bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective moduli of perforated viscoelastic substances
Authors: Gaunaurd G. , Überall H.
Published: October 2005

We have obtained expressions for the effective moduli of visco-elastic media containing multiple perforations, and have included the effect of resonances on these effective moduli. This allows a determination of the phase velocities and attenuations of elastic waves in perforated viscoelastic media. Accordingly, the effective moduli, as well as the attenuations and phase velocities of the elastic waves, exhibit resonance effects which are strongest for the fundamental monopole resonance, located at low frequencies in the Rayleigh region. Low-frequency cross sections of elastic-wave scattering from fluid-filled cavities. including resonances, have been obtained and will be displayed. [The authors wish to thank the Independent Research Board of NSWC for its support. One of the authors (H. Überall, also at the Department of Physics, Catholic University, Washington, DC 20064) acknowledges additional support from Code 421, Office of Naval Research, Washington, DC.]
Ultrasonic investigations of a second bulk compressional wave in a porous solid
Authors: Plona Thomas J.
Published: October 2005

A second bulk compressional wave has been observed in water-saturated porous solids using a transmission ultrasonic immersion technique. In this technique, the bulk modes are generated in a solid layer based on the concept of mode conversion and refraction at liquid-solid interfaces. With this technique, the sound speeds of the normal compressional wave, shear wave, and second compressional wave were determined. The pulsed ultrasonic system incorporated commercially available pulser/receiver electronics and nondestructive testing type broadband transducers with a center frequency of about 1 MHz. The porous solids studied included samples composed of sintered glass spheres and samples from two types of commercially available filtration materials. The porosity of the samples ranged from 10%–40% and the fluid permeability ranged from 1–10 μm2 (i.e., 1–10 Darcy). Velocity data will be presented as a function of porosity and fluid permeability. The second compressional wave speed is approximately 25% of the normal compressional wave speed. The data will be interpreted in terms of the Biot theory of wave propagation in a fluid-saturated porous solid [J. Appl. Phys. 28, 168–178 (1956)].
Numerical modeling of wave propagation in an inhomogeneous medium
Authors: Lewis C. H. , Adams W. M.
Published: October 2005

Certain fundamental aspects of numerical modeling, such as order-of-error, truncation error, convergence, and stability are known from theory. Application of standard finite-difference procedures to a spatially and temporally varying velocity field, such as in a composite material, reveals some pragmatic requirements: the results should be observed after each time step. This monitoring of the computations allows the scientist to know when anomalies arise due to the modeling methods. For example, waves arising from mishandling of an interior interface may cause the “final” results to be affected. Heuristically, the making of a movie is an inexpensive way to document the entire computations. Cell-to-cell energy and mass transfer may occur according to numerous equations—or cases—and statistical monitoring of the cases will either find errors, improve intuition, or both. The grid size in time or space limits the highest frequency content of (1) input wave, (2) all interfaces, and (3) all moving interfaces, such as evolve during the course of the computations. A movie will be shown to illustrate these findings.
Elastic-wave propagation and scattering in layered media containing random and periodic distributions of scatterers
Authors: Varadan Vijay K. , Varadan Vasundara V. , Flax Lawrence
Published: October 2005

In this paper, we study the reflection and transmission coefficients of an elastic wave propagating in a two-layered elastic or viscoelastic media containing random and periodic distributions of 2-D scatterers. The scatterers are assumed to have either (a) parallel, (b) perpendicular, or (c) random orientation with respect to the interface connecting the two elastic/viscoelastic media. The wave is assumed to be incident obliquely to the interface. The problem is analyzed using T-matrix approach in conjunction with suitable statistical and effective moduli theories. Numerical results displaying the transmission and reflection coefficients, and attenuation and absorption as a function of frequency for various concentrations of scatterers and shapes, will be presented and compared with those of homogeneous layers.
Analytic determination of effective shear modulus for flexural and extensional waves in an unloaded thick plate
Authors: Dubbelday Pieter S. , Rudgers Anthony J.
Published: October 2005

Thin plate theory does not predict the proper phase speed of flexural and extensional waves in the limit of high frequency or large plate thickness. The Mindlin-Timoshenko theory corrects this for the case of flexural waves by introduction of transverse shear; the “effective shear modulus” is represented by a correction factor that is fixed in such a way that the ensuing dispersion relation approaches the Rayleigh wave speed at high frequency. In this paper an analytic determination of the correction factor is presented, obtained by applying the results of exact elasticity theory (Lamb waves). The expression for the correction factor can be shown analytically to reproduce the Rayleigh wave speed at high frequency. An analogous treatment of symmetric waves leads to a thick plate theory for extensional waves, with a corresponding effective shear modulus. The expression for the pertinent correction factor leads also in this case to the Rayleigh wave speed at high frequency.
Basilar membrane mechanics in the guinea pig cochlea—Details of nonlinear frequency response characteristics
Authors: LePage Eric L. , Johnstone Brian M.
Published: October 2005

