bluuebunny/crossref_metadata_2025 huggingface dataset:
To Devolve or Not To Devolve? Welfare Reform in the States
Authors: Gainsborough Juliet F.
Published: October 2003

This article analyzes variation in the degree to which states have responded to the devolution of welfare at the federal level by devolving authority over welfare policy to local government. I find that to the extent that states have devolved authority to lower levels of government, they tend to be states that already had a high degree of involvement of local government in welfare provision. In states without this record of local government involvement, the devolution that has occurred has not generated greater involvement of local government, but rather responsibility has been devolved to regional entities with ties to workforce development and with a substantial degree of business involvement. As states gain increasing authority over a redistributive policy, they may begin to treat it as a subset of a larger developmental policy—workforce development.
The Politics of Employee Discharge: Triggering, Representation, and Venue
Authors: Wallihan James
Published: October 2003

This article analyzes the failed effort to reform employment termination policy in the United States during the 1980s and early 1990s using the procedures of the National Conference of Commissioners on Uniform State Laws. This effort sought to replace the common law doctrine of employment‐at‐will with state “just cause” arbitration statutes that would grant limited rights to discharged employees while capping the remedies available to prevailing claimants. The resulting Model Employment Termination Act and the failure of states to adopt it are explained by structural and strategic factors, including movement of the judicial “trigger,” the configuration and representation of interests, and the choice of policy venue.
Policy Learning and Uncertainty: The Case of Pension Reform in Estonia and Latvia
Authors: Tavits Margit
Published: October 2003

This article addresses the question, under what conditions does the need for urgent solutions to societal problems lead to transferring a policy designed for another political system? The argument developed in the article is based on the theoretical frameworks of learning and historical institutionalism. I have posited that the urgent need for quick solutions to existing policy problems is a catalyst for policy transfer only if there is not enough prior successful experience with self‐designed policy reforms. The theoretical argument is tested using the case of pension reform in Estonia and Latvia, which proves to be difficult to explain with the arguments in the existing policy transfer literature.
Religion, Policy, and Secrecy: The Latter Day Saints and Masons
Authors: Rich Paul , Merchant David
Published: October 2003

On a vanished secret order: “Had politics, as in Masonry, been its main object, it would have held on with tenacity to its principles, as to the threads of life, and, disregarding its departure from sound morals, or patriotism, would still have contended, with the infatuation of a Mormonite, for the enjoyment, in secret, of that which in the eye of the public would overwhelm its members in confusions.”“A Traveller in the United States”, A Ritual and Illustrations of Free‐Masonry and the Orange and Odd Fellows’ Societies, Accompanied by Numerous Engravings, and a Key to the Phi Beta Kappa, S. Thrne, Devon (Shebbear, near Hatherleigh, England), 1835, 251.
Beampattern control of a microphone array to minimize secondary source contamination
Authors: Jordan Peter , Fitzpatrick John A. , Meskell Craig
Published: October 2003

A null-steering technique is adapted and applied to a linear delay-and-sum beamformer in order to measure the noise generated by one of the propellers of a 18 scale twin propeller aircraft model. The technique involves shading the linear array using a set of weights, which are calculated according to the locations onto which the nulls need to be steered (in this case onto the second propeller). The technique is based on an established microwave antenna theory, and uses a plane-wave, or far field formulation in order to represent the response of the array by an nth-order polynomial, where n is the number of array elements. The roots of this polynomial correspond to the minima of the array response, and so by an appropriate choice of roots, a polynomial can be generated, the coefficients of which are the weights needed to achieve the prespecified set of null positions. It is shown that, for the technique to work with actual data, the cross-spectral matrix must be conditioned before array shading is implemented. This ensures that the shading function is not distorted by the intrinsic element weighting which can occur as a result of the directional nature of aeroacoustic systems. A difference of 6 dB between measurements before and after null steering shows the technique to have been effective in eliminating the contribution from one of the propellers, thus providing a quantitative measure of the acoustic energy from the other.
Time-frequency analyses of transient-evoked stimulus-frequency and distortion-product otoacoustic emissions: Testing cochlear model predictions
Authors: Konrad-Martin Dawn , Keefe Douglas H.
Published: October 2003

Time-frequency representations (TFRs) of otoacoustic emissions (OAEs) provide information simultaneously in time and frequency that may be obscured in waveform or spectral analyses. TFRs were applied to transient-evoked stimulus-frequency (SF) and distortion-product (DP) OAEs to test cochlear model predictions. SFOAEs and DPOAEs were elicited in 18 normal-hearing subjects using gated tones and tone pips. Synchronous spontaneous (SS) OAEs were measured to assess their contributions to SFOAEs and DPOAEs. A common form of TFR of measured OAEs was a collection of frequency-specific components often aligned with SSOAE sites, with each component characterized by one or more brief segments or a single long-duration segment. The spectral envelope of evoked OAEs differed from that of the evoking stimulus. Strong emission regions or cochlear “hot spots” were detected, and sometimes accounted for OAE energy observed outside the stimulus bandwidth. Contributions of hot spots and multiple internal reflections to the OAE, and differences between measured and predicted OAE spectra, increased as stimulus level decreased, consistent with level-dependent changes in the estimated cochlear reflectance. Suppression and frequency-pulling effects between components were observed. A recursive formulation was described for the linear coherent reflection emission theory [Zweig and Shera, J. Acoust. Soc. Am. 98, 2018–2047 (1995)] that is well suited for time-domain calculations.
Behavioral criterion quantifying the edge-constrained effects on foams in the standing wave tube
Authors: Pilon Dominic , Panneton Raymond , Sgard Franck
Published: October 2003

