bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasound-mediated transformation of prokaryotic cells
Authors: Young Jane A. , Clark Joseph A. , Jones William R.
Published: July 2002

Ultrasound-mediated transfection of mammalian cells has been reported in the literature [Kim et al., ‘‘Ultrasound-mediated transfection of mammalian cells,’’ Human Gene Therapy 7, 1339–1346 (July 10, 1996)]. Optimum results were obtained using continuous wave insonification at a carrier frequency of MHz, peak pressures of 319–411 kPa, exposure times of 20–60 s, and ambient temperatures 23−37°C. Cavitation was shown to be a key mechanism for the insertion of plasmid DNA into cells. Prokaryotic cells appear to present a greater challenge to ultrasound approaches because of their smaller size and stronger membranes. This talk will report results of a series of ultrasound-mediated transformation experiments on prokaryotic cells, specifically bacteria. Conditions required to obtain a lethal dose for 50% of the cells (LD50) and transformation of cells will be presented. Effects of peak pressure levels, pulse duration, quiescent time between pulses, static pressure, and number of exposures will be discussed. This work could have broad applications, from disinfection of aquacultural and agricultural systems to genetic engineering.
Modeling the role of nonhuman vocal membranes in phonation
Authors: Herzel Hanspeter , Mergell Patrick , Fitch Tecumseh
Published: July 2002

Although the mammalian larynx exhibits little structural variation compared to sound-producing organs in other taxa (birds or insects), there are some morphological features which could lead to significant differences in acoustic functioning, such as air sacs and vocal membranes. The vocal membrane (or ‘‘vocal lip’’) is a thin upward extension of the vocal fold that is present in many bat and primate species. The vocal membrane was modeled as an additional geometrical element in a two-mass model of the larynx. It was found that vocal membranes of an optimal angle and length can substantially lower the subglottal pressure at which phonation is supported, thus increasing vocal efficiency, and that this effect is most pronounced at high frequencies. The implications of this finding are discussed for animals such as bats and primates which are able to produce loud, high-pitched calls. Modeling efforts such as this provide guidance for future empirical investigations of vocal membrane structure and function, can provide insight into the mechanisms of animal communication, and could potentially lead to better understanding of human clinical disorders such as sulcus vocalis.
Microphone calibration techniques
Authors: Rasmussen Gunnar
Published: July 2002

Primary calibration of microphones is well described and standardized by IEC 1094-2 using the reciprocity technique. When the standard microphone is calibrated, a reference source is needed for transfer of the calibration value to the acoustical measuring devices or systems employing the working measurement microphone. A reliable transfer device is the pistonphone. Another method may be the use of a comparison against a working standard microphone. Sound reference sources called ‘‘calibrators’’ are standarized by IEC in 60942:1997. Sound calibrators may often be inferior in accuracy and stability to the systems they are being applied to. They should therefore be labelled check devices. Other techniques have been employed for many years. The use of a reference voltage coupled to the system input is widely used. This may be extended to incorporate the preamplifier and incorporate features like modulating the polarization voltage whether internal or external or incorporating the cartridge capacity into a capacitive voltage divider. These techniques do not allow a calibration but only supply a means of injecting a signal in the electrical system to check the ability to transfer a signal. Calibration is not obtained.
Experimental investigation of bending waves in ultrasonic reactors
Authors: Niederdraenk Torsten , Thaden Rainer
Published: July 2002

A number of practical applications like ultrasonic cleaning, sonochemistry, and others use the effects of high, intense ultrasound. In general, the high-pressure sound fields can be obtained by different arrangements of piezoelectric compound transducers, which have to be optimized according to each application. A commonly used setup is a planar array transducer, consisting of one or more transducer elements. A tool to design and develop the transducer arrangements is given by simulations of the electromechanical equivalent circuit, although the results are often based on several assumptions. This paper reports on vibroacoustic investigations of compound transducer arrangements. Laser-optical measurements give evidence for arising bending waves on the radiating surface of the transducers that may affect the generated sound field and which have some effect on the total power distribution. The influence of bending waves has been included in the equivalent circuit; some simulations are presented.
Mechanical impedance of wheeled tractor steering mechanism
Authors: Merkevičius Stanislovas , Vagusevičius Ričardas
Published: July 2002

There are fairly many wheeled tractors of 6 kN class made in CIS (Community of Independent States). The characteristics of noise and vibration are inadequate for valid standards. Vibrations of especially high levels having the effect on hands are generated through the steering wheel to the person’s (operator’s) hands. If fitting in vibroisolating or vibrodepherisating elements to the driving mechanism details junctions (joints), it is partly possible to lessen the vibration level having the effect on the person. It would be more effective and more rational to discuss the possibilities of absorbing spreading vibration and vibroisolation when there is enough information about the vibration of the steering wheel mechanism. Applying the methods of mechanical impedance, the mathematical model of steering mechanism, consisting of the steering wheel mechanism and the steering wheel has been made, giving an opportunity to analyze the interaction of the steering wheel, the person (operator), and the spreading vibration.
Control index of the upright and grand piano actions
Authors: Boutillon Xavier , Grijalva Robert
Published: July 2002