Since reporting a highly vulnerable nonlinear mechanical impulse response of the guinea pig basilar membrane [E. L. LePage and B. M. Johnstone, Hear. Res. (to be published)], we now present more comprehensive data showing: (1) The relationship between the degree of nonlinearity as functions of frequency and neural threshold determined from the N 1 response to tone pips; (2) A sharp intensity-dependent notch part way down the high-frequency slope accompanied by a rapid phase lag of 2 π radians; (3) The notch appears as the focus of the nonlinear region and often appears to separate regions of compression and expansion; (4) The rapid phase shift at the notch frequency appears to act as a breakpoint between two approximately linear phase segments. On the high-frequency side the phase may continue to lag for several cycles at up to -26 cycles/octave and is difficult to resolve; (5) The notch region may persist as nonlinear even after the nonlinear behavior has disappeared at the cutoff frequency; (6) The frequency of the notch often decreases with stimulus intensity. The discussion will refer to the way in which several factors appear to contribute to the observed basilar membrane response and their possible relevance to the second filter, and also to parallels in other cochlear data.
Two-tone suppression with relation to cochlear processing
Authors: Javel E.
Published: October 2005

Under appropriate conditions of stimulation, the response of an auditory nerve fiber to an excitatory tone (f1) can be reduced by introducing a second or suppressor tone (f2). Suppression may be studied using two techniques: When f2 is non or weakly excitatory, suppression magnitude can be measured using reduction in overall discharge rate as an indicator. And when f2 is strongly excitatory, suppression can be studied by employing low-frequency tones for f1 and measuring reductions in discharge synchronization at the f1 frequency caused by the introduction of f2. When it occurs, suppression behaves in a manner which is both orderly and independent of the ability of f2 to elicit spikes. Suppression exists throughout a fiber's response area, and its magnitude depends only on the parameters of the suppressor tone. Suppression at a given f2 intensity is maximal when f2 = CF, and its threshold is close to the excitation threshold for f2. “Iso-suppression contours,” which show the frequencies and intensities required to suppress any f1 by a given amount, indicate that the suppression bandwidth at threshold is greater than the excitation bandwidth at threshold, and that the isosuppression bandwidth narrows as more suppression is induced. These and other lines of evidence support the notion that suppression effects are governed by mechanical aspects of the cochlear response. The implications of these findings for cochlear processing and the “second filter” will be discussed, and recent data on the spatial extent of suppression will be presented. [Work supported by NIH.]
Interferometric measurement of basilar membrane vibrations in cats
Authors: Khanna S. M. , Leonard D. G. B.
Published: October 2005

A laser interferometer capable of measuring vibrations down to 3 × 10−12 cm was utilized. Basically, a short tube was cemented to the bony wall of the cochlea just apical to the round window, and then a hole was drilled through this tube to expose the basilar membrane. Chemically grown, gold mirrors (approximately 100 μ wide) were dropped onto the basilar membrane using a special probe. The membrane was not touched and the perilymph was not drained. The cochlea was sealed by placing a cap on the tube. Interferometric measurements were carried out through a glass window in the cap. Early measurements showed that the shape of the frequency response of the basilar membrane is similar to that measured by Wilson and Johnstone [J. Acoust. Soc. Am. 51, 705 (1975)] in guinea pigs. Nonlinearities in response were not found. However, both cochlear microphonic measurements and histology showed damage to the cochlea. Experiments were carried out to determine the cause of the damage. Steps were taken to reduce the damage. Measurements on relatively undamaged cochleas are now in progress. [Work supported by NIH.]
Nonlinearity, physiological vulnerability, and frequency selectivity of cochlear responses
Authors: Kim D. O. , Molnar C. E. , Matthews J. W. , Neely S. T.
Published: October 2005

A popular, traditional view has been that a linear, broadly tuned response of the basilar membrane drives a sharply tuned, so-called “second filter” unidirectionally, leading to sharp cochlear neural tuning. This view is challenged by recent studies. Physiologically vulnerable nonlinear behavior has been observed, not only in electrophysiological responses of the cochlea, but also in mechanical responses such as ear-canal sound pressure [e.g., Kemp, J. Acoust. Soc. Am. (1978); Kim et al., J. Acoust. Soc. Am. (1979); Kim, Hearing Res. (1980)]. These results corroborate the observations of physiologically vulnerable nonlinear behavior in basilar-membrane motion [Rhode, in Basic Mech. Hearing, (1973); LePage and Johnstone, Hearing Res. (1980)], and dispute the linearity of basilar-membrane motion. As to whether the tuning of basilar-membrane motion in a normal, intact cochlea is considerably broader than that of a cochlear nerve fiber response, we take the view that the evidence available now is inconclusive. This reflects our belief that the tuning of basilar-membrane motion is a normal, undisturbed cochlea at a low sound pressure level near 0 dB re 20 μPa could be much sharper than indicated by the existing measurements obtained with invasive methods at higher sound pressure levels because the frequency selectivity is affected by both the physiological vulnerability and the nonlinearity. Evidence will be reviewed in support of the working hypothesis that the mechanism of mechano-electrophysiological transduction in the cochlear partition is bi-directional and underlies the following: (1) generation of mechanically present nonlinear phenomena such as distortion products (2f1 − f2) and (f2 − f1); (2) vulnerability of various responses to physiological disturbances such as anoxia, fatigue, poisoning, etc.; and (3) active behavior of mechanical response whereby metabolic energy in the cochlear partition is utilized in enhancing the sensitivity and frequency selectivity of cochlear-partition motion. [Supported by NIH grants NS07498, NS00162, RR00396, and GM01827.]
Nonlinear damping in cross plied laminates
Authors: Plunkett Robert
Published: October 2005

