bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ measurements in marine sediment
Authors: Thomson P. Philip , Dunlop John I.
Published: July 2002

Investigations on the acoustic properties of marine sediments have been carried out on wide range of core samples from the Australian continental shelves over a wide range of frequencies. In situ measurements in marine sediments are providing better data for characterizing the propagation of acoustic signals in shallow water environments. An in situ acoustic probe has been designed and used to measure the p-wave velocity at 50 kHz using pulse transit timer. The transducer probe is inserted about 100 mm into the sediment with minimum distortion, the transmitter-receiver distance being about 150 mm. The dilatational velocity measurements were found to be of acceptable precision between those of in situ and laboratory measurement. Four sets of three matched piezoelectric transducers each have been mounted in colinear frames to enable measurements of sound speed ratio and attenuation constant at higher frequencies in the laboratory. The experimental and theoretical results were in good agreement and well fitted to mathematical models based on Biot–Stoll theory.
Sound-speed profile estimation using empirical orthogonal functions for stochastic propagation over poro-elastic sediments
Authors: Jaye Michael , Siegmann William L. , Badiey Mohsen
Published: July 2002

The efficacy of empirical orthogonal functions (EOFs) in modeling ocean fluctuations for acoustic propagation predictions is well known, and recent work has demonstrated their advantages for sediment sound-speed variabilities. In this study, using EOFs for the direct estimation of sediment sound speed, density, and attenuation profiles is described, when relatively extensive data sets such as those from the Atlantic Generating Station (AGS) site are available. First, interpolations are generated based on minimizing mean-square errors. The resulting fields are appraised and compared thoroughly with those obtained from universal kriging, a method which is commonly employed by geostatisticians. Not only do the EOF interpolations have advantages in numerical efficiency, but also their construction is modified here to incorporate lateral terrain orientations as occur at the AGS site. Uncertainties in the geoacoustic fields are then modeled by stochastic variations in the EOF coefficients. The field representations are used for environmental input to propagation modeling of poro-elastic sediments in the AGS region. Statistics of transmission loss fluctuations are discussed in terms of geoacoustic variabilities. [Work supported by ONR.]
Numerical simulation of shallow-water reverberation
Authors: Minassian George R.
Published: July 2002

A computer model of monostatic shallow-water reverberation is described. The model includes two types of reverberation: surface and bottom. In this paper, hydrophysical and acoustical characteristics of a shallow-water environment needed for reverberation modeling are described. The Pierson–Moskowitz and Leikin–Rosenberg spectra of wind seas are used to compute surface-scattering coefficients in the base of a two-scale model. The Lysanov-Ivakin models of bottom roughness are applied to compute bottom-scattering coefficients. A numerical procedure for computing the reverberation angular power spectrum as a function of time is described. A procedure for generating a random quasistationary reverberation time series at the array output is given. The computer simulation results are presented.
The Cooper Union ‘‘super monitor’’ speaker system
Authors: Kim Seho , Raichel Daniel R. , Torres John
Published: July 2002

A pair of three-way transmission-line speaker systems was designed, constructed, and tested for the purpose of providing a high-accuracy reference monitor capable of reproducing the full audio range with extremely low harmonic distortion and fast transient response with minimal coloration. Each of the speaker cabinets is a mirror image of the other; and edges are made rounded to minimize diffraction effects. The use of six mid-range drivers enclosed separately from the woofer in each of the extremely stiff cabinets ensure linear operation even at fairly high levels of power input. The tweeters, also enclosed separately, are arranged to provide wide dispersion. While a three-way crossover network is incorporated, separate input jacks allow for bypass in order to accommodate tri-amplified inputs. The transmission line provides a perfectly resistive termination to the woofers, functions as a low-pass filter and virtually eliminates cabinet resonance. Damping material varies in density, tapering off from 0.5 lb/ ft3, where the last 30 cm of the transmission line is unfilled. Directivity through 180° proved be extremely even in the test ranges of 101 to 13 212 Hz.
Bass handbells of aluminum
Authors: Rossing Thomas D. , Mansell Edward R. , Gangadharan Deepak , Malta Jacob H.
Published: July 2002

In order to obtain a higher radiation efficiency and thereby enhance the sound of bass handbells, Malmark has created a new bell design using aluminum rather than the traditional bronze. These bells are larger in diameter, and they have lower coincidence frequencies, both of which lead to more efficient radiation of bass notes. Using holographic interferometry, vibrational modes of a new aluminum bell are compared with those of a bronze bell having the same fundamental frequency. Sound radiation studies of these large bells reveal a prominent sixth-harmonic partial that is not present in smaller handbells.
Theory on streaming generated by a bubble in an ultrasound field
Authors: Wu Junru , Du Gonghuan
Published: July 2002

