bluuebunny/crossref_metadata_2025 huggingface dataset:
Spherical wave scattering by an elastic solid cylinder of infinite length
Authors: Piquette Jean C.
Published: October 2005

The problem of the scattering of a spherical acoustic wave by an elastic (lossless) solid cylinder of infinite length immersed in an infinite, inviscid fluid medium is investigated theoretically. The solution is obtained by imposing appropriate boundary conditions (involving stress and normal displacement) at the fluid–solid interface on the relevant differential equations. In order to be able to solve the differential equations, an approximation is made that is equivalent to assuming that the most significant additional contributions to the scattered wave appearing in the fluid (compared with the contributions to the scattered wave arising in the incident plane-wave case) are those associated with the waves propagating along the z axis within the solid. Numerical results are presented for a 1000-Hz wave incident on a 2-cm-diam metallic cylinder in water. This is a low ka calculation (where k is the wavenumber in the fluid and a is the radius of the scatterer). Several different metals are considered. The results are compared to those obtained for an incident plane wave. The scattered pressure wave resulting from an incident spherical wave is shown to differ in amplitude by as much as 20 dB from that resulting from an incident plane wave. (This difference is nontrivial, i.e., it does not result from a minor repositioning of nulls in the scattering pattern.)
Inversion of the two-dimensional S
H elastic wave equation for the density and shear modulus
Authors: Hooshyar M. A. , Weglein A. B.
Published: October 2005

In this paper, a method for simultaneously reconstructing the two-dimensional shear modulus and density configurations from SH data is presented. The method requires a complete suite of surface receivers for each of two source locations. This is in contrast to previous multiparameter, multidimensional inversion methods, which require complete source coverage for each one of a continuous set of surface receiver locations. The method presented here is a multiparameter extension of the recent single source, single parameter, multidimensional acoustic velocity inversion procedure of Esmersoy, Oristaglio, and Levy [J. Acoust. Soc. Am. 78, 1052–1057 (1985)]. A simple change of variables allows the multiparameter procedure to be directly applied to the acoustic inversion problem, i.e., to identify the multidimensional acoustic velocity and density configurations.
Stopbands in a corrugated parallel plate waveguide
Authors: Sandström Sven-Erik
Published: October 2005

The stopband structure of a two-dimensional periodically corrugated waveguide is investigated by means of the null-field method. In the numerical examples, the walls are assumed to be hardwalled with symmetric, antisymmetric, or one-sided sinusoidal corrugations. The interaction pattern and the stopband widths are determined for the lowest modes. The resonances are found to be of the stopband type, and it appears that geometrical symmetries of the boundaries suppress well-defined sets of resonances.
Numerical techniques for three-dimensional steady-state fluid–structure interaction
Authors: Mathews Ian C.
Published: October 2005

The application of a coupled finite element–boundary integral approach to the analysis of vibrating elastic, arbitrary-shaped, three-dimensional structures in an infinite media is presented. A feature of the methodologies implemented is the utilization of the isoparametric concept from finite element theory. The same shape functions are used both to model the surface of the structure and to interpolate the acoustic variables over the radiating surface. The boundary integral formulation used for the exterior acoustic field is a formulation that ensures uniqueness and existence of solutions for the entire frequency range. An assessment of the accuracy was made after comparing the solutions attained for a vibrating submerged sphere for various excitation loads and frequencies with the exact solution.
The effect of hydrostatic pressure fields on the structural and acoustic response of cylindrical shells
Authors: Keltie R. F.
Published: October 2005

The effects of external hydrostatic pressure fields and fluid loading on the structural and acoustic response of a point-driven infinitely long circular cylindrical shell were examined over a range of frequencies. The external pressure field was modeled using static prestress terms in the shell equations of motion, and the structural response was characterized by the driving point admittance and the circumferential resonant frequencies. The acoustic response was quantified through calculation of the radiated sound power, both in an overall sense and on an individual modal basis. The analysis was performed for the in-air case as well as for the in-water case. The structural response was found to be strongly affected by fluid and pressure, resulting in significant resonant frequency shifts. However, the overall acoustic response was shown to be nearly independent of the external pressure field, both in air and in water. In addition, it was shown that relatively fewer modes contribute significantly to the sound radiation for the submerged shell as compared to the shell in air. In both cases, the sound generation was controlled by the low-order nonresonant modes.
A comparison of high-resolution seismic methods for determining seabed velocities in shallow water
Authors: Brocher Thomas M. , Ewing John I.
Published: October 2005