Previous work by Gibson and Plunkett has shown that the damping factor in laminated composites of fiberglass with an epoxy matrix is independent of strain level up to about 2000 microstrain. Subsequent work at strains up to 10 000 shows that these large strains cause a permanent increase in damping factor with no measurable change in storage modulus. Low strain damping can be calculated from the dynamic modulus properties of the matrix and the static modulus of the glass fibers which shows that there is no interface dissipation. Prestraining above a certain critical level causes permanent cracks in the matrix material. The increased energy dissipation due to prestrain may be calculated reasonably well from the local crack density, an experimentally determined factor linking crack opening to energy dissipation, and a dissipation-volume fraction integral. Such a calculation is consistent with a physical picture ascribing the additional energy dissipation to cracks opening and closing under tensile strain with a residual stress pattern due to permanent deformation during the initial overstrain. [This work was supported by NSF.]
Plate flexural-wave damping by a fluid-loaded, lossy, compliant layer
Authors: Kerwin Edward M. , Berkman E. F.
Published: October 2005

Significant levels of damping of flexural waves on a coated plate are achievable when a compliant coating is worked against the impedance provided by fluid loading. This damping is due to thickness deformations of the coating, and is not available unless fluid loading is present (except at high frequencies where there is wave propagation in the coating). This paper describes the plate/coating/fluid system qualitatively and quantitatively through the use of appropriate analytical models. The several allowable types of wavenumber and frequency solutions describing the propagation of free waves are described, as are the relations determining system damping. A specific example is analyzed in detail, and laboratory experimental results are compared with calculations. There is generally good agreement between calculations and experiment. As a result of these comparisons we see that the levels of damping are indeed significant (i.e., high), and are reasonably calculable. It is therefore possible to design a plate/coated/fluid system to take advantage of this mechanism of damping in engineering applications.
Applications of viscoelastic material damping
Authors: Medaglia J. M. , Stahle C. V.
Published: October 2005

Applications of viscoelastic material damping in conjunction with metal and fiber reinforced plastic structures are surveyed. Since the theories for analysis of layered planar structures and for three dimensional structures are known, this survey concentrates on the variety of applications possible and discusses general systems design considerations involved in successful damping approaches. Integrally damped designs are stressed for weight, volume, and performance efficiency in preference to additive damping intended to rescue an overly responsive or noisy structure. Damping has been found the most desirable solution for many production designs and shows wide possibilities in developmental design studies. Constrained layer damping examples for printed wiring boards, 38in.-thick steel beams or plates, equipment support suspensions which obviate creep, acoustic protective shrouds, and equipment support structures are given. Most of the primary structure is metal. The damping material is an epoxy based formulation having a material loss factor of about 1.0 over a broad frequency range and a modulus of 8000 psi at 100 Hz. The constraining layer is either metal, glass fiber reinforced plastic, or graphite reinforced plastic. Damping of plastic reinforced with high modulus fibers is discussed. If high damping is desired (response magnification less than five) to survive a strong forcing function, the best current approach is a layered structure using a “rigid” matrix plastic for the constraint of a core composed of a damping material which is relatively soft and weak. The total structure is, of course, strong, well damped, and stiff due to the sandwich construction.
Acoustic Tests of Three Single Stream Referee Nozzles at the NASA-Lewis Research Center Outdoor Jet Acoustic Facility
Authors: Gutierrez Orlando A.
Published: October 2005

The characteristics of the jet noise produced by three single stream referee nozzles have been investigated statically at the NASA—Lewis Research Center outdoor jet acoustic facility. These nozzles were a 712-cm-diam conical convergent, a 10-cm-diam conical convergent, and an 8-lobe daisy nozzle with 712-cm equivalent diameter flow area. The same nozzles have been previously tested in other facilities such as the Royal Aircraft Establishment 24 ft acoustic wind tunnel, and the NASA Ames Research Center 40 × 80 wind tunnel. The test conducted covered pressure ratios from 1.4 to 2.5 at total temperatures of 810°K and ambient. Data were obtained using four different acoustic arena arrangements. Data taken with the different arrangements are compared. The results obtained are also compared with data from other facilities and with a prediction procedure developed elsewhere [i.e., Stone and Montegani (1979)].
Jet noise source location via nearfield-farfield correlations
Authors: McLean Ian R. , Richarz Werner G.
Published: October 2005

