bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic diagnostic for the polar front
Authors: Shang E. C. , Wang Y. Y.
Published: July 2002

The Polar frontal zone is known to have the highest contrast between properties of the divided water masses in Nordic seas. Acoustically, it is a strongly range-dependent environment. Numerical simulations of acoustic propagation in the frequency range of 20–200 Hz have been conducted for typical cases by using the IFD-PE and KRAKEN codes. The adiabaticity is strongly frequency dependent. For lower frequency, the inverted results of the frontal parameters based on the adiabatic modal travel time and modal horizontal refraction data can be obtained analytically using a simple ‘‘few parameter model’’ proposed by Kuz’kin [Acoust. Phys. 39(4), 402 (1993)]. The possibility of estimating the frontal parameters for a more complex realistic model will also be discussed. [Work supported by ONR and NOAA.]
Temporal and spectral information in echoes for biomimetic object recognition
Authors: Kuc Roman B.
Published: July 2002

Typical echolocation sounds produced by bats and dolphins have a wide bandwidth. This allows the echoes to contain information in the time and frequency domains. Temporal information includes the evolution of the energy in the perceived echo packet. However, if the initial echoes in a packet are weak, they may not exceed the perceptual threshold at a repeatable time, making temporal comparisons difficult. Spectral cues are more robust in that a time delay in an echo packet does not effect the power spectrum. However, because the emitted beam pattern and the reception patterns of the ears are frequency dependent, spectral comparisons are difficult. This paper describes methods for using temporal cues to aid in the spectral comparisons and methods for using spectral cues to aid in the temporal comparisons. The methods are illustrated using experimental results obtained with a biomimetic sonar mounted at the end of a robot arm that is used to recognize a variety of objects. [This research was funded through a grant from the NSF IRI-9504079.]
Bubble collapse emissions suggest mechanism for transient response imaging
Authors: Everbach E. Carr , Li Shouping , Porter Thomas R.
Published: July 2002

Transient response imaging (TRI) is the increase in apparent myocardial contrast with reduced image frame rate (PRF) when perfluorocarbon-filled echo-contrast agents are infused. TRI allows improved estimation of myocardial perfusion, but its mechanism is not known. Recent work suggests that contrast microbubbles are destroyed by imaging at conventional frame rates (30–40 Hz), while less destruction occurs at cardiac-synchronized frame rates. Using a 20-MHz passive cavitation detector, acoustic emissions were recorded from within the myocardium of two anesthetized dogs in vivo during ultrasonic imaging with a clinical scanner. Strong correlations among root-mean-square detector output, videodensity, and PRF point to bubble emissions themselves as possibly responsible for the improved contrast. [Work supported by Nebraska AHA.]
Pressure-tolerant network interface cards for sensor arrays
Authors: Walrod John
Published: July 2002

Pressure-tolerant ATM and Ethernet network interface cards (NICs) were developed for towed array data acquisition and telemetry. The card functions include sensor signal conditioning, analog-to-digital conversion, network protocol processors, and network interface transceivers. Design and fabrication techniques were developed to achieve space constraints, power constraints, and operation at 2500-psi pressure in oil or saltwater submersion without the use of pressure vessel housings. The development included the testing of candidate electronic components and NIC assemblies for pressure, temperature, and oil tolerance. Components and assemblies which failed testing were analyzed, and design rules were established for future designs. Generally, the elimination or minimization of voids by proper component selection and fabrication was found to be critical. Pressure-tolerant fabrication techniques were developed such as temperature cycle screening, encapsulation in low-viscosity polyurethane, pressurized curing, and compression sealed wires. High-density printed circuit boards and minimalist circuit designs were used to minimize NIC size. Low-voltage components, selective component location, and thermally conductive packaging were used to minimize operating temperatures. Commercially available components and open standard interfaces were used to minimize costs.
Effectiveness of random edge barriers: Further studies
Authors: Rosenberg Eric J. , Busch-Vishniac Ilene J.
Published: July 2002

Previously, the idea of introducing a random height fluctuation to the conventional straight edge of a noise barrier was discussed as a way to increase insertion loss and improve acoustic performance. Here, an exhaustive set of experiments is discussed to more accurately discern the effects of the random edge. Experimental results were obtained using a spark source and a plywood barrier with interchangeable metal edges serving as the various edge profiles. Unlike the past experiments, which reported peak-to-peak sound pressures, results were obtained for the energy spectral density. The results indicate that the insertion loss data obtained with a random edge are not solely a function of Fresnel number as they are with a straight edge, and that local effects may dominate when considering the energy measured at a point in space. [This work was supported by a Texas Advanced Technology grant.]
Focusing of sonic boom noise penetration into a homogeneous wavy ocean: Complex surfaces and wavelength comparisons
Authors: Rochat Judith L. , Sparrow Victor W.
Published: July 2002