The ability to resolve both the seismic velocity of the seabed in shallow water and the lateral variability of these measured velocities using four conventional seismic methods is compared. The four methods described here differ in the ease and efficiency in which the field data are collected and interpreted, and in the resolution of the velocity of the seabed they provide. Narrow-aperture refraction studies provide limited constraints due to the frequent absence of first-arriving sediment refractions in the narrow portion of the wave field that is sampled. Wide-aperture refraction experiments using ocean bottom seismometers provide high resolution of both the compressional- and shear-wave velocities of the seabed but are time-consuming to perform and to interpret. Narrow-aperture multichannel reflection data are easily collected, and are ideal for areal mapping of sedimentary sequences, but resolution of seismic velocities is low unless the aperture of the multichannel streamer is several water depths in length. Wide-aperture multichannel reflection profiling generally provides the highest resolution in velocity in all geoacoustic environments, including those which produce little or no precritical reflected energy and little dispersion of the acoustic normal modes. Moreover, difference seismic wave fields calculated by subtracting a reference seismic wave field from adjacent wave fields provide an objective means of rapidly mapping the lateral variability of the seabed.
Rate discrimination of high-pass-filtered pulse trains
Authors: Cullen John K. , Long Glenis R.
Published: October 2005

Difference limens for trains of 30-μs pulses were determined for repetition rates of 50, 100, 200, 400, and 800 pulses per second under conditions of no filtering and high-pass filtering (115 dB/oct) with corner frequencies of 2.5, 5.0, 7.5, and 10 kHz. Low-pass-filtered noise was mixed with the trains of impulses to preclude discrimination on the basis of potential low-frequency signal components. Measures were obtained from four trained listeners at a signal level of 30 dB SL relative to individually determined thresholds for each filter condition and repetition rate. The data support the hypothesis that resolution of pulse-train repetition rate involves both temporal- and frequency-based processes—the latter becoming ineffective when frequency resolution of the ear is insufficient to resolve separate harmonics of the signal. Inter- and intra-individual differences are interpreted as reflecting frequency resolution capacity.
Cochlear microphonics and the initiation of spikes in the auditory nerve: Correlation of single-unit data with neural and receptor potentials recorded from the round window
Authors: Ruggero Mario A. , Robles Luis , Rich Nola C.
Published: October 2005

On the basis of comparisons of responses of guinea pig ganglion cells and inner hair cells to intense low-frequency tones, Sellick et al. [Hear. Res. 7, 199–221 (1982)] have proposed that basal inner hair cells can be depolarized (and thus, VIII-N. spikes generated) by the extracellular microphonic generated during hyperpolarization of outer hair cells. VIII-N. data for the chinchilla have been presented that, to a first approximation, support such a hypothesis [Ruggero and Rich, J. Acoust. Soc. Am. 73, 2096–2108 (1983)]. However, an apparent discrepancy exists in our results, vis à vis Sellick et al.’s hypothesis, in that basal fiber near-threshold responses precede maximal negativity of the round window microphonic (i.e., maximal hyperpolarization of outer hair cells) by up to 90° (but generally less than 45°), depending on frequency. It is shown here that the discrepancy is resolved if certain nonlinear phase changes and overall distortion of the microphonic waveshapes, both of which occur at intense stimulus levels, are taken into account. It is also shown that compound action potentials (AP’s), superimposed on the round window microphonics, can be identified at multiple times within each stimulus cycle, closely matching the near-threshold response phases of single-unit excitation. AP1 is nearly synchronous with the negative-to-positive transition of round window microphonics and with the excitation of fibers innervating apical-to-middle cochlear regions. AP2 is synchronous with the positive-to-negative transition of the microphonics and with the excitation of basal fibers. One or two other AP’s probably reflect ‘‘peak splitting’’ in the responses of both basal and apical fibers.
Relationship between vibrational and acoustical intensity for an infinite plate
Authors: Piaud J. B. , Nicolas J.
Published: October 2005

The vibrational intensity is compared to the acoustical intensity in the general case of any flexural progressive wave, using the geometrical optics theory applied to the farfield of a thin plate. The vibrational and acoustical intensities are obtained using that theory. They are shown to be equivalent when the acoustical intensity is measured near and parallel to the plate. The theoretical expression for the vibrational intensity suggests a simple method of measurement using two accelerometers. The validity of the method is analyzed in the theoretical case of the mechanical excitation of an infinite plate by a point force and by a force moment. Experimental results are shown to validate the theoretical predictions.
Acoustic ringing response of the individual resonances of an elastic cylinder
Authors: Numrich S. K. , Howell W. E. , Subrahmanyam J. V. , Überall H.
Published: October 2005

The results of a theoretical and experimental study concerning the ringing response of the individual resonances of a submersed elastic cylinder, insonified at normal incidence by sinusoidal pulses of relatively long duration, are presented. This ringing consists of a series of superimposed responses, comprising the specular reflection, and a succession of creeping waves which at resonance add in phase to synthesize the ringing response of an individual elastic-body resonance, provided the pulse spectrum is sufficiently narrow; off resonance, the ringing disappears. Analytically and experimentally obtained echoes from cylindrical targets support this interpretation and are correlated with complex-frequency poles of the scattering amplitude.
Design of a topologically dispersive acoustic soliton tank
Authors: Banerjee P. P. , Korpel A.
Published: October 2005