Many source locating schemes require a considerable investment of hardware and software. The method due to Fisher et al. [M.J. Fisher, M. Harper-Bourne, and S. A. L. Glegg, J. Sound Vib. 51, 1 (1977)] appears to be the most readily implemented. The present procedure is an “economy” version of the former approach: time delays between signal reception by several observers are used in a generalized triangulation algorithm to yield estimates of virtual source positions of jet noise. The delays are measured by means of cross correlations of narrowband near- and farfield microphone signals. Source distributions computed therefrom are compatible with those derived from more elaborate source locating techniques. The method is well suited for a “quick-look” analysis [Work supported by NSERC, Canada.]
V/C ratio as a postvocalic voicing cue
Authors: Port Robert F.
Published: October 2005

Changes in the phonological voicing of English obstruents following stressed vowels cause inverse durational effects on the vowel and following consonant. Several experiments extended our previous results suggesting that the relative duration of the V to C is an important cue for phonological voicing of the C when dominant cues of closure voicing and aspiration are absent. Synthetic stimuli of the words dibber and dipper, created with five durations of dib (140–260 ms) and nine medial stop closure durations (20–140 ms), were identified by 16 listeners. The boundary along the stop duration continuum was different for each dib duration, but, when plotted as the ratio of the stop closure to the preceding vowel, all curves were superimposed. In a matching 8xperiment with digger-dicker, the same effect was found except that the V/C ratio boundary was different for the velars—as was expected from production results. These findings, similar to the V:C-VC: syllable-type contrasts in other Germanic languages, imply that the voicing effect on preceding vowels cannot be handled insightfully with a postsegmental temporal implementation rule that modifies the vowel [D. H. Klatt, J. Acoust. Soc. Am. 59, 1208–1221 (1976)] since production and perception data now agree that the phonologlcally relevant parameter is an abstract ratio between these two intervals appropriate for a particular context. [Work supported by NIH.]
Labeling of VOT continua with fixed versus varied fundamental frequency
Authors: Bernstein Lynne E.
Published: October 2005

Bernstein [J. Acoust. Soc. Am. Suppl. 1 65, S112 (1979)] reported that children and adults use fundamental frequency (F0) in labeling stimuli from “gate”-“Kate” voice onset time (VOT) continua. Haggard, Ambler, and Callow [J. Acoust. Soc. Am. 47, 613–617 (1970)] reported similar results for the voiced/voiceless distinction between prestressed bilabial stops. The current study tested the assumption that F0 at the onset of voicing is typically taken into account in the perceptual process. Two groups of adult subjects participated. Group I, hearing all 24 stimuli (8 VOT and 3 F0 values) randomized across blocks, replicated previous results. That is, Group I subjects differentially moved the voiceless boundary towards lower VOT values as F0 increased. Group II, presented with each VOT-F0 combination separately, did not make use of the F0 cue. Thus, F0 appears to be an optional cue. The consistency with which Group I subjects differentially used the two cues supports some type of active “source assignment process” [A. E. Ades, J. Exptl. Psychol. Hum. Percept. Perf. 3, 673–685 (1977)] which takes account of an entire stimulus set and weights cue values within subsets of the whole. [Research supported in part by an NIH Post-Doctoral Grant No. NS07108, and NIH Grant No. NSI2045 awarded to Frederic Wightman.]
On generalizing the rabid-rapid distinction based on silent gap duration
Authors: Lisker Leigh
Published: October 2005

Several studies have reported that the duration of a silent gap affects listeners' decision in identifying an auditory stimulus as rabid or rapid. It appears to be accepted that silent gap duration is a cue to stop voicing. Several implications of this asserted connection between silent gap duration and the phonetic feature of voicing deserve some discussion. First of all, since the voicing feature is commonly said to distinguish the two phoneme sets/bdg/ and /ptk/, we should like some assurance that silent gap duration operates independently of stop place of articulation. Data exists which indicate that the effectiveness of silent gap duration is far from uniform for /b/-/p/, /d/-/t/, and /g/-/k/. Secondly, if a short silent gap elicits rabid responses, and /b/ is said to be voiced, i.e., characterized by glottal signal during closure, then we might expect listeners not to distinguish between presence and absence of such signal. In fact listeners can detect this difference, and some can indeed give it a phonetic interpretation. Thirdly, we may enquire whether the variation in silent gap duration needed to effect a shift in linguistic identification falls within the range observed in natural speech. A comparison of experimentally determined category boundaries with measurements of natural speech shows that the connection is not always close. [The support of the National Institute of Child Health and Human Development is gratefully acknowledged.]
Laryngeal adjustments in Japanese voiceless sound production
Authors: Yoshioka H. , Lö A. , Hirose H.
Published: October 2005