The last decade has seen a revived interest in the study of sonic booms; this is due to an upcoming new breed of supersonic passenger aircraft along with a heightened awareness of marine environmental issues. Sonic boom noise penetrating into a flat, homogeneous ocean is a topic several researchers have already addressed. The primary goal of the authors’ research is to study the effects of realistic ocean features on noise penetration. These features include a wavy ocean surface and bubbles near the surface. This presentation will focus on a wavy ocean surface, specifically on somewhat complex surface profiles and on sonic boom effective wavelength/ocean wavelength comparisons. Results using finite difference simulations indicate that a somewhat complex wavy ocean surface profile slightly augments the underwater pressure field (as compared to a flat surface); this result was also found when studying simple surface profiles. Some of the trends observed, however, were not as obvious as seen when studying the simple surface profile. This prompted a study on how the sonic boom effective wavelength compared to the ocean wavelength affects the amount of augmentation to the underwater pressure field. [Work supported by the NASA Langley Research Center.]
Improvement in quality of speech received by a mistuned receiver at suppressed carrier SSB
Authors: Kaneko Shin’ichiroh , Suzuki Jouji , Sjimamura Tetsuya
Published: July 2002

Single sideband modulation (SSB) is the most efficient speech transmission system from the viewpoint of power consumption and bandwidth occupation. It is widely used in amateur radio, mobile radio, and others. At suppressed carrier SSB(SCSSB), the receiver should tune to the carrier frequency accurately. Manual tuning, however, is very difficult due to the lack of the carrier signal. It fails in fine tuning at the reception and the quality of received speech degrades seriously owing to the shift of speech spectrum. This paper proposes a method to improve the quality of speech degraded at SCSSB. Received speech is transformed into the log spectrum and its autocorrelation function (ACLOS) is calculated. If tuning is carried out correctly, the log spectrum of voiced sound has a harmonic structure. Mistuning gives a spectrum shift on that frequency axis. On the other hand, ACLOS is always a periodic signal that corresponds to the harmonic structure. By calculating a cross-correlation function between ACLOS and the log spectrum, mistuning frequency can be easily estimated. This method is able to estimate the mistuning frequency within the accuracy of 10 Hz, even in noisy channels. After obtaining the mistuning frequency, the shifting spectrum of received speech is carried out and more natural speech is obtained.
An acoustic model of gesture overlap: Further studies
Authors: Weismer Gary , Berry Jeff
Published: July 2002

Previous work from our laboratory has suggested that certain acoustic measures may serve as indices of the extent of overlap for successive articulatory gestures. These experiments have employed speaking-rate variation as a means to vary the extent of articulatory gesture overlap, in a number of different syllable types. Explicit models have been used to predict how rate-induced variation in gesture overlap would be realized in the acoustic output of the vocal tract. Specifically, the F2 onset and offset values at CV and VC interfaces, respectively, where C and V are constant, have been shown to be sensitive to the rate variable, sometimes approaching the magnitude of variation associated with CV syllables where C is constant and V is varied (i.e., the classic vowel-induced coarticulation paradigm). However, the results to date appear to be dependent on specific syllables, but the reasons for this specificity are unknown. In the present study, some systematic analyses of vowel effects on the acoustic model of gesture overlap are presented. Results will be discussed in terms of the goodness of the model and theories of coarticulation.
Interarticulator programming in VCV sequences
Authors: Lofqvist Anders , Gracco Vincent L.
Published: July 2002

This study examined the coordination of tongue body and lip movements in VCV sequences, where the consonant is a bilabial stop /p, b/, and the vowel one of /i, a, u/; only asymmetrical vowel contexts were analyzed. Lip and tongue timing and vowel-to-vowel tongue body kinematics were examined. The movements were recorded using a magnetometer system. Four subjects participated and produced ten tokens of each sequence. The phasing between the onset of the lip closing movement and the onset of the tongue body movement from the first to the second vowel varied across subjects, with no obvious pattern according to consonant voicing or vowel context. Overall, the onset of the tongue movement to the second vowel started earlier relative to the lip closing movement as the length of the tongue movement trajectory increased. During the oral closure, 40%–80% of the tongue movement path was traversed, again with no clear pattern across subjects. Consonant voicing reliably influenced the tongue movement from the consonant release to the second vowel. During this interval, the tongue traversed a longer path for voiceless than for voiced stops, reflecting the longer voice onset time for the voiceless stops. [Work supported by NIH.]
Facial animation using visual polyphones
Authors: Hällgren Åsa , Lyberg Bertil
Published: July 2002

Today, synthetic speech is often based on concatenation of natural speech such as polyphones. So far there has mainly been two ways of adding a visual modality to such a synthesis: Morphing between single images or concatenating video sequences. In this study, however, a new method will be presented where recorded natural movements of points in the face are used to control an animated face. During the recording of polyphones to be used for synthesis, the movements of a set of markers placed in the face of the speaker are simultaneously registered in three dimensions. Connected to each acoustic polyphone will be a perfectly synchronized set of dynamic movement patterns, a visual polyphone. These visual polyphones are then concatenated in the same manner as the acoustic polyphones, and used to control the movements of an animated face. In the presented system, demisyllables are used as units both for the acoustic and the visual polyphones and it seems as these units will, in a good way, reflect the coarticulation process in natural speech.
Matched-field processing for multitonal source localization
Authors: Michalopoulou Zoi-Heleni
Published: July 2002

