bluuebunny/crossref_metadata_2025 huggingface dataset:
Noise suppression using data-adaptive polarization filters: Applications to infrasonic array data
Authors: Olson John V.
Published: October 2005

We shall describe the construction of a data-adaptive filter which is based upon the multivariate coherence of signals from an array of sensors. The measure of coherence used, called the degree of polarization, is constructed from invariants of the spectral matrix composed from the data and is rotationally invariant. Application of this filter to an infrasonic data suite is shown in which signal-to-level contrasts are enhanced by as much as 20 dB.
Free vibration of a stiffened trapezoidal cantilever plate
Authors: Irie Toshihiro , Yamada Gen , Ida Hajime
Published: October 2005

An analysis is presented for the free vibration of a stiffened trapezoidal cantilever plate. For this purpose, a trapezoidal plate is transformed into a square plate of unit length by the transformation of variables. The transverse deflection of the transformed square plate is expressed in a series of the products of the deflection functions of a cantilever beam and a free–free beam parallel to the edges of the plate, and the frequency equation is derived by the Ritz method. The elements of the equation are calculated by numerical integration, since they cannot be expressed analytically. The present method is applied to square, parallelogram, or trapezoidal cantilever plates with several stiffeners; the natural frequencies and the mode shapes are calculated numerically up to higher modes, and the effects of stiffeners on the vibration are studied.
Hypersonic velocity and compressibility of molten CdCl2
Authors: Knape H. E. Gunilla
Published: October 2005

Brillouin scattering studies have been performed in molten CdCl2 to investigate the frequency dependence of sonic propagation in this ionic liquid. The hypersonic velocity and compressibility have been determined in the temperature range 840–980 K at three different scattering angles (42.0 °, 93.3 °, and 141.6 °) corresponding to frequency shifts of ∼2.6, ∼5.4, and ∼7.0 GHz, respectively. A comparison of the results obtained at these hypersonic frequencies with corresponding ultrasonic data indicates that these measurements have been performed in a frequency region below any relaxation frequency.
Properties of a periodically stratified acoustic half-space and its relation to a Biot fluid
Authors: Schoenberg Michael , Sen P. N.
Published: October 2005

The problem of the reflection of acoustic waves from a periodically layered acoustic half-space is solved exactly at all frequencies. Pass and stop bands and the associated complex slowness surfaces of propagation through the periodic medium are found. In the low-frequency limit, when the wavelength normal to the layering is much greater than one period, it is shown that there always exists a homogeneous ideal fluid with the same reflection properties as the layered medium. However, the effective acoustic medium that models transmission as well as reflection at low frequencies has a bulk modulus Keff given by 〈K−1〉−1 where the brackets denote a volume weighted average, and, for the inertial density appearing in the equations of motion, the effective medium has a transverse isotropic density tensor with ρ∥, the density component parallel to the layering, given by 〈1/ρ〉−1, and ρ⊥, the density component perpendicular to the layering given by 〈ρ〉. The range of wavespeeds speeds as a function of angle is shown to parallel the range of speeds in a Biot fluid as a function of the Biot coupling parameter. Normal propagation corresponds to full locking of the two phases in a Biot material and parallel propagation corresponds to the fully uncoupled case. The relation between the angle of propagation θ measured from the normal to the layering, and the corresponding Biot coupling parameter α is that α−1 is proportional to cot2 θ.
Kramers–Kronig relationships and wave propagation in composites
Authors: Beltzer A. I.
Published: October 2005

A new method is presented for analysis of the dynamic response of disordered particulate composites. The method consists of computation of the losses due to scattering by inclusions and subsequent application of the Kramers–Kronig relationships to derive the phase velocity of the wave. Explicit expressions are given for a porous elastic medium.
RST analysis of monostatic and bistatic acoustic echoes from an elastic sphere
Authors: Gaunaurd G. C. , Überall H.
Published: October 2005

We readdress the basic problem of the scattering of acoustic waves by an elastic sphere, now under the dissecting knife of the Resonance Scattering Theory (RST), with the purpose of illustrating the power of the method, and the versatile options and information it offers. These options include ease of understanding, novel physical interpretation of the phenomenon, and striking calculational simplicity. The principal findings presented here include: (a) the actual modal resonances, quantitatively separated from the corresponding modal backgrounds in the frequency (the ‘‘acoustic spectrogram’’—already a target-identification tool) domain, and in the combined frequency and mode-order domain (the ‘‘response surface’’). (b) The bistatic plots of the scattering cross section, to illustrate the point that if the cross section is redetermined at certain selected observation angles, the resonance contributions from each individual mode can actually be isolated from those of all other modes. (c) A study of the nulls or dips present in the partial waves (i.e., modes), and in the summed cross section. We show the cause and physical meanings of these dips analytically and computationally, in both instances. (d) A derivation of the analytic conditions predicting the nulls and also the influence of the elastic resonance (SEM) poles in the scattered echoes. These conditions, which emerge from our scattering approach, are shown to be in agreement with early results of Love [A Treatise on the Mathematical Theory of Elasticty (Dover, New York, 1944)], obtained on a purely vibrational basis. A tungsten carbide sphere is used in all the examples, since this is a favorite target for experimental calibrations. Our future work will underline the intimate connection between his direct approach, and that (leading to the solution) of the inverse scattering problem for sonar target identification.
Wind-generated surface noise source levels in deep water east of Australia
Authors: Burgess A. S. , Kewley D. J.
Published: October 2005

