/ as F1 was increased. It is proposed that the phonetic effects of these extraneous components result from the excitation they evoke at neighboring harmonic frequencies in the excitation pattern evoked by the vowel. This increases the effective levels of these harmonics, which, in turn, changes the perceived F1 frequency of the vowel. This proposal, called the excitation-pattern hypothesis, was evaluated by creating vowel continua designed to model the effects of adding extraneous sounds in the F1 region. Each model stimulus was created by adjusting the level of each harmonic in the F1 region to match the excitation levels at harmonic frequencies in that region when the extraneous sound was present. In general, similar shifts in the phoneme boundary were obtained to those resulting from the addition of the extraneous sound, irrespective of whether that sound was periodic or aperiodic. The success of the excitation-pattern hypothesis is discussed in the context of the roles of perceptual inference and temporal information in sound segregation. The center-of-gravity hypothesis is also considered as a possible alternative account of the data.
Ultrasound speckle analysis based on the K distribution
Authors: Weng Li , Reid John M. , Shankar P. Mohana , Soetanto Kawan
Published: October 2005

The departure of speckle magnitude from Rayleigh statistics was applied to examine insonated phantoms with both low and high concentrations of scatterers. A mathematical model, the K distribution of Jakeman, was used to characterize non-Rayleigh statistics. This model contains a parameter, α, which characterizes the clustering of the scattering sites in a medium. It is shown from phantom experiments that alpha is linearly proportional to the log-scaled scatterer concentration in a range from about 1 to 30 scatterers per sample volume.
The acoustic scattering by a submerged, spherical shell. II: The high-frequency region and the thickness quasiresonance
Authors: Sammelmann Gary S. , Hackman Roger H.
Published: October 2005

This article presents a fundamentally oriented analysis of the complex-ka plane pole structure of the S matrix for spherical shells in the thickness range 0.02a⩽h⩽0.10a (a is the outer radius of the sphere) for the high-frequency region (100<ka<1000); the Poisson’s ratio for these shells is fixed at σ=0.34 (aluminum). Surprisingly, this analysis reveals that the most dominant feature in the backscattered form function of a thin spherical shell is a single prominent high-frequency peak. The underlying modal structure and accompanying regions of negative group velocity are related to this feature, which is interpreted as a thickness “quasiresonance.” In particular, the significance of stationary values of the group velocity to the relative amplitude of modal excitation is emphasized.
On the representation of cavity fields in terms of laterally guided waves
Authors: Price Gary H.
Published: October 2005

Lateral-wave representation of forced acoustic oscillations in a homogeneous gas contained within a perfectly rigid cavity are compared for two cases that differ only by the presence in one case of a rigid inner core in addition to the rigid outer shell of the cavity. The two representations exhibit increasingly similar laterally propagating modes as the core of the one case is made smaller relative to the wavelength of the oscillation, although significant differences persits near the mode cutoffs. When the core is present, the propagating modes are accompanied by a discrete spectrum of evanescent lateral modes. The evanescent modes become increasingly dense as the size of the core is reduced, to be replaced entirely by a continuous evanescent spectrum in the absence of the core. This continuous spectrum, which is shown in the present instance not always to be negligible, arises mathematically in a manner similar to the “background” continuum found in lateral-wave decompositions of the scatter of acoustic waves from penetrable cylinders and spheres.
Synthesis of acoustic matching networks by discrete space Fourier transform method
Authors: Kenney J. Stevenson , Hunt William D.
Published: October 2005

This paper describes a method used to analyze and synthesize acoustsic plane-wave matching structures between a transducer and a medium of arbitrary characteristic impedance. The analysis is applicable to multilayer structures with periodic discontinuities in characteristic impedance. It is shown that the frequency response of such structures is approximately equal to the discrete Fourier transform of the individual layer reflection coefficients. The synthesis procedure uses the inverse discrete time Fourier transform to generate a sequence of layer reflection coefficients, and applies a boundary condition to calculate the characteristic impedances. Using this method, wide bandwidth matching structures can be obtained using finite impulse response (FIR) filter topologies as a model. A numerical example is presented to show how the procedure is implemented, and a linear analysis is performed which models the layers of the synthesized structure as ideal transmission lines. The results of the analysis are in good agreement with the response predicted by the Fourier method.
Acoustic propagation in the western Greenland Sea frontal zone
Authors: Mellberg Leonard E. , Johannessen Ola M. , Connors Donald N. , Botseas George , Browning David G.
Published: October 2005