Recent studies with simulations and real data have shown that multiple frequency information can lead to increased robustness in matched-field estimation. This observation generates the question of how this information should be combined for best results. In this work an estimator is proposed that is suitable for matched-field inversion involving multitonal sources. The processor operates on the basis of an interfrequency spatially coherent framework. Designed for passive problems, it does not require knowledge of the source spectrum, an advantage over other coherent schemes. Moreover, the processor has the additional advantage of a simple implementation. Using synthetic data, the new coherent processor was compared to the conventional Bartlett processor with incoherent averaging across frequencies. The results indicate that the new processor is, in general, preferable to the conventional Bartlett processor. Interestingly, the superiority of the coherent processor is most pronounced when the receiving array undersamples the propagation medium, making the processor attractive for its cost effectiveness. [Work supported by ONR.]
Broadband signal detection: Comparison of vertical aperture arrays using adaptive matched-field processing and a horizontal line array using adaptive plane-wave beamforming
Authors: Booth Newell O. , Schey Phil W. , Hodgkiss W. S.
Published: July 2002

Detection and localization of low spectral-level, broadband signals in the presence of surface interference are described and illustrated with examples obtained in the May 1996 Shallow Water evaluation cell Experiment (SWellEx-96). The experiment was carried out west of Point Loma in 200-m water of complex bathymetry. A 118-m vertical line array (VLA) was deployed next to an identical line array tilted at 45 deg (Tilted VLA). A 240-horizontal line array was also deployed nearby. The detection performance of each of the vertical arrays with adaptive broadband matched-field processing (MFP) is measured and compared with the performance of the horizontal array with adaptive broadband plane-wave beamforming.
Matched-field processing using Bartlett sidelobe interference structures
Authors: Thode Aaron M. , Kuperman W. A. , D’Spain Gerald L.
Published: July 2002

Waveguide invariants [e.g., G. A. Grachev, Acoust. Phys. 39(1), 33–35 (1993)] predict the local behavior of interference maxima/minima of acoustic intensity in the frequency-range plane. These invariants are independent of the detailed environment of the waveguide. As the Bartlett matched-field processor (MFP) ambiguity surface has a physical interpretation in terms of a time-reversed acoustic field, with the sidelobes analogous to local interference maxima, these invariant concepts are reformulated for application to MFP. The theory predicts that when a series of perfectly matched range-independent Bartlett surfaces computed over small increments of frequency are stacked and then sliced along a constant depth, the resulting sidelobe contours in the range-frequency plane display interference patterns that converge to the correct range. Indeed, these patterns are demonstrated to exist in simulated data, broadband source tows, and blue whale vocalizations recorded off San Miguel Island last year. Using the Radon transform, it is even possible to localize a source at the correct range and depth using only the trajectories of the sidelobes of the MFP surfaces. The robust nature of the range-frequency invariant suggests that incoherent postprocessing based on this concept might yield results insensitive to environmental mismatch. [Work sponsored by ONR.]
Coherent and incoherent broadband matched-field processing with SWellEX-96 data
Authors: Orris Gregory J. , Nicholas Michael , Perkins John S.
Published: July 2002

Several approaches to passive broadband matched-field processing have been proposed. In most cases, an incoherent average over a narrow band is quite successful in driving down unwanted sidelobes. The ability of coherent broadband techniques to out perform this simple approach may require additional phase information about the source that, in general, may not be available. In this paper, a fully coherent method that can out perform an incoherent average is derived, although its practical application is problematic. In other words, the simple incoherent average may be the most efficient approach. These ideas are demonstrated using data from the SWellEx-96 experiment. Given the environmental conditions under which these data were taken, the new coherent approach has some physical advantages over other broadband methods since it more efficiently uses variations of range dependence exhibited by the different frequency components of the signal. The net result is that the range, depth, and azimuth ambiguities have comparable spatial extent.
Paul S. Veneklasen, Father, mentor
Authors: Veneklasen Lee H.
Published: July 2002

Early recollections included making things, riding bikes, sailing, boy scouts, skiing, many of the usual things that a father does with his son, but my father, Paul was different. He wanted us to learn why and how did it work; was there a better way of doing it? This atmosphere created a desire for learning and innovation. My father encouraged my education and revelled as I approached his field of electron-beam lithography from experiment and the machine shop, much as he approached acoustics. My brother, Mark, a wonderful craftsman, developed a new French Horn, with the help of my father’s patient advice and occasional prodding. A few anecdotes illustrate a lifetime of memories.
Paul S. Veneklasen: A glimpse into his early years at UCLA, 1938–1942
Authors: Gales Robert S.
Published: July 2002