The motion of the piano hammer between its resting position and the contact with the strings follows two phases. At first, the motion is imposed by the pianist’s finger on the key. When it escapes from the main action, within 2 mm from the string, the hammer possesses the velocity ve. During the second and brief phase before impact, the hammer is only subject to gravity, friction of its pivoting axis, and to the action of an additional spring in the case of the upright piano. Finally, the hammer hits the strings with velocity vi. The difference between ve and vi, and the threshold on ve below which the hammer does not even touch the strings, are a nuisance for the musician. Although inevitable, this second phase also affects the aptitude to control nuances, so important in music. To quantify this notion, the control index ic=dve/dvi is introduced, which can be easily calculated. Its limit is 1 for fortissimo but it approaches 0 for pianissimo. For the pianist, this corresponds to a steeply increasing difficulty to phrase music at low rather than at high dynamic levels. Differences between the grand and the upright piano will be discussed.
Eurosabot field measurements—Methods and results
Authors: Bühler Stefan
Published: July 2002

Eurosabot is a European research project focused on rolling noise reduction of block braked railway vehicles. While braking, the interaction between block and wheel generates roughness patterns on the wheel which become the major excitation for rolling noise. The objective was to find a brake block (material and design) which combines the advantages of common cast-iron blocks with lower roughness generation without common drawbacks of other block families. Measurements of most relevant parameters were already available before Eurosabot, but boundary conditions and other parameters were different, inconsistent, or even unknown, which made it difficult to gain a reliable understanding of how roughness is generated. Therefore, Eurosabot’s measuring campaigns were focused on strictly simultaneous monitoring of all relevant parameters under known and real boundary conditions. The following parameters were monitored over a long-term period in normal service: wheel and block wear, wheel roughness, braking distance, residual stress (wheel rim). During a concentrated campaign, rail roughness, rail impedance, rail accelerations, sound pressure, and sound power distribution were measured wayside, as well as sound pressure (on board), wheel and block accelerations, wheel and block temperature distribution, and friction coefficient on the vehicle. Results show that this method enables a complete judgment of the behavior of a block.
Communication and warning signal perception
Authors: Edworthy Judy
Published: July 2002

Warning signals are used throughout industry and commerce, and often provide vital sources of information. Due to developments in digital technology, it is now possible to deign any sort of auditory signal, some of which may be effective, some of which may not. In this paper a methodology is outlined which takes a step-by-step, user-centered approach to the design and implementation of warning signals in noisy environments with the aim of creating warning signals which are both easy to understand and to act upon. It begins with the selection of referents (the events to be signaled), through an iterative design process which involves tests of appropriateness, learning and confusion, urgency, and recognition, to operational testing which includes adaptation to the noise environment, consideration of the complete warning set, and so on. The methodology is based on a standardized procedure for designing and implementing public information systems [ISO 7001, ‘‘Specification for public information systems’’ (1979)]. The paper describes the methodology in detail.
Noise declaration for hand-held machinery
Authors: Kyttälä Ilkka , Airo Erkko P.
Published: July 2002

A study on noise declarations and safety of hand-held machinery was executed in Finland in 1995–1996. Acceptable declarations were available for 77% of pneumatic and 94% of combustion-type machinery but only for 50% of electric machinery. This problem of machinery not having noise declaration can be corrected by national or international market control operations. For example, such a project on pneumatic hand-held machinery is going on in Finland by the occupational safety and health administration. The results will be presented at the beginning of 1999. Another problem is that the available noise declarations were usually correct but not necessarily valid. Laboratory measurements showed that declared values were correct, but the sound-pressure levels at the operator’s position were higher in practical use. For example, angle grinders’ declared idling SPLs were 80–86 dB, in a workshop they were 90–95 dB, and during metal processing the SPL was 110 dB. The reason for this is obvious: the quiet simulated, standardized operating conditions produce less noise than the typical use. The purpose of the system, the possibility to choose a low-noise machine, is partially lost. Too low declared values may also lead to false conclusions about the need of hearing protection.
Polish system of workers’ protection against noise
Authors: Pawlas Krystyna
Published: July 2002

In Poland, like in other industrial countries, the protection of workers’ health against hazards of occupational environment is a subject of many regulations. The basic act is the Code of Labor. Executive regulations connected with the Code are edited by the Ministry of Health and Social Welfare and the Ministry of Labor and Social Affairs. The Ministry of Health controls the organization of occupational health services, e.g., requirements for persons performing health examinations, principles of hearing examination, assessment of hearing disability, and the principle of certification of the hearing damage as occupational disease as well as monitoring of noise at workplaces. The Ministry of Labor establishes maximum allowable levels, organizes safety and hygiene services, and sets the principles of education in the field of occupational hygiene. The Ministry of Labor recommends standards for measuring and assessing noise at workplaces. These regulations are the basis for the hearing conservation programs. Polish legislation has been adjusted recently to harmonize with the currently standing legislation in the European Community. The main principles at present are the same as those accepted by the EC, but there are some differences concerning details of legislation and the organization of medical as well as occupational hygiene services.
Source data for small arms noise
Authors: Pater Larry L.
Published: July 2002