Recordings of ambient sea noise from four deep water sites between Australia and New Zealand have been examined for correlation between the narrow-band spectrum level and the observed local wind speed. Significant wind dependence is observed at all frequencies between 37 and 800 Hz. When the results are reprocessed to examine only locally generated noise (horizontally arriving sound from distant sources is rejected by making use of the directional properties of a steerable vertical hydrophone array), it is found that the wind dependence of the observed noise at low frequencies is significantly enhanced. The rate of increase of locally generated noise with wind speed is very similar to published values for Australian waters, except for frequencies below 100 Hz, and much lower than most reported measurements in northern hemisphere waters. By steering upward-looking beams, the levels of sound radiated (per steradian) from the surface, at various wind speeds, were measured. The measurements were adjusted, where necessary, to account for variations in bottom loss at different sites, using measured normal incidence bottom reflection losses. At the higher wind speeds the spectrum of the estimated surface source level appears to be almost flat across the band of frequencies observed, which is a feature of recent published results from other oceans. At lower wind speeds the results rise with decreasing frequency below 100 Hz suggesting the addition of noise from a different source which has not been identified.
Plate response to a circularly orbiting mass
Authors: Raske T. F.
Published: October 2005

An analysis based on linear theory is presented for a mass traveling in a circular orbit with small amplitude about the center of a simply supported rectangular plate. The determination of the one-half and full boundaries for the regions of dynamic instability is based on the Bolotin technique. Examples are included for a square plate, an almost square plate, and a rectangular plate.
Pitch shifts contingent on the modulation frequency of an adaptation tone
Authors: Smith A. T. , May J. G. , Lyman R. R.
Published: October 2005

Following adaptation to a frequency-modulated tone, the perceived pitch of a similarly modulated tone of slightly higher frequency is shifted upwards, while that of a tone of lower frequency is shifted downwards. These shifts are greatly reduced or absent when the adaptation and test tones are frequency modulated at different rates.
An equivalent bottom for use with the split-step algorithm
Authors: Bucker Homer P.
Published: October 2005

The split-step algorithm is the standard method for calculating complex (i.e., amplitude and phase) sound fields in a range dependent ocean environment. However, in ocean areas with strong bottom interaction, density discontinuities, sediment rigidity, and bottom roughness should be taken into account. It is easy to incorporate the effects of density discontinuities and rigidity in a specular bottom reflection coefficient R, and it is reasonable to assume that some of the complications of moderately rough bottom interfaces can also be included. Once R has been defined, a systematic procedure is given for generating an equivalent bottom that is compatible with the split-step algorithm and provides an accurate accounting of bottom interaction.
Sound absorption measurements at 10–650 kHz in arctic waters
Authors: Garrison G. R. , Francois R. E. , Early E. W. , Wen T.
Published: October 2005

The absorption of sound in near-freezing seawater was measured from ice floes in northern waters during April 1979, March 1980, and September 1980. Analysis of the data obtained shows that the relaxation frequency for the magnesium sulfate contribution is appreciably lower than predicted by extrapolating the Schulkin–Marsh equation or the Fisher–Simmons equation to temperatures below 0 °C. There is good agreement, however, with the Glotov equation. The measured absorption is lower than the Schulkin–Marsh equation predicts at all frequencies. The results are in good agreement with the Fisher–Simmons equation except near the magnesium sulfate relaxation frequency. Specifically, for the excess absorption equation αE=ASf2f2/(f22+f2)—with frequency f in kilohertz, salinity S of 32%–34%, and temperature at −1.6 °C—we find for the constants, A×103=14±2 dB/km and f2=36±3 kHz.
Acoustic reflection from transversely isotropic consolidated sediments
Authors: Oakley David W. , Vidmar Paul J.
Published: October 2005

Measurements of an excess of horizontal to vertical velocity (averaging 10% for shales) have been made in consolidated marine sediments and in sedimentary rocks. In this paper, the proposed causes of such anisotropies are reviewed, and the reflection coefficient for a homogeneous, solid, transversely isotropic seafloor is derived from plane-wave solutions of the anisotropic wave equations. Bottom loss calculations are used to show that anisotropy can affect the reflectivity of exposed consolidated sediments at the ocean floor. Studies of bottom loss are also used to develop a method for estimating the elastic parameter C13 (frequently not measured for sedimentary material) for consolidated materials.
Reflection of ultrasonic waves at a liquid–cubic–solid interface
Authors: Atalar Abdullah
Published: October 2005