As part of a series of investigations on the production of sequences of unvoiced sounds in different languages, the current experiment was conducted using the combined techniques of photoelectric glottography, fiberoptics, and electromyography. Particular attention was paid to devoiced vowel production in various voiceless consonantal environments including geminates. The movement data show that the glottal opening gesture during a voiceless sequence containing a devoiced vowel is characterized by a monomodal pattern, unless the vowel occurs between voiceless fricatives. The results also suggest that the velocity and size of the glottal opening gesture vary according to the nature of the adjacent voiceless obstruents. The speed of the opening phase is slow when a stop precedes the vowel, and fast when a fricative precedes it. The peak glottal opening during the devoiced vowel is larger when a fricative either precedes or follows it, and smaller when the vowel is surrounded on both sides by single or geminated stops. [Work supported by NINCDS and BRSG.]
Aircraft flight tracking: An assessment procedure to determine noise impact
Authors: Bragdon C. R. , Thames Allan
Published: October 2005

Most airports rely on the tower and airline operators for flight information to assess aircraft noise. Such information usually differs from what actually occurs. A method is described to determine actual flight track data. Such a procedure is an important step in validating field data as well as developing noise contour information.
A method of measuring the acoustic impedance of the ground by using two or more microphones
Authors: Glaretas Constantine , McDaniel O. H. , Reethof Gerhard
Published: October 2005

This paper reports the results of a new experimental method to measure the real and imaginary parts of the ground impedance assuming the validity of Thomasson's model. A small loudspeaker placed above the ground is fed by a sweeping pure tone and the sound field is recorded by two or more microphones. The ratio of pressures at two microphone locations provides two equations (real and imaginary part) which are sufficient to determine the real and imaginary part of ground impedance. This method does not require knowledge of the spectrum and strength of the sound source. There are no assumptions as to the nature of ground cover except that of local reaction. For a given pair of microphones there is a frequency range of maximum excess attenuation difference where this method is most sensitive in determining ground impedance. The sensitivity can be extended by taking more than two microphone position measurements. [Work supported by FHWA.]
Prediction of impulsive noise levels and annoyance from meteorological data
Authors: Lewis N. D. , Luz G. A.
Published: October 2005

Changes in meteorological conditions can cause impulsive noise events to be inaudible at one time and highly annoying several hours later. Over 30 dB increases in level have been measured at many locations. To predict the expected levels from an event in the surrounding communities, a ray tracing computer prediction technique has been adapted to a field portable minicomputer. The computer program uses the vertical wind and temperature profiles, directly available from the minicomputer's primary use, to trace the acoustic rays and locate the areas of noise focusing. Knowing where the focusing occurs, the impact of the noise producing operation, in terms of annoyance, can be predicted.
Acoustic streaming in a nematic liquid crystal
Authors: Candau S. , Waton G. , Letcher S.
Published: October 2005

The acoustically induced birefringence has been studied in homeotropic cells of nematic liquid crystal. The observed features of the optical pattern reveal the coexistence of several streaming mechanisms. From the spatial distribution of the optical signal, both the velocity and the flow pattern have been experimentally determined for different test cell configurations. At oblique incidence of the acoustic beam on the cell, the dominant acousto-optic effect has been shown to be due to a two-dimensional streaming in the plane of the liquid crystal film. At normal incidence of the sound beam, the streaming is in the direction of the sound propagation. The dependence of the optical pattern on the acoustical intensity and on the thickness of the liquid crystal layer was found in good agreement with the previously developed models based on acoustic streaming [S. Nagai, A. Peters, and S. Candau, Rev. Phys. Appl. 12, 21–30 (1977); S. Candau et al. Mol. Cryst. and Liquid Cryst. (to be published)]. [Work partially supported by DRME and NATO.]
Pulse response of a nematic liquid crystal acousto-optic conversion cell
Authors: Hamidzada W. , Letcher S. , Candau S.
Published: October 2005

We have studied the response of a nematic liquid crystal acousto-optic conversion cell to a pulsed ultrasonic signal. It has been established (see previous abstract) that a streaming mechanism is responsible for the acousto-optic effect when using a cw signal, but a pulsed signal has been little studied in spite of its practical importance. We report on the effect of pulse width, pulse amplitude, and repetition rate of a 4-MHz wave on the integrated optical transmission and on the spatial representation of the sound beam. [Work partially supported by NSF and NATO.]
Amplification of sound by gas-phase reactions
Authors: Detsch R. M. , Bass H. E.
Published: October 2005

The amplification of sound in a reacting gas mixture has been observed. Energy for the amplification was provided by a photo-induced, exothermic H2/Cl2 reaction. A sound wave traveling through the gas can be regarded as a modulation of temperature about some steady-state value. As most chemical reaction rates increase with temperature, the regions of higher temperature experience an increase in the rate of the H2/Cl2 reaction. Since the H2/Cl2 reaction is exothermic, this increase in reaction rate causes an additional increase in temperature. Conversely, in regions of low temperature, the H2/Cl2 reaction is slowed causing a relative decrease in temperature. Thus the initial acoustic signal is amplified. The measured gain was 1.8 at 2 kHz compared to a gain of 4 predicted by Ellis and Gilbert [J. Acoust. Soc. Am. 62, 245–249 (1977)]. The source of this difference has not been resolved. [Work supported by NSF.].
Ultrasonic analysis of cumulative internal damage in filled polymers
Authors: Knollman G. C. , Martinson R. H. , Bellin J. L.
Published: October 2005