The influence of mounting conditions on the measurement of the sound absorption coefficient is investigated. More specifically, the effects of a circumferential edge constraint applied on elastic foams in a standing wave tube are studied. The objective is to identify the foams for which it is possible to measure the theoretical absorption coefficient using the tube. This identification relies on the evaluation of a new parameter, the Frame Acoustical Excitability (FAE), based on the foams’ physical properties. In order to quantify the difference between the measured and theoretical absorptions, a linear correlation coefficient is evaluated for a wide range of foams with various sample sizes. The calculated correlation coefficients are then sorted in terms of the FAE. It is shown that as the value of FAE increases, the difference between the measured and theoretical absorption coefficients becomes more significant. A critical value of FAE, below which the theoretical absorption can be efficiently measured using the tube, is established. Through the use of this elasto-acoustic criterion, an experimenter can make an educated guess as to which absorption is measured with the tube: the theoretical absorption or one that is affected by either the edge constraint or the sample’s dimensions.
Frequency response of nonlinear oscillations of air column in a tube with an array of Helmholtz resonators
Authors: Sugimoto N. , Masuda M. , Hashiguchi T.
Published: October 2003

Nonlinear cubic theory is developed to obtain a frequency response of shock-free, forced oscillations of an air column in a closed tube with an array of Helmholtz resonators connected axially. The column is assumed to be driven by a plane piston sinusoidally at a frequency close or equal to the lowest resonance frequency with its maximum displacement fixed. By applying the method of multiple scales, the equation for temporal modulation of a complex pressure amplitude of the lowest mode is derived in a case that a typical acoustic Mach number is comparable with the one-third power of the piston Mach number, while the relative detuning of a frequency is comparable with the quadratic order of the acoustic Mach number. The steady-state solution gives the asymmetric frequency response curve with bending (skew) due to nonlinear frequency upshift in addition to the linear downshift. Validity of the theory is checked against the frequency response obtained experimentally. For high amplitude of oscillations, an effect of jet loss at the throat of the resonator is taken into account, which introduces the quadratic loss to suppress the peak amplitude. It is revealed that as far as the present check is concerned, the weakly nonlinear theory can give quantitatively adequate description up to the pressure amplitude of about 3% to the equilibrium pressure.
Nonlinear characteristics of single-reed instruments: Quasistatic volume flow and reed opening measurements
Authors: Dalmont Jean-Pierre , Gilbert Joël , Ollivier Sébastien
Published: October 2003

A wind instrument can be described as a closed feedback loop made up of a linear passive element—the resonator—and a lumped nonlinear element—the mouthpiece. A method for measuring the nonlinear characteristics of the mouthpiece—nonlinear flow relationship—in static condition is given. An artificial mouth is used in which the volume flow is deduced from the pressure difference between both sides of a constriction (orifice) which takes place in the resonator. The orifice also plays the role of a nonlinear absorber, thwarting possible reed oscillations. This allows the measurement of the complete characteristics. In addition, the reed opening is measured using an optical device. Results are compared to a model in which the reed is reduced to its stiffness and the flow is governed by the Bernoulli equation. It is shown that the reed stiffness and the ratio of the effective surface of the jet and the reed opening are constant in a large range of openings. Standard range values of embouchure parameters are given.
Evaluation of rosette infrasonic noise-reducing spatial filters
Authors: Hedlin Michael A. H. , Alcoverro Benoit , D’Spain Gerald
Published: October 2003