The results of numerical calculations are presented for the reflection coefficient of sound waves incident on a liquid–cubic–solid interface. The reflection coefficient is calculated numerically for the (001) face of various cubic crystals. It is found that for certain orientations there is a null in the reflection coefficient. At this orientation all the power is coupled into a quasishear wave inside the solid. An explanation based on impedance theory is presented. The explanation given predicts that there might be reflection nulls for other liquid–solid interfaces where the solid is any anisotropic solid not just cubic.
Inter-laboratory variability of sound absorption measurement
Authors: Halliwell R. E.
Published: October 2005

Sound absorption measurements have been made at a number of acoustical laboratories in Canada and the United States using the same specimen and the same measurement equipment and procedure. The results provide insight into the effect of reverberation room and diffuser geometry on measured absorption coefficients.
Monaural and binaural auditory frequency resolution measured using bandlimited noise and notched-noise masking
Authors: Hall Joseph W. , Tyler Richard S. , Fernandes Mariano A.
Published: October 2005

Several studies using bandlimited masking noise have indicated that NOSO frequency resolution is better than that for NOSπ. The present study examined NOSO and NOSπ frequency resolution with two different masking methods: bandlimited noise and notched noise. Noise spectrum levels of 10, 30, and 50 dB/Hz were used. Thresholds were determined for a 500-Hz signal,using a three-alternative forced-choice adaptive procedure, as a function of masker bandwidth and notchwidth. For NOSO presentation, 3-dB down points were comparable for the notched-noise and bandlimiting methods. For NOSπ presentation, 3-dB down points were generally greater for the bandlimiting method than the notched noise method. Furthermore, for NOSπ presentation, the 3-dB down estimate increased as noise level increased for the bandlimiting method, but stayed constant for the notched-noise method. It is suggested that the two masking methods measured different aspects of binaural processing.
Simultaneous masking and unmasking with bandlimited noise
Authors: Lutfi Robert A.
Published: October 2005

This study examines how simultaneous masking of a tone by bandlimited noise may be affected by nonlinear interactions among spectral components of the noise. Simultaneous masking patterns (signal threshold versus signal frequency) were obtained with three types of maskers: (A) a narrow-band noise, 50 Hz wide with variable center frequency  fv, (B) pairs of narrow-band noises, each band 50 Hz wide with center frequencies  fl and  fu, and (C) wide-band noise formed by filling the spectral gap between the two bands of (B). The variable frequency  fv was set to 1.0, 1.1, 1.2, and 1.3 of (B). The variable frequency  fv was set to 1.0, 1.1, 1.2, and 1.3 kHz:  fl was fixed at 1.0 kHz, and  fu had values of 1.1, 1.2, and 1.3 kHz. In most conditions, the two-band maskers and the wideband maskers produced more masking than would be predicted from the masking produced maskers, adding noise to fill the spectral gap of the two-band masker actually resulted in a 3- to 15-dB release from masking. These results reveal factors that may operate to confound modern measures of frequency selectivity.
Lateralization based on interaural phase differences: Effects of frequency, amplitude, duration, and shape of rise/decay
Authors: Abel Sharon M. , Kunov Hans
Published: October 2005

Experiments in lateralization were performed to evaluate the relative contribution of envelope and phase cues in binaural hearing with particular reference to the effects of frequency, amplitude, shape of rise/decay, and duration of peak amplitude. Pure-tone signals were presented with interaural phase shifts ranging between 90° and 360°. For a given value of phase shift, the leading signal was presented randomly to the right or left ear over a block of 100 trials, and the laterality of the resultant image was judged. Rise/decay time was varied from 5 to 200 ms across blocks. The results confirmed our previous finding that a rise/decay time of at least 200 ms is required to secure a psychophysically steady-state signal. This value will, however, depend on the values chosen for the other signal parameters. Within limits, decreasing intensity could be compensated for by decreasing rise/decay, suggesting the psychophysical importance of the initial segment of the signal (precedence effect). For low frequencies of 650 to 1250 Hz, performance is sensitive to interaural phase shift and largely independent of frequency. For higher frequencies of 1500 and 2000 Hz, lateralization is independent of the phase cue and also largely insensitive to change in rise/decay time. Finally, performance remains unchanged with variation in peak duration ranging from 25 to 200 ms.
Pure tone pitch perception and low-frequency hearing loss
Authors: Turner Christopher , Burns Edward M. , Nelson David A.
Published: October 2005