Paul joined the acoustics program of the UCLA Physics Department in 1938, shortly after receiving his M.S. in physics and mathematics from Northwestern University. He was a spirited contributor to Professor Vern Knudsen’s weekly seminars dealing with nearly all aspects of acoustics: propagation, architectural, hearing, music, etc. Here, he shared ideas with other students: Dick Bolt, Cyril Harris, Bob Leonard, Walter Rosenblith, Izzy Rudnick, Ludwig Sepmeyer et al., and mentors: Leo DelSasso, Vern Knudsen, and Norman Watson. In 1941 Paul became a key contributor to a new research effort to develop improved hearing protection devices as military acoustics became important in those pre-World War II years. This paper is a brief anecdotal glimpse into this short period of Paul’s early professional life.
Acoustic tuning mechanisms in reptilian hair cells
Authors: Eatock Ruth Anne
Published: July 2002

Tuning by hair cells can be mechanical or electrical. The best-studied examples of each class are from reptilian ears. In the free-standing region of the alligator lizard’s cochlea, where hair cells have acoustic characteristic frequencies (CFa’s) that range systematically from 1 to 4 kHz, acoustic tuning can be explained by micromechanical resonances of the hair bundles [D. M. Freeman and T. F. Weiss, Hear. Res. 48, 37–68 (1990)]. In the turtle cochlea, hair cells have CFa’s from 30 to 700 Hz and the acoustic tuning derives from electrical resonance of the hair cell membrane, reflecting the interplay of capacitive current and several ionic currents [Y.-C. Wu et al., Prog. Biophys. Mol. Biol. 63, 131–158 (1995)]. Tonotopic variation in CFa arises from variation in hair bundle height in the lizard and from variation in ion channel kinetics and number in the turtle. Coupled mechanical and electrical tuning [T. F. Weiss, Hear. Res. 7, 353–360 (1982)] seems likely but has not been demonstrated. Hair bundle height varies with Cfa in the turtle cochlea, suggesting a micromechanical contribution. Hair cells dissociated from the liquid cochlea resonate electrically, but at frequencies tenfold lower than their CFa’s [R. A. Eatock et al., J. Neurosci. 13, 1767–1783 (1993)].
Bat jitter discrimination, adaptive channel equalization, and the critical interval
Authors: Altes Richard A. , Simmons James A.
Published: July 2002

When simulated echoes have a bandwidth between 20 and 80 kHz, bats (Eptesicus fuscus) can discriminate between pulse-to-pulse delay jitter and constant echo delay with a sensitivity of 10 ns [Simmons et al., J. Comp. Physiol. A 167, 589–616 (1990)]. To investigate this amazing acuity, high-pass and low-pass filters were inserted into the channel between the simulated target and the bat. The effect of such filters on jitter acuity was measured. The data are explained by a receiver model that attempts to equalize the channel filter. The equalizer uses a smeared version of the actual channel transfer function, where spectral smearing induces relatively slow cutoff. Spectral smearing occurs in spectrogram (short-time Fourier transform) analysis. Smearing varies inversely with the impulse response duration of the analysis filters. This impulse response duration corresponds to the critical interval, which is frequency dependent for proportional bandwidth filtering. Bat jitter discrimination data imply channel equalization with a smeared version of the actual channel transfer function. This smearing is commensurate with critical intervals that are obtained from other experiments [Simmons et al., J. Acoust. Soc. Am. 86, 1318–1332 (1989)]. Bats apparently use time-frequency echo representations to perform environmentally adaptive filtering.
Quantitative and qualitative analysis of the descent, up–down, and down–up frequency whistles of tucuxi, Sotalia fluviatilis, in the Sepetiba Bay, Rio de Janeiro, Brazil
Authors: Pereira Tereza C. C. L. , Simao Sheila M. , Siciliano Salvatore
Published: July 2002

Sotalia fluviatilis was the only cetacean species observed in all 16 boat surveys (82 h) conducted in the Sepetiba Bay (22° 58′S, 44° 02′W), between December 1993 and August 1995. Previously, S. fluviatilis whistles were bioacoustically poorly characterized. The objective of this research was a quali–quantitative characterization of tucuxi’s acoustic emissions of descent, up–down, and down–up frequency. The sound analysis was based on sonograms from 30 min of a subaquatic recording obtained on 5 January, 1995. The qualitative analysis resulted in 390 whistles classified in 3 subclasses (descent, up–down, and down–up frequency), 21 types, and 46 subtypes. The quantitative analysis was based on: number of harmonics; number of inflexions; beginning, final, maximum, and minimum frequencies; duration; and frequency modulation. Minimum, maximum, and average values, standard deviation, and coefficient of variation were calculated for each type and subtype of whistle. The S. fluviatilis whistles are extremely diverse (high coefficient of variation values for each subclass, type, and subtype) and frequent (38.5 whistles/min), seeming to have an important role in the social relations among these animals. Such whistle diversity and quantities could be explained by the composition of the dolphin group, i.e., it was exclusively formed by young and subadult animals.
Variations in the vocal repertoire of the manatee in the Caribbean (Trichechus manatus manatus)
Authors: Alicca Jose A. , Harvey James , Mignucci-Giannoni Antonio
Published: July 2002