This paper presents results from recent tests of rosette infrasonic noise-reducing spatial filters at the Pinon Flat Observatory in southern California. Data from 18- and 70-m aperture rosette filters and a reference port are used to gauge the reduction in atmospheric wind-generated noise levels provided by the filters and to examine the effect of these spatial filters on spatially coherent acoustic signals in the 0.02- to 10-Hz band. At wind speeds up to 5.5 m/s, the 18-m rosette filter reduces wind noise levels above 0.2 Hz by 15 to 20 dB. Under the same conditions, the 70-m rosette filter provides noise reduction of up to 15 to 20 dB between 0.02 and 0.7 Hz. Standing wave resonance inside the 70-m filter degrades the reception of acoustic signals above 0.7 Hz. The fundamental mode of the resonance, 15 dB above background, is centered at 2.65-Hz and the first odd harmonic is observed at 7.95 Hz in data from the large filter. Analytical simulations accurately reproduce the noise reduction and resonance observed in the 70-m filter at all wind speeds above 1.25 m/s. Resonance theory indicates that internal reflections that give rise to the resonance observed in the passband are occurring at the summing manifolds, and not at the inlets. Rosette filters are designed for acoustic arrivals with infinite phase velocity. The plane-wave response of the 70-m rosette filter has a strong dependence on frequency above 3.5 Hz at grazing angles of less than 15° from the horizontal. At grazing angles, complete cancellation of the signal occurs at 5 Hz. Theoretical predictions of the phase and amplitude response of 18- and 70-m rosette filters, that take into account internal resonance and time delays between the inlets, compare favorably with observations derived from a cross-spectral analysis of signals from the explosion of a large bolide.
High-sensitivity photoacoustic leak testing
Authors: Huang Eric , Dowling David R. , Whelan Timothy , Spiesberger John L.
Published: October 2003

The photoacoustic effect may be exploited for the detection and localization of gas leaks from otherwise sealed components. The technique involves filling the test component with a tracer gas, and radiating the component to produce photoacoustic sound from any leak site where tracer gas is present. This paper describes demonstration experiments utilizing 10.6-μ radiation from a carbon-dioxide laser and sulfur hexafluoride as a tracer gas for photoacoustic leak testing at leak rates between 6×10−5 cm3/s (1 cm3 in 4.6 h) and 5×10−9 cm3/s (1 cm3 in 6.3 years). The technique may reach or exceed the capabilities of the most sensitive commercial leak test systems using helium mass-spectrometers. In addition, comparison of the measured results to a simple scaling law suggests that tracer gas cloud geometry influences the photoacoustic signal amplitude.
Measurement and reproduction accuracy of computer-controlled grand pianos
Authors: Goebl Werner , Bresin Roberto
Published: October 2003

The recording and reproducing capabilities of a Yamaha Disklavier grand piano and a Bösendorfer SE290 computer-controlled grand piano were tested, with the goal of examining their reliability for performance research. An experimental setup consisting of accelerometers and a calibrated microphone was used to capture key and hammer movements, as well as the acoustic signal. Five selected keys were played by pianists with two types of touch (“staccato” and “legato”). Timing and dynamic differences between the original performance, the corresponding MIDI file recorded by the computer-controlled pianos, and its reproduction were analyzed. The two devices performed quite differently with respect to timing and dynamic accuracy. The Disklavier’s onset capturing was slightly more precise (±10 ms) than its reproduction (−20 to +30 ms); the Bösendorfer performed generally better, but its timing accuracy was slightly less precise for recording (−10 to 3 ms) than for reproduction (±2 ms). Both devices exhibited a systematic (linear) error in recording over time. In the dynamic dimension, the Bösendorfer showed higher consistency over the whole dynamic range, while the Disklavier performed well only in a wide middle range. Neither device was able to capture or reproduce different types of touch.
Seabed reflection measurement uncertainty
Authors: Holland Charles W.
Published: October 2003

The seabed reflection coefficient is a fundamental property of the ocean waveguide. Measurements of the frequency and angular dependence of the reflection coefficient can provide information about the geoacoustic properties of the seabed or can be used as an input to propagation models. The uncertainty of the measurements must be known in order to determine prediction uncertainties for the acoustic field and/or the geoacoustic properties. Analysis indicates that the reflection measurements have a standard deviation from ±0.5–1 dB at full angular resolution depending on frequency and experiment geometry. The dominant contribution to the error is source amplitude variability, and a new processing approach was developed that reduces the error for frequencies above a few hundred Hz. Further reduction in the uncertainty can be obtained by averaging in angle, for example, a ±1° angle averaging leads to a standard deviation of less than ±0.5 dB. Errors in the angle estimate are a few tenths of a degree from 0–34° grazing angle: the crucial angular range for predicting long-range propagation or for geoacoustic property inversion.
An approximate transfer function for the dual-resonance nonlinear filter model of auditory frequency selectivity
Authors: Lopez-Poveda Enrique A.
Published: October 2003

The dual-resonance nonlinear filter [Meddis et al., J. Acoust. Soc. Am. 109, 2852–2861 (2001)] was presented as a digital time-domain algorithm to model nonlinear auditory frequency selectivity. This report extends previous work by presenting an approximate analytic transfer function that allows calculating and analyzing its level-dependent frequency-domain response. The transfer function is derived on the assumption that the filter behaves linearly for any given input amplitude. It matches accurately the response (gain and phase) of the digital filter for tones. Practical uses for the transfer function are suggested.
Passively minimizing structural sound radiation using shunted piezoelectric materials
Authors: Bulent Ozer M. , Royston Thomas J.
Published: October 2003