Pitch perception for pure tones was investigated in a group of listeners with low-frequency sensorineural hearing loss. Pitch judgments from each listener were compared with results from psycho-acoustic tasks which provide information on the ‘‘place’’ of cochlear response. The pitch measures employed were: (1) binaural pure-tone pitch matching in a listener with unilateral hearing loss, (2) octave judgments in listeners with musical ability, and (3) pitch-intensity functions in other listeners. Cochlear place of response was inferred from psychophysical tuning curves (PTC’s). Two distinct types of PTC’s for low-frequency probe tones were observed. Three listeners demonstrated ‘‘abnormally tuned’’ PTC’s. For these listeners the frequencies that were most effective at masking the probe were considerably higher than the probe frequency. The three remaining listeners demonstrated ‘‘normally tuned’’ PTC’s. Listeners with abnormally tuned PTC’s were suspected of having an extremely abnormal place of response for low-frequency tones; this response pattern being located more toward the base of the cochlea than in the listeners with normally tuned PTC’s. Sensitivity thresholds measured in the presence of high-pass masking noise supported this hypothesis. Small pitch-frequency irregularities were observed in many listeners, although they were not consistently related to the inferred place of response for that frequency. The individual listeners’ pitch judgments failed to distinguish between two types of PTC’s. In particular, listeners who demonstrated abnormally tuned PTC’s did not exhibit correspondingly large pitch irregularities. These results are difficult to explain on the basis of a classical ‘‘place’’ theory of pitch perception.
Production and perception of rise time in the voiceless affricate/fricative distinction
Authors: Howell Peter , Rosen Stuart
Published: October 2005

Rise times of affricates and fricatives were measured when the test material occurred in sentences, in isolated words, and in isolated nonsense syllables. The rise times of affricates were significantly shorter than those of fricatives as has been reported previously. The measured rise times varied with the type of test material and for all types of material were significantly longer than those reported by L. J. Gerstman [unpublished doctral dissertation, New York University (1957)]. Differences in the way the previous measurements were made do not appear to explain the discrepancy. Because rise time varies with type of test material, no single value of rise time can serve to distinguish affricates from fricatives. Listeners were asked to categorize a speech or nonspeech continuum varying in rise time; substantially different estimates of the category boundary were obtained if a range of rise times based on the earlier measurements is used rather than one indicated by the present measurements. Hence, no perceptual sensitivity at a single rise time value can be responsible for the perceptual distinction between affricates and fricatives.
Response of underwater structures to convective component of flow noise
Authors: Chandiramani K. L.
Published: October 2005

Convective component of flow noise (for example, a turbulent boundary layer) is characterized by length scales of the order U/ f, where U is the mean flow speed and f is the frequency. Nonresonant response of underwater structures to the convective component of flow noise is often of interest. An exact theory of transmission of sound across an isotropic flat plate, involving longitudinal and shear waves, is modified so as to apply at high, convective wavenumbers. Closed form results are presented. Such results can in turn be used as inputs to scattering analyses, and as a guide to treating more complicated problems involving multiple-layered structures. However, these later topics are not the subject of this paper.
Horizontal covariance of surface reverberation: Comparison of a point-scatterer model to experiment
Authors: Wilson Gary R. , Frazer Marshall E.
Published: October 2005

A theoretical model of reverberation developed by D. Middleton was implemented to predict the spatial–temporal covariance of surface reverberation. The implementation assumed narrow-band transmissions and point scatterers treated as perfect point reflectors distributed uniformly over the plane of the mean surface level. The implementation of the model under these assumptions is presented, and the results are compared to experimental measurements of the covariance of surface reverberation measured by a horizontal array of receivers. The dependence of the covariance on spatial separation of the receivers, time, and time difference was modeled. The modeled results were found to agree well with the experimental measurements. The effects of off-axis scattering due to the azimuthal directivity of the projector and the bandwidth of the projector and receivers were shown to be significant and were also shown to be properly taken into account by the model.
The dependence of sound extinction on the parameters of thermal turbulence in the atmospheric boundary layer
Authors: Shamanaeva Lyudmila G.
Published: October 2005

Scattering coefficients and normalized scattering phase function were calculated using the Von Karman spectrum of temperature fluctuations in the atmospheric boundary layer which enabled one to take into account the outer scale of turbulence. It was shown that the scattering coefficient had a scale of turbulence. At the same time, the scattering cross section was proportional to the cube root of the sound frequency which agreed with the previously obtained results. The normalized scattering phase function was calculated for small scattering angles. It was shown that in the presence of small scale inhomogeneities in the atmosphere the portion of power removed from the original beam increases because the lateral scattering becomes prevailing. The obtained results are in good agreement with the experimental data.
Laser-acoustic measurements for remotely determining bathymetry in shallow turbid waters
Authors: Hickman G. Daniel , Edmonds John A.
Published: October 2005

A laser technique is described that has the potential for being developed into an airborne remote sensing system for bathymetric mapping of shallow-turbid waters. This hybrid system consists of an infrared CO2 laser transmitter and a highly sensitive microphone receiver located in the air. The interaction of the laser beam with water generates acoustic signals in water having pulse widths of 20–30 μs and a frequency spectrum peaking between 15–25 kHz. Measurements have been made from both a floating laboratory and an operating ship. These measurements were made using a 5 to 15-J CO2 laser to generate a sound pressure level (SPL) of 185–195 dB re: 1 μPa in water at a depth of 1 m. Measurements made in quiescent waters recorded water depths of 20±0.1 m, while the maximum water depth obtained aboard ship was 13±1 m. The two major problem areas encountered were environmental noise and the angular dependence of the bottom sediment echoes as they penetrated a ‘‘wavy’’ water surface.
Free vibration of cantilever quadrilateral plates
Authors: Srinivasan R. S. , Babu B. J. C.
Published: October 2005