Theory has been developed to calculate microstreaming velocity inside and outside an isolated air bubble in a liquid produced by a bubble-scattered sound field, taking account of two predominant modes of the bubble’s motion: a monopole (pulsation) and a dipole (translational harmonic vibrations). It has been demonstrated that streaming velocity inside a bubble is much greater than that outside the bubble. It has also been shown that the microstreaming is most pronounced for a bubble undergoing volume resonance, which is in agreement with Elder’s experimental observations [S. A. Elder, J. Acoust. Soc. Am. 31, 54–64 (1959)]. If the viscosity of the gas medium in a bubble is neglected in theory, the results obtained agree qualitatively with Davidson and Riley’s [B. J. Davidson and N. Riley, J. Sound Vib. 15, 217–233 (1971)].
Comparative testing of acoustic properties of cinder blocks packed with recycled materials for noise barrier applications
Authors: Jamgocian Alek , Raichel Daniel R. , Yapijakis Constantine
Published: July 2002

In the search for more effective noise attenuation methods, a number of candidate materials for road noise barriers and partition walls were tested at the Cooper Union Acoustics Research Center in a specially constructed enclosure divided into two sections by a wall constructed of these materials. The transmission losses of cinder blocks filled with various recycled materials constitute the acoustical property of principal interest. Three tests were executed for each type of material: (1) transmission loss measurements; (2) absorption coefficient measurements; and (3) diffraction effects. The intended applications of the designed materials are as noise barriers for urban highways and subway stations, and as partition walls for factories, classrooms, libraries, etc. Recycled materials experimented with would normally end up in land fills or incinerators. [See NOISE-CON Proceedings for full paper.]
Determining sound power using sound intensity in a reverberation room and other spaces
Authors: Hickling Robert , Lee Peng , Wei Wei
Published: July 2002

Tests were conducted with two sound-power reference sources (Bruel and Kjaer model 4204) in three different acoustical environments: half of a reverberation room (overall room dimensions 6.7×5.5×4.1 m), a large semi-anechoic room, and an indoor work space. Sound power (narrow band 136–6400 Hz) was determined using a semicircular array of eight sound-intensity probes rotated in steps of 20 deg (72 measurement positions) over a hemispherical integration surface, radius 1.52 m, with the source at the center. The floor base completing the surface enclosing the source was assumed to be rigid with zero normal intensity. Despite prevailing concerns about sound-intensity measurement in diffuse fields and reverberant spaces, it was found that there was quite close agreement between sound power determined in the reverberation room and sound power determined in the other two environments. Sound power determined in the semi-anechoic room and work space was found to be highly repeatable, within 2%. For both sources the sound power was about 10% less than the manufacturer’s calibrated value. With the source outside the integration surface, sound power determined in the semi-anechoic room was two orders of magnitude less than sound power with the source inside. [See NOISE-CON Proceedings for full paper.]
Sound quality evaluation of vehicle interior power train noise
Authors: Kim J.-W.
Published: July 2002

In this paper, the sound quality of interior noise of three 1500-cc passenger cars driving at constant speed is evaluated. Paired comparison for three different cars and engine rpm was applied for subjective assessment with respect to important factors, i.e., booming, roughness, sharpness, powerfulness, and loudness. Based on the results, loudness is the most important factor on the perceived annoyance. Finally, an objective measure to evaluate: Each of five factors was conducted and each of these measures had good correlation and subjective evaluation. [See NOISE-CON Proceedings for full paper.]
Laser-generated nonlinear Rayleigh waves with shocks
Authors: Lomonosov A. , Mikhalevich V. G. , Hess P. , Yu. Knight E. , Hamilton M. F. , Zabolotskaya E. A.
Published: July 2002

Intense laser radiation was used to generate a Rayleigh wave pulse of finite amplitude in fused quartz [A. Lomonosov and P. Hess, Proc. 14th ISNA, edited by R. J. Wei (Nanjing, 1996), pp. 106–111]. The laser beam was focused with a cylindrical lens to form a strip having dimensions 6 mm×50 μm on the solid. Measurements of the vertical (normal) component of the particle velocity at the surface were made with a second laser beam at distances 2.3 and 18.3 mm away from the irradiated strip. The horizontal (in-plane) component is related through the Hilbert transform. A Rayleigh wave pulse of duration 50 ns, velocity amplitude 30 m/s, was measured at 2.3 mm and used as the initial condition for numerical calculations based on a theoretical model for nonlinear Rayleigh waves in isotropic solids [E. A. Zabolotskaya, J. Acoust. Soc. Am. 91, 2569(A) (1992)]. Numerical predictions for the waveform at 18.3 mm are in close quantitative agreement with the measurement. Nonlinear propagation effects produced well-defined shocks with cusped spikes in the horizontal velocity waveform, and a nearly doubling of the pulse duration due to the different propagation speeds of the head and tail shocks. [Work supported by Volkswagen, ISF, NSF, and ONR.]
Acoustic wave propagation and reflection on nonlinear boundaries
Authors: Solodov Igor Yu.
Published: July 2002

