bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Bayesian Decomposition for analysing microarray
data
Authors: Moloshok T. D. , Klevecz R. R. , Grant J. D. , Manion F. J. , Speier W. F. , Ochs M. F.
Published: July 2002

Motivation: Microarray and gene chip technology provide high throughput tools for measuring gene expression levels in a variety of circumstances, including cellular response to drug treatment, cellular growth and development, tumorigenesis, among many other processes. In order to interpret the large data sets generated in experiments, data analysis techniques that consider biological knowledge during analysis will be extremely useful. We present here results showing the application of such a tool to expression data from yeast cell cycle experiments.

Results: Originally developed for spectroscopic analysis, Bayesian Decomposition (BD) includes two features which make it useful for microarray data analysis: the ability to assign genes to multiple coexpression groups and the ability to encode biological knowledge into the system. Here we demonstrate the ability of the algorithm to provide insight into the yeast cell cycle, including identification of five temporal patterns tied to cell cycle phases as well as the identification of a pattern tied to an ∼ 40 min cell cycle oscillator. The genes are simultaneously assigned to the patterns, including partial assignment to multiple patterns when this is required to explain the expression profile.

Availability: The application is available free to academic users under a material transfer agreement. Go to http://bioinformatics.fccc.edu/ for more details.

Contact: td_moloshok@fccc.edu; RKlevecz@coh.org; jd_ grant@fccc.edu; fj_ manion@fccc.edu; speier1@prodigy.net; m_ ochs@fccc.edu

* To whom correspondence should be addressed.
Risky Arbitrage, Limits of Arbitrage, and Nonlinear Adjustment in the Dividend‐Price Ratio
Authors: Gallagher Liam A. , Taylor Mark P.
Published: July 2002

We provide a simple test of two alternative views of arbitrage activity: the risky arbitrage hypothesis and the limits of arbitrage hypothesis. For the U.S., the speed of reversion of the market log dividend‐price ratio towards the fundamental equilibrium is a nonlinear, increasing function of the degree of mispricing, providing evidence supporting the risky arbitrage hypothesis. Further research might concentrate on particular sectors where the risks of arbitrage are greatest and its effect is therefore likely to be weakest.
Patterns of fish calling in a nearshore environment in the Great Barrier Reef
Authors: McCauley Robert D. , Cato Douglas H.
Published: July 2002

Long–term sea–noise statistics have been obtained from a region of the central section of the Great Barrier Reef. Fish calling was a major contributor to sea–noise levels. Calling was either in choruses, where groups of fishes called
en masse
, or as isolated calls repeated
ad nauseam
. Four calling types predominated, with each displaying unique call characteristics and calling patterns through time and space. Analysis of call types offered information on the fish's calling physiology, behaviour and, through the call's interaction with the local environment, on the location of the caller. Call types ranged from less than 10 ms to several seconds long, and were comprised from one to nearly 40 pulses. The structure of each pulse was related to swim–bladder mechanics; normally swim–bladders were lightly damped. Fish calling was most common during the Australian summer with one call type also displaying lunar trends. All calls had daily patterns of sound production with highest activity levels generally at night. There was some spatial separation of zones of highest call rates, but sources avoided competition for the ‘sound space’ primarily by offsetting the time of chorus or maximum call rate. On some occasions, a call type attributed to nocturnal planktivorous fishes may have ensonified much of the Great Barrier Reef.
Prion protein interconversions†
Authors: Caughey Byron
Published: July 2002

The transmissible spongiform encephalopathies (TSEs), or prion diseases, remain mysterious neurodegenerative diseases that involve perturbations in prion protein (PrP) structure. This article summarizes our use ofin vitromodels to describe how PrP is converted to the disease–associated, protease–resistant form. These models reflect many important biological parameters of TSE diseases and have been used to identify inhibitors of the PrP conversion as lead compounds in the development of anti–TSE drugs.
A self–consistent approach to paternity and parental effort
Authors: Houston A. I. , McNamara J. M.
Published: July 2002

We review the relationship between optimal parental effort and paternity, and emphasize the need for a self–consistent approach. A fundamental consistency condition is what we refer to as the conservation of paternity. Every offspring has exactly one father. If a male has a paternity of less than unity, then another male or other males must have gained the lost paternity. Our approach also emphasizes that paternity emerges as the result of interactions between males and females. From this viewpoint, if paternity changes it is because some aspect of the interaction changes, and the correlation between effort and paternity depends on the aspect that has changed. This has implications for comparative analyses of paternity. The conclusions that are drawn about the correlation between effort and paternity within a population depend on, for example, the types of male in the population and how their abilities are correlated. It is easy to construct models that predict negative correlations between effort and paternity.
Male–only care and classical polyandry in birds: phylogeny, ecology and sex differences in remating opportunities
Authors: Owens I. P. F.
Published: July 2002