Small arms source data are required for calculation of far-field noise levels. Advantages and disadvantages of various methods of obtaining source data for small arms noise are discussed, and specific examples are presented. Important issues include nonlinear effects, directivity of muzzle blast and projectile shock noise fields, isobar shapes, wavefront shapes, and blast wave temporal characteristics, particularly shape and duration. A methodology is presented for obtaining source data that is free of inaccuracies due to ground reflections and ground impedance effects. Source data have been measured for a number of small weapons, both rifles and pistols. Example data are presented as waveforms, peak levels, overall sound exposure levels, and spectral distribution of 1/3-octave-band sound exposure levels. Data are presented separately for muzzle blast and projectile shock, and special attention is paid to the effect of interactions of the blast noise sound wave with the ground. [Work supported by U.S. Army.]
Air–ground interaction effects in the propagation of low-frequency impulse noise
Authors: Madshus Christian , Kaynia Amir M. , Hole Lars R.
Published: July 2002

Four large-scale sound propagation experiments performed in Norway from 1994 to 1996 under both summer and winter conditions clearly demonstrate that air–ground interaction has a significant effect on the propagation of low-frequency impulse noise. During the experiments, specific measurements were made for detailed investigation of this interaction. The paper will present the instrumentation used, and some typical measured data. Various numerical simulations of the experiments are made, covering both poro-elastic and visco-elastic description of the ground. Based on the measured data, theoretical considerations, and the numerical simulations, the paper will discuss mechanisms for acoustic energy loss from the air into the ground. Special emphasis will be put on the effect of the interaction of the propagating air pressure with the slow p-waves and with the dispersive Rayleigh waves in the ground. The relative importance of these two interaction mechanisms on the energy loss and thus on the sound attenuation will be examined for various ground conditions.
Validation of a new procedure for rating shooting sounds with the help of field survey data
Authors: Vos Joos
Published: July 2002

In previous laboratory studies it was shown that an almost perfect prediction of the annoyance caused by shooting sounds was obtained on the basis of the outdoor A-weighted and C-weighted sound exposure levels (ASEL and CSEL; LAE and LCE). For single events, the rating sound level, Lr, is given by Lr=LAE+β(LCE−LAE)(LAE−α)+12 dB. The second term β(LCE−LAE)(LAE−α) implies (1) that the annoyance is dependent also on the ‘‘heaviness’’ of the sound (characterized by LCE−LAE), and (2) that the additional annoyance (β>0) increases with ASEL for LAE>α dB, and decreases with ASEL for LAE<α dB. In the present study, the procedure for rating shooting sounds, as described above, was validated with the help of data from a German field survey on the annoyance caused by artillery and road-traffic sounds: α and β were determined for which Lr for shooting sound would, overall, numerically correspond to the A-weighted day–night level of equally annoying road-traffic sound. For all relevant impulsive sources, the required ASELs and CSELs received in the various residential areas were determined by TNO Institute of Applied Physics. The results showed that a proper rating sound level was obtained with α=40 dB and β=0.025.
Analyses of continuous brain waves in relation to subjective preference of the sound field
Authors: Chen Chiung Yao
Published: July 2002

Two factors comprising a standard of time are prevailing for designing a music hall: (1) initial time delay gap between the direct sound and the first reflection (Δt1); (2) subsequent reverberation time (Tsub). In brain researches of sound cognition, auditory-evoked potential (AEP) was frequently applied. However, it is undetectable in studying the variation of Tsub and Δt1 by a longer stimulus. In the present study, a method for measuring a human’s responses on continuous brain waves (CBW) was arranged with respect to the subjective preference of a music sound field. First, the ‘‘effective duration’’ (τe) was defined by the effective gap of the initial deduction (0.1 envelope) of the autocorrelation function of CBW. Results show the values of τe efficiently prolong (pi=0.05) on the left hemisphere when the scale values (SVs) of preference increases by changing Δt1. Second, this relationship was extended to examine changing Tsub. The longer (pi=0.01) τe were found as the SVs increased in the range of Tsub=0.2 to 1.2 s. Finally, as the auditory tempo was varied, the differences of values of τe show a closer correlation (r=0.80, pi=0.01) to the differences of SVs on the left hemisphere.
HYPERION—A computational tool for the investigation of the sound transmission loss of periodically structured plates
Authors: Maysenhoelder Waldemar , Horvatic Bozica , Nasshan Klaus
Published: July 2002