While different life history parameters for the manatee have been well studied in Florida, little is known about these aspects of manatee biology in the Caribbean. As part of a multifaceted study in Antillean manatee life history, the geographical and individual variability in vocal repertoires of Antillean manatees from Puerto Rico and the Dominican Republic were examined and compared to the repertoire of the Florida manatee. Differences in structural sound characteristics (frequency, duration, and relative power of each harmonic), usage (number of call types), and the associated behavior were studied from recordings of wild and captive animals. Over 100 h of recording were obtained from six different natural localities in Puerto Rico and one natural locality in Florida. Captive manatees were recorded in the Dominican Republic (1), in Puerto Rico (2), and Florida (13), in addition to recording seven semicaptive individuals in Florida. The recording of underwater vocalizations has been suggested as a useful tool for the study of marine mammals distribution. In the turbid waters of rivers, bays, and lagoons where manatees congregate in the Caribbean, these acoustic data might be useful for estimating population distribution and habitat use.
A source–filter model of humpback whale (Megaptera novaeangliae) vocal sound production
Authors: Mercado Eduardo
Published: July 2002

Acoustic waveforms produced by vocalizing humpback whales are well described by a source–filter model. This model characterizes vocalizations as the output of a time-varying signal generator (the source) passed through a time-varying resonator (the filter). For most humpback whale vocalizations, the source can be modeled as either a quasiperiodic impulse train, white noise, or a combination of these two signal types; the resonator can be modeled as an all-pole filter. The source–filter model is useful because it (a) provides a way to quantitatively characterize humpback whale vocalizations that can be automated and that allows for the ‘‘resynthesis’’ of sounds; (b) facilitates the application of advanced speech processing technologies to the analysis of humpback vocalizations; and (c) can potentially provide clues about the actual mechanisms humpback whales use to produce sounds. Currently, it is not known how humpback whales internally produce sounds, although structures in the larynx are thought to be involved. Source–filter-based analysis of humpback vocalizations revealed characteristic regions of frequency enhancement (formants) that may correspond to resonant frequencies of a physiological ‘‘filter.’’ Distribution of formants varied with pitch in a manner that appeared similar to pitch-related formant variation in human singers, suggesting that both species use analogous production mechanisms.
A refined four-load method for the evaluation of in-duct acoustic source characteristics
Authors: Jang Seung-Ho , Ih Jeong-Guon
Published: July 2002

By using the four-load method, one-port source characteristics can be determined in the duct system. In this study, a modification is made to avoid the instability problems occurring in the conventional four-load method. In the present method, the acoustic power spectra are measured at the inside or outside of the duct varying the acoustic loads, and an error function based on the linear time-invariant source model is obtained. It is numerically shown that the method is less sensitive to input errors compared to the conventional four-load method. The two methods are utilized to obtain the source parameters of a loudspeaker and a centrifugal fan using various types of loads. The estimated impedance values are compared with those obtained from the direct measurement method. As a direct measurement method, the multiple sensor method is adopted using three microphones. It is observed that the conventional four-load method results in large errors, whereas the present method yields far better agreement with the actual source characteristics.
Novel configurations for acoustophoresis
Authors: Brooks Todd L. , Apfel Robert E.
Published: July 2002

Separation of particles by their acoustomechanical properties can be accomplished by acoustophoresis, which depends on both primary and secondary acoustic radiation forces. In an acoustic standing wave, particles are moved either toward the pressure nodes or the antinodes depending on the relative contrasts in the particle density and compressibility with the surrounding host liquid. Because particles reradiate the sound waves, there are secondary interparticle forces as well. These secondary forces can either hinder or enhance the separation process. If two species which are to be separated attract each other because of interparticle forces, the separation will be compromised. But if several like particles aggregate, then primary forces are much stronger and the separation occurs more rapidly. When flow is superimposed on the system, as is common in practical applications, then drag forces must also be accounted for. In the present work, novel field configurations have been explored, and the trajectories of particles have been computed for a number of frequencies, flow speeds, field strengths, and property contrasts. Based on these simulations, experiments have been designed to optimize the efficiency of acoustophoresis, especially for biotechnology applications. [Work supported by NASA through Grant NAG8-1351.]
Could optical radiation pressure be used to move a sonoluminescing bubble to the pressure antinode of an acoustic standing wave?
Authors: Thiessen David B. , Marston Philip L.
Published: July 2002

It is generally recognized that in SBSL, the bubble is displaced slightly above the antinode of the acoustic standing wave which drives the bubble oscillations. This is because the acoustic radiation force must balance the average buoyancy of the bubble. For scientific purposes and to simulate SBSL in microgravity, it would be desirable to reposition the bubble at the antinode. One strategy to achieve that repositioning where the buoyancy force would be balanced entirely by the average optical radiation pressure of a downward propagating laser beam has been numerically investigated. Optical levitation of small bubbles has been previously demonstrated [B. T. Unger and P. L. Marston, J. Acoust. Soc. Am. 83, 970–975 (1988)]; however, it is not trivially applied to SBSL; with cw illumination of a quiescent bubble, the laser power required increases as the cube of the bubble radius. To simulate the large-radius phase of SBSL bubble oscillations, a modified Rayleigh–Plesset equation was numerically integrated. The required power for cw and pulsed laser beams was estimated. The average power is significantly reduced if the beam is pulsed to coincide with the large-radius phase of the oscillations so as to maximize the relevant optical cross section.
Spoken-word recognition
Authors: Connine Cynthia M.
Published: July 2002