In this paper, a numerical method for the free vibration analysis of cantilever quadrilateral plates of general shape is presented. Using quadrilateral coordinates and integral equation of beams, the expressions for the strain energy and kinetic energy have been developed. The formulation and derivation of equations are in the matrix form ‘‘ab initio.’’ Then the eigenvalue problem is solved for frequencies and mode shapes. Numerical work has been done for particular cases and the results compared with those of other investigators. The effect of sweep back angle has also been studied.
A time-averaging transient testing method for acoustic properties of piping systems and mufflers with flow
Authors: Lung T. Y. , Doige A. G.
Published: October 2005

A time-averaging transient testing technique has been developed to allow for a rapid measurement of the matrix parameters and other frequency-dependent characteristics of acoustical systems with or without mean flow. The technique is applicable to systems with substantial flow noise contamination which is either random or periodic in nature. Flow and no-flow experiments were conducted on laboratory models of exhaust mufflers, variable area ducts, and complex piping networks. Excellent agreement between theoretical and experimental results was obtained. This success not only demonstrated the feasibility of the experimental technique for a range of practical industrial applications but also confirmed certain theoretical postulations that have not yet been verified adequately through comparison with experimental results.
Estimation of acoustic velocity, surface velocity, and radiation efficiency by use of the two-microphone technique
Authors: Forssen Bjorn , Crocker Malcolm J.
Published: October 2005

In this paper a theoretical derivation is presented for the spectral density of the acoustic velocity in terms of the auto-and cross-spectral densities of the signals from two closely spaced microphones. This result, together with a Fast Fourier Transform minicomputer and a two-microphone probe, was used to measure the surface velocity of a vibrating flat panel. The surface velocity thus measured agrees quite well, below the panel critical frequency, with that measured by an accelerometer. The two-microphone probe was then used to measure the acoustic intensity, and by summation, the acoustic power radiated by the same panel when it was acoustically and mechanically excited. The panel radiation efficiencies were calculated from these results for the acoustic and mechanical excitation cases. Satisfactory agreement was obtained with the theoretical panel radiation efficiency. This two-microphone approach described is thus shown to be a noncontacting method of measuring the surface velocity, radiation efficiency, acoustic intensity, and acoustic power of vibrating flat, uniform thickness, homogeneous panels. Further experimental work is needed to see if it can also be used with other more complicated structures. Research could also be conducted to investigate the possible use of this method to plot the acoustic velocity mode shapes excited in cavities.
Cavity resonances in engine combustion chambers and some applications
Authors: Hickling Robert , Feldmaier Douglas A. , Chen Francis H. K. , Morel Josette S.
Published: October 2005

Cavity resonances in engine cylinders are caused by combustion events such as the rapid rate of pressure rise that occurs during compression ignition in diesels or from knock in gasoline engines. These resonances generally occur at frequencies greater than 4 to 5 kHz where the engine structure is not an efficient acoustical radiator. However, when they occur at lower frequencies such as in engines with a large bore or in indirect injection diesels, they can be important in the noise generation process. They are also important for knock detection in gasoline engines. Current knock detection systems are tuned to the frequency band of the lowest cavity resonance in the combustion chamber. It is shown in the paper that higher order resonances can also be detected by a knock vibration sensor on the surface of the engine. Another use for the cavity resonances is to determine the bulk temperature of the gas in the combustion chamber as a function of crank angle. This technique is demonstrated in the paper for a heavy-duty two-stroke diesel. Also, the results of several fundamental investigations of cavity resonances in engine combustion chambers are reported briefly. Good agreement is obtained between theoretical prediction of the resonant frequencies and experimental observation. The splitting of degenerate modes into two components is discussed.
Inverse methods in the reconstruction of acoustical impedance profiles
Authors: Schwetlick Horst
Published: October 2005

Three methods for the reconstruction of inhomogeneities in a one-dimensional lossless medium from incident and reflected wave signals are presented in this paper: the method of characteristics, the Gel’fand–Levitan method, and the newly developed method of iterative local regulization. Reconstructed results from numerical experiments are compared with emphasis on inversion in the presence of noise, and on general excitations. An error analysis and a study of computation requirements are also presented.
Measurement of fish target strength and associated directivity at high frequencies
Authors: Dahl P. H. , Mathisen O. A.
Published: October 2005

A technique for measuring fish target strength and directivity in the yaw (coronal) plane is described. Measurements were made at 420 kHz on 40- to 60-cm-long salmonids, these are expressed through polar plots. Since fish-length-to-wavelength ratios generally were greater than 100, the estimated square root of backscattering cross section, or its equivalent peak envelope voltage, approaches a Rayleigh distribution. This was verified experimentally. Expressions for the expected value of target strength and its variance were derived.
Assessment of significant acoustical parameters for rating sound insulation of party walls
Authors: Vian Jean-Paul , Danner William F. , Bauer Jay W.
Published: October 2005