HYPERION offers a generalization of Cremer’s famous treatment [Akust. Z. 7, 81–104 (1942)] of the sound transmission of thin homogeneous plates in several respects: (i) periodically inhomogeneous plates, (ii) anisotropic bending stiffness, and (iii) different fluids on both sides of the plate. [A detailed account of the theory including some examples has been given in Acustica/acta acustica 84, 668–680 (1998).] The spatial periodicity generates propagating and nonpropagating diffracted waves, which may lead to several conspicuous features of the sound transmission loss curve. The most surprising phenomena are total reflection and total transmission below the critical frequency. These and other effects pertaining to refraction, near fields, and diffraction will be illustrated by an 8-min video film. Besides, it is worth mentioning that the computation of the transmission loss for diffuse-field excitation is rather time consuming, since a two-dimensional integration has to be performed over the two angles of incidence. The complexity of the integrand will be demonstrated graphically. [Financial support from the Deutsche Forschungsgemeinschaft is gratefully acknowledged.]
Effect of internal inhomogeneities on acoustic scattering from finite cylindrical shell bounded by hemispherical endcaps
Authors: Touraine Nicolas , Décultot Dominique , Maze Gérard , Klauson Aleksander , Metsaveer Jaan
Published: July 2002

The acoustic scattering from an air-filled finite cylindrical shell with hemispherical endcaps is considered. In axial incidence, experimental studies have shown formation of compressional wave S0 resonances. These resonances are predicted and identified by applying the phase-matching condition over the meridian circumference. However, frequency irregularities observed experimentally on spectra have suggested that the assemblage quality during the manufacturing of the object may be not negligible. Indeed, internal nonuniformities of the shell at the junctions of cylindrical and hemispherical shells are present and modify certain wave propagation phenomena. The aim of this study is to discover these experimental conditions of the studied object through a numerical model with internal annular inhomogeneities localized at the junctions of the substructures and for two different b/a ratios (internal to external radius ratio) equal to 0.97 and 0.99. In the studied frequency range (50–300 kHz), in addition to the S0 wave, another peripheral wave A can be generated for the ratio b/a=0.97. The numerical approach is based on the discretization of the shell and determination of its eigenmodes (FEM). Acoustical pressure field is found by the boundary integral equation procedure (BEM). The comparison of numerical and experimental results is presented in frequency and time domains.
The acoustical power radiated by a planar annular plate for the form of vibrations (0,n)
Authors: Rdzanek W. P. , Engel Z.
Published: July 2002

The acoustic power radiated by a thin annular plate fixed rigidly, with both internal/external edges, into a planar rigid infinite baffle is analyzed. These processes are considered sinusoidal in time. It is assumed that the annular plate vibrates axially symmetric. The radiated acoustic power integral formula is transformed with the introduction of the contour integral at the plane of complex variable. Then the Cauchy theorem about residua is used. An elementary, useful for calculations in case of high frequencies, form of the formula of the radiated acoustic wave is obtained. This formula represents the acoustic power with the assumption that the annular plate vibrates with the nth axially symmetric mode.
Effects of geometric discontinuities and filter lengths on active control in ducts
Authors: Duhamel Denis , Sergent Philippe
Published: July 2002

The active control is often used to reduce noise propagation in ducts, usually in straight sections. However, industrial ducts often contain discontinuities where the secondary source of an active system can or must be placed. The possibility of active control in such situations is studied and compared to the case of a straight duct. It is shown that a correct position for the secondary source allows one to take advantage of both passive and active attenuations, and can improve the global system. For a right angle or a resonator, simple analytical formulas can be obtained for the active attenuation, and it can be proved that the power output of the secondary source is null. The influence of other important parameters such as the number of coefficients of the FIR filter in a filtered-X LMS algorithm, and the sampling frequency used for the control or the loss factor in the duct, are also estimated by analytical formulas. This gives, for instance, explanations for the frequency bands over which the control efficiency is low. In each case, comparisons with experimental data are provided and they support the theoretical conclusions quite well.
Experimental investigations on active suppression of sound propagation in a fluid-filled pipe
Authors: Lippold Roland , Scheuren Joachim
Published: July 2002

The control of sound propagating along fluid-filled pipes is complicated because of the strong coupling between the structural and the fluid transmission path. If the propagation along the structural path is supressed (e.g., by passive compensation in the case presented), it is possible to reduce the propagating sound by active means only acting on the fluid. This statement was proved by several experiments. The experimental setup consisted of one pipe made of aluminum (length 4 m, wall thickness 5 mm, inner diameter 90 mm) and two pipes made of steel (3 m / 1.5 m, 2.5 mm, 70 mm) which were connected via 90-deg bends and filled with water. For excitation and compensation of sound in the fluid, shaker driven pistons acting perpendicular to the pipe axes were used. The frequency of the harmonic excitation in the frequency range from 600 up to 800 Hz was known to the compensation algorithm. If the passive compensation of the structural path was sufficient, the reductions of sound pressure in the fluid achieved at and behind the error sensor were between 10 and 20 dB. Otherwise, reductions of the same order were locally restricted to the position of the error sensor.
Automobile gas-exchange systems low-frequency noise reduction using active noise control units
Authors: Vassiliev Andrei V.
Published: July 2002