The design of a topologically dispersive acoustic soliton tank, in which KdV solitons of desired amplitudes and widths may be generated and propagated, is presented. A potential application of the system as a traveling wave lens in acousto-optic beam deflectors is also mentioned.
Time-domain farfield scattering of plane acoustic waves by a penetrable object in the Born approximation
Authors: Quak Dirk , de Hoop Adrianus T. , Stam Hendrik J.
Published: October 2005

The low-contrast or (first-order) Born approximation is applied to the time-domain scattering of a plane acoustic wave by a penetrable object of bounded extent embedded in a homogeneous fluid. Closed-form analytic expressions are obtained for the spherical-wave farfield scattering amplitude related to homogeneous objects of the following shapes: an ellipsoid, an elliptic cone of finite height, an elliptic cylinder of finite height, and a tetrahedron. Relaxation effects are included. The results are, amongst others, useful as test cases for time-domain inverse-scattering algorithms.
Attenuation and speed of ultrasound in lung: Dependence upon frequency and inflation
Authors: Dunn F.
Published: October 2005

The dependence of the speed of sound and the attenuation coefficient upon exposure frequency, in the range of 1–5 MHz, and upon level of inflation, in the range of mass density 0.35–0.7 g/cm3, are reported. The speed of sound increases linearly and the attenuation coefficient increases exponentially, for all levels of inflation studied.
Sentence intonation in textual context—Supplementary data
Authors: Thorsen Nina Gro/nnum
Published: October 2005

The experiment presented here is a sequel to a previous investigation [N. G. Thorsen, J. Acoust. Soc. Am. 77, 1205–1216 (1985)] and was designed to show whether a sequential fundamental frequency lowering of individual sentence components is present in a semantically, but not necessarily syntactically, coherent sequence (a text), when the number of sentences exceeds three. The results show that such a sequential lowering may appear, though it is not evenly distributed across the text. However, the textual intonation contour is sensitive not only to the number of sentences that make up the text, but also to the length of individual sentence components.
Auditory brain stem responses from human adults and infants: Restriction of frequency contribution by notched-noise masking
Authors: Folsom Richard C. , Wynne Michael K.
Published: October 2005

The frequency contribution to the click-evoked ABR wave V was examined in adults and 3-month-old infants through the use of notch-filtered broadband noise. Notch center frequencies were set at 1.0, 4.0, and 8.0 kHz. Responses were obtained at 20, 40, and 60 dBnHL during the simultaneous presentation of each notched-noise masker as well as in an unmasked condition. The ABR wave V was analyzed for absolute latency and amplitude, as well as latency and amplitude changes resulting from the introduction of masking. Analyses showed wave V latency and amplitude values to be similar for adults and infants within the 1.0-kHz notch. Differences between adult and infant groups were observed as the notch was shifted to the high frequencies. Further, latency and amplitude shifts resulting from the introduction of masking noise produced differential effects on infant responses when compared to adults.
The mechanical point impedance of the human head, with and without skin penetration
Authors: Håkansson Bo , Carlsson Peder , Tjellström Anders
Published: October 2005

The fact that a titanium screw can be implanted into the mastoid portion of the human skull, at the same time establishing a permanent, reaction-free skin penetration, has made it possible to attach a new bone conduction hearing aid directly to the skull. To understand and improve this new method of bone stimulation, the mechanical point impedance of the titanium screw–skull system was measured. The conventional point impedance of the skin-covered mastoid portion of the temporal bone was also measured and the difference in magnitude between the two impedances was calculated. An impedance head (Brüel & Kj1r 8001) and an FFT analyzer (Hewlett–Packard 5423) were used for mechanical point impedance measurements. Seven patients have been investigated. The magnitude of the impedance for the screw–skull system was found to be generally between 10 and 30 dB higher than that for the conventional skin-covered mastoid bone. One conclusion is that the conventional point impedance of the skin-covered mastoid portion of the human skull is essentially due to the properties of the skin and subcutaneous soft tissue. Another conclusion is that a much lower stimulation velocity is needed, with skin penetration, to produce a given hearing sensation.
Hazard from intense low-frequency acoustic impulses
Authors: Price G. Richard
Published: October 2005

It was predicted that because the ear is spectrally tuned, it should be most affected by intense impulses with spectral peaks near the frequency where it is tuned best (3.0 kHz for the human ear) and progressively less affected by impulses at lower frequencies [G. R. Price, Scand. Audiol. Suppl. 16, 111–121 (1982)]. This prediction is counter to all the DRCs for impulse noise; therefore an adequate test is essential. In order to augment the data on hearing loss to low-spectral-frequency impulses, three groups of cats (eight, nine, and ten animals) were exposed on one occasion to 50 impulses from a 105-mm howitzer at peak SPLs of 153, 159, and 166 dB. Threshold shifts were measured electrophysiologically on the day of exposure (CTS) and following a 2-month recovery period (PTS). Maximum PTSs appeared at 4 kHz (even though the spectral peak of the impulse had been at about 100 Hz), and CTSs recovered into PTSs about half as large. Furthermore, for group data, even small CTSs tended to have a permanent component. These data raise the question as to whether or not any threshold shift persisting an hour or two after exposure to high levels should be considered tolerable. When compared with data from rifle fire exposures, the data confirmed the earlier prediction that as the spectral frequency drops, hazard declines at the rate of a little more than 3 dB/oct, contrary to the rating by existing DRCs.
Predictors of speech intelligibility in rooms
Authors: Bradley J. S.
Published: October 2005