It has been argued recently that the combination of male–only parental care and classical polyandry in birds is the most interesting and yet the least understood of all avian breeding systems. Despite a huge number of hypotheses, careful comparative analyses have repeatedly failed to identify consistent ecological differences between species showing male–only care and closely related species showing other patterns of care. This has led to the suggestion that such analyses fail because the crucial differences are between ancient lineages rather than between closely related species. Here, therefore, I use comparisons between families to test three well–known hypotheses: that male–only care is associated with: (i) a low rate of fecundity; (ii) large egg size relative to female size; or (iii) female–biased opportunities for remating. Families showing male–only care do not differ from families showing female–only care with respect to rate of fecundity or relative egg size. There is, however, a significant difference between these two groups of families with respect to an index of remating opportunities, nesting density. Families showing female–only care nest at high density, while those showing male–only care nest at very low density. This is one of the first times a consistent ecological correlate has been identified for male–only care in birds. It suggests that female–only care arises (or persists) in families where remating opportunities are abundant for both sexes, whereas male–only care arises (or persists) in families where remating opportunities are rare for both sexes and particularly scarce for males. This in turn suggests that sex differences in remating opportunities are the key ecological factor in determining male–only care and classical polyandry in birds.
Relating paternity to paternal care
Authors: Sheldon B. C.
Published: July 2002

Intuition suggests, to most people, that parents should be selected to care for their offspring in relation to how certain they are of being the parents of those offspring. Theoretical models of the relationship between parental investment and certainty of parentage predict the two to be related only when some other assumptions are made, few of which can be taken for granted. I briefly review the models and their assumptions, and discuss two kinds of difficulty facing an empiricist wishing to test the models. The first is the problem of unmeasured (and immeasurable) variables. The second is the problem that even the most extensive models do not capture the complexity that can be demonstrated in real systems. I illustrate some of these problems, and some qualitative tests of the models, with experimental work on a population of the collared flycatcher. My conclusion is that although there are some cases where the models have qualitative support, we are a long way from understanding whether paternal care is commonly adjusted in relation to certainty of paternity.
Sensory–perceptual episodic memory and its context: autobiographical memory
Authors: Conway Martin A.
Published: July 2002

Episodic memory is reconceived as a memory system that retains highly detailed sensory perceptual knowledge of recent experience over retention intervals measured in minutes and hours. Episodic knowledge has yet to be integrated with the autobiographical memory knowledge base and so takes as its context or referent the immediate past of the experiencing self (or the ‘I’). When recalled it can be accessed independently of content and is recollectively experienced. Autobiographical memory, in contrast, retains knowledge over retention intervals measured in weeks, months, years, decades and across the life span. Autobiographical knowledge represents the experienced self (or the ‘me’), is always accessed by its content and, when accessed, does not necessarily give rise to recollective experience. Instead, recollective experience occurs when autobiographical knowledge retains access to associated episodic memories. In this reworking of the ‘episodic memory’ concept autobiographical memory provides the instantiating context for sensory–perceptual episodic memory.
Changes in Gene Expression Associated with Developmental Arrest and Longevity in Caenorhabditis elegans
Authors: Jones Steven J.M. , Riddle Donald L. , Pouzyrev Anatoli T. , Velculescu Victor E. , Hillier LaDeana , Eddy Sean R. , Stricklin Shawn L. , Baillie David L. , Waterston Robert , Marra Marco A.
Published: July 2002

Gene expression in a developmentally arrested, long-lived dauer population of Caenorhabditis elegans was compared with a nondauer (mixed-stage) population by using serial analysis of gene expression (SAGE). Dauer (152,314) and nondauer (148,324) SAGE tags identified 11,130 of the predicted 19,100 C. elegans genes. Genes implicated previously in longevity were expressed abundantly in the dauer library, and new genes potentially important in dauer biology were discovered. Two thousand six hundred eighteen genes were detected only in the nondauer population, whereas 2016 genes were detected only in the dauer, showing that dauer larvae show a surprisingly complex gene expression profile. Evidence for differentially expressed gene transcript isoforms was obtained for 162 genes. H1 histones were differentially expressed, raising the possibility of alternative chromatin packaging. The most abundant tag from dauer larvae (20-fold more abundant than in the nondauer profile) corresponds to a new, unpredicted gene we have named tts-1 (transcribed telomere-like sequence), which may interact with telomeres or telomere-associated proteins. Abundant antisense mitochondrial transcripts (2% of all tags), suggest the existence of an antisense-mediated regulatory mechanism in C. elegansmitochondria. In addition to providing a robust tool for gene expression studies, the SAGE approach already has provided the advantage of new gene/transcript discovery in a metazoan.
Dosimetric effects of source‐offset in intravascular brachytherapy
Authors: Chibani Omar , Li X. Allen
Published: July 2002