The main automobile aerodynamic noise sources radiating into the environment are internal combustion engine gas-exchange systems (intake and exhaust). Practical possibilities of active noise control unit applications for automobile gas-exchange system low-frequency noise reduction are discussed. Existing technical constructions of active noise control units (including those patented by author) for automobile intake and exhaust noise reduction are concerned. New construction of a unit is proposed. Its peculiarity is joint intake and exhaust noise reduction possibility. The signal of engine rotation frequency pick-up is input into the control system through the low-pass filter and transducer and then transmitted by the loudspeakers through the special waveguides into the zones of compensation near the intake and exhaust pipe open ends. Throttle opening angle is accounted for. Calculative results show the efficiency of such a construction operation.
Noise reduction for speech signals by operations on the modulation frequency spectrum
Authors: Strube Hans Werner , Wilmers Hans
Published: July 2002

A new method is presented for enhancing the contrast between speech and background noise, which might be useful as a preprocessor for speech recognizers or even for improving the audible speech signal. As in the brain a representation of the acoustic modulation spectrum exists, it is suggested to use similar methods for signal separation. Previous models have shown the possibility of selecting frequency channels based on modulation frequency (MF) analysis, if the signals to be separated have sufficiently different modulations. Instead of selecting or weighting frequency channels, in the present approach the MF spectrum is processed directly. This seems to be less prone to produce ‘‘musical noise.’’ The dominant common MF (mostly corresponding to F0) is enhanced by an adaptive bandpass filter in each frequency channel, and the low-MF components are artificially reconstructed before transforming back. No explicit F0 measurement is required. Nonstationary sounds (detected by the width of the low-MF part) are specially treated, for instance, by channel-dependent mixing with the original signal. The method is tested with a HMM recognizer (at Univ. Oldenburg) and compared to classic methods such as spectral subtraction. Intelligibility measurements are planned. Examples of processed speech will be presented.
Prosody templates in word-level synthesis
Authors: Holm Frode , Hata Kazue
Published: July 2002

This paper describes an approach to word-level prosody with the goal of achieving natural-sounding human intonation. This study comprised about 3000 words in sentence initial position, uttered by a female native speaker of American English. From these recordings general F0 and duration templates were extracted, initially based on stress-pattern alone. Results with regards to F0 templates [F. Holm and K. Hata, ICSLP (1998)] had previously been reported, which showed great promise for a practical synthesis implementation. In this paper duration templates will be focused on. Obtaining temporal prosody patterns is a much harder problem than it is for F0 contours. This is largely due to the fact that one cannot separate a high-level prosodic intent from purely articulatory constraints merely by examining individual segmental data. This methodology relies on a concept of stretchability, which gives a clear measure of how much a given cluster of segments can change its duration in natural speech. The higher this measure is, the more of the speaker’s intentional temporal adjustment is expected to be found in that cluster. Using this concept, a template-generating procedure has been formulated that achieves a very high prediction rate of a speaker’s duration patterns.
Production of Japanese durational contrasts by native and nonnative speakers
Authors: Hirata Yukari
Published: July 2002

Non-native speakers’ production of Japanese durational contrasts, and the development of their abilities, are examined in relation to native speakers’ production. Two native speakers and two beginning learners produced 2–4 mora words contrasting in either consonant or vowel length. The learners also produced the same set of words after 4 weeks of perceptual training [Y. Hirata, CLS34 Phonetics Panel (forthcoming)]. Acoustic analyses of the native speaker productions indicate durational systematicity not only in the consonant pairs, as in M. Han [Phonetica 49, 102–127 (1992)], but also in the vowel pairs: the average ratio of short to long vowels was 1:1.8–2.0 regardless of context and speaker. Furthermore, a linear relationship was found between the number of morae and word duration, extending Port et al. [J. Acoust. Soc. Am. 81, 1574–1585 (1987)]. The learners’ results before training indicate an inability to produce the durational contrasts, e.g., subject A’s average durational ratio for the vowel pairs was 1:1.2. After training, the ratio became closer to that of the native speakers, viz., 1:1.6–1.7, while subject B’s did not show a linguistically significant change. Subject A’s results contrast even with those of Han’s advanced subjects, and illuminate the upper limit for L2 learners with training.
Aerodynamic constraints on sound change: The case of syllabic sibilants
Authors: Yu Alan C. L.
Published: July 2002