Unlike optics reflection phenomenon in acoustics has long been considered a linear process. In the present paper a general approach to acoustic reflection problems at nonlinear solid–solid and liquid–solid interfaces will be discussed in terms of perturbation theory. Fresnel formulas for the second-order reflection waves were derived for ideally bonded contacts of isotropic solids. Nonlinear bulk wave reflection was shown to result in efficient second harmonics generation, particularly, for overcritical angles of incidence. Unlike the linear case, nonlinear reflection generally leads to the rotation of the polarization plane for the harmonics of shear waves. Reflected harmonics are to be observed even when acoustic impedance is continuous across the boundary forbidding linear reflection to exist. Based on the nonlinear sound reflection problem, the method for analysis of boundary wave nonlinear propagation has been developed. It uses the idea of partial mode decomposition in wave reflection and takes into account self- and cross-interactions of acoustic waves reflected and transmitted at complex angles. The examples of analytical solutions for the second harmonics, as well as numerical calculations of nonlinear wave profiles, will be demonstrated for the Rayleigh, Stoneley, and Stoneley-Sholte wave propagation along nonlinear boundaries. The results obtained permit general characteristics of boundary acoustic nonlinearity that were shown to be different from those in the bulk of nonlinear medium to be defined.
A structural model of the head-related impulse response
Authors: Brown C. Phillip , Duda Richard O.
Published: July 2002

A signal-processing model is proposed for the head-related impulse response (HRIR). As in earlier work by Genuit [K. Genuit, ‘‘A model for the description of outer-ear transmission characteristics,’’ Ph.D. thesis, Rheinisch-Westfalischen Technichen Hochschule Aachen (1984)], different components of the model account for the directionally dependent filtering by the head, shoulders, and pinnae. Interaural-polar coordinates produce a natural separation of the azimuth- and elevation-dependent effects. The parameters of the head model depend only on head diameter. The parameters of the pinna model depend on pinna shape, and were derived from an image representation of the HRIR. The relative timing of the pinna ‘‘echoes’’ was found to be much more critical than their amplitudes or spectra. In a formal evaluation, subjects compared the apparent locations of virtual sources synthesized using the model to virtual sources synthesized using the subjects’ individualized HRIRs. The effectiveness of the model was evaluated by having three subjects match the apparent location of a sound source. With a 500-ms Gaussian white noise burst heard through Etymotic Research ER-2 in-ear phones, the average error in matching elevations was less than 23 deg. [Work supported by NSF.]
Auditory units enhance their response to sinusoidal AM in the presence of low-frequency modulation
Authors: Bibikov Nikolay
Published: July 2002

Phase-locking responses to long sinusoidally amplitude-modulated best-frequency tones were recorded in midbrain auditory units of the curarized grass frog. The reproduction of the periodic AM (with modulation depths in the range 10%–30% and modulation frequencies in the 20- to 100-Hz range) was studied in the presence of low-frequency (0–50 or 0–150 Hz) noise added to the envelope waveform. The remarkable steadiness of periodicity extraction was observed in the presence of a low-frequency masker. Moreover, in some units, both the average firing rate and the phase-locking with a periodical modulation increased in the presence of noise. The last effect was especially pronounced when the modulation frequency (70–100 Hz) was located outside of the masker frequency band (0–50 Hz). The responses of torus semicircularis units to the best frequency tone amplitude modulated by a low-frequency two-tone complex were also studied. The typical observation was an increase in the synchronization index for the modulation frequency in the 20- to 40-Hz range with a low-frequency modulation (in 2- to 5-Hz range) being added to the signal. For both effects, the enhancement was even more pronounced if the Rayleigh statistic which took into account average firing rate was computed.
Estimation of far-field sound-pressure levels based on near-field sound-pressure level data for various industrial equipment
Authors: Dicke Andrew , Ferren W. Brent
Published: July 2002

In order to estimate the noise radiated by an industrial facility, it is essential to accurately determine the far-field noise emissions of each piece of equipment. However, many times the only available equipment to determine acoustic information is near-field noise data. Therefore, accurate conversion of near-field to far-field noise data is necessary to determine equipment noise emissions at distant locations. This paper examines the process for converting measured near-field sound levels to far-field sound levels in actual equipment installations. Near-field data for various types of equipment are converted to sound power level and then extrapolated to a far-field sound level. The extrapolated sound levels are then compared to direct measurement data to verify the accuracy of near- to far-field calculations. The sensitivity of measurement results to environmental factors such as background noise and reflective planes is also addressed. The measurements and sound power level calculations are conducted in accordance with applicable ISO noise standards.
Theoretical study of diffraction by a jagged-edge noise barrier
Authors: Menounou Penelope , Blackstock David T.
Published: July 2002