An ultrasonic technique is presented for studying dewetting and cumulative internal damage in filled polymers. A quantitative theoretical model is developed relating measured sound speed and attenuation in a polymer material to specific internal damage parameters such as effective vacuole size and number density. Ultrasonic assessment of cumulative damage has been conducted for applied uniaxial tension, compression, and shear strains. Estimates of the acoustic measures of damage obtained by applying the analytical model to experimental data on filled polymer materials are in excellent agreement with independent microscopic observations. The ultrasonic assessment approach which is presented for determining cumulative internal damage in filled polymers can provide a basis for age determination and estimation of residual lifetime. [Work supported by the Lockheed Independent Research Program.]
Use of ultrasonic spectroscopy to characterize calcified arterial lesions
Authors: Rooney J. A. , Gammel P. M. , Hestenes J.
Published: October 2005

Analysis of the minima in the spectra received from an unknown reflector as a function of angle can be used to determine the size and orientation of the reflector. The theory for received spectral minima resulting from the directivity patterns of reflectors was generalized to include arbitrary orientations of the target with respect to the receiver. Tests of the theory were performed using test objects and a reflective-mode time-delay spectrometer operating in the frequency range from 1 to 9 MHz. Results obtained for spectra from stainless steel rod targets with diameters from 0.16 to 0.64 cm were in good agreement with the theory. Measurements were made as a function of angle of the frequencies for which minima occurred in the spectra received from calcified lesions in in vitro arterial specimens. Computer analysis of the data yielded accurate values for the effective diameter and orientation of the calcified lesions. [This work was supported in part by the National Institutes of Health via contract NO1-HV-799301 and the National Research Council through its Research Associateship Program.]
Vibrational dynamics of gaseous bodies trapped in microscopic pores at megahertz frequencies
Authors: Miller Douglas L. , Nyborg Wesley L.
Published: October 2005

We have reported previously on the significance of microscopic gas-filled pores to the action of ultrasound on biological cells at low intensity levels. In this paper we describe progress in characterizing the oscillations set up in such pores when their dimensions are of the order to a few microns or less and frequencies are in the megahertz range. In one promising model for the gaseous oscillator the air-liquid interface vibrates as a membrane, fixed at its periphery, with tension equal to the air-liquid surface tension. Expressions for the resonance frequency, damping coefficients, and vibrational amplitude for cylindrical pores which are filled or partially filled with gas have been obtained. In addition, the expected scattering characteristics were determined for this model. Comparisons were made with experimental results on backward and forward scattering from commercial pore-containing membranes. [Work supported by NIH Grant GM-08209.]
Individual differences in auditory capabilities: A preliminary test battery
Authors: Johnson D. M. , Jensen J. K. , Watson C. S.
Published: October 2005

On occasion, listeners are encountered in psychoacoustic studies who have audiometrically normal hearing but seem unable to perform certain auditory tasks at the same level as other people. In addition, clinical research has related individual differences in auditory processing to some disorders of communication, cognition, and learning. However, it is difficult to label performance on many auditory tasks as “impaired,” in the absence of a normative data base. To this end, an auditory test battery is being developed. The first version includes masked and quiet thresholds; intensity, frequency, and temporal discrimination; and discrimination of tonal sequences. The components of the test battery were chosen to sample the auditory capabilities that underlie complex auditory processing, including speech perception. Each test is continued until asymptotic performance is observed in an adaptive psychophysical procedure. Although most audiometrically normal listeners perform very much like one another on all of the subtests, a few individuals show patterns of significantly deviant (<2σ) performance for specific clusters of subtests, such as those requiring frequency resolution or those requiring temporal discrimination. [Work supported by NIH.]
Broadband noise adaptation of RT at speech frequencies
Authors: Davis James M. , Weiler Ernest M. , Goldman Tom , Gunn Walter
Published: October 2005

As a follow-up to previous studies, 62 college students were adapted to 7 min of random noise. Changes in reaction time (RT) were measured at 0.5, 1, and 3 kHz. Adaptation as measured by an increase in reaction time was measured at all three frequencies. There was a significant decline in RT adaptation as frequency increased. Relation to other findings will be discussed.
Effects of noise on performance
Authors: Mulligan B. E. , Goodman H. Z. , Goodman L. S.
Published: October 2005