High vowels are known to assimilate in place of articulation and frication to a preceding sibilant. Such an assimilation process is found in an historical sound change from Middle Chinese to Modern Mandarin (e.g., */si/ became [sz] ‘‘poetry’’). However, such assibilation is systematically absent when the vowel is followed by a nasal consonant. This paper investigates the co-occurrence restriction between nasalization and frication, demonstrating that pharyngeal pressure is so significantly vented during the opening of the velic valve that the necessary pressure buildup behind the constriction of a fricative is consequently severely diminished, resulting in no audible turbulence. It reports the aerodynamic effects of nasalization on vowels, as spoken by a native speaker of American English (presumed to parallel the phonetic conditions present in Middle Chinese). The results reveal that in comparison to oral vowels the pharyngeal pressure, volume velocity, and particle velocity decrease dramatically when high vowels are nasalized. Based on this study, a physical motivation for the phonological patterns with respect to the interaction between syllabic sibilants and nasal is advanced. [This work is supported by the President’s Undergraduate Fellowship 1997–1998.]
Does interspeaker variation in habitual speaking rate predict the size of the acoustic vowel space?
Authors: Tsao Ying-Chiao , Weismer Gary
Published: July 2002

In a previous study [Tsao and Weismer, J. Speech Lang. Hear. Res. (1997)], it was demonstrated that interspeaker variation in habitual speaking rate is predictive of interspeaker variation in maximal speaking rate. Thus speakers who are habitually slow speakers do not seem to be able to produce as fast a maximum rate as speakers who are habitually fast. This finding was interpreted to mean that some component of interspeaker variation in habitual speaking rate reflects neurological predispositions, rather than (for example) voluntary ‘‘choices’’ of different rates. The present study explores the hypothesis that habitually slow and fast speakers may have differently sized acoustic vowel spaces. The hypothesis is derived from previous observations that within speakers, the size of the acoustic vowel space fluctuates with speaking rate. Results suggest that there is substantial overlap between the vowel spaces of habitually slow and fast speakers, but that the slow speakers do tend to have larger vowel spaces. [Work supported by NIH.]
Identifying novel samples of spoken Korean
Authors: Bond Z. S. , Stockmal Verna
Published: July 2002

Listeners can identify familiar foreign languages without understanding them on the basis of their sound or acoustic signature. Listeners need only brief exposure to a novel language to learn to identify it from its sound pattern [Bond et al., Lang. Sci. 20, 353–367 (1998)]. The current experiments replicated the previous study using a different target language. In the first experiment, listeners distinguished Korean from languages which employ syllable rhythm. In the second experiment, listeners separated Korean from other East Asian languages. In both experiments, listeners made judgments either without exposure (control) or after exposure to 10 min of spoken Korean. Listener responses were converted to A, a nonparametric measure of discriminability. In experiment 1, listeners in the control condition responded at chance, mean A=0.47. After exposure, listeners identified Korean above chance levels, mean A=0.71. Listeners tended to confuse Korean with Asian languages rather than with African or European languages, suggesting that voice and speech style influenced their judgments. In experiment 2, the control group had extreme difficulty identifying Korean, mean A=0.28. Brief exposure enabled listeners to develop a representation of the sound of Korean in that they produced more hits and fewer misses to the target (mean A=0.71).
Spatial audio for telepresence
Authors: Rimell Andrew
Published: July 2002

Developments in communications technology, such as audio–visual conferencing and telepresence, have created a new set of demands for audio delivery systems. In the past, a telephone handset, with its limited transducers, was adequate for simple spoken communication; however, future multiuser communication systems and immersive machine interfaces will be greatly enhanced by using high-quality three-dimensional audio. Such three-dimensional sound systems can position individual talkers’ voices in space around the user, creating a greater feeling of immersion and improving intelligibility. This presentation discusses the design and implementation of a number of spatial audio system implementations. The applications range from a SmartSpace chair (a single-user environment using a transaural system) through to a VisionDome (a large multiuser environment using a combination of ambisonics and nonlinear panning). Theoretical design and practical implementation issues are discussed, including problems encountered and how they were overcome.
Autonomous hydroacoustic stations in support of CTBT-monitoring technology and event screening
Authors: Wille Peter C.
Published: July 2002

No more than six hydroacoustic receiver stations will be monitoring the three world oceans in the framework of the CTBT. Together with five T-wave stations they will synergetically cooperate with the seismic network which alone can neither provide the required accuracy of localization on the southern hemisphere nor the capability of reliable event discrimination of the oceans. To maintain the function of the sparse hydroacoustic network in case of an irretrievable station breakdown, an autonomous auxiliary unit for temporary replacement of fixed cable connected stations has been developed by FWG. The battery-supplied autonmous station, like the permanent stations, suspends the hydrophone at the depth of the SOFAR channel axis. The lightweight construction permits quick deployment and retrieval. The received acoustic signals are processed for prescreening at the station by algorithms with adjustable criteria to discriminate large explosions from natural events of similar energy turnover such as sea quakes and volcanic eruptions. The characteristics of the signals are transmitted by a surface buoy radio link via low orbit satellites to the data center, together with unprocessed, highly suspicious signals for expert analysis.
An optical fiber infrasound sensor
Authors: Zumberge Mark , Berger Jonathan
Published: July 2002