Spoken-word recognition is an efficient and generally error-free process that occurs under a variety of speaking and listening conditions. The talk will focus on the mapping process between the speech signal and access of form and meaning. The nature of the representation that supports spoken-word recognition will be discussed with a focus on the consequence of ambiguity and mismatching information. Research has been conducted in the past few years suggesting that activation of lexical representations is accomplished via feature mapping. It is argued that this architecture permits lexical activation given incomplete or erroneous input. Phonological variation and some recent work concerning representation and processing of common variants will also be discussed.
Lexical neighborhood and phoneme frequency effects in phonetic processing
Authors: Sawusch James R.
Published: July 2002

The phonetic coding of speech reflects both a stimulus driven process and influences from the mental lexicon. There are at least three distinct forms of influence of the mental lexicon on phonetic processing: lexical status (is the item a word), lexical neighborhood (how many words is the item similar to), and phoneme frequency (how often does the phoneme occur in the language). Using natural speech series, the identification of an ambiguous phoneme is influenced by both the lexical neighborhood of the stimulus (syllable), and the probability of occurrence of the target phonemes in the language. Listeners consistently identify ambiguous phonemes with the label that corresponds to the end of the series with a larger lexical neighborhood, and listeners are biased to report more probable phonemes. Neighborhood and phoneme frequency effects are also found in a lexical decision task for clear, unambiguous tokens. Together with other work on higher-level influences on phoneme perception, these results indicate that phoneme perception is the result of an interaction between acoustic–phonetic information and the lexical knowledge of the individual, regardless of whether the target item is a word or not. [Work supported by NIDCD Grant No. R01 DC00219 to SUNY at Buffalo.]
Transitional probability, not lexical knowledge, influences compensation
Authors: McQueen James M. , Pitt Mark A.
Published: July 2002

The perceptual system compensates for fricative–stop coarticulation. Ambiguous stops between /t/ and /k/ tend to be heard as /k/ after /s/-final words and as /t/ after /S/-final words, even when the word–final fricatives are replaced with an ambiguous phoneme [J. L. Elman and J. L. McClelland, J. Mem. Lang. 27, 143–165 (1988)]. Biases in the transitional probabilities (TPs) of /s/ and /S/ in the words in that study mean that the effect following ambiguous fricatives could be due either to lexical involvement in prelexical compensation for coarticulation or to a sensitivity to TP at the prelexical level. In three experiments, listeners categorized nonword–final fricatives with TP biases, word–final fricatives where TPs were controlled, and word–initial stops following both fricative contexts. Categorization of ambiguous fricatives and stops was influenced by the TPs of the fricatives in the nonwords. But although there was a lexical bias in the categorization of the word–final ambiguous fricatives, there was no lexical influence on the categorization of the stops. These results suggest that the lexicon does not influence prelexical processing, and that the prelexical level is sensitive to TP. [Work supported by NIDCD, the Human Frontiers Science Project, and the Max Planck Society.]
Channel-sensitive matched filter processor: Sensitivity and optimization study
Authors: Haralabus Georgios , D’Amico Angela
Published: July 2002

The detection performance of the channel-sensitive processor (CSP) [D. Alexandrou and G. Haralabus, SACLANTCEN Report No. SR-263 (1997)] has been tested in dense multipath conditions. It has been demonstrated that for a known propagation channel the CSP method outperforms the conventional matched filter technique. However, in an uncertain environment, the probability of detection of CSP degrades according to the degree of mismatch between the assumed and the actual channel characteristics. It has been found that the processor is more sensitive to geometric parameters (source range and depth) than to environmental parameters (sound velocity profile, sediment-subbottom interface, sediment depth). To overcome the performance degradation due to channel mismatch, the CSP method has been utilized in conjunction with two nonlinear optimization algorithms: the classical simulated annealing (SA) and the multilayer simulated annealing (MUSA) method. At the expense of processing time, it has been found that the optimization methods reduce the channel mismatch effect and considerably improve the detection performance of the CSP.
Detection and tracking of land vehicle activity by offshore underwater acoustic arrays
Authors: D’Spain Gerald L. , Berger Lewis P. , Hodgkiss William S. , Kuperman William A. , Dorman LeRoy M. , Gaines William A.
Published: July 2002