In intravascular brachytherapy (IVBT), radioactive sources can be displaced (offset) laterally from the center of the lumen and/or longitudinally from the desired location due to the cardiac motion and/or the absence of a source‐centering device. The purpose of this work is to study the dosimetric impact of such a source offset. Dose effects of both lateral and longitudinal source offsets with or without the presence of a calcified plaque or a metallic stent are calculated for the three most commonly used sources and The MCNP Monte Carlo code is used in the calculation. Static and random source offsets are considered. The major results include that (a) dose can be changed significantly (by a factor of up to 4) due to a static lateral source offset; (b) this dose variation is reduced if the lateral source offset is considered as random moving within the vessel (the dose at the 2 mm reference radial distance is increased by 5–15 % for the three sources in the case of the 2D random offset studied); (c) the presence of a calcified plaque and/or a metallic stent worsens the dosimetric effects; (d) the longitudinal random source offset results in a reduction (15–18 %) in the effective treatment length; (e) the dose effects of source offsets for the beta source are higher than those for the gamma source. The data presented in this paper may be used for IVBT treatment planning or for dosimetric analysis of treatment outcome. The dose change due to the source offset should be considered in dose prescription. The reduction of effective treatment length should be taken into account in selection of a proper source length to ensure an adequate coverage of the treatment target.
Resource Letter: TE-1: Teaching electronics
Authors: Henry Dennis C.
Published: July 2002

This Resource Letter examines the evolution, roles, and content of courses in electronics in the undergraduate physics curriculum, and provides a guide to resources for faculty teaching such courses. It concludes with a brief section addressing problems of electromagnetic interference in electronic systems, and provides an introduction to the literature and practice of electromagnetic compatibility. I have included textbooks, reference books, articles, collections of laboratory experiments and projects, sources of equipment and parts, software packages, videos, and websites.
Acoustic nonlinearity parameter tomography for biological tissues via parametric array from a circular piston source—Theoretical analysis and computer simulations
Authors: Zhang Dong , Chen Xi , Gong Xiu-fen
Published: July 2002

The acoustic nonlinearity parameter B/A describes the nonlinear features of a medium and may become a novel parameter for ultrasonic tissue characterization. This paper presents a theoretical analysis for acoustic nonlinear parameter tomography via a parametric array. As two primary waves of different frequencies are radiated simultaneously from a circular piston source, a secondary wave at the difference frequency is generated due to the nonlinear interaction of the primary waves. The axial and radial distributions of sound pressure amplitude for the generated difference frequency wave in the near field are calculated by a superposition of Gaussian beams. The calculated results indicated that the difference frequency component of the parametric array grows linearly with distance from the piston source. It therefore provides a better source to do the acoustic nonlinearity parameter tomography because the fundamental and second harmonic signals both have a near field that goes through many oscillations due to diffraction. By using a finite-amplitude insert substitution method and a filtered convolution algorithm, a computer simulation for B/A tomography from the calculated sound pressure of the difference frequency wave is studied. For biological tissues, the sound attenuation is considered and compensated in the image reconstruction. Nonlinear parameter computed tomography (CT) images for several biological sample models are obtained with quite good quality in this study.
Loudness summation for pulsatile electrical stimulation of the cochlea: Effects of rate, electrode separation, level, and mode of stimulation
Authors: McKay Colette M. , Remine Maria D. , McDermott Hugh J.
Published: July 2002

The aim of these two experiments was to gain systematic data on the amount of loudness summation measured for dual-electrode stimuli with varying temporal and spatial separation of current pulses. Loudness summation is important in the implementation of speech processing strategies for implantees. However, the loudness mapping functions used in current speech processors utilize psychophysical data (thresholds and comfortable loudness levels) derived using single-electrode stimuli, and do not take into account the temporal and spatial patterns of the speech processor output. In the first experiment, the current reduction required to equalize the loudness of a dual-electrode stimulus to that of its component (and equally loud) single-electrode stimuli was measured for three electrode separations (0.75, 2.25, and 7.5 mm), three repetition rates (250, 500, and 1000 Hz), and two loudness levels (comfortably loud, and mid-dynamic range). It was found that electrode separation had little effect on loudness summation, except for interactions with level and rate effects at the smallest separation. More current adjustment (in dB) was required for higher rates and lower levels of stimulation. The second experiment investigated the effects of mode (monopolar versus bipolar) and pulse duration on loudness summation. More current adjustment was required in bipolar mode than in monopolar mode at the lower level only. The main effects in both experiments, and their interactions, are consistent with a loudness model in which the neural excitation density is first obtained by temporal integration of excitation at each cochlear place, then converted to specific loudness via a nonlinear relationship, and finally integrated over cochlear place to obtain the loudness. The two important features which affect the loudness relationships in dual-electrode stimulation in this model are the shape of the excitation density function and the amount by which the neural spike probability per pulse is reduced in areas of overlapping excitation due to refractory effects.
Spatial and temporal factors in auditory saltation
Authors: Phillips D. P. , Hall S. E.
Published: July 2002