As part of the International Monitoring System of the CTBT, infrasound signals in the band 0.02 to 4 Hz must be detected in the presence of ambient noise generated chiefly by wind. The effectiveness of acoustic filters employed in standard infrasound sensors is limited by pressure propagation and attenuation characteristics within the filter. To improve the signal-to-noise ratio, an optical fiber instrument for sensing the integrated pressure variations along a line has been designed. The sensor design consists of optical fibers inside a long, fluid-filled tube, deployed along the ground surface. Integrated pressure variations along the fiber’s length are sensed by interferometrically monitoring changes in the optical path length of the fiber. The optical fiber sensor can average over kilometer-scale lengths of arbitrary geometry with an averaging bandwidth governed by the speed of light and thus should offer significant practical advantages in reducing the effect of wind noise, increasing the signal-to-noise ratio over a wide bandwidth.
Comparison of mode-shapes-only source depth estimation with conventional matched field source localization and the impact of array tilt on these processes
Authors: Hursky Paul , Hodgkiss William S. , Kuperman William A.
Published: July 2002

Matched field processing (MFP) typically exploits acoustic mode structure using both mode shapes and wave numbers to estimate source location. It is also possible to use mode shapes alone to estimate source depth [E. C. Shang, J. Acoust. Soc. Am. 77, 1413–1418 (1985); T. C. Yang, ibid. 82, 1736–1745 (1987)]. Measurements of multiple frequency towed source transmissions using a vertical line array spanning the lower duct of a summer sound-speed profile (SwellEx 96) were used to compare conventional MFP processing with several variants of mode-shapes-only depth estimation. Sensitivity of these processes to reduced aperture, array tilt, and signal-to-noise ratio was studied in simulated and measured data. Array tilt mismatch was successfully corrected to improve source localization results significantly.
The upper frequency range in pigeon hearing: Response properties in auditory nerve and cohlear nucleus—is tuning different in birds?
Authors: Smolders Jean W. Th. , Mueller Marcus , Klinke Rainer
Published: July 2002

Information on responses of auditory nerve fibers in birds is generally limited to the low and mid-frequency ranges of hearing, due to anatomical constraints using the standard ganglion cell approach through the opened tympanic recess. Intracranially recorded responses of single units from the auditory nerve and the overlying cochlear nuclei in the pigeon (Columba livia) were compared to those recorded from the ganglion. Characteristic frequencies (CFs) of auditory units ranged from 0.08–5.7 kHz with intracranial compared to 0.06–1.6 kHz with intrascalar recordings. Response properties were qualitatively and quantitatively comparable in the overlapping CF ranges (0.08–1.6 kHz). Mean spontaneous firing rate decreased monotonically with CF. The CF thresholds were lowest (0–5 dB SPL) in the CF range 0.6–1.5 kHz. Mean sharpness of tuning (Q10 dB) varied nonmonotonically with CF, with a maximum near 2 kHz. In addition, Q10 dB of pigeon auditory units up to CFs of 2 kHz was much higher than that of gerbil (Meriones unguiculatus) primary fibers in the same CF range, recorded in the same setup. As it is highly improbable that mechanical tuning in birds would by far exceed that in mammals, this finding is further evidence for a difference in avian and mammalian tuning mechanisms. [Work supported by the DFG, SFB 269.]
Modeling the target strength of Meganyctiphanes norvegica
Authors: Francis David T. I. , Knutsen Tor , Foote Kenneth G. , Calise Lucio
Published: July 2002

The euphausiid Meganyctiphanes norvegica is modeled as a fluidlike body having the actual shape of the head and thorax, as reconstructed from dorsal and lateral views recorded with a video camera with macrolens. The mass density has been measured for individual specimens in a density-gradient column, and the longitudinal-wave sound speed in the body, estimated from the measured sound speed through an assemblage of animals in a velocimeter. Theoretical target strength spectra are computed by the boundary element method at a number of discrete frequencies spanning the range 25 kHz to 3.2 MHz. [Support by the following is acknowledged: EU through RTD Contract No. MAS3-CT95-0031, Norwegian Research Council through Grant No. 113809/122, and Bergen Large-Scale Facility (LSF) for Marine Pelagic Food Chain Research.]
Inference of material properties of zooplankton from acoustic and conductivity measurements
Authors: Chu Dezhang , Wiebe Peter
Published: July 2002

In order to infer correctly biological information from raw acoustic data, various acoustical models have been developed and much progress has been made both in laboratory experiments and field applications. However, the acoustic properties of biological scatterers, such as sound-speed and density, have a profound influence on the target strength estimate or volume scattering strength. A 1%–2% variation in sound speed and density can lead to an error in target strength prediction by as much as 20 dB or a tenfold bias in biomass estimate, which could be much greater than that due to the choice of different acoustic models. There is a dearth of information about the material properties of the live zooplankton because measurement of them is difficult. An instrumented chamber was used to collect simultaneously acoustic and conductivity data with and without the presence of live zooplankton. The acoustic measurement characterizes both the back- and forward-scattering patterns, while the conductivity measurement provides an estimate of the fraction of volume the animals occupy (volume fraction). The combined information can then be used to infer the material properties of the animal. The experimental results will be presented and discussed. [Work supported by NSF.] Resubmission number: asae166
Digital transducer, novel technology for acoustical oceanography and fisheries research
Authors: Acker William , Wiggins Dan , Burczynski Janusz
Published: July 2002

