bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of cracks in plates using guided waves
Authors: Eisenhardt Christoph , Jacobs Laurence , Qu Jianmin
Published: July 2002

This research combines laser ultrasonic techniques with the two-dimensional Fourier transform (2-D-FFT) to investigate the effect of cracks on the dispersion of Lamb waves propagating in thin aluminum plates. The high fidelity and broad bandwidth of these optical techniques are critical elements to the success of this work. The experimental procedure consists of measuring a series of equally spaced, transient waves in aluminum plates containing notches; a crack is simulated with a 1-mm-thick saw-cut notch. The frequency spectrum (dispersion curves) for each plate is obtained by operating on these transient waveforms with the 2-D-FFT; this procedure extracts steady-state behavior from a series of transient waveforms. This study quantifies the effect of notch depth (two notch depths are examined: one-fourth and one-half of plate thickness) on the dispersion curves of three different plate thicknesses (nominal thicknesses of 1, 1.5, and 3 mm). These dispersion curves show that a notch reduces the transmitted energy by an amount that is directy proportional to a notch’s depth. In addition, scattering by a notch causes definitive reductions in energy (evident in all modes) at certain frequency–wave-number combinations, thus providing experimental evidence of the relationship between crack size and the scattered Lamb wave field.
Development of an acoustics curriculum for architectural engineers
Authors: Muehleisen Ralph T.
Published: July 2002

The University of Colorado is currently developing a series of acoustic classes for undergraduate Architectural Engineers and graduate students in the Building Systems Program of the Department of Civil, Environmental, and Architectural Engineering. The two classes currently undergoing development emphasize noise control in buildings and the design of acoustic venues. The goal of the classes is to teach the fundamentals of acoustics as needed by Architectural Engineers in order to design quieter buildings and interact with acoustic consultants. In the classes, the students are given both theoretical and practical problems which involve both analysis and design. In addition, students get hands on experience by taking measurements of real rooms using standard equipment.
A method for evaluating automotive steering column noise
Authors: Kennedy Allan K. , Niehoff William E.
Published: July 2002

Automotive component suppliers are often called on to supply components which meet very vague requirements such as no audible noise from component. As odd as this might seem, this type of specification usually has a number associated with it. This number could be the measured A-frequency weighted sound pressure level, the total loudness, some averaged band sound pressure level, or even a vibration response level. The irony comes from the fact that most of these components do not generate noises on their own but only when subjected to intense vibration. To deal with this, component suppliers must somehow construct a measurement system which will capture these squeaks and rattles as the component is vibrated. This paper describes a measurement system and method for evaluating the noises generated by automobile steering columns. Descriptions are given of the various vibration inputs used, the equipment required, and the parameters measured.
Disk brake squeal analysis using the ABLE algorithm
Authors: Lou G. , Wu T. W. , Bai Z.
Published: July 2002

Disk brake squeal noise is due to unstable friction-induced vibration. In order to study the stability of the disk system, the finite element method (FEM) is used to model a typical assembly that includes one rotor and two pads. Coulomb’s friction law is applied at the contact interface between each pad and the rotor. Due to continuity of displacement in the normal direction, some degrees of freedom are condensed out. The FEM matrices of the dynamic system then become unsymmetric, which will yield complex eigenvalues. Any complex eigenvalue that has a positive real part will indicate an unstable mode. In real-world applications, the FEM model could include thousands of degrees of freedom. Fortunately, the resulting FEM matrices are sparse and a dynamic allocation scheme can be used to store only the nonzeros. Then a recently developed iteration method called ABLE (Adaptive Block Lanczos Method) is used to search only the complex eigenvalues with a positive real part in a certain user-specified frequency range. This algorithm has been shown to be very efficient and effective in predicting the unstable vibration modes.
Development of a screening version of the communication profile for the hearing impaired
Authors: Demorest Marilyn E. , Wark David J. , Erdman Sue Ann
Published: July 2002

The 163-item CPHI provides a diagnostic profile of scores on 25 scales that describe a client’s adjustment to hearing impairment. Factor structure of the instrument shows that two important factors it assesses are communication performance (an aspect of hearing disability) and psychosocial adjustment to hearing impairment (an aspect of handicap). The goal of this study was to develop a brief instrument, to be used in conjunction with standard audiometric assessment, to screen for disability and handicap. A pseudo-random sample of 1000 cases was drawn from a large, heterogeneous clinical database. Item response theory was used to derive item characteristic curves, and item selection was based primarily on item discrimination. Nine items were chosen to screen for communication performance, and 11 were chosen to screen for psychosocial adjustment. Pass/Fail criteria were developed, and sensitivity and specificity were evaluated in a holdout sample of 319 cases.
Sensitivity of resonance-frequency shifts to defect location in adhesive-bonded joints
Authors: Hopkins Deborah , Nakagawa Seiji , Nihei Kurt , Neau Guillaume
Published: July 2002