Land-based vehicle activity can be tracked by underwater acoustic sensors located at least as far as 3.4 km offshore. This capability is demonstrated with data from two near-surf-zone experiments as part of the Marine Physical Laboratory’s Adaptive Beach Monitoring program. In one case, four tracked vehicles spaced every 150 m traveled down the beach. Spectra estimated from a single hydrophone of a bottom line array 1.5 km offshore in 12-m water show a high-pass character compared to land geophone recordings because of the coupling characteristics between the land seismic and underwater acoustic fields. Adaptive plane-wave beamforming over the 30- to 70-Hz band shows, at times, beam-peak-to-background levels exceeding 35 dB. The acoustic tracks agree with those from visual logs and suggest that the four vehicles can be enumerated acoustically, particularly when combined with results from the 120- to 130-Hz band. In a second case, plane-wave beamforming results for two tracked vehicles traveling on the beach and recorded by a bottom array 3.4 km offshore in 20-m water show a beam-peak-to-background level approaching 20 dB. A videotape shows the evolution of 2-D wave-number spatial spectra during the vehicle transit. [Work supported by ONR, Code 32.]
Acoustic image analysis by color mapping
Authors: Boyle Frank A.
Published: July 2002

Acoustic returns from different types of structures can appear very similar, making acoustic image classification difficult. Current research is aimed toward developing novel methods of generating acoustic images that convey relevant information for target identification and classificatin. A color-mapping method [Boyle and Chotiros, J. Acoust. Soc. Am. 99(4), 2553(A) (1996)], which maps an image’s spectral content into color has been applied to several examples of broadband acoustic data, with apparent success. Structural features that produce similar echoes in amplitude and duration often emerge with clear differences in color according to their spectral signature. Possibilities for using color to convey acoustic properties other than spectral content are also being explored. One such method maps the phase of a signal into colors, while another is based on wavelet filtering of signals. The presentation will include descriptions of color mapping and related methods, and examples of their application to acoustic data.
Uncertainty in fisheries echosounder calibrations
Authors: Demer David A. , Soule Michael A.
Published: July 2002

Calibration of echosounders for fish stock assessment are commonly performed using the standard sphere method. A complete calibration includes characterization of system sensitivity versus detection angle for measuring target strengths (TS) of individual scatterers and the equivalent beam angle for measuring backscattering strengths of insonified volumes. To explore the accuracy of the method, on-axis TS measurements were made of three standard spheres (23-mm copper and 33.0- and 38.1-mm tungsten carbide), under controlled conditions at a frequency of 120 kHz (bandwidth = 1.2 kHz). The TS measurements, derived by both integrated and peak intensities, were compared to their theoretical counterparts. Also, system sensitivities and split-beam detection angles were characterized versus target bearings. To investigate measurement precision, a commercial echosounder (Simrad EK500) was used to measure the TS of the spheres over 15-h periods with constant pulse duration (0.3 ms) and water temperature (19 °C). To characterize the temperature dependence of the calibrations, measurements of system gain and transducer admittance were made versus water temperature (0–17 °C). Finally, bootstrap simulations were used to estimate the combined uncertainty in 120-kHz echosounder calibrations using optimal standard spheres and over ranges of temperatures typically encountered in fisheries surveys.
ATOC signal enhancement using adaptive filtering
Authors: Bold Gary E. J. , Tan Sze M.
Published: July 2002

A moored, autonomous recording system deployed off the east coast of New Zealand in early 1996 acquired signals from the Pioneer seamount ATOC source. Unfortunately, the data were corrupted by a very strong, aliased interfering signal electrically coupled from a malfunctioning power supply which drifted in frequency by over 400 Hz, and also by a mechanically coupled vibration at the rotation frequency of the hard disk used to store the data. Pulse compression of the biphase modulated psuedorandom sequence used to encode the transmission spreads the energy in these signals across the desired signal’s spectral passband, degrading the signal-to-noise ratio of the receptions. Since both unwanted components are unstable in frequency, classical digital filters are unable to eliminate them. However, an adaptive LMS filter has been used to track and virtually remove the interfering signals before pulse compression, resulting in signal-to-noise ratio gains of up to 6 dB.
An acoustic transponder based tracking, data-telemetry, and logging system for real-time monitoring of 3-D positions and collection of other data from large marine vertebrates
Authors: Flagg Marco , Norris Thomas F. , Croll Donald
Published: July 2002

An acoustic tracking/telemetry/data-logging system is being developed for real-time monitoring of underwater movements and behaviors of free-ranging whales from a vessel. This system consists of an acoustic transponder ‘‘tag’’ attached to the animal. Upon interrogation from a ‘‘surface’’ station, the transponder produces a high-frequency (38-kHz) signal. An array (either short or ultrashort base line) of transducers at the surface station receive and compute the underwater location of the tag. Locations are computed based on the return time and time or phase delay of the received signal. Multiple tags can be monitored simultaneously and relative underwater positions can be integrated with data from a GPS on the tracking vessel (resulting in a latitude, longitude, and depth). A microprocessor on the tag controls basic functions and can be programmed to record and store up to seven channels of data from attached sensors (e.g., water temperature, velocity, etc). Data are stored internally on the tag’s RAM memory or can be telemetered acoustically to the surface station. Preliminary field testing in the open ocean resulted in an effective range of over 1 km. This system is being developed for determining movements and eventually acoustic behaviors of individual blue and fin whales. [Work supported by ONR.]
The Connections Project: An interactive look at the fine arts, mathematics, and physics
Authors: Chiaverina Christopher J.
Published: July 2002