Three different types of acoustical measures were compared as predictors of speech intelligibility in rooms of varied size and acoustical conditions. These included signal-to-noise measures, the speech transmission index derived from modulation transfer functions, and useful/detrimental sound ratios obtained from early/late sound ratios, speech, and background levels. The most successful forms of each type of measure were of similar prediction accuracy, but the useful/detrimental ratios based on a 0.08-s early time interval were most accurate. Several physical measures, although based on very different calculation procedures, were quite strongly related to each other.
A model for insertion loss degradation for parallel highway noise barriers
Authors: Bowlby William , Cohn Louis F.
Published: October 2005

An algorithm is developed and validated for the prediction of the reduction, or degradation, of traffic noise barrier insertion loss when a second barrier is placed on the opposite side of the highway. The algorithm combines the basic emission, propagation, and barrier attenuation features of the Federal Highway Administration traffic noise prediction model with a geometrical acoustics approach for multiple reflections. The resultant model can accommodate any number of source lanes or receivers, three vehicle categories, and independently variable barrier heights and absorption coefficients. The model was validated against mathematical, scale model, and full scale field data received from other researchers, and has proved to be a good predictor of insertion loss degradation.
Acoustic imaging of high-temperature hydrothermal plumes at seafloor spreading centers
Authors: Palmer D. R. , Rona P. A. , Mottl M. J.
Published: October 2005

We explore the possibility of using active sonar techniques to acoustically image high-temperature ‘‘black smoker’’ hydrothermal plumes. We examine recent sonar images of a hydrothermal vent field at 11°N on the East Pacific Rise obtained from DSRV Alvin which may show the presence of plumes. For vent fields on the East Pacific Rise estimates are obtained of the minimum detectable concentration of precipitates as a function of the range between the sonar and the plume boundary. These estimates are compared with measured concentrations. Some of the anticipated advantages of acoustic imaging are discussed. We conclude that acoustic imaging techniques have the potential of providing a coherent framework for point sampling of physical and chemical properties of hydrothermal plumes and for determining the dynamics of their injection into the surrounding water mass.
Finite amplitude distortion and dispersion of a nonplanar mode in a waveguide
Authors: Ginsberg J. H. , Miao H. C.
Published: October 2005

The perturbation method of renormalization is used to study the effect of nonlinearity on a hard-walled rectangular waveguide. The excitation would induce only the fundamental nonplanar symmetric mode if the system were linear. The analysis develops a solution that satisfies a nonlinear wave equation for the velocity potential, as well as all boundary conditions. The response consists of a pair of oblique planar waves that interact through second-order excitation of the true planar mode. The investigation discloses that in the high-frequency limit the signal has a quasiplanar behavior. In contrast, for very low frequencies exceeding the cutoff value, the oblique waves are essentially independent. The distortion is then a result of self-refraction, in which the particle motion shifts the wave fronts and rays. The transition between the low- and high-frequency limits is marked by the appearance of nonlinear frequency dispersion, which produces asymmetrical distortion of the waveform.
Extensional-wave and flexural-wave contributions to the sound field radiated by a fluid-loaded infinite plate
Authors: Rudgers Anthony J. , Dubbelday Pieter S. , Fagerstrom Lisa A.
Published: October 2005

A structural thick-plate theory that accounts for the propagation of both extensional and flexural waves in an infinite elastic plate is used to calculate the farfield directional response of the sound radiated by a plate with fluid on one side. The plate is driven by a harmonic point force, and the radiation in the farfield of the driving point is considered. Computations are made for metal plates and plates composed of polymeric materials in water and in air. Anelastic behavior of the plates is considered. The computations, which are made in order to compare the radiated fields of plates in which only flexural waves or only extensional waves can propagate, or in which both wave types can propagate concurrently, show that the radiation caused by extensional waves can make an important contribution to the sound field of an elastic plate.
Comments on ‘‘On the acoustic response of a deeply corrugated periodic surface—a hybrid T-matrix approach’’ [J. Acoust. Soc. Am. 7
8, 2100–2104 (1985)]
Authors: Wirgin Armand
Published: October 2005

The consequences, in the context of the T-matrix approach, of the use of either the incoming (Waterman) or outgoing (Rayleigh) surface-field representations are discussed in relation to the hybrid ansatz used by A. Lakhtakia, V. K. Varadan, and V. V. Varadan, J. Acoust. Soc. Am. 78, 2100–2104 (1985).
The frequency of flexural vibration of completely free composite piezoelectric polymer plates
Authors: Ricketts Donald
Published: October 2005