Two methods are presented to determine optimal inductance and resistance values of the shunt circuit across a piezoceramic material, which is bonded to a simply supported plate in order to minimize sound radiation from the plate. The first method (DH) makes use of den Hartog’s damped vibration absorber principle. The second method (SM) uses the Sherman Morrison matrix inversion theorem. The effectiveness of each method is compared with regard to minimizing total acoustic sound-power radiation and acoustic pressure at a point. Optimization algorithms and case studies are presented using a linearized model for the piezoceramic and using a nonlinear model for the piezoceramic that accounts for the inherent dielectric hysteresis. Case studies demonstrate that the second method (SM) results in superior performance, under both linear and nonlinear system assumptions. Studies also illustrate that, if the nonlinearity in the system is significant, it must be incorporated in the optimization process.
Inversion for sediment geoacoustic properties at the New England Bight
Authors: Potty Gopu R. , Miller James H. , Lynch James F.
Published: October 2003

This article discusses inversions for bottom geoacoustic properties using broadband acoustic signals obtained from explosive sources. Two different inversion schemes for estimating the compressional wave speeds and attenuation are presented in this paper. In addition to these sediment parameters, source–receiver range is also estimated using the arrival time data. The experimental data used for the inversions are SUS charge explosions acquired on a vertical hydrophone array during the Shelf Break Primer Experiment conducted south of New England in the Middle Atlantic Bight in August 1996. The modal arrival times are extracted using a wavelet analysis. In the first inversion scheme, arrival times corresponding to various modes and frequencies from 10 to 200 Hz are used for the inversion of compressional wave speeds. A hybrid inversion scheme based on a genetic algorithm (GA) is used for the inversion. In an earlier study, Potty et al. [J. Acoust. Soc. Am. 108(3), 973–986 (2000)] have used this hybrid scheme in a range-independent environment. In the present study results of range-dependent inversions are presented. The sound speeds in the water column and bathymetry are assumed range dependent, whereas the sediment compressional wave speeds are assumed range independent. The variations in the sound speeds in the water column are represented using empirical orthogonal functions (EOFs). The replica fields corresponding to the unknown parameters were constructed using adiabatic theory. In the second inversion scheme, modal attenuation coefficients are calculated using modal amplitude ratios. The ratios of the modal amplitudes are also calculated using time-frequency diagrams. A GA-based inversion scheme is used for this search. Finally, as a cross check, the computed compressional wave speeds along with the modal arrival times were used to estimate the source–receiver range. The inverted sediment properties and ranges are seen to compare well with in situ measurements and historical data.
Spectral pattern, harmonic relations, and the perceptual grouping of low-numbered components
Authors: Roberts Brian , Brunstrom Jeffrey M.
Published: October 2003

Mistuning a harmonic increases its salience and produces an exaggerated change in its pitch. The effects on component grouping of spectral pattern, global pitch, and local harmonicity were explored using these phenomena. Stimuli were either harmonic (F0=200 Hz) or frequency shifted by 25% of F0. Component 1 or 2 was replaced by one of a set of sinusoidal probes in the same spectral region. Listeners either matched the probe pitch by adjusting the frequency of a pure tone (experiments 1 and 3) or matched the probe loudness by adjusting the level of a tone of identical frequency (experiment 2). Probe positions corresponding to greatest perceptual fusion were estimated from the variations in pitch shift and loudness across frequency. Both measures gave similar estimates. For harmonic stimuli, fusion was greatest at harmonic values. For shifted stimuli, fusion was greatest close to the suboctave (225 Hz) and the frequency (450 Hz) of component 2. The latter value moved downwards to near 433 Hz (2:3 ratio with component 3) when component 1 was removed. Together, these results indicate that the lowest component of a shifted complex is grouped by local harmonicity, whereas the higher components are grouped by common spectral spacing. Global pitch did not influence component grouping.
Scale-model study of the effectiveness of highway noise barriers
Authors: Busch Todd , Hodgson Murray , Wakefield Clair
Published: October 2003

A scale-model facility was developed to test the insertion loss (IL) of highway noise barriers. Three model materials were utilized to simulate packed-earth berms and ground (expanded polystyrene), vertical walls (dense polystyrene), and roadways (varnished particleboard). Thirty-eight noise-barrier configurations were tested and used to compare how IL varied with changes to the barrier profile for walls, berms, and combinations of walls and berms for receivers at a representative, highway-adjacent location. The atmospheric conditions were assumed to be homogeneous and nonrefracting. Changes of barrier surface impedance were also assessed. A highway line source was simulated by positioning both an air-jet point source and a receiver microphone at a series of equally spaced points, in order to form an array of source-receiver measurement pairs making differing angles of propagation to the noise-barrier crest line. The IL measurement results are presented in unweighted third-octave bands. In addition, total A-weighted insertion losses (ILA) were obtained by applying an A-weighted, traffic-noise spectrum. When a berm was modeled with surface impedance closely matching that of packed earth, it was found that walls outperformed berms by 1 to 2 dBA. When the surface impedance of a berm was modeled to be acoustically soft, the ILA increased sufficiently to favor berms by about 2 dBA. The result for an acoustically soft berm does not support the long-standing practice of assuming that earth berms outperform walls by 3 dBA, but is consistent with the performance predicted by newer prediction algorithms. When the slopes of berms were made shallower, the IL generally decreased for a berm alone, but generally increased in cases with a wall atop the berm.
Random walk approach to wave propagation in wedges and cones
Authors: Budaev Bair V. , Bogy David B.
Published: October 2003