An approximate analytical method for calculating the diffraction field behind a jagged-edge noise barrier, idealized as a thin rigid half-plane having an irregular edge, is presented. Experimental studies have shown that for apertures, disks, and plane barriers, making the edge irregular can significantly decrease the diffracted signal [Bailey et al., J. Acoust. Soc. Am. 92, 2359(A) (1992); Ho et al., J. Acoust. Soc. Am. 101, article in press (1997)]. Straight-edge diffraction from a rigid half-plane has a known exact solution for plane, cylindrical, and spherical incident waves. It is observed that in all three cases the shadow zone signal, in the far field, is equivalent to radiation from an infinite line source, but modified by a certain directivity function. In the present work the jagged edge is modeled as a crooked line source having the same directivity as a straight edge. The radiation is calculated by treating the crooked line as an infinite set of point sources, summing their contributions, and adding the appropriate directivity. The method is simple to apply. Results are compared with those found by other methods. [Work supported by Texas Advanced Technology Program.]
Continued investigation of noise reduction by a random-edge barrier
Authors: Rosenberg Eric , Busch-Vishniac Ilene J.
Published: July 2002

Recent experimental work [Ho et al., J. Acoust. Soc. Am. (to be published)] indicates that replacing the straight-edge top of a noise barrier with a random edge of the same average height can result in improved insertion loss, except at low frequencies. It is thought that the jaggedness reduces the coherence of the sound diffracted off the edge so that the signal amplitude is diminished. These experimental results were obtained in a laboratory using a spark source and defining the maximum peak-to-peak sound pressure at the receiver as the metric. However, because the jagged edge has the effect of increasing the time of duration of sound observed from an impulsive source, it is not clear from the original results that the random-edge barrier reduces the sound energy received. Here the results of a new set of experiments using a similar test setup, but with more rigorous signal analysis are reported. This permits determination of whether the introduction of the randomness reduces the energy received. Additionally, it allows one to determine more precisely the conditions under which the jagged-edge barrier performs worse than a straight-edge barrier.
Music: A vehicle for science—Workshop for teachers
Authors: Hansen Uwe J. , Rossing Thomas D.
Published: July 2002

With ASA technical initiative support, approximately ten acoustics workshops for teachers have been conducted by members of the technical committee on musical acoustics in the past six years. Workshop content emphasizes laboratory and demonstration skills for high school and college level teachers. The workshops for elementary teachers have been more concerned with generating excitement for science. Music is an ideal vehicle to accomplish that. Elementary teachers in the workshops participate in monochord construction and receive training in the use of a number of pieces of equipment which they take back to the classroom. Basic wave properties are illustrated and related to string harmonics and musical intervals. Workshop content and training approaches will be discussed.
Amplitude modulation detection thresholds and associated psychometric functions.
Authors: Gifford René H. , Trine Timothy D. , Grantham D. Wesley
Published: July 2002

Amplitude modulation detection thresholds for broadband stimuli were measured as a function of modulation frequency in seven listeners with normal hearing. Two adaptive procedures (1-down, 1-up and 4-down, 1-up) were used to track the 50% and the 84% correct levels in a three-interval, three-alternative, forced-choice task. Preliminary data show that the temporal modulation transfer functions for the two criteria are parallel for lower modulation frequencies but tend to converge with increasing modulation frequency. The resultant two-point psychometric functions associated with the modulation detection data demonstrate an increase in slope with increasing modulation frequency. Time constants were calculated from a least-squares fit of the equation y=k/(f+a) and further illustrate the effects of the changes in psychometric function slope. These data have implications for comparisons of temporal acuity estimates across data sets.
Observer weighting of binaural information in source and echo clicks
Authors: Stellmack Mark A. , Dye Raymond H. , Guzman Sandra J.
Published: July 2002

Relative weights given to interaural differences of time (IDTs) of source and echo clicks were computed for a range of echo delays (1–256 ms) for stimuli presented over headphones. On each trial, source and echo IDTs were selected randomly and independently (μ=0 μs, σ=100 μs). Listeners were instructed to indicate the direction of the IDT, left or right, of the source or echo (in separate conditions). Weights were obtained by computing the correlation between the source or echo IDT and the listener’s binary responses. In all conditions, little weight was given to the echo at short echo delays (<8 ms), but the echo was given weight equal to or greater than that of the source at intermediate echo delays (8–32 ms). For echo delays >32 ms, listeners gave greater weight to the source or echo, as appropriate. For all echo delays, when listeners were instructed to indicate the direction of the source IDT, the percent correct was lower when the echo DT varied across trials than when it was fixed at 0 μs, indicating that the binaural information of the echo was not completely suppressed in any condition. [Work supported by NIH, NIDCD, and AFOSR.]
Measurements of binaural temporal resolution using an analog of gap detection
Authors: Akeroyd Michael A. , Summerfield Quentin
Published: July 2002