The frequency expression for flexural vibrations of the completely free composite piezoelectric polymer plate given in an earlier paper [J. Acoust. Soc. Am. 77, 1939–1945 (1985)] for all modes of the type p/q (p, q=2,3,4,...) is extended to cover all modes of this type for p, q=0,1,2,..., where p and q are the number of nodal lines in the coordinate directions x1 and x2, respectively. Because of the stiffening effect of electrodes deposited on the polymer surface, the expressions for the flexural and twisting rigidities of the composite plate given in the earlier paper for 2n layers are rewritten with the electrodes treated as layers separate from the polymer. Expressions are also given for the rigidities of the composite plate for an odd number of layers, a case not considered in the earlier paper. The frequencies of several modes are computed for a completely free composite piezoelectric polymer plate, a configuration which has application to hydrostatic polymer hydrophones.
Vowel errors in noise and in reverberation by hearing-impaired listeners
Authors: Nábělek Anna K. , Dagenais Paul A.
Published: October 2005

The effects of noise and reverberation on the identification of monophthongs and diphthongs were evaluated for ten subjects with moderate sensorineural hearing losses. Stimuli were 15 English vowels spoken in a /b–t/ context, in a carrier sentence. The original tape was recorded without reverberation, in a quiet condition. This test tape was degraded either by recording in a room with reverberation time of 1.2 s, or by adding a babble of 12 voices at a speech-to-noise ratio of 0 dB. Both types of degradation caused statistically significant reductions of mean identification scores as compared to the quiet condition. Although the mean identification scores for the noise and reverberant conditions were not significantly different, the patterns of errors for these two conditions were different. Errors for monophthongs in reverberation but not in noise seemed to be related to an overestimation of vowel duration, and there was a tendency to weight the formant frequencies differently in the reverberation and quiet conditions. Errors for monophthongs in noise seemed to be related to spectral proximity of formant frequencies for confused pairs. For the diphthongs in both noise and reverberation, there was a tendency to judge a diphthong as the beginning monophthong. This may have been due to temporal smearing in the reverberation condition, and to a higher masked threshold for changing compared to stationary formant frequencies in the noise condition.
Superior lateral pharyngeal wall movements in speech
Authors: Parush Avraham , Ostry David J.
Published: October 2005

Medial movements of the lateral pharyngeal wall at the level of the velopharyngeal port were examined by using a computerized ultrasound system. Subjects produced CVNVC sequences involving all combinations of the vowels /a/ and /u/ and the nasal consonants /n/ and /m/. The effects of both vowels on the CVN and NVC gestures (opening and closing of the velopharyngeal port, respectively) were assessed in terms of movement amplitude, duration, and movement onset time. The amplitude of both opening and closing gestures of the lateral pharyngeal wall was less in the context of the vowel /u/ than the vowel /a/. In addition, the onset of the opening gesture towards the nasal consonant was related to the identity of both the initial and the final vowels. The characteristics of the functional coupling of the velum and lateral pharyngeal wall in speech are discussed.
Sound localization of frequency-modulated sinusoids by Old World monkeys
Authors: May Brad , Moody David B. , Stebbins William C. , Norat Mary A.
Published: October 2005

Directional hearing acuity, as measured by the minimum audible angle (MAA), was determined in four Old World monkeys, Macaca radiata. The acoustic stimuli were linear changes in frequency (sweeps) for different frequency ranges and sweep rates. The sweeps ranged between 0.5 and 1.3 kHz, at two durations, 100 and 200 ms. In upsweeps which began at 0.5 kHz and were 200 ms in duration, MAA decreased as sweep rate and frequency range increased. These thresholds were compared to MAAs of sweeps which traversed the same range of frequencies but at a different rate, to MAAs of sweeps with identical rates but over different frequency ranges, and to the MAAs of downsweeps. These comparisons indicated that range, and not sweep rate, exerts the greatest effect on the MAA. Interaural phase differences derived from the upper limits of the frequency range are discussed as potential FM localization cues.
Mean path length in random acoustic fields in solids
Authors: Ivanov Dentcho V. , Burov Julian I.
Published: October 2005

An acousto-optic method is presented for measuring the reverberation times of the diffuse acoustic fields excited in crystal enclosures on the analogy of the diffuse sound fields in large auditoria. It is shown experimentally that the mean path length formula 〈l〉=4 V/S, where V and S are the volume and the surface of the enclosure, holds true in the case of a random acoustic field in a well-mixing low-loss enclosure.
The transmission of ultrasonic waves at oblique incidence through a thin layer
Authors: Dreyer John F.
Published: October 2005

An investigation of the production of birefringence in a layer showed sharp frequency peaks that were highly responsive. These peaks were also sensitive to incident angle. The variation of the frequency versus thickness of the layer identified these sharp peaks as being shear waves. A study of oblique incidence transmission was made since shear waves, at mainly perpendicular incidence, produce birefringence. The harmonic resonance equation was found to apply to the longitudinal wave transmission and indicates that the longitudinal waves in the layer are perpendicular to the interface regardless of the incident angle. The relationship of the incident angle to frequency is a modified form of Snell’s law for the longitudinal waves, and a complex modified form for the shear waves. Conversion of longitudinal waves to shear waves and shear waves to longitudinal was found to occur at low harmonics and at incident angle smaller than the first critical angle.
Effects of frequency response characteristics on speech discrimination and perceived intelligibility and pleasantness of speech for hearing-impaired listeners
Authors: Byrne Denis
Published: October 2005