Techniques based on frequency shifts and mode-shape analysis are being investigated to determine their feasibility for characterizing defects in adhesive-bonded joints in automotive structures. It is well known (Rayleigh–Ritz derivation) that introduction of a crack-like defect into a structure reduces its stiffness and results in a corresponding downward shift in resonance frequencies. Experimental and modeling results show that analysis of resonance-frequency shifts is much more complicated for bonded joints where the defect consists of a gap in the adhesive layer. Structures containing a defective joint sometimes exhibit higher-resonance frequencies than a structure with an undamaged joint. Such results have been observed in laboratory experiments on aluminum plates with adhesive-bonded T joints, and in finite-element simulations for a variety of structures. In all cases, the defects studied are gaps in the adhesive layer of the joints. While the reduction in mass associated with a gap in the adhesive layer is very small, the mass effect overwhelms the frequency-decreasing effect of the reduced stiffness when the defect is located in a low-stress region of the joint. Thus, the direction and magnitude of frequency shifts depend on the resonance mode and the location of the defect.
High-frequency transfer function model of the vocal tract sections using FEM matrix condensation and transfer matrix techniques
Authors: El-Masri Samir , Miki Nobuhiro
Published: July 2002

Using numerical tools such as the Finite Element Method (FEM) for acoustical modeling of the vocal tract would require a huge number of nodes and elements. In this paper, the matrix condensation and transfer matrix techniques [A. Craggs, J. Sound Vib. 132, 393–402 (1989)] adapted to a three-dimensional model of the vocal tract section analysis will be introduced and discussed. Using these new FEM techniques, which use only the nodes at the input and output of the structure, the transfer function can be computed with a very small matrix comparing to standard FEM. The second goal of this research is to attempt to discover some geometrical parameters which could influence the transfer function. This investigation could be useful to make a new electrical vocal tract model which would consist of cascade transfer functions controlled by parameters. The study of the transfer functions will be carried out in low and high frequencies. [Work partly supported by Japanese CREST project.]
Automatic ToBI prediction and alignment to speed manual labeling of prosody
Authors: Syrdal Ann K. , Hirschberg Julia , McGory Julie T.
Published: July 2002

ToBI (Tones and Break Indices) prosodic labeling of a speech corpus is a slow, labor-intensive process that typically takes from 100 to 300 times real time, even with experienced labelers. An experiment was conducted to determine: (1) whether manual correction of automatically assigned ToBI labels would speed up the labeling process; and (2) whether default labels introduced any bias in label assignment. A group of four graduate linguistics students previously trained in ToBI labeling were paid participants in the study. A large speech corpus of one female speaker reading several types of texts was labeled over a period of nine months. Half of each recording was labeled in the normal fashion ‘‘from scratch’’ without default labels, and the other half was presented with preassigned default labels for labelers to correct. Default ToBI labels were predicted from text using techniques developed for text-to-speech synthesis. Both labeling methods used standard Entropic waves+ tools developed for ToBI transcription. A log file was created during the labeling of each file that identified labeler, filename, method, and beginning and ending times of each session. Results indicate that labeling from defaults was faster than standard labeling, and that defaults had relatively little impact on label assignment.
Continuum mechanical model of the tongue and mouth floor
Authors: Wilhelms-Tricarico Reiner
Published: July 2002

In this new model, the mouth floor and the tongue body are treated as blocks represented by tri-quadratic finite elements in which the muscles are modeled as continuous directed fields of the fiber direction. Collision with the hard palate and other rigid structures is modeled by subdividing the surface into small triangles for rapid collision detection and through calculating forces by a penalty method to enforce impenetrability of the rigid structures. A similar method is provided for the more complicated case of the collision between tongue body and soft floor of the mouth. The model can be coupled with a model of the jaw and hyoid where muscles may be modeled as contracting strings. The moving hyoid and jaw provide kinematic constraints for the tongue/mouth-floor model. Active muscle stress is generated by a Hill model of muscle shortening combined with a rational extension for muscle elongation, and a polynomial curve represents the relation between muscle length and stress. The stiffness matrix and damping matrix of the system (used for the implicit time stepping method solving the equations of motion) are derived directly from the continuum mechanical muscle model. An overview of the theory and numerical examples will be presented.
The use of spectral versus temporal cues to recognize speech
Authors: Mandal Arindam , Davis Laura J. , Espy-Wilson Carol , Matthies Melanie
Published: July 2002

Previous work has shown that listeners are able to use temporal information to identify spectrally limited consonants [Shannon et al., Science 303–304 (1995)]. In this study, we used spectrally impoverished speech to: (1) investigate the performance of a temporal-based automatic classifier; (2) describe the performance of human listeners; and (3) compare the performance of the classifier with human listeners. For the automatic classifier, acoustic events are extracted from a cross-spectral temporal measure that computed onsets and offsets of acoustic energy. The strength and time difference between these acoustic events served as input to the classifier. The results from human listeners showed that their ability to identify nasality and voicing remained fairly good. In addition, recognition of manner for stops and fricatives remained high. As the speech signal was degraded, listeners often confused sonorants with fricatives. The temporal-based classifier did not make such confusions. The classifier is able to identify manner, voicing and nasality well and the results remain fairly consistent across different levels of degradation. Thus, these results show the importance of temporal information and they suggest that human listeners may not optimally combine all cues to identify spectrally impoverished consonants. [Work supported by ONR Supervised MURI grant Z883402.]
Time-frequency analysis of the backscattering by tilted finite cylindrical shells
Authors: Morse Scot F. , Marston Philip L.
Published: July 2002