This report describes three experiments on auditory saltation, studied with click stimuli presented at interclick intervals (ICIs) from 30 to 240 ms. In experiment 1, subjects rated the strength of the saltation illusion evoked by trains of six monaural clicks (i.e., three presented to one ear followed by three to the other ear), and six dichotic clicks on which were imposed either a 500-μs interaural time difference or a 9-dB interaural level difference (ILD). The interaural disparity of the clicks was reversed at the midpoint of the train. Subjects reported equivalent strengths of saltation for the dichotic clicks, but weaker saltation for the monaural ones. These data indicated that saltation is supported by dichotic clicks. regardless of the stimulus manipulation used to generate the lateralized images. In experiment 2, subjects rated the strength of the saltation evoked by six click trains lateralized, in separate trials, by ILDs ranging from 9 to 30 dB, and by a train of monaural clicks. In all ILD conditions, the level of the clicks at the “quiet” ear was above click-detection threshold when presented monaurally. Saltation weakened with increasing ILD, and approximated that seen with monaural clicks when the ILD was 30 dB. These data indicated that for the range of ICIs used here, saltation weakened as the stimuli became more strongly lateralized. In experiment 3, the number of dichotic clicks preceding the disparity reversal was, in separate trials, varied from 3 to 10, and subjects were asked to detect the presence of spatial stationarity in the click train. By plotting the subjective ratings as a function of the length of the leading click train, it was shown that the temporal window within which the saltation effect operates varies between listeners, but is usually less than about 350–400 ms.
Relations among early postexposure noise-induced threshold shifts and permanent threshold shifts in the chinchilla
Authors: Hamernik Roger P. , Ahroon William A. , Patterson James H. , Qiu Wei
Published: July 2002

Threshold shifts (TS) were measured at various times following a wide variety of noise exposures on over 900 chinchillas. An analysis of postexposure TS measures and noise-induced permanent threshold shift (PTS) showed that, across audiometric test frequency, there was a consistent relation between these variables of the form PTS (dB)=α(eTS/β−1), where, for a given test frequency, α (dB) and β (dB) are constants. TSs were measured immediately following exposure (TS0), 24 h after exposure (TS24), and at several intermediate times in order to estimate the maximum TS (TSmax). Correlation between TS and PTS at the various test frequencies was highest for TS24. An analysis of the 90th-percentile PTS showed a linear growth of PTS with TS24 of approximately 0.7 dB PTS/dB TS24. These data provide some support, in the chinchilla model, for a variation of the three postulates originally presented by Kryter et al. [J. Acoust. Soc. Am. 39, 451 (1966)]. Specifically: (i) TS24 is a consistent measure of the effects of a traumatic noise exposure. (ii) All exposures that produce a given TS24 will be equally hazardous. (iii) Noise-induced PTS in the most susceptible animals, following many years of exposure, is approximately equal to (0.7)TS24 measured after an 8-h exposure to the same noise.
Discrimination of sound source velocity in human listeners
Authors: Carlile Simon , Best Virginia
Published: July 2002

The ability of six human subjects to discriminate the velocity of moving sound sources was examined using broadband stimuli presented in virtual auditory space. Subjects were presented with two successive stimuli moving in the frontal horizontal plane level with the ears, and were required to judge which moved the fastest. Discrimination thresholds were calculated for reference velocities of 15, 30, and 60 degrees/s under three stimulus conditions. In one condition, stimuli were centered on 0° azimuth and their duration varied randomly to prevent subjects from using displacement as an indicator of velocity. Performance varied between subjects giving median thresholds of 5.5, 9.1, and 14.8 degrees/s for the three reference velocities, respectively. In a second condition, pairs of stimuli were presented for a constant duration and subjects would have been able to use displacement to assist their judgment as faster stimuli traveled further. It was found that thresholds decreased significantly for all velocities (3.8, 7.1, and 9.8 degrees/s), suggesting that the subjects were using the additional displacement cue. The third condition differed from the second in that the stimuli were “anchored” on the same starting location rather than centered on the midline, thus doubling the spatial offset between stimulus endpoints. Subjects showed the lowest thresholds in this condition (2.9, 4.0, and 7.0 degrees/s). The results suggested that the auditory system is sensitive to velocity per se, but velocity comparisons are greatly aided if displacement cues are present.
Coherence of acoustic modes propagating through shallow water internal waves
Authors: Rouseff Daniel , Turgut Altan , Wolf Stephen N. , Finette Steve , Orr Marshall H. , Pasewark Bruce H. , Apel John R. , Badiey Mohsen , Chiu Ching-sang , Headrick Robert H. , Lynch James F. , Kemp John N. , Newhall Arthur E. , von der Heydt Keith , Tielbuerger Dirk
Published: July 2002