Frequency response characteristics were selected for 14 hearing-impaired ears, according to six procedures. Three procedures were based on MCL measurements with speech bands of three bandwidths (1/3 octave, 1 octave, and 1 2/3 octaves). The other procedures were based on hearing thresholds, pure-tone MCLs, and pure-tone LDLs. The procedures were evaluated by speech discrimination testing, using nonsense syllables in noise, and by paired comparison judgments of the intelligibility and pleasantness of running speech. Speech discrimination testing showed significant differences between pairs of responses for only seven test ears. Nasals and glides were most affected by frequency response variations. Both intelligibility and pleasantness judgments showed significant differences for all test ears. Intelligibility in noise was less affected by frequency response differences than was intelligibility in quiet or pleasantness in quiet or in noise. For some ears, the ranking of responses depended on whether intelligibility or pleasantness was being judged and on whether the speech was in quiet or in noise. Overall, the three speech band MCL procedures were far superior to the others. Thus the studies strongly support the frequency response selection rationale of amplifying all frequency bands of speech to MCL. They also highlight some of the complications involved in achieving this aim.
Auditory spaciousness: Some further psychoacoustic analyses
Authors: Blauert Jens , Lindemann Werner
Published: October 2005

Psychoacoustic investigations have confirmed the known high correlation of auditory spaciousness and preference in concert-hall types of sound fields. Further, they have provided exploratory results which gave rise to the following interpretations: (a) Auditory spaciousness is a multidimensional perceptual attribute, predominantly caused by early lateral reflections. Low-frequency reverberation may also contribute slightly, but is sensitive with respect to individual taste. (b) All spectral components of early lateral reflections contribute to spaciousness. Spectral restriction of the reflections leads to less favorable judgments. (c) Early lateral reflections which do not contain spectral components above about 3 kHz mainly create image expansion in the front–back direction, thus adding to the sense of envelopment of the listener. If components above about 3 kHz are present, image broadening is prominent. (d) By means of a model of binaural signal processing which takes interaural arrival-time differences as well as interaural level differences into account, a quasiobjective measure of auditory spaciousness can be derived.
A systematic study of power-law decays in reverberation rooms
Authors: Kawakami Fukushi , Yamaguchi Kiminori
Published: October 2005

A space-ensemble average decay curve {〈S2(t)〉}NO, obtained in a reverberation room, shows a smooth but notable curvature at low frequencies, implying a lack of diffusion. It is closely approximated by L(t), the theoretical curve for power-law decays given by Schroeder [5th ICA, paper G31 (1965)], and can be quantitatively characterized by only two parameters for L(t), i.e., by T0 (initial decay time) and Q30 (curvature index). This allows a quantitative evaluation of the diffusion condition in the decay process, always relating it to the absorption coefficient (αrev) evaluated from the identical {〈S2(t)〉}NO. The validity of {〈S2(t)〉}NO has been verified by its application in the design of a large-scale reverberation room (570 m3) provided with a huge rotating vane (6 m in diameter) on the ceiling. A large contribution of the vane to the linearization of {〈S2(t)〉}NO, and hence, to the increase in measured αrev has been clearly established after the construction. Theoretical analysis of the effectiveness of the vane has revealed that a lack of diffusion positively bends {〈S2(t)}NO without affecting the initial decay rate. Accordingly, the conventional reverberation time T5-35 increases with the curvature Q30, inducing a negative systematic error in the αrev measurement, while T0 is almost fixed to the value for perfect diffusion, greatly reducing the error and scatter. The Q30 notation could be used for the qualification of reverberation rooms, since it refers to the diffusivity of the room itself, not of a certain specified point in it.
Air absorption of motor vehicle noise
Authors: Makarewicz Rufin
Published: October 2005

Expressions for A-weighted sound pressure and A-weighted sound exposure of a motor vehicle passby are derived. It has been assumed that geometrical spreading and atmospheric absorption are major factors, influencing propagation. The Doppler shift and convective changes of the source’s directivity, as results of motion, are analyzed.
Impulse noise: Critical review
Authors: Henderson D. , Hamernik R. P.
Published: October 2005

A review of the last 10 years of research on impulse noise reveals certain insights and perspectives on the biological and audiological effects of exposures to impulse noise. First, impulse noise may damage the cochlea by direct mechanical processes. Second, after exposure to impulse noise, hearing may recover in an erratic, nonmonotonic pattern. Third, even though the existing damage-risk criteria evaluate impulse noise in terms of level, duration, and number, often parameters such as temporal pattern, waveform, and rise time are also important in the production of a hearing loss. Fourth, the effects of impulse noise are often inconsistent with the principle of the equal energy hypothesis. Fifth, impulse noise can interact with background continuous noise to produce greater hearing loss than would have been predicted by the simple sum of the individual noises.
Geoacoustic models for the Icelandic Basin
Authors: Frisk George V. , Doutt James A. , Hays Earl E.
Published: October 2005