Previous experiments and analysis have shown that the backscattering from thick-walled finite cylindrical shells can be significantly enhanced in and above the coincidence frequency region over a large range of angles of the incident sound [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998)]. In this presentation, impulse backscattering measurements performed with a wide bandwidth PVDF sheet source are analyzed in terms of a simple joint time-frequency representation. When plotted for a sequence of specific tilt angles, it is possible to identify and then observe the progression of individual ray contributions as the coupling conditions to the shell are changed. In the frequency range investigated, where ka<45 and kh<3.4, several of the surface waves excited are highly dispersive and as a result are launched on the shell over a wide range of frequencies and tilt angles, including end-on incidence. The analysis described also confirms various features of the responsible scattering mechanisms predicted by ray theory. The results show the importance of time-frequency analysis to the identification of back scattering in a situation where no exact reference solution is available. [Work supported by the Office of Naval Research.] a)Currently with Naval Research Laboratory, Code 7136, 4555 Overlook Ave. SW, Washington, DC 20375.
Target strength
Authors: Dragonette Louis
Published: July 2002

Chapter 9 of Urick’s Principles of Underwater Sound is titled ‘‘Reflection and Scattering by Sonar Targets: Target Strength’’ [R. Urick, Principles of Underwater Sound (McGraw–Hill, New York, 1975), p. 263], and while this chapter gives an excellent review of target strength definitions, simple echo formation processes, and echo characteristics, it is the table, ‘‘Target Strength of Simple Forms,’’ compiled by Urick from several obscure sources, that is invaluable to those who deal with target strength issues on a routine basis. A typical first approximation to the target strength (TS) of a body of interest is made by approximating the scatterer as a combination of the simple shapes listed in the table, and then summing up the separate rigid-body responses to produce a first-order target strength prediction. Some common-sense principles that derive from such an exercise are discussed as well as comparisons between such first-order predictions and the results and understanding obtained from modern theoretical and experimental approaches. [Work supported by ONR.]
Transient signal processing for marine animal localization
Authors: Ferguson Brian G. , Cleary Jane L. , Lo Kam W.
Published: July 2002

A technique for locating a point source in a constant velocity medium using time delay measurements from a passive stationary sensor array is applied to the localization of underwater biological transient sources. The curvature of the spherical wave front emanating from a source is sensed at a three-element linear receiving array by estimating the inter-sensor time delays, which are then processed to extract the range and bearing of the source. The technique is used to estimate the source positions of snapping shrimp sounds recorded in Sydney Harbour (Australia) during a high-frequency sonar experiment. Plotting the source positions for a series of acoustic transient events produces a spatial distribution of the local snapping shrimp population. Passive ranging errors caused by imperfect knowledge (noncollinearity) of the sensor positions are discussed. In addition, an acoustic method is presented for estimating the in situ sensor positions of the array by processing the sensor data for mechanical transients produced by spatially distributed sources with known positions.
Rapid estimation of dolphin whistle bearings using a sparse towed hydrophone array
Authors: Thode Aaron M. , Norris Thomas , Barlow Jay
Published: July 2002

Acoustic bearings were obtained from modulated dolphin whistles (3–20 kHz range) using a three-element towed array with a 9-m aperture. This system has performed reliably on animals whose range was known to be greater than 3 km away. It also has worked well under Beaufort five sea states. The algorithm presented here is unusual in that the signals are beamformed in the frequency domain, instead of being cross-correlated in the time domain. Beamforming on such a sparse array is feasible because the signals are broadband, allowing beams to be computed at multiple frequencies. The grating lobes, or false locations, shift their bearings with frequency, while the true source position remains fixed and can thus be identified. Frequency beamforming may complement temporal cross-correlation methods in situations when the signals are heavily contaminated with noise and multipaths, when multiple animal calls are received simultaneously, or when long time sequences need to be processed and compactly stored to memory. [Work funded by U.S. Dept. of Commerce.]
Acoustic detection and identification of singing cicadas (Homoptera: Cicadoidea) in Europe and in S.E. Asia
Authors: Gogala Matija
Published: July 2002