The 1995 Shallow Water Acoustics in a Random Medium (SWARM) experiment [Apel et al., IEEE J. Ocean. Eng. 22, 445–464 (1997)] was conducted off the New Jersey coast. The experiment featured two well-populated vertical receiving arrays, which permitted the measured acoustic field to be decomposed into its normal modes. The decomposition was repeated for successive transmissions allowing the amplitude of each mode to be tracked. The modal amplitudes were observed to decorrelate with time scales on the order of 100 s [Headrick et al., J. Acoust. Soc. Am. 107(1), 201–220 (2000)]. In the present work, a theoretical model is proposed to explain the observed decorrelation. Packets of intense internal waves are modeled as coherent structures moving along the acoustic propagation path without changing shape. The packets cause mode coupling and their motion results in a changing acoustic interference pattern. The model is consistent with the rapid decorrelation observed in SWARM. The model also predicts the observed partial recorrelation of the field at longer time scales. The model is first tested in simple continuous-wave simulations using canonical representations for the internal waves. More detailed time-domain simulations are presented mimicking the situation in SWARM. Modeling results are compared to experimental data.
Acoustic competition in the gulf toadfishOpsanus beta: Acoustic tagging
Authors: Thorson Robert F. , Fine Michael L.
Published: July 2002

Nesting male gulf toadfish Opsanus beta produce a boatwhistle advertisement call used in male–male competition and to attract females and an agonistic grunt call. The grunt is a short-duration pulsatile call, and the boatwhistle is a complex call typically consisting of zero to three introductory grunts, a long tonal boop note, and zero to three shorter boops. The beginning of the boop note is also gruntlike. Anomalous boatwhistles contain a short-duration grunt embedded in the tonal portion of the boop or between an introductory grunt and the boop. Embedded grunts have sound-pressure levels and frequency spectra that correspond with those of recognized neighbors, suggesting that one fish is grunting during another’s call, a phenomenon here termed acoustic tagging. Snaps of nearby pistol shrimp may also be tagged, and chains of tags involving more than two fish occur. The stimulus to tag is a relatively intense sound with a rapid rise time, and tags are generally produced within 100 ms of a trigger stimulus. Time between the trigger and the tag decreases with increased trigger amplitude. Tagging is distinct from increased calling in response to natural calls or stimulatory playbacks since calls rarely overlap other calls or playbacks. Tagging is not generally reciprocal between fish, suggesting parallels to dominance displays.
Reciprocity calibration of acoustic emission transducers in Rayleigh-wave and longitudinal-wave sound fields
Authors: Hatano Hajime , Watanabe Tetsuo
Published: July 2002

A new system was developed for the reciprocity calibration of acoustic emission transducers in Rayleigh-wave and longitudinal-wave sound fields. In order to reduce interference from spurious waves due to reflections and mode conversions, a large cylindrical block of forged steel was prepared for the transfer medium, and direct and spurious waves were discriminated between on the basis of their arrival times. Frequency characteristics of velocity sensitivity to both the Rayleigh wave and longitudinal wave were determined in the range of 50 kHz–1 MHz by means of electrical measurements without the use of mechanical sound sources or reference transducers.
Vertical coherence of ambient noise in shallow water overlying a fluid seabed
Authors: Deane Grant B. , Buckingham Michael J. , Tindle Christopher T.
Published: July 2002

Broadband (200 Hz–20 kHz) measurements of the vertical coherence of ambient noise in two well-surveyed, shallow-water channels with fluid, sedimentary seabeds are reported. The noise at one of the sites, the StrataForm natural laboratory off Eureka, northern California, was occasionally found to be exclusively wind generated, with negligible contributions from surface traffic and biological sources. Under these conditions, the theoretical coherence, computed using the known properties of the sediment at Eureka, closely follows the coherence data up to a frequency of 20 kHz. Subtle effects due to the finite depth of the sources, that is, the bubbles produced by wave breaking, are evident in both the theory and the data. At the second site, in Jellicoe Channel, New Zealand, some 64 km north of Auckland, wind noise again was a major factor, but much of the time local shipping also contributed to the overall noise field. Two sets of coherence data from the New Zealand site are examined, the first taken in near-isovelocity conditions, when the noise was due to wind plus a local ship, and the second recorded in the absence of shipping, when the channel showed a mildly linear, downward refracting profile. In both instances, the coherence data over a 5-kHz band compare well with theoretical curves computed using the known geoacoustic parameters of the sediment in the region.
Acoustic scattering by atmospheric turbules
Authors: Goedecke George H. , Auvermann Harry J.
Published: July 2002

Atmospheric turbulence is modeled as a collection of self-similar localized eddies, called turbules. Turbulent temperature variation and solenoidal velocity structure function spectra and the corresponding average acoustic scattering cross sections are calculated for several isotropic homogeneous turbule ensembles. Different scaling laws for turbule strengths, number densities, and sizes produce different power-law spectra independent of turbule morphology in an “inertial range” of the spectral variable K. For fractal size scaling and Kolmogorov power law ∝K−11/3 in the inertial range, not only do turbule strengths scale like the one-third power of the size, but also the turbule packing fractions are scale invariant, as are the expressions derived for the structure parameters (CT2,Cv2). The inertial range boundaries of the spectral variable and scattering angles are easily estimated from the inner and outer scales of the turbulence. They depend weakly on turbule morphology, while the spectra and cross sections outside the inertial ranges depend strongly on it. Scattering at angles outside the inertial range, which occurs in practical cases, is much weaker than predicted by the Kolmogorov spectrum. For Gaussian turbule ensembles, quasianalytic forms are obtained for the spectra and scattering cross sections and for the structure functions themselves.
Relevant acoustical cues in the identification of Western orchestral instrument tones
Authors: Hajda John M.
Published: July 2002