One method for estimating the temporal resolution of the monaural auditory system is to measure the shortest silent gap, placed in a noise burst, that is detectable. An analog of this method was developed to estimate the temporal resolution of the binaural auditory system. The shortest burst of interaural-uncorrelated noise, placed between two bursts of interaural-correlated noise, that listeners could detect was measured. The spectrum level (40 dB SPL), bandwidth (100 Hz), and center frequency (250 to 1000 Hz) of the three bursts were the same. Its threshold duration depended upon center frequency: 6.5 ms at 250 Hz and 35 ms at 1000 Hz (silent-gap thresholds were 15 ms at 250 Hz and 13 ms at 1000 Hz). The interaural-correlation jnd was also measured: 0.03 at 250 Hz and 0.10 at 1000 Hz. The results were modeled using a Gaussian temporal window. Its duration is determined by both the threshold duration and the jnd: The values varied little with center frequency, i.e., 260 ms at 250 Hz and 230 ms at 1000 Hz. This lack of variation differs considerably from the variation of the experimental thresholds. The results are compatible with binaural temporal resolution being independent of center frequency.
Minimum audible angle and minimum audible movement angle in the median sagittal plane as a function of stimulus spectrum and reference elevation
Authors: Figueiredo Jamie M. , Grantham D. Wesley
Published: July 2002

Minimum audible angle (MAA) and minimum audible movement angle (MAMA) were measured employing a pseudo-virtual method of stimulus presentation. All stimuli were digitally recorded through KEMAR’s two ears while he was positioned in an anechoic chamber with fixed and moving loudspeakers presenting sounds in his median sagittal plane; these recorded binaural stimuli were subsequently played through insert earphones to subjects seated in a darkened sound-insulated room. For the measurement of MAA, subjects had to say which of two stationary 300-ms sounds was higher in elevation; for the measurement of MAMA, subjects had to say whether a single moving sound moved up or down. Velocities in the MAMA experiment ranged from 20°/s to 150°/s. Stimuli were Gaussian noise bursts that were either wide band, 4-kHz low passed, or 4-kHz high passed. Reference elevation was either 0° or 45° elevation. Results will be discussed in terms of static and dynamic pinna cues that underlie elevation discrimination for high-frequency stimuli and the possible shoulder-bounce cue that may enable elevation discrimination for low-frequency stimuli. [Work supported by NIDCD 00185.]
Magnitude estimation of perceptual fusion of multiple sound sources
Authors: Guzman Sandra J. , Yost William A.
Published: July 2002

The precedence effect states that the first sound wave arriving at a listener has more influence on the perception of location than later arriving echoes. When a source plus echoes is perceived approximately at the location of the source, the image is said to be ‘‘fused.’’ The following set of experiments introduces a new procedure to estimate fusion of clicks. Listeners are presented with a source click plus a single echo click at a variety of delays. Stimuli are rated between a value of ‘‘0’’ and ‘‘100,’’ with ‘‘0’’ indicating a single source and ‘‘100’’ indicating more than one source. These ratings are used to determine delays which are perceived as a single source (receive a rating of ‘‘0’’) and delays which are perceived as multiple sources (receive a rating of ‘‘100’’). These anchor stimuli are then presented on each trial. The stimulus which received a rating of ‘‘0’’ is presented first, followed by the sound to be rated. The stimulus which received a rating of ‘‘100’’ is presented last. This procedure was used to determine fusion as a function of location and number of echoes presented. [Research supported by a program project grant from NIDCD.]
The D.O.R.T. method
Authors: Prada Claire
Published: July 2002

The D.O.R.T. method (Décomposition de l’Opérateur de Retournement Temporel) generalizes the principle of acoustic time reversal mirrors. It applies to detection and focusing with large arrays of transducers [Prada et al., J. Acoust. Soc. Am. 99 (1996)]. A transducer array insonifying a scattering medium is characterized by its frequency-dependent transfer matrix K(ω). The time-reversal process is then described by time-reversal operator K(ω)K*(ω). The eigenvalue decomposition of this hermitian operator provides a classification and a localization of the scattering centers in the medium. The two main steps of the D.O.R.T. method are the measurement of the interelement impulse responses of each pair of elements in the array and the diagonalization of the corresponding time reversal operator at chosen frequencies. The method is efficient for the detection and selective focusing in an inhomogeneous multiple target medium. It also applies to the recognition of shells, in particular to the detection and characterization of circumferential waves propagating around the shell. The D.O.R.T. method and recent experiments of detection through channels and through inhomogeneous media will be presented.
Imaging with eigenfunctions of the scattering operator
Authors: Waag Robert C. , Liu D.-L. (Donald) , Mast T. Douglas , Nachman Adrian I.
Published: July 2002

An inverse scattering method that uses eigenfunctions of the scattering operator has been applied to obtain quantitative images of various scattering objects. The eigenfunctions of the scattering operator constitute a basis of an operator that is essentially equivalent to the time-reversal operator previously defined by others. The scattering objects span regions that are large compared to the wavelength of the acoustic illumination. Among the images are results for patterns of wires, homogeneous cylinders, and cylinders with wire inclusions. The eigenfunction method is compared to the method of filtered backpropagation implemented in each of two ways: numerical quadrature and fast Fourier transform. The results show the capability of the eigenfunction method to image objects with large ka. The results also show the eigenfunction method can be more efficient than the filtered backpropagation method when the scattering operator has few eigenvalues. [Work supported in part by NIH and USAMRMC.]
Improved giant magnetostrictive materials: New and improved Terfenol-D
Authors: Snodgrass Jonathan D. , Calkins Frederick T. , Dapino Marcelo J. , Flatau Alison B.
Published: July 2002