Acoustic methods of detection and identification of species can be effectively used in the field for singing cicadas (Homoptera: Cicadoidea). In many cases they emit acoustic signals loud enough and containing such frequencies that they can be detected by the unaided human ear. Nevertheless, many species emit high-frequency songs, which are not easily audible. For detection of such signals ultrasonic detectors can be successfully used. In Europe calling songs of most species differ mainly in rhythmic or amplitude patterns. In Slovenia and Croatia all existing species can be with high certainty detected, recognized and located with the use of suitable recording equipment (ultrasonic detectors included). Completely different is the situation in tropical forests of S.E. Asia, where many species emit also frequency or frequency band modulated songs. There the main problem for using acoustic approach for detection and identification of single species is not in recording technique or in recognition of species specific patterns, but in identification of cicadas and in matching the species with recorded songs. These difficulties can be to some extent overcome with recording of caged specimens, stimulated with various methods to sing under such conditions.
Blueback herring respond to brief ultrasonic stimulus sounds
Authors: Schilt Carl R. , Nestler John M.
Published: July 2002

Captive schools of Blueback Herring (Alosa aestivalis) were subjected to 1-h long treatments of short 118-kHz sounds applied from a piezoelectric transducer submerged outside a vinylized canvas pen that was suspended in Richard B. Russell Reservoir on the Savannah River. In the experiments reported here, the effect on herring distrbution of 3.8-ms long bursts at 13 repetitions/s (5% duty cycle) was compared to the effect of both another 118-kHz sound treatment (with a different duty cycle but the same source level) and a sound-off treatment. Each experiment compared herring distributions in the pen with the three treatments applied in a cross-over design. The experiments lasted six days each with six 1-h treatments per day. All of the several combinations of pulse duration and repetition rate contained the herring near the end of the pen farthest from the sound source but hour-long continuous wave treatments produced only a brief startle response at stimulus onset. [Work supported by U.S. Army Engineer District, Savannah of the U.S. Army Corps of Engineers.]
Vaporization of micrometer size droplets in simulated in vivo environments
Authors: Kripfgans Oliver D. , Miller Douglas L. , Fowlkes J. Brian , Carson Paul L.
Published: July 2002

Droplets were generated for a range of albumin (bovine) concentrations. Resulting emulsions were examined for size distribution, number density and yield. Albumin concentrations as low as 1 mg per ml were capable to form stablized droplets. Changes in number density and mean size were observed. Reducing the amount of albumin by a factor of 16 resulted in an increase of the number density by a factor of 40 while the mean droplet size decreased by a factor of 2.5. The measured droplet yield was approximately 30%. Droplets were vaporized using short ultrasonic tone bursts for frequencies ranging from 1.5 to 8 MHz. Two 1-cm Zerdine 81 layers of acoustic attenuation of 0.5 dB/MHz/cm were overlaid on the flow tube used. Droplets were phase transitioned in saline and in blood. Pressure thresholds for vaporization were acquired for conditions with and without Zerdine as well as saline or blood as bulk fluid. It has been seen that the threshold in saline increased by approximately 25% by introducing the Zerdine layers (1.5 MHz) and 60% for the Zerdine-blood combination. [Work supported in part by PHS Grant No. R01 HL54201 from the National Heart, Lung and Blood Institute.]
Computer simulation of a plane progressive wave within a sphere produced by directional sources on the surface of the sphere
Authors: Lubell Alan H.
Published: July 2002

A 34-year-old paper by the author gave a prescription for a closed surface array based on the Helmholtz Integral Theorem [Alan H. Lubell, ‘‘Use of Directional Probes for Nearfield Measurements,’’ USNJUA 1150–1152, June 1965]. The referenced paper stopped short of physically describing the required transducers. The present paper gives a generic description of a directive source in terms of orientation, spacing, and feeding of a pair of small nondirectional reciprocal transducers. Directive pattern and required time delay for a given position on the sphere is specified. Since these transducers operate in a compliance controlled mode, they are amenable to simple computer simulation. 916 total sources making 408 directional sources are carefully positioned on two concentric and closely spaced spherical surfaces and maps made of the contained field. Excellent results are obtained over a wide range of frequencies both as regards uniformity of the contained field and the null property outside the sphere. This proves the value of the array for simulating a distant receiver for the purpose of measuring the transmitting patterns of a large directional transducer in a facility of limited size.
Photoacoustic localization of small gas leaks on cylindrical surfaces
Authors: Yönak Serdar H. , Dowling David R.
Published: July 2002

Detecting and localizing leaks in or on manufactured components that contain pressurized gases or liquids is a critical quality control process. Previous work has shown that gas leaks on a flat surface with a leak rate on the order of one cubic centimeter per day can be reliably detected and accurately localized using photoacoustic signals, four microphones, and incoherent broadband matched-field processing (MFP). However, leaks may not lie on flat surfaces. This work considers a case in which the surface where the leak resides is cylindrical. Photoacoustic sound is generated by rapidly scanning a carbon dioxide laser tuned to 10.6 micrometers (μm) over the suspected leak area. Sulfur hexafluoride, which has strong spectroscopic absorption near 10.6 μm, is the tracer gas. Localization results obtained using Bartlett MFP and minimum variance MFP are compared. The physics behind photoacoustic signal generation is discussed. Experimental results are presented. [Sponsored by Ford Motor Company.]
Computer modeling and analysis of a cylindrical piezoceramic transducer with interior solid filling
Authors: Balabaev Sergey M. , Ivina Natalia F.
Published: July 2002