Novel digital transducer architecture designed and produced by BioSonics Inc. offers many advantages over older analog designs. By digitizing the signal at the transducer element, the cable-coupled noise is eliminated. The signal is sampled at a high rate and accuracy (0.13%), and wide instantaneous dynamic ranges (132 dB). This allows simultaneous capture of extremely small and large echoes (single plankton specimen or bottom return) with no loss in detail or signal saturation. The data acquisition system is virtually automatic since most of the decisions are done by software. Row data is stored on PC hard drive. Data acquisition and data analysis software packages are user friendly and operate in WindowsTM environment. Many data processing tools are already developed as separate implementaiton of various algorithms. Digital transducers have already been successfully applied in various field projects in both marine and fresh waters: (i) monitoring and estimates of fish and plankton, (ii) fish tracking, and (iii) bottom plants estimate and seabed classification. The digital sonar is available in various packages and it can be installed on different platforms as portable systems for boats and ships, fixed platforms on dams, and in river in systems. The digital transducers are available in a wide range of frequencies (38 kHz to 1 MHz), in a single, dual, or split beam configurations.
Measurements of multi-megameter travel-time bias and coherence
Authors: Dzieciuch M. , Worcester P. , Birdsall T. , Metzger K. , Howe B. , Mercer J. , Spindel R.
Published: July 2002

The quality of ocean acoustic travel-time measurements depends on the coherence as well as the bandwidth of the signal. Ocean internal-wave fields are thought to be responsible for the loss of coherence in low-frequency acoustic signals. If the coherence bandwidth is less than the signal bandwidth, it is possible to consider sub-bands of the signal as separate measurements. The separate measurements can then be combined incoherently to improve the quality of the travel-time measurement. Theoretical work and computer simulations also predict that the travel-time of acoustic signals is biased by the ocean internal wave field. The path-integral theory for scattering predicts that the size of the travel-time bias depends on the logarithm of the center frequency of the acoustic signal, thus separate sub-bands would have different travel times and incoherent recombination would not be an optimal procedure. A recent experiment, in which two acoustic signals with different center frequencies were transmitted simultaneously, makes it possible to measure the bias experimentally and to determine the efficiency of sub-band averaging. Preliminary results suggest that the bias is about 50 ms at 3500-km range, which is roughly as large as expected.
On the existence of nearly stable dynamics in long-range sound propagation through oceanic mesoscale structure
Authors: Wolfson Michael A. , Tomsovic Steven
Published: July 2002

A dynamical system, motivated by ocean acoustic pulse propagation in the horizontal plane along the sound channel axis, is constructed using a potential derived from an idealized mesoscale eddy field. This problem is known to exhibit chaotic behavior in that rays are exponentially sensitive to both their initial condition and the position and strength of the individual eddies. The measure of chaos for the system has been expressed by deriving a Lyapunov exponent which determines the mean growth rate for the envelope of one of the elements of the stability matrix [M. A. Wolfson and F. Tappert, J. Acoust. Soc. Am. (to be published, 1998)]. However, the individual stability matrix elements are seen to fluctuate wildly from one ray to another. It turns out that many rays exhibit absolute traces of the stability matrix with values of O(1) even at basin scale ranges. This implies that much of the dynamics involves only local rotations as the flow evolves in phase space. Estimates are presented for a range-dependent measure of this nearly stable dynamical feature. Its relation to tomographic inversions of some features of mesoscale eddy fields is discussed.
The effects of temperature on the characteristics of the focal region in high-intensity focused ultrasound
Authors: Curra Francesco P. , Mourad Pierre D. , Crum Lawrence A.
Published: July 2002

The application of high-intensity focused ultrasound uses the transformation of ultrasonic energy into thermal energy to raise the temperature of tissue rapidly and induce necrosis of tumor cells. Targeting and control of the heated region and the amount of energy delivered are important issues. These numerical simulations couple sound propagation with the bio-heat equation to investigate tissue heating over time. The temperature rise affects both sound speed and attenuation. These, in turn, influence the spatial boundaries and magnitude of the ultrasonic time average intensity which, in turn, drives the temperature. In this model, the dependence of the sound speed and tissue attenuation on temperature is based on experimental results obtained in pig liver [Bloch et al., Proc. 16th Intl. Cong. Acoust., Seattle, WA, 1065–1066 (1998)]. The results show a spatial shifting of the focal region toward the transducer accompanied by a reduction in the magnitude of the ultrasonic time average intensity depending upon the on-time of the transducer and the initial pressures at which it is driven. The temperature response follows the same behavior, with a spatial shift of the hottest spot and a decrease in its peak value, although thermal conduction tends to counteract the process. [Work supported by DARPA.]