The giant magnetostrictive terbium-iron alloy material, Terfenol-D, offers the highest strain of any magnetostrictive material at room temperature using practical drive fields. The increasing use of Terfenol-D in a wide variety of production devices and systems has driven the development of new, advanced manufacturing techniques in material production to provide greater strain performance, uniformity, rod size, and production capacity. As more applications for this smart material are developed, the demand for reliable design data to enable applications engineers to take advantage of Terfenol-D’s superior properties has also grown. Recent developments in production techniques have made strides to fulfill needs in both areas. The ETREMA crystal growth (ECG) system, based on the modified Bridgman process, is capable of producing larger rod sizes (65-mm diameter and 175-mm length) with greater quality control, performance, material homogeneity, and uniformity. These improvements are quantified with material property data. Terfenol-D samples are characterized in a transducer under a wide variety of real-world operating conditions. Results show greatly improved consistency of material performance, in terms of material properties, from test to test.
Effects of preceding liquids and fricatives of different places of articulation on perception of stop consonants
Authors: Brancazio Lawrence
Published: July 2002

In listener classifications of tokens along a /da/–/ga/ continuum, more /g/ judgments are given if the syllables are preceded by /al/ or /as/ than /ar/ or /a■/ [Mann, Percept. Psychophys. 28, 407–412 (1980); Mann and Repp, J. Acoust. Soc. Am. 69, 548–558 (1981)]. These effects may reflect perceptual compensation for coarticulatory effects of consonants on a following stop: A front constriction causes fronting in the stop. Thus fronted preceding consonants induce more /g/ responses. These effects were investigated by contrasting /r/ with a ‘‘front’’ /l/ with an exaggerated tongue-tip gesture and a ‘‘back’’ /l/ with no tongue-tip gesture. /s/ and /■/ were contrasted with the velar /x/. These consonants were produced in /aC/ or /εC/ syllables, and were followed by synthetic /da/’s and /ga/’s. Both /al/ variants resulted in more /g/ judgments than did /r/. However, when the vowel was /ε/, only the back /l/ produced this effect, contradicting the compensation explanation. The effect of /x/ relative to /s/ and /■/ depended on the syllables’ original context (preceding /da/ or /ga/). Finally, the syllables were tested with F2 /ba/–/da/ and /ba/–/ga/ continua. Results will be discussed with regard to gestural and acoustic explanations.
A review of the effects of exposure to noise in combination with organic solvents and metals
Authors: Murphy William J. , Franks John R. , Morata Thais C.
Published: July 2002

The effect of noise exposure in combination with other ototraumatic agents (e.g., solvents, metals, and pharmacologic agents) is an emerging area of concern for the development of comprehensive standards for hearing loss prevention. Noise exposure primarily damages the organ of Corti, while solvent exposures exhibit both central and peripheral effects in rats. Organic solvent-induced hearing loss presents impairment which is similar to noise-induced hearing loss in humans. Exposures to metals tend to affect the central nervous system. The effects of lead exposure on auditory brainstem response exhibit an increased threshold across all frequencies and increased latencies in humans. However, other metals, such as zinc and copper, do not produce similar effects. Combined exposures of noise with metals or solvents can produce nonadditive interactions both in humans and animals. This paper reviews the effects of exposure to commonly used organic solvents and metals found in occupational settings. The interactions of several solvents and metals will be classified according to their effects on the peripheral or central auditory system both in laboratory animals and humans.
On the need for noise labeling standards
Authors: Schomer Paul D.
Published: July 2002

Currently, ‘‘quiet’’ is being advertised as an attribute of certain products. For example, one can purchase ‘‘quiet’’ dishwashers. Other products have had their own labels for years. For example, some home bathroom fans have carried a rating in sones. But no standard, uniform method exists to label such products. This paper discusses the need for such standards and some of the attributes such standards might possess.
HPD labeling issues
Authors: Casali John G. , Robinson Gary S.
Published: July 2002

Issues related to label content are analyzed from a human factors perspective. Current labeling requirements are critiqued, and the need for additional information or the presentation of existing information in a different form is examined. Some of the specific questions addressed include the following. Who are the users and how do the information requirements of the individual selecting the hearing protection devices (HPDs) for the employer differ from those of the end user/wearer? What are the responsibilities of the government regulatory agencies (i.e., EPA, OSHA), the HPD manufacturer, and the employer, relating to the accuracy of the reported attenuation performance of the HPD? Should comfort data be obtained and reported? How should the fitting instructions be presented? What special workplace conditions (signal detection, speech intelligibility, dust, dirt, temperature, etc.) should be considered in the HPD selection process, and should these factors be addressed in the HPD label?
Important labeling considerations in production environments
Authors: Royster Larry H.
Published: July 2002