A computer model of cylindrical piezoceramic transducer with interior solid filling based on the mixed finite element—boundary element method is examined. The work of the transducer with calculation of acoustic radiation to water is considered. The transmitting voltage responses and beam patterns of the transducer are presented. If the filling has small acoustic resistance, the transmitting voltage response of this transducer has two maxima, thus the transducer with interior solid filling is similar to free-flooded transducer. The first (low-frequency) maximum is connected with the resonance of the interior filling, the second maximum is connected with the resonance of the piezoceramic cylinder. If the filling has great acoustic resistance, the transmitting voltage response of this transducer has one maximum only. The optimum length of the transducer is determined. At the optimum length the frequency characteristic of the radiation-voltage response becomes uniform and wide band; i.e., at this length, the responses at the volume and radial resonances are approximately equal, and the response flatness (the difference between the values at the two resonances and at a minimum between them) is within 3 dB.
Design and development of a parametric sounder for sodar
Authors: Chandra Mukesh , Gera B. S.
Published: July 2002

Sodar is an acoustic remote sensing technique for monitoring the atmospheric boundary layer. Conventional sodar uses a parabolic dish with a transducer at its focus to transmit acoustic burst at 2 kHz. System performance depends upon the antenna directivity and transducer sensitivity which in turn are functions of the dish diameter and operational frequency. To achieve directional beam with nearly zero sidelobes, even at lower frequencies, a parametric sounder has been designed and developed. The parametric acoustic signal is realized by nonlinear interaction of two high-power ultrasonic waves of frequencies in the vicinity of 20 kHz and of acoustic pressure of 140 dB (approx.). The directional and propagation characteristics of the resulting audio signal have been studied to ensure parametric nature of the virtual source. The resulting audio beam is narrow with a semi beam-angle of less than 3 deg at 3-dB down points. The directional pattern shows the absence of side-lobes. The transmitting system is capable of sending a coded signal in any desired direction. The performance of the new and inexpensive parametric sounding system for sodar application has been evaluated and discussed in the light of comparative observation.
Penn State World Campus courses in noise control engineering
Authors: Burroughs Courtney B.
Published: July 2002

One of the first offerings in the Penn State World Campus is a series of four graduate-level courses in noise control engineering. These courses use computer-based technology to deliver the courses to students at a distance. Therefore students can take the courses from any location on a very flexible schedule, making the courses available to students who are committed to a career and/or family. Course material is sent to students on CD-ROM and interactions between students and with faculty are conducted via an e-mail server. Computer technology permits illustrative animations in the text. Assignment involves interactive animations and virtual experiments. Students collaboate on realistic noise control projects which involve measurements and analyses conducted using virtual instruments. Descriptions of the courses, the multimedia used to develop and deliver the courses, and the interactions between students and faculty are presented.
Temporal fine structure of organ sounds in churches
Authors: Meyer Jürgen
Published: July 2002

The impressive sound of an organ is based on a typical frequency and time structure of the sound field which is created by the instrument’s properties as well as by the room. Flue pipes have onset times of about 100 ms for middle pitch increasing to 1 s for the lowest pipes. Additionally, the onset time of the ‘‘full organ’’ may be prolongated by the building-up time of the wind pressure. Often, the definition of the tonal onset is supported by a short articulation noise. As the 60-dB decay time is extremely short, the organ particularly needs the reverberation of the room. The reverberation time of most historic churches is not only rather long but shows a typical frequency characteristic depending on the architectural style: representive examples include churches playing an important role in J. S. Bach’s musical life. The long reverberation leads to a rather long onset time of the statistical sound field in the room and often, the early reflections arrive divided into two groups: higher frequencies coming from columns and (later on!) lower frequencies coming from sidewalls. This effect additionally prolongates the onset of low tones and creates the characteristic ‘‘heavy and sacral’’ sound of the organ.
Using visitor responses to rank-order national park soundscapes
Authors: Miller Nicholas P.
Published: July 2002

Simultaneous collection of acoustic data and surveying of visitors at sites in national parks has permitted development of ‘‘dose-response’’ curves. These curves show what percent of visitors reported annoyance or interference with ‘‘natural quiet’’ from tour aircraft noise, as a function of the aircraft sound. Two measures of aircraft sound correlated reasonably with the visitor responses: percent of time aircraft were audible and difference between the aircraft and the nonaircraft produced equivalent level, Leq. Using the relationships between these two visitor responses and these two measures of aircraft sound, a framework is developed that permits a rank ordering of park locations in terms of visitor reaction, once these two metrics have been measured at the location.
Respondents’ interpretations of impact measures for dose-response studies
Authors: Baumgartner Robert
Published: July 2002