To test the adequacy of French regulations for sound isolation in buildings, subjects were asked to rate their annoyance with samples of music filtered by electronic ‘‘insulation curves’’ representing different party walls. The insulation curves differed in their shape but all provided an A-weighted level difference of 51 dB with a pink noise source, measured over a 1/3-octave bandwidth of 40 Hz–10 kHz. However, the different insulation curves did not provide the same degree of sound isolation with various music samples due to source spectral differences. A statistically significant correlation was observed between annoyance and the A-weighted level difference ratings of the insulation curves when bandlimited pink noise (125 Hz–4 kHz) was used as a source. This correlation was not present when broadband (40 Hz–10 kHz) pink noise was used for the performance rating. Subjects showed a preference for insulation curves with steeper slopes (9 and 12 dB/oct), thus preferring a greater relative attenuation at higher frequencies. Additionally, the presence of coincidence dips was found to have an effect on subject preference that appeared to depend upon both the frequency range at which they occurred and the slope. The bandwidth of the music signals and the intelligibility of speech in the intruding sounds were also found to influence the annoyance ratings. These results indicate that the level difference method for rating sound insulation could better predict occupant response if the above results were accounted for in the procedure.
Rays and local modes in a wedge-shaped ocean
Authors: Arnold J. M. , Felsen L. B.
Published: October 2005

Conventional normal mode theory cannot be applied to the nonseparable problem of wave propagation in an ocean with sloping bottom. For small bottom slopes, the sound field may be expressed approximately in terms of adiabatic modes, but this description fails when a mode propagating upslope passes through cutoff. An alternative solution by ray acoustics, valid at high frequencies, contains many multiply reflected contributions, and also undergoes difficult trapped to leaky ray transitions upslope. To address these transition problems, the conventional ray solution is used here as a convenient starting point for collective treatment of ray fields and their conversion into local modes. First, the ray fields are generalized by associating with each ray trajectory from source to observer a bundle of local plane waves that is multiply reflected between the boundaries and remains valid also in the transition regions. When the generalized ray series is subjected to Poisson summation and subsequent asymptotics on the transform integrals, it is found to furnish local modes which coincide with the conventional adiabatic modes where these exist. The local mode integrals also yield transition functions which smoothly continue an originally trapped adiabatic mode through cutoff to the leaky regime. The transition behavior agrees with that found by Pierce [J. Acoust. Soc. Am. 72, 523–531 (1982)] by an entirely different approach, and with that predicted by the spectral Green’s function method of Kamel and Felsen [J. Acoust. Soc. Am. 73 xxx–xxx (1983)]. The ultilization of rays and local modes in each step of the analysis here grants physical insight and therefore clarifies the mechanism of propagation in this range-dependent environment.
Multiple scattering with applications to fish-echo processing
Authors: Stanton T. K.
Published: October 2005

A general expression has been derived and evaluated for the backscattered echo energy of an acoustic pulse due to a collection of identical randomly distributed isotropic scatterers. Excess attenuation of the signal due to the extinction cross section of the scatterers as well as second-order scattering have been taken into account. Special attention is focused toward the numerical evaluation of second-order scattering effects. The expression is evaluated for three scattering geometries. It is shown in each geometry that when the absorption cross section of the scatterers is small, second-order scattering can be a factor in the backscattered energy. In this case, second-order scattering at least partially offsets effects due to excess attenuation in the low-to-moderate attenuation region. When applied to fish-echo processing, it was shown that in most cases the results represent an upper bound for the processed signal from a school of fish. The directional characteristics, acoustic frequency of the pulse in relation to the resonance frequency of the swimbladder (if any), and degree of randomness of the spatial distribution of the fish determine the degree to which second-order scattering plays a role in this area.
Reply to ‘‘Comments on ‘ear dominance and sequential interactions’ ’’ by E. William Yund
Authors: Deutsch Diana
Published: October 2005

The author presents a reply to E. William Yund [J. Acoust. Soc. Am. 71, 1287–1290 (1982)].
Target detection in reverberation by an echolocating Atlantic bottlenose dolphin (T
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Authors: Au Whitlow W. L. , Turl Charles W.
Published: October 2005

An experiment was conducted to determine the ability of an echolocating Atlantic bottlenose dolphin (Tursiops truncatus) to detect targets in the presence of reverberation. Reverberation was induced by a clutter screen consisting of forty-eight 5.1-cm-diam cork spheres spaced 15.2 cm apart and arranged in a rectangular array, located behind the targets. Hollow aluminum cylinders having the same outer diameter and wall thickness and three different lengths were used as targets. The dolphin was trained to station in a hoop, 6 m from the targets, and to echolocate the target upon the reception of an audio cue. Only one of the targets would be presented in a target-present trial. Data were collected on the animal’s detection performance as a function of the separation distance between the clutter screen and the targets. The animal’s performance for the smallest cylinder varied from 91% to 55% correct as the separation distance decreased from 10.2 to 0 cm. The target strength of the clutter screen and the cylinders were measured both in terms of the energies and the maximum peak-to-peak amplitudes of the incident and reflected echoes. These measurements indicated that when the target-clutter screen separation distance was 0 cm, the dolphin’s 50% correct detection occurred at an energy echo-to-reverberation ratio of approximately 0.25 dB and at a peak-to-peak echo-to-reverberation ratio of 2.6 dB. The results also indicated that the dolphin’s performance varied almost linearly with the echo-to-reverberation ratio. The animal’s pulse emissions were monitored by a microprocessor system and the results are presented in terms of the average number of clicks and the average response latency, as a function of the separation distance.
Pitch of narrow-band signals
Authors: Stover Lisa J. , Feth Lawrence L.
Published: October 2005