The use of labels to warn workers of potential hazards (noise and vibration) in production environments has been of interest to many professionals for several years. At the present time, at least in the USA, the use (or nonuse) of labels has been strongly influenced by the legal process. This presentation will focus mainly on the use of, and potential effectiveness of, labels as a warning tool in real-world production environments. In addition, a limited discussion of warning label activities in other countries will be presented.
How should we measure hearing protector attenuation?
Authors: Barry John P.
Published: July 2002

There has been an ongoing controversy relative to hearing protector effectiveness. The American National Standards Institute (ANSI) sets consensus guidelines to measure hearing protector attenuation (S3.19-1974 through S12.6-1990). Beginning with Padilla in 1976, field studies have consistently shown that laboratory data greatly overestimate the attenuation typically received in the workplace. The ubiquitous NRR (noise reduction rating) also overpredicts actual workplace attenuation because it is derived from laboratory data. Occupational fit is usually poorer than laboratory fit. Reusable hearing protectors deteriorate due to repetitive use and aging of materials. Interaction with other protective equipment can reduce hearing protector attenuation. Both the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) have proposed workplace attenuation derating factors for the NRR. However, the development of employer hearing protector fit testing procedures analogous to respirator fit testing in concert with a fully effective hearing conservation program will be the only effective answer to this question.
Application of a turbulence generation model for atmospheric propagation calculations
Authors: Stinson Michael R. , Daigle Gilles A.
Published: July 2002

Realizations of atmospheric turbulence, used as input for parabolic equation (PE) calculations, are commonly generated using a two-dimensional Fourier representation of the spatial fluctuations in refractive index, i.e., the turbulence field. A number of factors affect the nature of the generated turbulence and determine the character of the acoustic propagation. These factors include the turbulence spectrum (e.g., Gaussian, Kolmogorov, or von Karman spectra) and the number of Fourier modes included in the representation. The Green’s function PE is used to calculate sound field characteristics in the case of upward refraction above an impedance plane using different turbulence fields.
An intelligent ventilation system to attenuate the intermittent transportation noise
Authors: Mohajeri Ramin , Atkinson John , Fricke F. R.
Published: July 2002

The level of intermittent transportation noise into the bulding is controlled by activating an intelligent control system to close the window when the noise occurs. This method is a possible solution for conflict between passive noise control and natural ventilation for places with a moderate climate. A knowledge-based control strategy has been implemented to control the position of the window using acoustic feedback. There are three major steps, training, source classification, and control, in which fuzzy logic and rule-based algorithms are implemented. If somebody plays music or speaks near the window, the intelligent window must not react even though the level of the sound may be higher than an approaching aircraft or vehicle. To identify an approaching noise source, centroid of the Wigner–Ville distribution and the peaks of STFT are used. The cross correlation between output data from indoor and outdoor microphones indicates the effect of outdoor transportation noise on the indoor noise level. A training software is considered to update the thresholds of noise classification. The experimental result of a prototype intelligent window is presented. A noise attenuation of more than 10 dB in Leq and Lmax in each single noise events is achieved. [Work supported by RTA of NSW.]
Rate encoding of binaurally alternating low-frequency tone bursts in macaque A1
Authors: Reser David H. , Fishman Yonatan I. , Arezzo Joseph C. , Steinschneider Mitchell
Published: July 2002

Integration of sequential components is an essential feature of auditory scene analysis. Humans consistently underestimate by 35–50% the frequency (F) of click trains, when the component clicks alternate between ears, and F exceeds 10 Hz [Axelrod et al., J. Acoust. Soc. Am. 43, 51–55 (1968)]. This suggests a boundary for integration of sequential components. Multiunit Activity (MUA) and current source density (CSD) in A1 of the awake monkey were used to explore neural correlates of this illusion. Phase-locked responses of cortical neuronal ensembles correlate with the perceptions of human listeners [Soc. Neurosci. Abstr. 22:637.18 (1996)]. Above 10 Hz, inhibition in thalamorecipient layers suppressed the response to each ipsilateral click in the train, in regions of high best frequency (BF). Here these observations are extended to low BF sites, which respond poorly to clicks. Responses to 25-ms low-frequency alternating tone bursts exhibit a boundary above 10 Hz, in agreement with click train data. The consistency of this physiologic boundary across the tonotopic map of A1 may represent an important neural substrate for assigning individual components to perceptual streams. [Work supported by DC00657 and the Institute for Music and Neurologic Function of Beth Abraham Hospital.]
The use of a piezoelectric double amplifier active-skin in the control of panel radiation
Authors: Johnson Brody D. , Fuller Chris R. , Burdisso Ricardo A.
Published: July 2002