Previous research indicates that noise is likely to produce decrements in performance (not due to masking) only if task loads are high. We hypothesize that noise acts to increase task load such that noise and tasks may be interchangeable. This hypothesis was confirmed in an experiment involving two tasks—math problem solving M and auditory tracking T—performed individually and simultaneously with, and without, noise N. Equal numbers of male and female undergraduates participated in all conditions. A significant (p < 0.01) decrement in math performance was found only under the M + T + N condition, and the contributions of T and N to this decrement were not found to be different. Similarly, the largest significant (p < 0.01) decrement in tracking performance was obtained under the M + T + N condition. A small, but significant (p < 0.01), tracking decrement also was found under the T + N condition, probably the result of masking. Otherwise, the contributions of M and N to the tracking decrement were not different. These findings suggest that the effects of M, N, and T were functionally equivalent. Sex and interaction effects were not statistically significant. [Work supported by USDA USFS.]
Some effects of noise exposure on early development in the albino rat
Authors: Smiley C. S. , Wilbanks W. A.
Published: October 2005

Data will be presented on some effects of noise exposure on early physical and behavioral development in the albino rat (Rattus norvegicus). Twenty-four rat pups, age 9 days, were divided into three groups of eight pups each, matched by weight. One group was exposed to continuous narrow-band noise at a level of 80 dBA for 3 h on each of 30 successive days. A second group was exposed to the same noise for 3 h on each of 30 days at a level of 100 dBA. The third group (control group) was observed for 3-h periods for 30 days in the colony room with an average ambient noise level of about 60 dBA. The weight of each animal was measured daily. Behavioral measures (grooming, sleeping, play, locomotion-active, and locomotion-stationary) were taken during the 1st and last 15 rain of each of the sessions. Open field measures were taken on the last 3 days. The animals were then sacrificed, and their stomachs and adrenal glands were removed for histological examination. In terms of the behavioral measures taken, the 80- and 100-dB group showed greater activity levels, with incidence of grooming being the most affected. The animals exposed to 100-dB noise showed least weight gains. Stomach ulceration occurred only in the 80- and 100-dB groups. Adrenal gland weights of the 100.rib animals tend to be larger than those of the other groups.
Progress Report—Department of Labor study of noise and hearing loss
Authors: Melnick William
Published: October 2005

There is still considerable debate concerning the relationship of the physical parameters of noise to hearing loss. Under the Federal Employees' Compensation Act hearing loss compensation is a schedule award provided Federal Civilian employees who incur permanent hearing loss while performing their work tasks. The annual growth of hearing loss compensation claims has increased rapidly from 200 in 1966 to 8900 in 1976, totally 37 200 for that period. In evaluating claims the Office of Workers Compensation must decide whether or not the loss was occupationally related. Fulfilling this responsibility would be aided significantly if OWCP had a reasonable estimate of the distribution of hearing loss to the parameters of noise exposure including level, frequency, and duration not only for steady-state noise but also for fluctuating noise including impulse and impact noise. To this end, the Department of Labor has contracted a study of the information available particularly since 1974 and development of the needed distributions of hearing loss as a function of noise exposure. This will be a description of the investigative approach and the progress thus far. [Work supported by U.S. Department of Labor.]
Wave boundary conditions for a driven separated shear layer
Authors: Elder Samuel A.
Published: October 2005

Examination of the wave boundary conditions at the point of separation of a driven “free” shear layer leads to a number of new insights: (1) In the presence of an external driving field, shear layer waves move in an accelerated frame, causing a shortening of their natural wavelength. This has a significant effect on the timing of sheartone and cavity tone oscillations. (2) Stability parameters of a separated shear layer can be predicted from the structure of the upstream boundary layer. (3) Amplitude and phase of a driven stability wave are not arbitrary, but bear a fixed relation to the driving wave phasor at the separation point. (4) For a driving wave of constant amplitude, the initial growth of the stability wave must be spatial rather than temporal. It will be shown how these conclusions all follow from the continuity of velocity and shear stress at the edge of separation. Supporting data will be presented. [Work supported by a GHR contract with the Naval Ship System Command, administered by the DWT Navy Ship R & D Center.]
Frequency selectivity in hearing-impaired listeners after exposure to noise
Authors: Feth L. L. , Kidd G. , Burns E. M. , Mason C. R.
Published: October 2005

Psychophysical tuning curves (PTC's) were obtained before, and immediately after, exposing listeners to moderately intense noise. Our previous work with listeners having normal hearing has shown postexposure broadening of PTC's for noise exposures that produced essentially no temporary threshold shift. This report presents our initial results from several listeners with hearing losses attributed to cochlear pathologies. Again the results suggest that frequency selectivity measures may be more sensitive indicators of the deleterious effects of noise exposure than TTS. [Work supported by grants from the National Institutes of Health, U.S. Public Health Service.]
Discrimination of time-varying signals by hearing-impaired listeners
Authors: Collins M. J. , Levitt H.
Published: October 2005