Two- and three-dimensional Helmholtz equations in wedge-shaped and conical domains are addressed by the random walk method. The solutions of the Dirichlet problems in such domains are represented as mathematical expectations of specified functionals on trajectories of multidimensional random motions whose radial components run in a complex space while the angular components remain real valued. This technique is applied to the Sommerfeld problem of diffraction by a semi-infinite screen which is explicitly solved here in the probabilistic form. The numerical results confirm the efficiency of the random walk approach to the analysis of wave propagation.
Objective measures of breathy voice quality obtained using an auditory model
Authors: Shrivastav Rahul , Sapienza Christine M.
Published: October 2003

While several acoustic measures have been proposed to quantify listener ratings of breathy voice quality, most have failed to give a consistent and high correlation with perceptual ratings of breathiness. One reason for these limitations is that most acoustic measures do not address the nonlinear processes that occur in the peripheral auditory system during the auditory perceptual process. It was hypothesized that modeling such nonlinear events during signal processing may provide objective parameters that better correspond to perceptual ratings of breathy voice quality. Ten listeners rated 27 voice stimuli using a five-point rating scale. Acoustic measures were determined from these stimuli and were selected based on their history of having a moderate to strong correlation to perceptual ratings of breathiness. The stimuli were also analyzed using an auditory model proposed by Moore, Glasberg, and Baer [J. Audio Eng. Soc. 45(4), 224–239 (1997)], and new measures were calculated from the output of this model. These measures included the partial loudness of the signal and the loudness of the aspiration noise. Measures obtained from the output of the auditory model were found to account for a high amount of variance in the perceptual ratings of breathiness.
Hearing protection: Surpassing the limits to attenuation imposed by the bone-conduction pathways
Authors: Berger Elliott H. , Kieper Ronald W. , Gauger Dan
Published: October 2003

With louder and louder weapon systems being developed and military personnel being exposed to steady noise levels approaching and sometimes exceeding 150 dB, a growing interest in greater amounts of hearing protection is evident. When the need for communications is included in the equation, the situation is even more extreme. New initiatives are underway to design improved hearing protection, including active noise reduction (ANR) earplugs and perhaps even active cancellation of head-borne vibration. With that in mind it may be useful to explore the limits to attenuation, and whether they can be approached with existing technology. Data on the noise reduction achievable with high-attenuation foam earplugs, as a function of insertion depth, will be reported. Previous studies will be reviewed that provide indications of the bone-conduction (BC) limits to attenuation that, in terms of mean values, range from 40 to 60 dB across the frequencies from 125 Hz to 8 kHz. Additionally, new research on the effects of a flight helmet on the BC limits, as well as the potential attenuation from deeply inserted passive foam earplugs, worn with passive earmuffs, or with active-noise reduction (ANR) earmuffs, will be examined. The data demonstrate that gains in attenuation exceeding 10 dB above the head-not-covered limits can be achieved if the head is effectively shielded from acoustical stimulation.
Consistency and accuracy of perturbative inversion methods for group travel time data
Authors: Sperry Brian J. , McDonald B. Edward , Baggeroer Arthur B.
Published: October 2003

Perturbation theory for ocean acoustic modal group speed responses to small environmental changes is investigated with regard to its applicability to ocean acoustic tomography. Assuming adiabaticity, the inverse problem for each vertical eigenmode is an integral equation whose kernel involves the eigenfunction and its frequency derivative. A proof is given for the equivalence of two dissimilar forms of the integral equation. Numerical examples are given for the inversion kernel for four types of sound-speed profiles, and then the parameter range (amplitude and scale size) in which perturbation theory is accurate is examined. It is found that the range of validity is determined not only by the amplitude of the perturbations, but also by their vertical scale size.
Development of an acoustic levitation technique to obtain foam material properties
Authors: Liu Li
Published: October 2003

Aqueous foam is an impermanent form of matter in which a kind of gas, often air, is dispersed as an agglomeration of bubbles that are separated from each other by films of liquid. Foams are of tremendous economical importance in industry. Foam material properties are sensitive functions of the void fraction. A “wet foam” is a bubbly liquid that cannot support shearing motion; inside the wet foam the individual bubbles are free to move around. A “transitional” or “critical foam” is composed of bubbles whose dynamics are strongly interacting and whose surfaces may be in mechanical contact with each other. Finally, a “dry foam” is composed of bubbles who have a fixed position in a lattice for low to moderate straining rates. An acoustic levitation technique is developed which provides a noncontact means of estimating the properties of the foam by acoustically levitating aqueous foam drops and exciting their spheroidal modes oscillation. Assuming linear oscillation of foam drops, experimental data for frequency and damping show good agreement with a bubble dynamics-based theoretical model.