Geoacoustic models inferred from amplitude versus range data at 220 Hz are presented for three locations in the Icelandic Basin. The data were obtained using a deep-towed pulsed cw source and two receivers anchored near the bottom. For ranges out to 4800 m, the data were analyzed using an iteration of forward models technique in which the parabolic equation method and a Hankel transform method were used sequentially to compute acoustic fields for different bottom parameters until best fits to the data were obtained. The inferred geoacoustic models consist of a sediment layer containing a positive, linear sound-speed gradient overlying an isovelocity sub-bottom. The geoacoustic parameters include the layer thickness, the sound-speed gradient, and the sound-speed discontinuities at the water–bottom and sub-bottom interfaces. The density and attenuation of the structures are also determined. The geoacoustic models are substantiated by other types of measurements, which include piston coring, 3.5-kHz seismic profiling, and in situ sediment profiling. These additional measurements, combined with the 220-Hz results, yield a consistent picture of the geoacoustic nature of the three areas. Specifically, the highly coherent character of the 220-Hz data, the clearly visible sub-bottom layering in the 3.5-kHz records, and the low values of attenuation are related to the fine-grained nature of the sediment at two of the sites. At the third site, the presence of coarse sediment provides an explanation for the major incoherent component in the 220-Hz data, the poorly discernible layering in the 3.5-kHz records, and an anomalously high value of attenuation.
On ultrasonic methods for measurement of the nonlinear parameter B/A in fluid-like media
Authors: Cain Charles A. , Nishiyama Hisashi , Katakura Kageyoshi
Published: October 2005

A composite waveform consisting of the sum of a low-frequency pump sinusoid and a higher frequency probe results in phase modulation of the probe by the pump in nonlinear media. The phase deviation in the probe at the pump frequency can be measured directly or inferred from measurement of the magnitude of the resulting sum or difference sidebands. The phase deviation (or sideband magnitude) increases linearly with pump pressure and with the slope as a function of the nonlinearity of the medium, thus providing a means for determination of B/A.
Articulation index predictions of contextually dependent words
Authors: Dirks Donald D. , Bell Theodore S. , Rossman Reva N. , Kincaid Gail E.
Published: October 2005

Three investigations were conducted to determine the application of the articulation index (AI) to the prediction of speech performance of hearing-impaired subjects as well as of normal-hearing listeners. Speech performance was measured in quite and in the presence of two interfering signals for items from the Speech Perception in Noise test in which target words are either highly predictable from contextual cues in the sentence or essentially contextually neutral. As expected, transfer functions relating the AI to speech performance were different depending on the type of contextual speech material. The AI transfer function for probability-high items rises steeply, much as for sentence materials, while the function for probability-low items rises more slowly, as for monosyllabic words. Different transfer functions were also found for tests conducted in quiet or white noise rather than in a babble background. A majority of the AI predictions for ten individuals with moderate sensorineural loss fell within ±2 standard deviations of normal listener performance for both quiet and babble conditions.
Comparisons of frequency selectivity in simultaneous and forward masking for subjects with unilateral cochlear impairments
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

Two experiments are described in which frequency selectivity was estimated, in simultaneous and forward masking, for each ear of subjects with moderate (25–60 dB HL) unilateral cochlear hearing losses. In both experiments, the signal level was fixed for a given ear and type of masking (simultaneous or forward), and the masker level was varied to determine threshold, using an adaptive, two-alternative forced-choice procedure. In experiment I, the masker was a noise with a spectral notch centered at the signal frequency (either 1.0 or 1.5 kHz); threshold was determined as a function of notch width. Signal levels were chosen so that the noise level required at threshold for a notch width of zero was similar for the normal and impaired ear of each subject in both simultaneous and forward masking. The function relating threshold to notch width had a steeper slope for the normal ear than for the impaired ear of each subject. For the normal ears, these functions were steeper in forward masking than in simultaneous masking. This difference was interpreted as resulting from suppression. For the impaired ears, significant differences in the same direction were observed for three of the five subjects, but the differences were smaller. In experiment II, psychophysical tuning curves (PTCs) were determined in the presence of a fixed notched noise centered at the signal frequency (1.0 kHz). For the normal ears, the PTCs were sharper in forward masking than in simultaneous masking. For the impaired ears, the PTCs were similar in simultaneous and forward masking, but those in forward masking tended to be sharper at masker frequencies far removed from the signal frequency. Overall, the results suggest that suppression is reduced, but not completely absent in cases of moderate cochlear hearing loss.
Resonance scattering by elastic cylinders and their experimental verification
Authors: Tsui Chung Y. , Reid Glenn N. , Gaunaurd Guillermo C.
Published: October 2005