This study investigated the pitch elicited by complex narrow bandwidth signals. These signals ranged from two-component tones to multiple-component approximations of narrow-band noise. All were contained within 10-, 20-, or 50-Hz bandwidths. Listeners were asked to adjust the frequency of a pure tone to match the pitch they heard in a given complex signal. A simple model suggests that the pitch of these complex signals should match that of a pure tone set to the center frequency. For a majority of the signals, the performance of three of our four listeners was not different from the model predictions. However, the two-component signals were apparently resolved and two simultaneous pitches were heard by some listeners. Our fourth listener heard two sequential pitches in many of the complex signals. We are unable to account for that performance although the pitch matches were very repeatable. These results have implications for an understanding of pitch coding and auditory spectral resolution.
The influence of inter- and intra-speaker tempo on fundamental frequency and palatalization
Authors: Cooper William E. , Soares Carlos , Ham Audrey , Damon Kristina
Published: October 2005

A study was concucted to examine the influence of speaking rate and emphatic stress on patterns of fundamental frequency (F0) and polatalization across word boundaries. Two groups of speakers, exhibiting characteristically fast versus slow speech, uttered preselected sentences at normal, fast, and slow rates. Acoustic analysis of F0 showed somewhat higher F0 peaks for characteristically fast speakers and for fast rates of speech. Emphatic stress was accompanied by a typical heightening of F0 on the emphasized word and by a lowering of F0 on a neighboring word. Palatalization across word boundaries was more frequent among characteristically fast speakers and at fast rates of speech. In addition, palatalization was more frequent in the absence of emphatic stress at the key site. The results for F0 were discussed in terms of the influence of vocal fold tension, while the results for palatalization were discussed in terms of the incompatibility of phonological processes of lengthening versus shortening as well as possible look-ahead restrictions.
Some effects of speaking rate on the production of /b/ and /w/
Authors: Miller Joanne L. , Baer Thomas
Published: October 2005

One of the acoustic properties distinguishing the syllable–initial stop consonant /b/ from the semivowel /w/ is the duration of the initial formant transitions; syllables beginning with /b/ have shorter transitions than those beginning with /w/. This experiment investigated the way in which the transition durations of /b/ and /w/ change as a function of speaking rate by examining tokens of /ba/ and /wa/ produced by four male speakers. At any given speaking rate the /wa/ transitions were, on average, longer than the /ba/ transitions, although pooled across rates, the distributions of transition duration for /ba/ and /wa/ were overlapping. In addition, the magnitude of the difference between average /ba/ and /wa/ transition durations increased with decreases in speaking rate. This is because as rate of speech decreased so that syllable duration increased, there was little change in the initial transition duration of /ba/, but a considerable increase in the initial transition duration of /wa/. Given the overall pattern of results, the transition duration that could optimally distinguish /ba/ from /wa/ was not constant, but increased with syllable duration. This is in accord with Miller and Liberman’s (1979) finding that when listeners identify /ba/ and /wa/ on the basis of transition duration, they do so in relation to the duration of the syllable.
Speech competition effects on synthetic stop-vowel perception by normal and hearing-impaired listeners
Authors: Gordon-Salant Sandra M. , Wightman Frederic L.
Published: October 2005

A triadic comparisons task and an identification task were used to evaluate normally hearing listeners’ and hearing-impaired listeners’ perceptions of synthetic CV stimuli in the presence of competition. The competing signals included multitalker babble, continuous speech spectrum noise, a CV masker, and a brief noise masker shaped to resemble the onset spectrum of the CV masker. All signals and maskers were presented monotically. Interference by competition was assessed by comparing Multidimensional Scaling solutions derived from each masking condition to that derived from the baseline (quiet) condition. Analysis of the effects of continuous maskers revealed that multitalker babble and continuous noise caused the same amount of change in performance, as compared to the baseline condition, for all listeners. CV masking changed performance significantly more than did brief noise masking, and the hearing-impaired listeners experienced more degradation in performance than normals. Finally, the velar CV maskers (gq and kq) caused significantly greater masking effects than the bilabial CV maskers (bq and pq), and were most resistant to masking by other competing stimuli. The results suggest that speech intelligibility difficulties in the presence of competing segments of speech are primarily attributable to phonetic interference rather than to spectral masking. Individual differences in hearing-impaired listeners’ performances are also discussed.
Perception of static and dynamic acoustic cues to place of articulation in initial stop consonants
Authors: Kewley-Port Diane , Pisoni David B. , Studdert-Kennedy Michael
Published: October 2005