The purpose of this research is to establish perceptually relevant operational definitions of the acoustical segments of isolated musical instrument tones. Previous research has yielded conflicting conclusions for continuant (nonpercussive) tones regarding the relative salience of the attack and steady-state portions. This study also examines the perception of impulse (percussive) instrument tones. A new model for the partitioning of continuant tones, the ‘‘amplitude/centroid trajectory,’’ divides the signal into four segments: The attack, attack/steady-state transition, steady state, and decay. The divisions are based on the direction of and relationship among the global rms amplitude and spectral centroid. Other operational definitions of signal partitions and reverse playback were included as editing treatments. Single isolated tones were used from six impulse and six continuant instruments. Nine subjects participated in a 246-item forced-choice identification experiment. It was determined that, for sustained continuant tones, the steady state alone provides sufficient and necessary information for the identification of the instrument. The coevolution of the amplitude and spectral centroid seem important, but the direction does not. A confounding of envelope with identification for staccato tones was found. For impulse tones, both the direction and coevolution of global components are necessary.
Use of measured data in the physical modeling of the classical guitar
Authors: Boullosa Ricardo R. , Orduña-Bustamante Felipe
Published: July 2002

A simple physical model consisting of a delay-network representation of the string and a radiation filter (which transduces bridge motion into sound pressure radiated at a distance) is used to synthesize the sound of the classical guitar. Parameters for the sound generation algorithm are obtained from mechanical and acoustical transfer functions measured in a guitar. These correspond to mechanical response at the bridge, or to acoustical response at a given point in the sound field, and involve mechanical excitation in the bridge at different string positions. The variation from string to string observed in these measurements, especially at high frequencies, suggests the need for individual characterization of each string in the physical model of the guitar. Other factors, such as stiffness (inharmonicity), internal string damping, and nonlinear string motion are also discussed as desirable additional features of more realistic sound generation algorithms.
Applications of the causality condition to acoustic scattering
Authors: McDaniel J. Gregory
Published: July 2002

The causality condition states that the response of a passive system cannot precede the cause. Under certain conditions, the causality condition leads to a Hilbert transform relation between the magnitude and phase of the complex Fourier transform of a system’s response. This relation has profound implications for those attempting to design passive structures whose desired scattering characteristics are expressed in the frequency domain. Unless the causality condition is satisfied in the frequency domain, the structure is not physically realizable. In this presentation, some novel applications of this relation are developed for a one-dimensional fluid-loaded structure which scatters incident sound in the backward and forward directions. In each application the reflection and transmission coefficients, which are the complex Fourier transforms of the reflected and transmitted pressures due to an impulsive incident pressure wave, are subject to the causality condition. The Weiner–Lee transform, which is derived from the Hilbert transform but is more easily implemented numerically, is used to find complex reflection and transmission coefficients given only their frequency-dependent magnitudes. By using this informa- tion and structural reciprocity, one can find an impedance matrix of a structure which scatters sound in a specified way.
Vibroacoustical multichannel diagnostics of energetic systems
Authors: Gelman Leonid M.
Published: July 2002

A new multichannel low-frequency vibroacoustical diagnostics method of energetic systems is considered theoretically and experimentally. The proposed method represents one of the approaches to efficient energy use and conservation. This method is based on processing of the low-frequency vibroacoustic noise of energetic systems. The main advantages of the method: early preventive nondemountable automatic diagnostics on all operating regimes of energetic systems.
Vibroacoustical multichannel nondestructive evaluation method of fatigue cracks
Authors: Bouraou Nadezhda I. , Gelman Leonid M. , Ossokina Natalia Yu.
Published: July 2002

For nondestructive testing (NDT) and nondestructive evaluation (NDE), the low-frequency vibroacoustical free-oscillation method is used. For the first time, a theoretical investigation is carried out to differentiate between spectral density and decrement of free oscillations of testing objects in the presence and the absence of fatigue cracks taking into account the internal friction in the object material. The new analytical dependencies of the spectral density and decrement of testing object-free oscillations from the relative crack size, factor of internal friction, duration of NDT(E), and initial object speed are received, on the basis of which the new multidimensional vector of testing data for NDT(E) is proposed. Experimental results with aircraft engine blades in the presence and the absence of fatigue cracks, which match with theoretical results, are presented. The received results are common; therefore, they have been found to be expedient in taking into account the obtained results for forced oscillation NDT(E) methods.
Loudspeaker array designs using drivers positioned to improve directionality
Authors: Sowden Christopher ‘‘Topper’’
Published: July 2002