Thesis advisor: R. Glynn Holt

Copies of this thesis may be obtained by contacting the advisor, Glynn Holt, Dept. of Aerospace and Mechanical Engineering, Boston University, 110 Cummington St., Boston, MA 02215. E-mail address: rgholt@bu.edu
Numerical simulation of the excitation of a Helmholtz resonator by a grazing flow
Authors: Mallick S. , Shock R. , Yakhot V.
Published: October 2003

The process of noise generation in a flow-excited Helmholtz resonator involves strong interaction between a time-dependent fluid flow and acoustic resonance. Quantitative prediction of this effect, requiring accurate prediction of time-dependent features of a flow over complex three-dimensional bodies, turbulence modeling, compressibility and Mach number effects, is one of the major challenges to computational fluid dynamics. In this paper a numerical procedure based on the lattice kinetic equation, combined with the RNG turbulence model, is applied to describe a well-controlled experiment on acoustic resonance excitation by a grazing flow [Nelson et al., J. Sound Vib. 78, 15–27 (1981)]. The achieved agreement between numerical and physical experiments is very good. The simulations reveal a universality transformation enabling comparison of the data for different inlet conditions.
Effects of contrast between onsets of speech and other complex spectra
Authors: Coady Jeffry A. , Kluender Keith R. , Rhode William S.
Published: October 2003

Previous studies using speech and nonspeech analogs have shown that auditory mechanisms which serve to enhance spectral contrast contribute to perception of coarticulated speech for which spectral properties assimilate over time. In order to better understand the nature of contrastive auditory processes, a series of CV syllables varying acoustically in F2-onset frequency and perceptually from /ba/ to /da/ was identified following a variety of spectra including three-peak renditions of [e] and [o], one-peak simulations of only F2, and spectral complements of these spectra for which peaks are replaced with troughs. Results for three-versus one-peak (or trough) precursor spectra were practically indistinguishable, suggesting that effects were spectrally local and not dependent upon perception of precursors as speech. Effects of complementary (trough) spectra had complementary effects on perception of following stops; however, effects for spectral complements were particularly dependent upon the interval between precursor and CV onsets. Results from these studies cannot be explained by simple masking or adaptation of suppression. Instead, they provide evidence for the existence of processes that selectively enhance contrast between onset spectra of neighboring sounds, and these processes are relevant for perception of connected speech.
Physiological vulnerability of distortion product otoacoustic emissions from the amphibian ear
Authors: van Dijk Pim , Narins Peter M. , Mason Matthew J.
Published: October 2003

The physiological vulnerability of distortion product otoacoustic emissions (DPOAEs) was investigated in the leopard frog, Rana pipiens pipiens. For each frog, DPOAEs were recorded from the amphibian and the basilar papillae. Measurements were taken before and after either the arrest of oxygen supply due to cardioectomy, or the destruction of the central nervous system (CNS). DPOAEs in response to high-level stimuli (>75 dB SPL) were rather robust to these insults during the first two hours post surgery. In contrast, DPOAE amplitudes in response to low-level stimuli (<75 dB SPL) decreased significantly. On average, low-level emissions from the amphibian papilla disappeared within 6 min for cardioectomy, and after 13 min for CNS destruction. In the basilar papilla, low-level DPOAEs disappeared more slowly: on average after 34 min following cardioectomy, and after 58 min for CNS destruction. The difference in physiological vulnerability between low- and high-level emissions is similar to that in mammals and a lizard. The difference between the DPOAE decay rate of the frog’s amphibian and basilar papillae suggests important differences between the hearing mechanisms of the papillae.
Phase effects in masking: Within- versus across-channel processes
Authors: Alcántara José I. , Moore Brian C. J. , Glasberg Brian R. , Wilkinson Alex J. K. , Jorasz Urszula
Published: October 2003

The effects of bandwidth and component phase on masking were investigated using 200-ms narrowband (1-ERBN) and broadband (5-ERBN) cosine-phase (CP) and random-phase (RP) harmonic complex maskers, centered at 1 or 6 kHz. A continuous notched-noise was used to restrict off-frequency listening. The masker fundamental frequency (F0) was 25 Hz. In experiment 1, thresholds were measured for sinusoidal signals at 1 and 6 kHz, gated with the maskers. Thresholds were lower in the CP than in the RP masker, for both bandwidths, but the effect was markedly greater for the wider bandwidth. For the CP maskers, thresholds were markedly lower for the 5-ERBN than for the 1-ERBN bandwidth; for the RP maskers, there was a small effect in the opposite direction. Experiment 2 used 1- and 6-kHz CP maskers. The masker components in the ERBN around the signal frequency were presented to one ear, and the remaining components were presented contralaterally. Thresholds were much higher than when all components were presented to the same ear, and were higher than for the 1-ERBN masker alone, suggesting that the low thresholds for broadband monaural presentation do not depend on “high level” across-channel comparisons. Simultaneous masked thresholds could be predicted well using a model based on a simulated auditory filter, a level-dependent compressive nonlinearity, and a sliding temporal integrator; it was not necessary to assume the involvement of across-channel processes or of selective listening in the masker dips.
Calculating the micrometeorological influences on the speed of sound through the atmosphere in forests
Authors: Tunick Arnold
Published: October 2003