Two recent accounts of the acoustic cues which specify place of articulation in syllable-initial stop consonants claim that they are located in the initial portions of the CV waveform and are context-free. Stevens and Blumstein [J. Acoust. Soc. Am. 64, 1358–1368 (1978)] have described the perceptually relevant spectral properties of these cues as static, while Kewley-Port [J. Acoust. Soc. Am. 73, 322–335 (1983)] describes these cues as dynamic. Three perceptual experiments were conducted to test predictions derived from these accounts. Experiment 1 confirmed that acoustic cues for place of articulation are located in the initial 20–40 ms of natural stop-vowel syllables. Next, short synthetic CV’s modeled after natural syllables were generated using either a digital, parallel-resonance synthesizer in experiment 2 or linear prediction synthesis in experiment 3. One set of synthetic stimuli preserved the static spectral properties proposed by Stevens and Blumstein. Another set of synthetic stimuli preserved the dynamic properties suggested by Kewley-Port. Listeners in both experiments identified place of articulation significantly better from stimuli which preserved dynamic acoustic properties than from those based on static onset spectra. Evidently, the dynamic structure of the initial stop-vowel articulatory gesture can be preserved in context-free acoustic cues which listeners use to identify place of articulation.
Optical probing of acoustic waves on rough surfaces
Authors: Jungerman R. L. , Khuri-Yakub B. T. , Kino G. S.
Published: October 2005

The problem of optically measuring acoustic displacements on samples with rough surface texture is examined. A focusing lens system which increases the amount of scattered light collected from a rough surface is presented. A computer-controlled scanning system for an all-fiber-optic acoustic surface wave probe is described which electronically divides out surface reflectance changes encountered while measuring rough samples. The probe demonstrates the ability to optically measure acoustic displacements on surfaces with a roughness comparable to that produced by most common manufacturing processes. An image of the acoustic field surrounding a defect in an aluminum test sample is presented.
Doppler time mapping
Authors: Gondeck Allan R.
Published: October 2005

The algorithm presented by D. W. Ricker [‘‘Echo waveform synthesis in a rapidly varying geometry,’’ J. Acoust. Soc. Am. 72, 1321–1323 (1982)] for describing time-mapping when the trajectories of both a moving target and the projector are known contained the problem that some of the vehicle motion is transparent and error is introduced. An alternative algorithm, described in this Letter, avoids this problem, is computationally more efficient, with no accumulative error, and is simple to program.
Finite amplitude method for the determination of the acoustic nonlinearity parameter B/A
Authors: Cobb Wesley N.
Published: October 2005

The acoustic nonlinearity parameter B/A is determined using a method based on the finite amplitude distortion of a sine wave emitted by a piston. The growth of the second harmonic component of this wave is measured by a piston receiver which is coaxial with and the same size as the source. In order to determine B/A, the experimental measurements are compared to a theory which incorporates the nonlinearity parameter. The theory developed for this study accounts for the influence of both diffraction and attenuation on the experimental measurements. For this reason, the method is more accurate than previous techniques that employ plane-wave theory for a lossless medium. To test the measurement method, experimental results for B/A in distilled water, ethylene glycol, and glycerol are compared to established values. The agreement between these values suggests that the measurement accuracy is ±4% for common liquids.
Normal mode identification for impedance boundary conditions
Authors: Koch Robert A. , Vidmar Paul J. , Lindberg Jo B.
Published: October 2005

A prescription is presented for identifying normal modes calculated using the plane-wave reflection coefficient (impedance condition) to represent bottom interaction. The new prescription reduces to the usual equality between mode number and number of eigenfunction zeros for a fluid layer over a homogeneous fluid bottom. For a more complex bottom composition, the mode number also has a contribution given by the number of times that, as a function of horizontal wavenumber, the reflection coefficient circles the origin in the complex plane.
Long-range Atlantic acoustic multipath identification
Authors: Legters George R. , Weinberg Norman L. , Clark John G.
Published: October 2005

Multipath data from three long-range (900 km) transmissions are examined. Two of the transmissions follow similar tracks, with one ending in the Gulf  Stream at the receiving end. The third, which is substantially free of Gulf Stream influence, has been extensively studied by Spiesberger et al. [J. Acoust. Soc. Am. 67, 2011–2017 (1980)]. The path structure of the transmission crossing the Gulf Stream was characterized by low S/N and appeared to be unstable. Path identification with ray calculations was attempted for the two transmission channels exhibiting stable multipath with success for the major features of the path structures. Excessive smoothing of the sound-speed profile which eliminates the influence of the Atlantic 18° water in the upper layers is shown to degrade the identification of early arrivals. The slight curvature of the ocean sound-speed profile around 4 km of depth also was critical to early arrival identification. The effect of weak range dependence was small while the effect of a gradual sloping bottom near one receiver was significant.