Dose-response studies conducted at several National Park Service areas showed that respondents reported higher levels of impact for interference with the appreciation of natural quiet and sounds of nature than for the traditional annoyance measure of were you bothered or annoyed by aircraft noise during your visit to [SITE]? These differences led to questions about respondents’ interpretation of the two measures and the appropriateness of each for policy decisions. To probe this issue, 21 cognitive interviews were conducted with respondents to a dose-response survey sponsored by the USAF at White Sands National Monument. The interviews probed respondents’ question understanding and their interpretation of key phrases (e.g., bothered or annoyed and interference with appreciation of the sights and sounds of nature). In addition, they were asked how they selected scale points for each response and what types of events or conditions would prompt them to change their selected point. These qualitative data indicated that interference and annoyance were related concepts, but measured different types of impacts. Interference was interpreted as more event-specific and transitory, whereas annoyance was a summary evaluative term indicating a threshold level of negative reactions.
Acoustic target characterization for inertial confinement fusion
Authors: Asaki Thomas J. , Hale Thomas C.
Published: July 2002

Numerous hurdles mark the path leading to successful inertial fusion energy and these tasks are being addressed in a multinational effort. Much work at Los Alamos National Laboratory (LANL) has focused on addressing theoretical target design, target fabrication, and target characterization. Favored target designs incorporate millimeter-size beryllium or plastic shells filled to near-critical density with hydrogen isotopes. This fuel is then solidified at cryogenic temperatures and allowed to symmetrize through the natural process of beta layering. Implosion physics constraints demand very strict design standards on these targets in terms of layer sphericity, concentricity, and surface smoothness. Design-size targets for the National Ignition Facility (NIF) have recently been manufactured at LANL. Resonant ultrasound spectrocopy (RUS) is now being implemented as a valuable tool in many aspects of target characterization and it is especially useful for examining the interior of opaque objects. RUS has now been used to determine general aspects of target construction, fill densities and pressures, and the shape of interior cavities. Studies continue in the areas of direct observation of beta layering in opaque shells and supporting fluids properties measurements. Improved sensitivity and practical usablity of ultrasound techniques have come through the implementation of optical vibration sensing.
Physical modeling and computer software for acoustic ecology problems
Authors: Kostarev Stanislav A. , Makhortykh Sergey A.
Published: July 2002

In the report physical modeling and the computer system for acoustic ecology problems based on it are presented. An investigation of acoustic fields and modeling of wave propagation in the case of media with a complex heterogeneous structure has been carried out. Both dissipation and nonhomogeneities were considered. In a particular case of soil, models were formulated and their computer analysis, including the problem of acoustic waves propagation, was carried out. Both bulk and shift waves were taken into account. Several types of elastic shells as the sources, merged in soil, were considered (including particular cases with realistic parameters of underground transport tunnel inner). Numerous measurements on the ground were carried out for the verification of proposed models. Computer realizations of described technology for acoustic and geophysics fields analysis have been obtained. In particular a software package for analysis of vibration and acoustic situation on the ground surface and estimations of possible measures for vibration reduction is proposed. A new combined digital-analytic method for physical problems investigation has been used. It is based on the adaptive expansions of considered functions in an adjustable orthogonal function basis. Obtained results were applied for modeling of the vibration field from underground railways and ground surface building operations.
Cat auditory nerve fiber recovery functions
Authors: Javel Eric
Published: July 2002

The literature contains few examples of auditory nerve fiber response recovery functions. To provide more information, hazard functions were compiled from 10–120 s samples of spontaneous and driven activity. Responses formed two groups that differed only in the amount of activity at short (<1.5 ms) inter-spike intervals. The larger group possessed hazard functions described by an equation with one time constant, i.e., R(t)=3D 1-e(S-t)/t, where R(t) is the amount of response recovery at time t, S is the starting time of the recovery process (analogous to absolute refractoriness), and t is the time constant. The other, smaller group possessed hazard functions similar to that reported by Gaumond et al. [J. Neurophysiol. 48, 856–873 (1982)], in which a portion of the response recovers rapidly at the end of the absolute refractory period and the remainder recovers more slowly. This behavior was described well by a two-process equation, i.e., R(t)=3DM (1−e(Se−t)/t e)+(1−M)=(1−e(Sl−t)/tl) where Se and Sl are the starting times of the ‘‘early’’ and ‘‘late’’ recovery processes, t e and t l are their time constants, and M is the amount of recovery attributable to the early process. S, Se and Sl ranged from 0.7–1.3 ms, t e ranged from 1.2–1.5 ms, t and t l ranged from 3–6 ms and usually decreased somewhat with level, and M ranged from 0.2–0.4.
Steady state response as an indicator of basilar membrane travel time
Authors: Ghiassi Saber , Buss Emily , Grose John , Hall Joseph
Published: July 2002