Members of New Trier High School’s fine arts, mathematics, and physics departments are using interactive exhibits to illustrate connections between seemingly disparate subjects areas. Teachers from these three departments, and their students, are producing hands-on displays that encourage learners of all ages to discover elements common to the arts, mathematics, and physics. This initiative has produced over 60 interactive exhibits that are being used in venues such as classrooms, instructional laboratories, school corridors, and art galleries. A number of exhibits demonstrate acoustical principles and their relationship to other disciplines. These and other Connections Project exhibits will be discussed.
Methodological study of sleep motility measurements
Authors: Silvati Laura , Pearsons Karl S.
Published: July 2002

A methodological study was undertaken to investigate the sensitivity of sleep motility to noise-induced disturbances. Indoor noise exposure and sleep motility of 22 test subjects were measured for 109 subject nights under a range of conditions of noise exposure and familiarity of sleeping quarters. Recording accelerometers stored the number of times that vertical motion of the wrist-worn devices exceeded 0.0002 g at frequencies below about 3 Hz during a 2-s interval. Noise monitors continuously recorded 2-s time histories of indoor noise levels throughout each night of data collection. Additional sequences of varying epoch durations were constructed analytically from the 2-s intervals of noise levels and sleep motility data. Analyses of accelerometric recordings in 2-, 4-, 6-, 8-, 10-, 20-, and 30-s epochs included an examination of the relationship between synchronous indoor noise level and motility, description of motility observations on a nightly basis, characterization of general serial dependence in motility measurements, and characterization of motility measurements in consecutive epochs with and without movement. Characterization of sleep motility in epochs of short duration provided limited practical benefits for measurement of noise-induced sleep disturbance.
Airbag noise hazard examined with a mathematical model of the human ear
Authors: Price G. Richard
Published: July 2002

When cat ears were exposed to an airbag impulse in an open, closed, or sealed passenger compartment, a mean-threshold shift of 60 dB occurred immediately and resolved into a 37-dB permanent threshold shift [Price et al., J. Acoust. Soc. Am. 99, 2464 (1996)]. A mathematical model of auditory hazard for the cat ear ‘‘explained’’ the results [Price and Kalb, J. Acoust Soc. Am. 99, 2464 (1996)]; but there was still a question as to what the implications would be for human ears exposed to such impulses. A parallel model has been created for the human ear and the hazard reevaluated. For the human ear, the presence of middle ear muscle activity is calculated to be a key element in preserving hearing as is the (paradoxically) protective effect of a closed or sealed passenger compartment as compared with one that is open. The individual exposed in a vented passenger compartment and who did not see the accident coming is, therefore, predicted to be at greatest risk. Algorithms are being developed and validated for connecting the model’s output (auditory damage units) to projected changes in threshold for a human population whose susceptibility is normally distributed.
Variation in estimates of excess risk among screened and unscreened populations
Authors: Prince Mary M.
Published: July 2002

Analyses of data from the NIOSH Occupational Noise and Hearing Survey (OHNS) have previously focused on 1172 highly ‘‘screened’’ workers. This paper examines excess risk estimates for an additional 894 male workers (609 noise exposed and 285 controls) who were excluded for various reasons (i.e., nonoccupational noise exposure, otologic or medical conditions affecting hearing, prior occupational noise exposure). Data are analyzed by age, duration of exposure, and sound level (8-h TWA) for different definitions of noise-induced hearing impairment. Hearing impairment was defined as a binaural average hearing threshold level greater than 25 dB at selected frequencies (1–4 kHz, 1–3 kHz, and 0.5, 1, and 2 kHz). The analysis suggests that excess risk estimates are sensitive to population characteristics as well as definition of impairment. Lifetime excess risk estimates for noise-induced hearing impairment are similar for the unscreened and screened populations for 8-h TWAs below 85 dB. However, compared to the unscreened population, higher excess risk estimates are observed for the screened population at A-weighted levels greater than 85 dB. This difference in excess risk was most marked for hearing-impairment definitions that include 3 and 4 kHz.
Categorical judgments of pathological voice quality
Authors: Kreiman Jody , Gerratt Bruce R.
Published: July 2002

Categorical judgments of vocal quality are often applied in studies seeking to synthesize particular voice types, and in studies of the acoustic correlates of particular qualities. However, listeners’ ability to reliably classify voices as ‘‘breathy’’ or ‘‘rough’’ has never been demonstrated. In this study, 15 listeners decided whether each of 160 voice samples was or was not primarily rough in quality; in a separate experiment, a second group of listeners judged whether each voice was primarily breathy. Although listener agreement exceeded chance levels, only a few voices were consistently categorized as breathy or rough. Many voices with a high probability of being judged ‘‘breathy’’ also had a high probability of being judged ‘‘rough.’’ Finally, the likelihood of a ‘‘rough’’ or ‘‘breathy’’ response correlated highly with the rated severity of vocal pathology. These results confirm that breathiness and roughness are not independent concepts, and that neither captures information apart from overall severity of pathology. Thus categorical descriptions of a pathological voice are probably not useful clinical or research tools. [Work supported by NIH.]