A key element in determining point-to-point acoustic transmission within and above forests is modeling the variation (with height above ground) of the effective speed of sound. Effective speed of sound is readily derived from estimates of air temperature, relative humidity, and wind velocity. However, meteorological models for the forest canopy vary from comparatively simple to academically complex, requiring different amounts and numbers of inputs and computer capabilities. In addition, not all canopy profile models are suitable for acoustic applications. In this paper, a meteorological computer model for the forest canopy is developed to derive continuous profiles of effective sound speed from the ground to 3h, where h is the height of the canopy. In turn, these profiles are used to make some initial approximations of short-range acoustic transmission loss through a uniform forest stand for typical clear sky, midday atmospheric conditions. Also, a radiative transfer and energy budget algorithm is incorporated into the model to obtain the appropriate heat source profile for any time of day. Thus, physics-based micrometeorology is coupled to acoustics for future applications of acoustic information in forest environments.
On the assessment of shooting sounds: Loudness-level weightings versus A- and C-weighted sound exposure levels (L)
Authors: Vos Joos , Geurtsen Frank W. M.
Published: October 2003

As an alternative to the A-weighted sound exposure level (ASEL) Schomer et al. [J. Acoust. Soc. Am. 110, 2390–2397 (2001)] used the equal-loudness level contours as a dynamic filter to determine the loudness-level-weighted sound exposure level (LLSEL). From their analyses they concluded that the LLSEL better orders and assesses traffic and impulsive sounds than the ASEL does. In the present study LLSELs were determined for a great variety of shooting sounds investigated by Vos [J. Acoust. Soc. Am. 109, 244–253 (2001)]. It was concluded that for the assessment of shooting sounds, the use of loudness-level weightings is less adequate than the use of A- and C-weighted sound exposure levels as proposed in Vos’s article.
A phenomenological model for the responses of auditory-nerve fibers. II. Nonlinear tuning with a frequency glide
Authors: Tan Qing , Carney Laurel H.
Published: October 2003

A computational model was developed to simulate the responses of auditory-nerve (AN) fibers in cat. The model’s signal path consisted of a time-varying bandpass filter; the bandwidth and gain of the signal path were controlled by a nonlinear feed-forward control path. This model produced realistic response features to several stimuli, including pure tones, two-tone combinations, wideband noise, and clicks. Instantaneous frequency glides in the reverse-correlation (revcor) function of the model’s response to broadband noise were achieved by carefully restricting the locations of the poles and zeros of the bandpass filter. The pole locations were continuously varied as a function of time by the control signal to change the gain and bandwidth of the signal path, but the instantaneous frequency profile in the revcor function was independent of sound pressure level, consistent with physiological data. In addition, this model has other important properties, such as nonlinear compression, two-tone suppression, and reasonable Q10 values for tuning curves. The incorporation of both the level-independent frequency glide and the level-dependent compressive nonlinearity into a phenomenological model for the AN was the primary focus of this work. The ability of this model to process arbitrary sound inputs makes it a useful tool for studying peripheral auditory processing.
A quasi-glottogram signal
Authors: Kochanski Greg , Shih Chilin
Published: October 2003

A novel, noninvasive experiment is proposed that reliably shows the strength of glottal oscillations. The quasi-glottogram (QGG) signal is generated from a microphone array that is trained to approximate the electroglottogram signal. The QGG may be useful to improve estimates of whether speech is voiced, to quantify partial voicing, and to reduce the phoneme effect when measuring the amplitude of speech signals. The technique is well adapted to the generation of text-to-speech systems, as it allows an estimate of the glottal flow during undisturbed, natural speech. For prosody studies, it can be used to provide an estimate of amplitude which is relatively unaffected by changes in phonemes, and is at least as reliable as standard estimators of amplitude.
Perceptual segregation of competing speech sounds: The role of spatial location
Authors: Drennan Ward R. , Gatehouse Stuart , Lever Catherine
Published: October 2003