It has been suggested that neural firing in response to a broadband stimulus can be maximized by a frequency sweep that counteracts the frequency-specific delays of basilar membrane propagation. To test this, synchrony of neural discharge across frequency was estimated by measuring steady state responses (SSRs) elicited by harmonic complexes whose components were in either negative or positive Schroeder phase. These stimuli reduce to periodic frequency glides, ramping upward (negative Schroeder) or downward (positive Schroeder) in frequency, but having unfiltered envelopes that are identical. The data from three normal-hearing listeners support the basic notion that an upward frequency glide can lead to improved neural synchrony. Higher levels of neural synchrony occurred at higher rates for higher center frequencies, consistent with shorter travel times as a function of frequency for higher center frequencies. The derived travel times were consistently faster than those typically predicted via passive models of basilar membrane wave propagation. Interpretation of these data require caution in light of possible effects of unbalanced evoked responses from the various frequency regions stimulated, nonlinear summation of responses across channels, or nonlinearity of frequency-dependent delays in basilar membrane propagation. [Work supported by NIH NIDCD RO1-DC01507.]
Hearing in the speech range as a key to a puzzle of loudness constancy and loudness adaptation
Authors: Maguire Tracy , Weiler Ernest M. , Boyce Suzanne , Dou Hongwei , Kretschmer Laura
Published: July 2002

Loudness adaptation has been a controversial phenomenon, partly due to differences in subject behavior at different frequencies, and partly to conflicting results from studies using different methodology. In this study, parallel experiments were run contrasting two methodological paradigms, the Ipsilateral Comparison Paradigm (ICP) and Simple Adaptation (SA). Both used magnitude estimation to assess loudness adaptation—decline—at 60-dB ANSI. Forty students with normal hearing (ages 18–45) were divided into four groups, tested at 1, 4, 6, or 8 kHz, with ICP vs SA as the within-groups variable. Results showed significantly greater adaptation in the ICP as opposed to the SA condition at 1, 4, and 6 kHz. There was no significant difference at 8 kHz. Thus mean differences between the two methods were greatest at the frequencies most closely coinciding with the meaningful frequency range of speech, as previously hypothesized [E. M. Weiler et al., J. Acoust. Soc. Am. 101 (1997)]. It is suggested that differences in subject behavior for speech and nonspeech frequencies may be modulated by differences in active processes of perception. These results will be discussed in the light of recent related work.
Do bilinguals perceive the tritone paradox as monolinguals do?
Authors: Chalikia Magdalene H. , Vaid Jyotsna
Published: July 2002

When a two-tone pattern in which the tones are related by a half-octave interval (tritone) is played in any key, listeners hear it as descending or ascending, on the basis of an individual pitch class template (Deutsch, 1986). Perception of this pattern has been reported to vary with the geographical region in which the listener grew up, and it has been suggested (Deutsch, 1994; Ragozzine and Deutsch, 1994) that the characteristics of ones pitch class template may vary among speakers of different dialects and languages. This hypothesis was tested by asking how bilingualism may influence the perception of the tritone pairs. Spanish/English bilinguals were tested and their performance was compared with that of a group of English speakers. All listeners were from Texas. The results indicate that bilinguals perceive the patterns differently than the monolinguals. Envelope influences will also be discussed.
Interstimulus interval as an effective measure of auditory spatial attention
Authors: Skelly Michael A. , Pastore Richard E. , Crawley Edward J.
Published: July 2002

Previous experiments investigating auditory spatial attention have focused on the importance of the stimulus onset asynchrony (SOA) between the spatial cue and target. These experiments have reported accelerated target discrimination judgments for longer SOAs. Although this measurement provided insight into the working mechanisms of spatial attention, there typically was a confound between SOA and the interstimulus interval (ISI). The present experiment was designed to evaluate the importance of SOA, ISI, and cue duration by systematic manipulation of these variables (where SOA is composed of cue duration and ISI). Each trial began with a binaural cue that provided no information about spatial (ear) location of the monaural target, but alerted the participant to the anticipated presentation of the target. Listeners responded by indicating the target ear. The results indicate that longer SOAs are not required to accelerate target discrimination. Instead, the presence of a silent gap between the presentation of the cue and target stimulus (ISI) is far more important for accelerating performance. Furthermore, listeners seem adept at using available information in developing effective attentional strategies.
Gap discrimination and speech perception in noise
Authors: Fagelson Marc A.
Published: July 2002

The relation between discrimination of silent gaps and speech-in-noise perception was measured in 20 normal-hearing listeners using speech-shaped noise as both the gap markers and the noise source for speech testing. In the gap discrimination experiment, subjects compared silent gaps marked by 60 dB SPL 250-ms noise bursts to standards of either 5, 10, 20, 50, 100, or 200 ms. The gap results were most similar to those reported by Abel [S. M. Abel, J. Acoust. Soc. Am. 52, 519–524 (1972)] as ΔT/T decreased non-monotonically with increased gap length. In a second experiment, the California Consonant Test (CCT) was administered at 50 dB HL via CD in three conditions: quiet, +10 S/N, and 0 S/N. Results from both experiments were correlated and the association between ΔT/T and CCT scores was generally negative. Listeners who discriminated the gaps with greater acuity typically had higher speech scores. The relation was strongest for the smaller gap standards at each S/N, or when performance for any gap duration was compared to the CCT results obtained in quiet.
A comparison of two auditory models using monaural, Doppler-like signals
Authors: Ericson Mark A. , Feth Lawrence L.
Published: July 2002