This paper provides a study of the design methodology used in the development of a central loudspeaker cluster for stadiums and arenas. The design criteria is compared with the actual constructed results to describe the effective use of the concept and use in future designs. The methodology for the design is based on the paper published in the Journal of the Audio Engineering Society in April of 1990 by Jefferson Harrell and Elmer Hixson. The paper by Harrell and Hixson discussed horizontal and vertical directionality of multidriver loudspeaker arrays when spaced a calculated distance from each other. This paper provides a demonstration of these concepts with systems recently completed at the Bryce Jordan Center at Penn State University, and Sun Devil Stadium at Arizona State University. The methodology was applied to an array with transducer spacings greater than 2 m and improved control of frequencies down to 50 Hz. Digital control of audio provides loudspeaker array control and alignment capabilities not previously possible through analog techniques. The paper discusses adjustment of the arrays installed at the above-mentioned facilities.
An improved constant directivity loudspeaker array
Authors: Breshears Vance , Heinz Ralph , Oppegaard Brian
Published: July 2002

A simple design goal for any loudspeaker cluster would be to provide even sound pressure levels and consistent frequency response for any seat in a listening space. To achieve this goal, many clusters are currently being designed around trapezoidal cabinets promising array ability. However, the resulting lobing, beaming, and comb filtering these types of arrays typically produce, make it nearly impossible to realize the design goal stated above. Even the best implementations of this type, using a trapezoidal cabinet or horn with consistent dispersion characteristics, result in a system whose low-frequency dispersion in the vertical plane does not match the level of controlled directivity of the mid- and high-frequency range. A new method has been developed that provides a systems approach to building coherent point source clusters with frequency invariant coverage from below 100 Hz to 18 kHz in both horizontal and vertical planes.
Finite-amplitude wave propagation in big sound systems
Authors: Czerwinski Gene , Voishvillo Alex , Alexandrov Sergei , Terekhov Alex
Published: July 2002

Propagation of large-amplitude sound waves is accompanied by the generation of air nonlinear distortion. This effect as related to audio signals was researched in the thirties by Thuras, Jenkins, and O’Neil. They investigated the waveform distortion of plane waves. The sound waves radiated by loudspeakers are all but plane waves. In real loudspeakers, the ‘‘degradation’’ of waveforms depends on such factors as directivity and the placement of loudspeakers. Therefore, the results derived from plane-wave tube propagation are hardly applicable. Since nonlinear distortion of loudspeakers interacts with waveform distortion, it is difficult to distinguish one from the other. Two groups of loudspeakers were used and single tones were put on each group to exclude distortion, inherent to loudspeakers. Therefore, intermodulation products indicative of the air distortion were measured. Intermodulation distortion was measured at different frequencies and SPL with progressively increasing path lengths, and various distances between loudspeakers. It was shown that this distortion is inherent to big sound systems, and the level of distortion can be significant. Waveform distribution was also simulated on computer by solving the KZK equation. Air distortion depends on SPL, frequency, distance, loudspeaker directivity, and placement. Some aspects to minimize air distortion in sound systems are discussed.
Inverse problems in radar measurements of stochastic processes in the ionosphere
Authors: Sahr John
Published: July 2002

This paper offers a short introduction to certain radar studies of the ionosphere. Emphasis will be placed on applications of ‘‘incoherent scatter’’ radars relying upon stochastic Thomson scattering to make remarkably detailed measurements of the temperature, density, composition, and other physical parameters in the Earth’s ionosphere. The total backscattered power is proportional to the density, but all the other parameters are derived by detailed inspection of the correlation function of density fluctuations. Measuring the correlation function is quite difficult because of the very small scattering cross section. Furthermore, the ionosphere is ‘‘overspread,’’ which means that density fluctuation decorrelates in significantly less time than it takes a radio pulse to transit the region of interest. Simply stated, this means that one cannot measure the correlation function of the ionosphere with a periodic pulse train. Following a very quick tour of the plasma physics and theoretical correlation function (the forward problem) the intricate interplay of the transmitter waveform design and the inverse problem for parameter estimation—including some unique robustness issues—is shown. It will also be shown that the highest performance transmitter waveforms today are themselves stochastic (or nearly stochastic) processes. The results have a pleasing analogy to the quantum mechanics notion of ‘‘observables,’’ and shed light on the very nature of measurement.
First symbiosis between rigorous ray tracing and the parabolic approximation
Authors: Floyd Edward R.
Published: July 2002

Rigorous ray tracing originates from the trajectory representation of quantum mechanics while the (Leontovich–Fock) parabolic equation was originally applied to electromagnetic propagation. Rigorous ray tracing (and quantum trajectory representation) have had theoretical success while the parabolic approximation has been a computational success. The parabolic approximation inspires a similar equivalent approximation to the generalized Hamilton–Jacobi equation for rigorous ray tracing. For separable coordinates, the resulting approximations render the same approximate wavefunction. In return, the rigorous ray leads to a parabolic approximation incorporating reflection. The trajectory representation has rendered a synthesized single wavefunction that includes an incident wave of coefficient α and a reflected wave of coefficient β. This synthesized wavefunction can generate a new alternative parabolic equation that incorporates reflection, which for small reflection (β≪α) becomes Fzz+i2k[1−(2β/α)cos(2kx)]exp[i(2β/α)sin(2kx/B)]Fx+(κ2−k2)F=0.
Wide-band source localization in the presence of internal waves
Authors: Book Paul J. , Nolte L. W.
Published: July 2002