Culling and Summerfield [J. Acoust Soc. Am. 92, 785–797 (1995)] showed that listeners could not use ongoing interaural time differences (ITDs) to achieve source segregation. The present experiments tested a free-field analog of their experiment. The stimuli consisted of narrow bands of noise, pairs of which represented the first and second formants of the whispered vowels “ar,” “ee,” “er,” and “oo.” A target noise-band pair (vowel) was presented at various angles on the listeners’ left while a complementary distracter was presented on the listeners’ right. Listeners correctly identified the target vowel in the free-field well above chance. Performance remained well above chance in headphone experiments that retained spatial cues but eliminated reverberations and head movements. The full range of cues that normally determine perceived spatial location provided sufficient information for segregation. Further experiments, which systematically evaluated the contribution of these cues in isolation and in combination, showed that some listeners, following training, exhibited the ability to segregate based on ongoing ITDs alone. Substantial individual differences were observed. The results show that listeners can use spatial cues to segregate simultaneous sound sources.
Sound absorption by suspensions of nonspherical particles: Measurements compared with predictions using various particle sizing techniques
Authors: Richards Simon D. , Leighton Timothy G. , Brown Niven R.
Published: October 2003

Knowledge of the particle size distribution is required in order to predict ultrasonic absorption in polydisperse particulate suspensions. This paper shows that the method used to measure the particle size distribution can lead to important differences in the predicted absorption. A reverberation technique developed for measuring ultrasonic absorption by suspended particles is used to measure the absorption in suspensions of nonspherical particles. Two types of particulates are studied: (i) kaolin (china clay) particles which are platelike in form; and (ii) calcium carbonate particles which are more granular. Results are compared to theoretical predictions of visco-inertial absorption by suspensions of spherical particles. The particle size distributions, which are required for these predictions, are measured by laser diffraction, gravitational sedimentation and centrifugal sedimentation, all of which assume spherical particles. For a given sample, each sizing technique yields a different size distribution, leading to differences in the predicted absorption. The particle size distributions obtained by gravitational and centrifugal sedimentation are reinterpreted to yield a representative size distribution of oblate spheroids, and predictions for absorption by these spheroids are compared with the measurements. Good agreement between theory and measurement for the flat kaolin particles is obtained, demonstrating that these particles can be adequately represented by oblate spheroids.
Acoustic wave propagation in bovine cancellous bone: Application of the Modified Biot–Attenborough model
Authors: Lee Kang Il , Roh Heui-Seol , Yoon Suk Wang
Published: October 2003

Acoustic wave propagation in bovine cancellous bone is experimentally and theoretically investigated in the frequency range of 0.5–1 MHz. The phase velocity, attenuation coefficient, and broadband ultrasonic attenuation (BUA) of bovine cancellous bone are measured as functions of frequency and porosity. For theoretical estimation, the Modified Biot–Attenborough (MBA) model is employed with three new phenomenological parameters: the boundary condition, phase velocity, and impedance parameters. The MBA model is based on the idealization of cancellous bone as a nonrigid porous medium with circular cylindrical pores oriented normal to the surface. It is experimentally observed that the phase velocity is approximately nondispersive and the attenuation coefficient linearly increases with frequency. The MBA model predicts a slightly negative dispersion of phase velocity linearly with frequency and the nonlinear relationships of attenuation and BUA with porosity. The experimental results are in good agreement with the theoretical results estimated with the MBA model. It is expected that the MBA model can be usefully employed in the field of clinical bone assessment for the diagnosis of osteoporosis.
Electrical field interactions in different cochlear implant systems
Authors: Boëx Colette , de Balthasar Chloé , Kós Maria-Izabel , Pelizzone Marco
Published: October 2003

The goal of this study was to evaluate electrical field interactions produced by the stimulation of different types of intracochlear electrodes in 12 adult subjects (three Ineraid™, four Clarion™ S-Series, three S-Series with the electrode positioning system-EPS and two Clarion™ HiFocus-I with the EPS). Psychophysical measurements were conducted with biphasic stimuli (813 pulse per second, 153.8 μs/phase). “Perturbation” signals (300 ms) were applied to one electrode chosen at the middle of the array and their effects on detection thresholds of “probe” signals (30 ms) were measured on the neighbor basal electrode. Perturbation levels were set below the detection threshold of the perturbation electrode (−2 dB re threshold). Measurements were first conducted for simultaneous stimulation of the probe and of the perturbation electrodes, for monopolar for all subjects and for bipolar stimulus configurations for both Clarion™ HiFocus-I subjects. The tested Clarion™ electrodes did not present lower monopolar interactions than the Ineraid™ electrodes. Nevertheless, considering the shorter distance between electrodes for the Clarion™ than for the Ineraid™, the tested Clarion™ electrodes might be more selective than the Ineraid™. We did not find any significant monopolar electrical field-interaction differences between subjects who received the S-Series array with and without the EPS. We did not find lower interactions for both subjects who received the HiFocus-I array than for subjects who received the S-Series. Electrical field interactions were lower for bipolar than for monopolar configurations for both HiFocus-I subjects. A second set of measurements was conducted for nonsimultaneous stimulation similar to the one used in continuous interleaved sampling sound strategy. These measurements showed that interactions evaluated for simultaneous biphasic stimuli were larger than for nonsimultaneous stimulation.