Detection threshold predictions of an excitation pattern and an intensity-weighted average of instantaneous frequency (IWAIF) model were compared with empirical data. Monaural changes in intensity and frequency of a moving sound source were simulated over headphones. A pair of 400-ms duration signals, separated by a 100-ms inter-stimulus interval, were utilized in an adaptive two-alternative, forced-choice procedure. Detection thresholds of velocity induced frequency and distance induced intensity changes were measured on seven listeners. Sound source motion was simulated along linear trajectories with three minimal distances of 1, 10 and 100 m at the point of closest passing. Two sets of stimuli were chosen to test the models. The first set consisted of puretones at frequencies of 200, 1000 and 5000 Hz. The second set contained three-tone, harmonic complexes with a fundamental frequency of 1000 Hz and harmonic frequency separations of 100, 200 and 400 Hz. With the pure-tone stimuli, the excitation pattern model underestimated the detection threshold at 5000 Hz. With the harmonic stimuli, the IWAIF correctly predicted slightly degraded thresholds with increasing frequency separation of the harmonics, whereas the excitation pattern model predicted a near constant detection threshold for all harmonic frequency separations.
Individual differences in effectiveness of cochlear implants
Authors: Pisoni David B.
Published: July 2002

The efficacy of cochlear implants has been firmly established. However, the effectiveness of cochlear implants varies widely and is influenced by demographic and experiential factors. First, there are enormous individual differences in both adults and children. Some patients show large changes in speech perception whereas others show only modest gains. Second, age of implantation and length of deafness affect outcome measures. Younger children do better than older children and children who have been deaf for shorter periods of time do better than children who have been deaf for longer periods of time. Third, communication mode affects outcome measures. Children from ‘‘oral-only’’ environments do much better than children who use ‘‘total communication.’’ Fourth, there are no preimplant predictors of outcome performance. The underlying abilities and skills ‘‘emerge’’ after implantation. Finally, there are no differences among devices or processing strategies. The pattern of results suggests that processes such as perception, attention, learning, and memory may play an important role in explaining the enormous individual differences. Investigations of the content and flow of information in the central nervous system and interactions between sensory input and stored knowledge may provide new insights into individual differences. [Work supported by NIH-NIDCD Grants DC00012 and DC00111.]
An overview of vibration-based damage detection research at Los Alamos National Laboratory
Authors: Farrar Charles R. , Doebling Scott W.
Published: July 2002

The ability to monitor the structural health of our aging infrastructure is becoming increasingly important. A wide variety of highly effective local nondestructive evaluation tools are available. However, damage identification based upon changes in vibration characteristics is one of the few methods that monitors changes in the structure on a global basis. The material presented herein will summarize the structural health monitoring research that has been conducted at Los Alamos National Laboratory over the last 8 years. First, the process of vibration-based damage detection will be described as a problem in statistical pattern recognition. This process has three portions: (1) data acquisition and cleansing; (2) feature selection and data compression; and (3) statistical model development. Current research regarding feature selection and statistical model development will be emphasized with the application of this technology to large-scale, in situ bridge structures and to bridge columns that were tested in a laboratory. In particular, the ability to quantify uncertainties in measured dynamic properties caused by variable environmental and operational conditions is addressed. The paper will conclude by summarizing some of the underlying technical issues associated with vibration-based global damage detection that continues to make this area of technology a challenging research topic.
Seismic testing of full-scale structures through applied ground motion
Authors: Mote Peter A. , Gefken Paul R.
Published: July 2002

The Nevada Testing Institute (NeTI) and SRI International (SRI), in partnership with prominent research universities and state and federal government, and industry, have been evolving since 1995 a unique concept of generating earthquake-like ground motion to test large- and full-scale structures and structural systems at the Nevada Test Site. The RESCUE technique is used to produce strong ground motion by simultaneously expanding a planar array of buried vertical sources. The ground motion sources consist of a rubber bladder wrapped around a steel rectangular mandrel. Propellant is burnt in the source to produce low pressures that expand the bladder to move the soil bed. Because pressures are low, the soil is not damaged, allowing for sequential pulses and multiple tests on test structures. Eighty cycles of ground motion over durations of up to 120 s will be available in full scale. Proof-of-concept testing was successfully completed in 1998 in California and Nevada. The tests show that ground motions with accelerations of 1g to potentially 3g, velocities of 100 to 140 cm/s, and displacements of 60 cm to greater than 100 cm can be produced at the full scale test center. Construction of the full-scale testing center beginning in 2000 is planned.