We present an experimental technique that verifies the theoretical predictions of the resonance scattering theory (RST) which were obtained for fluid-loaded elastic objects of separable shapes. The rationale in RST permits the separation of the ‘‘backgrounds’’ or rigid-body portions of the scattering patterns, from the ‘‘resonance’’ portions which are due to the object’s penetrability or elastic composition. For structures of separable shape, this decomposition can be theoretically accomplished for the individual modes, even when these are coupled due to the fluid loading. For general, nonseparable shapes, the decomposition holds for the summed cross sections, rather than for the individual partial waves, since in this case, the modes cannot be individually isolated. In either situation, however, the experimental method described here achieves this crucial RST decomposition of the returns by sampling the pulses scattered by the underwater structure at two temporal locations by means of suitable time-delay circuitry. One location is within the steady-state regime of the forced elastic vibration and the other is in the later transient regime of the free vibration (i.e., the ‘‘ringing’’). For the example of solid and hollow elastic cylinders in water, the technique measures the locations of the many modal resonances predicted by the RST in wide spectral bands. It also determines the skewness, amplitude, and the area under each of the resonance shapes. This goes beyond the achievements of any other experimental configuration. The background-subtracted ‘‘spectrogram’’ thus obtained is the active signature of the object which serves to characterize it uniquely. Once the method has been shown to accurately verify the theoretical RST prediction, in cases where such predictions can be generated, the technique can be used for any complex shape for which predictions may be difficult or impossible to produce. Thus the validity of the RST principles is experimentally confirmed, and an experimental method for active classification of underwater objects was devised and implemented at the place of development of the RST.
Speech intonation and focus location in matched statements and questions
Authors: Eady Stephen J. , Cooper William E.
Published: October 2005

An acoustical study of speech production was conducted to determine the manner in which the location of linguistic focus influences intonational attributes of duration and fundamental voice frequency (F0) in matched statements and questions. Speakers orally read sentences that were preceded by aurally presented stimuli designed to elicit either no focus or focus on the first or last noun phrase of the target sentences. Computer-aided acoustical analysis of word durations showed a localized, large magnitude increase in the duration of the focused word for both statements and questions. Analysis of F0 revealed a more complex pattern of results, with the shape of the F0 topline dependent on sentence type and focus location. For sentences with neutral or sentence-final focus, the difference in the F0 topline between questions and statements was evident only on the last key word, where the F0 peak of questions was considerably higher than that of statements. For sentences with focus on the first key word, there was no difference in peak F0 on the focused item itself, but the F0 toplines of questions and statements diverged quite dramatically following the initial word. The statement contour dropped to a low F0 value for the remainder of the sentence, whereas the question remained quite high in F0 for all subsequent words. In addition, the F0 contour on the focused word was rising in questions and falling in statements, regardless of focus location. The results provide a basis for work on the perception of linguistic focus.
Two- versus four-tone masking, revisited
Authors: Lutfi Robert A.
Published: October 2005

Canahl [J. Acoust. Soc. Am. 50, 471–474 (1971)] measured thresholds for a 1.0-kHz sinusoid masked either by two or by four surrounding tones. He reported four-tone masked thresholds that exceeded, by 5–7.5 dB, the energy sum of the masking produced by the individual tone pairs. The present paper reports on a series of experiments investigating the effects of several factors on this 5–7.5 dB ‘‘excess’’ masking. In each experiment, thresholds for a 1.0-kHz 250-ms sinusoid were measured as a function of the overall level of two or four equal amplitude sinusoids with frequencies arithmetically centered around 1.0 kHz. For conditions similar to those of the Canahl experiment, 5–6 dB of excess masking was obtained independent of the level of the masking tones. Randomly varying overall level across presentations had no effect on the excess masking. The excess masking was reduced or eliminated when the masking tones were generated using an amplitude modulation technique, when they were gated on and off with the signal, or when their waveshapes were fixed across trials. Canahl’s result may reflect listeners’ ability to detect the signal as a change in the waveshape of the multitone masker.
Multiple scattering of compressional and shear waves by fiber-reinforced composite materials
Authors: Varadan V. K. , Ma Y. , Varadan V. V.
Published: October 2005

A multiple scattering formalism using a T matrix to characterize the response of a single fiber to an incident wave is presented to describe P- and SV-wave propagation in a fiber-reinforced composite. A convenient numerical procedure is then developed to compute the effective elastic moduli, attenuation, and phase velocity as a function of frequency and fiber concentration.
Historical comment on a modification of the Galerkin method
Authors: Gottlieb H. P. W.
Published: October 2005

It is noted that a simple form of the method utilized by Laura et al., ‘‘A modification of the Galerkin method and the solution of the Helmholtz equation in regions of complicated boundary shape’’ [J. Acoust. Soc. Am. 77, 1960–1962 (1985)] has already appeared in Rayleigh’s classical treatise on the theory of sound [J. W. S. Rayleigh, The Theory of Sound, Vol. I (Dover, New York, 1945)].