A study, utilizing numerical experiments, of the environmental acoustic effects of the western Greenland Sea Frontal Zone in the summer of 1983 along a 185-km west to east transect is presented. The transect begins at the edge of the marginal ice zone in the East Greenland Current, then crosses the East Greenland Polar Front and terminates in the water of the Greenland Sea gyre. The transect contains several mesoscale eddylike features and a sharp front between Return Atlantic Intermediate Water and Greenland Arctic Intermediate Water, whose effects on an acoustic field have not been previously reported. This front can impart >15-dB increase in loss in <10 km. The effects of the frontal zone on acoustic propagation as a function of location and depth of the acoustic source and depth of the receiver for a nominal frequency of 50 Hz are discussed. Significant differences, sometimes greater than 20 dB, in the acoustic field were observed and are explained in the analysis for variations in any of the source and receiver parameters. The sound-speed structure on either side of the frontal zone makes propagation loss and the dominant acoustic modes very dependent on direction and location. The direction of propagation with the lowest loss (as much as 15-dB difference along the entire transect) can change with a modest shift in source from a 10-m depth to 150 m. As compared to the nonfrontal environment, propagation in the presence of the frontal zone, for any of the source and receiver depths studied, can result in changes in the levels and distribution of energy in the acoustic field by as much as 15 dB as well as changes in the mode of propagation (e.g., refracted/surface reflected to SOFAR). It can also result in an increase (>10 dB) in the sensitivity of propagation loss to changes in receiver depth (10–150 m) compared to the nonfrontal zone environment. A significant finding is that a longer transmission range (93 km) through the waters of a frontal zone can reduce the effects of crossing the front itself by as much as 15 dB. It was also observed that 75 km of upslope propagation that included two oceanic fronts was unaffected by a decrease in bottom depth of 2000 m within the 75-km range.
An instrument for the in situ measurement of sea surface noise from a depth of 1 m under low wind conditions
Authors: Updegraff Garr E. , Anderson Victor C.
Published: October 2005

An underwater package has been developed and deployed to determine the cause of surface noise generated at low wind speeds. The self-suspending instrument, tethered 1 km from a support ship, contains a video camera and four hydrophones, as well as orientation sensors. The signal from each hydrophone is filtered and digitized to cover a frequency range of 800–8000 Hz. Data recorded from a depth of 1–2 m indicates that considerable noise is generated by tiny surface spills. The sound from each spill is composed of distinct decaying oscillations which only last for a few milliseconds. These oscillations match the resonant bubble signatures described by Strasberg [J. Acoust. Soc. Am. 28, 20–26 (1956)] and Medwin and Beaky [J. Acoust. Soc. Am. 86, 1124–1130 (1989)].
Experimental observation of temporal fluctuations at the output of the conventional matched-field processor
Authors: Tran Jean-Marie Q. D. , Hodgkiss William S.
Published: October 2005

Temporal fluctuations of the conventional matched-field processor output are presented and analyzed. Sixteen-min-long transmissions of a 200-Hz continuous wave (cw) tone, projected by a source deployed at 20-m depth and 165-km range, were recorded in September 1987 by the Marine Physical Laboratory digital vertical line array. The various ambiguity surfaces calculated allow the identification of the source range, source depth, and receiving array tilt angle as well as their variability with time. The matched-field processing output power has high-frequency fluctuations related to the swell periods and lower frequency fluctuations with an apparent 8-min period related to internal waves. The analysis is complicated by the absence of acoustic navigation for the array which does not allow a direct and full separation of the time-varying environmental mismatch and the system mismatch. The lower half of the array is processed separately, being spatially more stable than the upper half of the array. The same output power fluctuations are observed as in the case of the full array. The analysis tends to indicate that the array motion is resolved and that internal waves, creating time varying environmental mismatch, are responsible for the observed fluctuations.
Wigner transforms, Gabor coefficients, and Weyl–Heisenberg wavelets
Authors: Dellomo Michael R. , Jacyna Garry M.
Published: October 2005

Many scientific and engineering applications require tools to perform analysis on a signal in the time-frequency domain. This paper establishes connections between several different time-frequency transforms: the Wigner transform, the Gabor coefficients, Weyl–Heisenberg wavelet transforms, and the ambiguity function. Both continuous and discrete versions of the transforms are investigated and the effects of more general time-frequency domain processing are examined. While this paper is primarily expository in nature, it also presents the resolution differences between various time-frequency transform techniques in a unified framework and suggests some improvements. Some examples from acoustics are provided.
New hearing threshold measurements for pure tones under free-field listening conditions
Authors: Betke Klaus
Published: October 2005

Hearing thresholds for pure tones were measured under free-field listening conditions in the frequency range of 40 Hz–15 kHz. Results are consistent with the standard threshold specified in ISO 226 for frequencies up to 250 Hz, but a few dB below the ISO curve at higher frequencies. Thresholds are distributed normally on a logarithmic level scale with a standard deviation of approximately 5 dB. No significant differences between thresholds of male and female subjects were observed.