The potential of a piezoelectric active-skin is analytically demonstrated for the reduction of broadband acoustic radiation from a vibrating panel in the frequency range from 0 to 750 Hz. The active-skin is comprised of a number of independently controllable piezoelectric double amplifier elements arranged in a contingent surface over the vibrating panel. Both the finite-element method (FEM) and the boundary element method (BEM) are employed in the development of numerical models for relation of the piezoelectric voltage excitation to vibrational and acoustic responses of these active-skin elements. The adaptive feedforward filtered-x least-mean-squares (LMS) algorithm is employed in the time domain simulation of control with the active-skin. Both FIR and IIR compensator types are investigated. ANC and ASAC perspectives are examined for the realization of the active-skin. Control performance is quantified using both sound power level (Lw) and sound pressure level (SPL) data. Simulation shows that an attenuation of 10 dB in the radiated power is possible over the investigated frequency range, which encompasses six modes of panel vibration. Conclusions regarding the potential for the active-skin for the broadband attenuation of structurally radiated sound are then made from the analytical results. [Work supported by ONR.]
Active cabin noise control in the time domain
Authors: Bao Xiao-Qi , Varadan Vasundara , Varadan Vijay
Published: July 2002

Active control of noise inside an enclosure from exterior noise sources is accomplished by the use of piezoelectric actuators and either piezoelectric or MEMS sensors placed on the enclosure wall. It is generally known that this approach provides very good results at the resonant frequencies of the cabin walls and if the excitation noise is at a single frequency. In the present study, broadband excitation is looked at from the exterior, in the time domain. A sensor mounted on the cabin wall provides the reference signal for the excitation; the error sensor can either be the piezoelectric sensor on the wall or a sound-level meter placed at an appropriate position inside the cabin. Different types of closed loop control are attempted using both analog and digital strategies. The study examines the number and placement of actuators on the wall relative to bandwidth of the external source, as well as control of wall vibration as a means of controlling the radiated noise.
Experimental results on active structural acoustic control using fiber-optic strain sensors
Authors: Masson Patrice , Berry Alain
Published: July 2002

A new strategy for the active control of the sound power radiated from a flexural vibrating beam is experimentally investigated. This strategy involves sensing the discrete structural strain using white-light interferometric multimode fiber-optic strain sensors. Two approaches are used to relate the radiated sound power to the structural strain. The first approach is based on the reconstruction of the transverse structural displacement field from the structural strain field using a finite-difference scheme, and a wave-number transformation of the structural displacement to obtain the radiated sound field. The second approach is based on an exact expression directly relating the radiated sound field to the wave-number transform of the structural strain. In both approaches, the wave-number transform is performed over the supersonic (radiating) components of the structural information. The dynamic strain measurements are first compared with polyvinylidene film strain sensors. As a second step, a straightforward control scheme is implemented into a multichannel filtered-x LMS algorithm to control the strain amplitudes on the beam actively. Finally, both strategies for using the strain information are implemented to perform the active control of the sound power radiated from the beam. Preliminary performance results of both strategies using four strain sensors are then presented.
Comparing listener’s perception of place coarticulation in voiceless stops with discriminant analysis
Authors: Peng Shu-hui , Nearey Terrance
Published: July 2002

Previous EPG study of place coarticulation in Taiwanese stop consonants suggested that place gestures of two adjacent stops separated by a word boundary (CVC1♯C2V(C)) overlapped each other to different degrees depending on speech rate. The place of articulation of C1 and C2 was either dental or velar. As speech rate increased, the perceptual categorization of C1 was affected. In faster speech rate, when the first word was heard in isolation, C1 tended to be perceived with the characteristics of C2 place gesture. However, there was no simple or consistent correlation between the patterns of gestural overlapping and the perception of C1. This lack of transparent relationship between articulatory gestures and perception motivates the current investigation on the acoustic dimension of place coarticulation. The purpose of the current study is to investigate the effect of place coarticulation on the spectral properties of CVC1. Discriminant analyses based on acoustic measures will be used to discriminate the dental stop from the velar stop. Estimated (posterior) probability of class membership of the stop consonants will be compared with the previous perception study to reveal how accurately the predicted probability of responses generated from discriminant analyses reflects the perceptual performance of listeners.
Context effects on English word-final stops by American and Mandarin speakers
Authors: Yi Yuan
Published: July 2002

The production of English word-final stops by Mandarin and English speakers in five contexts was examined. While studies show that the phonetic realizations of segments in native English speech are context sensitive [P. A. Luce and J. Charles-Luce, J. Acoust. Soc. Am. 78, 1949–1957 (1985)], such contextual effects have not been investigated in non-native speech. Six Mandarin speakers of English and six American speakers read 10 carrier sentences containing the test words back and ‘bag in utterance-final position or followed by words beginning with /s/, /t/, /n/, and the vowel /■/. Three repetitions of the words in each context were measured for the vowel duration and the word-final stop closure duration. The closure/vowel ratio was calculated, and the two subject groups were compared. Results show that for both groups, the vowel and closure durations varied with contexts: while utterance final position showed the strongest effect, among the other contexts, /n/ and /t/ triggered longer vowel and closure durations than /s/ and /■/ did for both speaker groups. The non-native speakers’ closure durations and the closure/vowel ratios were not nativelike and their articulatory gestures for the velar stops differed from those of native English speakers.