bluuebunny/crossref_metadata_2025 huggingface dataset:
Active vibration control of waves in simple structures with multiple error sensors
Authors: Pan X. , Hansen Colin H.
Published: July 2002

A numerical study is carried out to determine the improvement in vibration control of simple structures gained by using two sets rather than one set of error sensors. The structures considered are a beam, a plate, and a cylindrical shell. The control sources are driven to minimize the sum of the mean squared flexural displacement signal from all sensors with the view to reducing downstream vibration transmission. Results show that over a large frequency range there is an overall improvement in downstream attenuation resulting from the introduction of the second set of error sensors for each simple structure.
Three-dimensional wave propagation through single crystal solid–liquid interfaces
Authors: Lu Yichi , Wadley Haydn N. G.
Published: July 2002

Large differences in the ultrasonic velocity of the solid and liquid phases of semiconductors have stimulated an interest in the use of laser ultrasonic methods for locating and characterizing solid–liquid interfaces during single crystal growth. A previously developed two-dimensional ray tracing analysis has been generalized and used to investigate three-dimensional ultrasonic propagation across solid–liquid interfaces in cylindrical bodies where the receiver is located at an arbitrary position relative to the source. Numerical simulations of ultrasonic ray paths, wavefronts, and time of flight have indicated that ultrasonic sensing in the diametral plane is a preferred sensing configuration since the transmitted, reflected, and refracted rays all propagate in this plane, significantly simplifying analysis of the results. While other sensing configurations can also provide information about solid–liquid interfaces, they require a more complicated analysis because the planes in which reflected and refracted rays propagate are not known a priori, and fewer ray paths are accessible for interface interrogation because of large refractions.
Structural intensity of torsional vibration in solid and hollow cylindrical bars
Authors: Pan Jiaqiang , Pan Jie
Published: July 2002

This paper presents an exact analytical solution to the vibrational intensity of torsional waves in three-dimensional solid and hollow cylindrical bars of finite length. As the torsional response in circular cylindrical bars to the excitation of pure torsional moments is uncoupled with the motion of other degrees of freedom, its characteristics can be investigated independently. After verifying the orthogonal properties of the eigenfunctions of the torsional waves in a bar with fixed-free ends, the steady state response of the bar to a torsional moment was obtained analytically. The solution of the response was then utilized to calculate the vibrational intensity. Examples are used to illustrate the features of the torsional intensity in a hollow cylindrical bar.
Low-frequency amphibious hearing in pinnipeds: Methods, measurements, noise, and ecology
Authors: Kastak David , Schusterman Ronald J.
Published: July 2002

Aerial low-frequency (100–6400 Hz) hearing thresholds were obtained for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one northern elephant seal (Mirounga angustirostris). Underwater thresholds over a similar frequency range (75–6300 or 6400 Hz) were obtained for these three animals in addition to another California sea lion. Such data are critical, not only for understanding mechanisms about amphibious hearing and relating them to pinniped ecology and evolution, but also for identifying species at risk to man-made noise in the marine environment. Under water, the elephant seal was most sensitive, followed by the harbor seal and the sea lions. In air, the harbor seal was most sensitive, followed by the older of the two sea lions and the elephant seal. The following trends emerged from comparisons of each subject’s aerial and underwater thresholds: (a) the sea lion (although possessing some aquatic modifications) is adapted to hear best in air; (b) the harbor seal hears almost equally well in air and under water; and (c) the elephant seal’s auditory system is adapted for underwater functioning at the expense of aerial hearing sensitivity. These differences became evident only when aerial and underwater thresholds were compared with respect to sound pressure rather than intensity. When such biologically relevant comparisons are made, differences in auditory sensitivity can be shown to relate directly to ecology and life history.
On the acoustics and psychology of piano touch and tone
Authors: Askenfelt Anders , Galembo Alexander , Cuddy Lola L.
Published: July 2002

By way of ‘‘the touch,’’ a pianist is able to achieve two degrees of freedom in the control of the key motion. Besides the final hammer velocity, the pianist can control, to some extent independently, the force history between the key and finger. By controlling the acceleration history of the key, while keeping the final hammer velocity constant, the pianist can vary the duration of the key and hammer motion and the forces between the interacting parts of the action. This will influence the intensity of vibrations in the hammer shank and of a noise precursor in the radiated sound. This report addresses the pianist’s ability to change the touch parameters and to control them (at will) for musical purposes. The traditional controversy between physicists and some pianists raises a psychological question: ‘‘Why do some pianists think they are able to control a timbre of the individual tone by touch?’’ One hypothesis is that variations in touch change the perception of a tone for the pianist, but not for a listener, because for the pianist the tone perceived starts at finger–key contact, while for a listener it starts when the hammer hits the string.
Number of degrees of freedom of a lip-reed in brass-instrument playing
Authors: Boutillon Xavier
Published: July 2002