The effects of internal waves on low-frequency (25-Hz) wide-band source localization performance are investigated at a very long range (1000 km). Sound-speed perturbations induced by internal waves obeying the Garrett–Munk spectral model are incorporated into the normal mode solution to the wave equation using the adiabatic approximation. Source range estimates are limited by very random internal waves and do not improve with increasing SNR. In an attempt to combat this limitation due to environmental uncertainty, processors can benefit from the spectrum of the acoustic source. According to the hybrid Cramer–Rao lower bound (CRLB), significant improvements on range estimates are possible when using a coherent wide-band acoustic source with bandwidth of 10 Hz on the 25-Hz source. The CRLB provides valuable analytical insight into the limits on source range estimates, but the optimal signal processing algorithm is necessary to compute the actual limits on source localization. Using a coherent wide-band source with many discrete frequencies spanning the bandwidth, significant gains in range estimates are achieved by optimally incorporating this signal spectrum into the localization algorithm a priori.
Loudness of dynamic stimuli in acoustic and electric hearinga)
Authors: Zhang Chaoying , Zeng Fan-Gang
Published: July 2002

Traditional loudness models have been based on the average energy and the critical band analysis of steady-state sounds. However, most environmental sounds, including speech, are dynamic stimuli, in which the average level [e.g., the root-mean-square (rms) level] does not account for the large temporal fluctuations. The question addressed here was whether two stimuli of the same rms level but different peak levels would produce an equal loudness sensation. A modern adaptive procedure was used to replicate two classic experiments demonstrating that the sensation of “beats” in a two- or three-tone complex resulted in a louder sensation [E. Zwicker and H. Fastl, Psychoacoustics—Facts and Models (Springer-Verlag, Berlin, 1990)]. Two additional experiments were conducted to study exclusively the effects of the temporal envelope on the loudness sensation of dynamic stimuli. Loudness balance was performed by normal-hearing listeners between a white noise and a sinusoidally amplitude-modulated noise in one experiment, and by cochlear implant listeners between two harmonic stimuli of the same magnitude spectra, but different phase spectra, in the other experiment. The results from both experiments showed that, for two stimuli of the same rms level, the stimulus with greater temporal fluctuations sometimes produced a significantly louder sensation, depending on the temporal frequency and overall stimulus level. In normal-hearing listeners, the louder sensation was produced for the amplitude-modulated stimuli with modulation frequencies lower than 400 Hz, and gradually disappeared above 400 Hz, resulting in a low-pass filtering characteristic which bore some similarity to the temporal modulation transfer function. The extent to which loudness was greater was a nonmonotonic function of level in acoustic hearing and a monotonically increasingly function in electric hearing. These results suggest that the loudness sensation of a dynamic stimulus is not limited to a 100-ms temporal integration process, and may be determined jointly by a compression process in the cochlea and an expansion process in the brain. A level-dependent compression scheme that may better restore normal loudness of dynamic stimuli in hearing aids and cochlear implants is proposed.
Must sine wave analogs be perceived as implicit speech to be perceived categorically?
Authors: Kingston John , Kirk Cecilia J.
Published: July 2002

Sawusch and Gagnon [J. Exp. Psychol., HPP 21, 635–652 (1995)] obtained categorical responses to /la/–/ra/ sine wave analogs when listeners who heard the stimuli as nonspeech were frequently reminded of F3’s range or extremes. This result contrasts with responses to sine wave /la/–/ra/ obtained by Best et al. [Percept. Psychophys. 45, 237–250 (1989)] and responses to sine wave /wa/–/ja/ obtained by Johnson and Ralston [Phonetica 51, 195–209 (1994)]. Only those listeners who heard the analogs as (distorted) speech responded categorically. Instead of comparing speech and nonspeech listeners, the experiments tried to create an implicit expectation that sine wave analogs are (distorted) speech by playing listeners speech first. Listeners identified and discriminated members of sine wave /la/–/ra/ after identifying and discriminating either members of the original /la/–/ra/ speech continuum or of the same sine wave continuum. Other groups of listeners heard speech or sine wave /wa/–/ja/ before the sine wave /la/–/ra/; their performance allows us to separate acoustic from type similarity. If after hearing speech, listeners hear the analogs as implicit speech, they should perceive them more categorically than listeners who hear analogs first. Results show instead that listeners responses are as strongly categorical to the sine wave /la/–/ra/ in the second phase after all preceding stimulus types, even though the analogs are not heard as speech. Categorical perception thus does not depend on an implicit speech percept, nor are frequent reminders required to elicit it to sine wave analogs. [Work supported by NIH.]