For normal hearers, difference limens for tonal glides are larger for glides which precede fixed-frequency segments than for glides which follow the fixed-frequency segments [Collins and Stromberg, J. Acoust. Soc. Am. Suppl. 1 66, S9(A) (1979)]. In the present study similar measurements were made on each ear of two hearing-impaired subjects. The reference stimuli had 200-ms fixed-frequency segments of 2200 Hz and were preceded or followed by 30-ms glides with endpoints of 2710, 2200, 1690, or 1180 Hz. Difference limens were determined, using an adaptive procedure, on each side of each referent. The hearing-impaired subjects showed larger than normal difference limens, on the average. However, for frequency ranges where hearing loss was less severe, the results approximated normal. The deviations from normal were greater for glides which followed fixed-frequency segments than for those which preceded. Thus, the consistent difference between difference limens for preceding versus following glides for normal hearers was reduced in some instances and even reversed in others for the hearing-impaired listeners. [Work supported by NINCDS, Grant No. IF32 NS 06053.]
Digital processing of speech materials in the study of sensorineural hearing impairment
Authors: Bienvenue G. R. , Celmer R. D. , Prout J. H. , Michael P. L.
Published: October 2005

Existing literature suggests that the hearing mechanism deals with incoming speech material by filtering the signals into a series of frequency bands. The width of these bands has been referred to as the critical band and is a perceptual frequency bandwidth that is observed in a variety of psychoacoustic contexts. Researchers at the Environmental Acoustics Laboratory of The Pennsylvania State University have developed digital processing techniques for altering available recorded speech materials so that the frequency resolution available in the resultant materials may be controlled. Tapes have been produced wherein the frequency bandwidth resolution is limited to no better than one critical band and these tapes have been used in intelligibility testing. Some existing research indicates that the critical band is considerably widened in the individual with sensorineural hearing loss of cochlear etiology. The digital processing routines described above were also used in developing tape recorded materials with bandwidth resolution limits considerably wider than the normal critical band. The bandwidths chosen for this stage of the digital processing were based on empirical observations of the critical band of sensorineural hearing impaired patients. These recordings were also used in intelligibility testing with a variety of listeners. Implications of these studies for the clinical measurement of speech intelligibility and for the modeling of cochlear sensorineural hearing loss are discussed.
Effects of age and hearing acuity on response bias in auditory behavior
Authors: Blood Ingrid M. , Blood Gordon W.
Published: October 2005

The influence of age and hearing loss was investigated with respect to measures of sensory (d′) and decision (Beta) processes in an auditory signal detection task. Beta values obtained from a yes/no signal detection paradigm were used to estimate subject biases. Subjects were 12 normal hearing and 12 moderately hearing-impaired adults of two age groups (18–24 years and 65–76 years). The elderly subjects set more conservative criteria in reporting the presence or absence of faint auditory stimuli (higher Beta) than the younger ones regardless of hearing acuity. These higher criterion values suggest that the magnitude of hearing loss in the older population may be overestimated due to greater cautiousness on the part of the elderly. In the younger age group, more conservative responses were obtained for the normal hearing subjects than for the hearing impaired.
The fifty years with passenger rail cars
Authors: Cusick Leo J.
Published: October 2005

The problems in the early years prior to World War II did not focus on sound and vibrations but rather on passenger comfort, or perhaps convenience, when one thinks of the New York subway and its large passenger volume. After World War II, we entered into a new era as we had achieved many operating and passenger breakthroughs. As we think of rail cars in the latter part of the half century, or from about 1954, there still does not seem to be much concern about the sound and vibrations or the results of either, there was still the weight of the car, sheer impact on the existing structures, etc. As the art of car design supposedly increased, the problems appeared. There were many contributing factors, but perhaps the most important factor was a design to reduce weight, minimize maintenance on the car, and also on the track way. Many properties are continuing the example set in the mid fifties today. We should indicate to the transportation industry this “later day” concern for noise and vibration. It is as important as any other in designing and operating a rail car.
Suitability of existing vibration criteria for rail rapid transit systems
Authors: Paolillo A. W.
Published: October 2005

The rapid transit industry is faced with constructing and operating heavy rail rapid transit systems that do not impact adjacent communities. Groundborne vibration during construction and operation must be considered and appropriate criteria utilized. This paper reviews and compares numerous criteria relating to the effects of vibration on structures and occupants to vibration measurements and subjective response data accumulated by the New York City Transit Authority over the past 12 years. The levels of vibration measured have generally been below present criteria, yet strong reactions have occurred. Projects now underway to develop appropriate criteria are reviewed, and recommendations are made for additional study.
Measurement and analysis of the noise from and vibration in rapid transit elevated structures
Authors: Remington P. J. , Wittig L. E.
Published: October 2005

An analytical model of the vibration transmitted to and noise radiated from an elevated structure during the passage of a train has been developed. Using the roughness and discontinuities on the wheel and rail running surfaces as the starting point, the model is capable of predicting the effect on noise radiation of a number of noise control treatments. Field measurements of noise and vibration on a New York City Transit Authority elevated structure before and after installation of resilient fasteners have been compared with model predictions using parameters derived from laboratory measurements with acceptable agreement. Results of both field measurements and analytical model studies indicate that on the most common types of elevated structures in rapid transit use that noise directly radiated by the wheel and rail is equally as important as noise radiated by the structure.