A lip-reed is a double continuous system that potentially exhibits several degrees of freedom. Numerical simulations for sound synthesis as well as fitting a model with measurements naturally improve while increasing the number of degrees of freedom that are put into the model. However, this parameter is worth investigating as such. In a first approach, lips are coupled to a Helmholtz resonator whose resonance factor is actively reinforced, as described in Chen and Weinreich [‘‘Nature of lip reed,’’ J. Acoust. Soc. Am. 99, 1227–1233 (1996)]. The dimensionality of the attractor or permanent regime of this nonlinear dynamical system is computed with embedding techniques of the corresponding time-series and information-based measurements [Gershenfeld et al., Time Series Prediction (Addison-Wesley, Reading, MA, 1994)]. Preliminary results indicate a dimension of 1, 2 or 3 for different couplings between the lips and the resonator. The link with the number of freedom of the lip-reed will be discussed. [Work supported in part by CNRS and NSF.]
The assessment of environmental noise—ISO 1996
Authors: Flindell Ian H. , Porter Nicole D.
Published: July 2002

The concept of a grand ‘‘general noise annoyance model’’ which takes different noise sources and different situations into account by appropriate adjustments or correction factors is very attractive. On the other hand, it is well known that different people respond to different components of the overall situation (acoustic features) at different times, and that this selective attention process can be essentially unpredictable. In order to make progress in this field, it is essential that any new methods of assessment of environmental noise must take this inherent flexibility into account. This paper describes an input-process-outcome model which the authors have been working on as the underlying framework for the current revision of ISO 1996 ‘‘Description and measurement of environmental noise.’’ In essence, there are three possible outcomes of assessment (no impact, intermediate impact, and unacceptable impact) and three comparison processes (change in noise, new noise compared against existing background noise, and absolute criteria) which can be applied to the various inputs to determine the assessment outcome. The model allows sufficient flexibility to accommodate most existing national noise assessment procedures, reflects current scientific thinking, and provides a sound basis for choosing the best balance between the costs and benefits of noise control action.
An experimental study of the peripheral auditory mechanics in the goldfish (Carassius auratus) and oscar (Astronotus ocellatus)
Authors: Hastings Mardi C. , Finneran James J. , Derenburger Corrie
Published: July 2002

Dynamic mechanical responses of peripheral auditory organs in the goldfish (Carassius auratus), considered a hearing specialist because of its coupling via the Weberian ossicles between the swimbladder and inner ear, and the oscar (Astronotus ocellatus), an auditory nonspecialist, were measured in vivo using a noncontact, noninvasive ultrasonic system. Motion of the auditory organs was induced under water using pure tones at frequencies ranging from 12.5 to 3000 Hz. Measurements were made in both species with swimbladders intact and swimbladders deflated. Results from 23 goldfish and 38 oscars show that the swimbladder controls auditory bandwidth not only in hearing specialists, but also in nonspecialists which have no special coupling between the swimbladder and inner ear. Dual resonances routinely observed in the response of the anterior swimbladder, and motion of the Weberian ossicles transmitted to the saccular otolith at higher frequencies, contribute to the relatively broad auditory bandwidth of the goldfish. Although data were recorded only in the medial-lateral direction, they clearly indicate that displacement of the saccular otolith relative to its sensory epithelium in both the goldfish and oscar correlates with auditory thresholds for these animals reported in the literature. [Work supported by ONR Grant No. N00014-94-1-0337.]
Detection of ultrasound and marine mammal echolocation clicks by the American shad (Clupeidae)
Authors: Mann David A. , Lu Zhongmin , Popper Arthur N.
Published: July 2002

Clupeid fishes (herrings and shads) are among the main prey of echolocating cetaceans. Recent studies have shown that some clupeids are repelled by intense sounds from ultrasonic transducers. The hearing thresholds of a clupeid, the American shad (Alosa sapidissima) was determined using classical conditioning. Shad could detect sounds from 0.2 to 180 kHz, with two regions of best sensitivity, one from 0.2 to 0.8 kHz and another from 25 to 150 kHz. American shad were also able to detect simulated bottlenose dolphin (Tursiops truncatus) echolocation clicks with a threshold that suggests they could detect an echolocating dolphin at distances up to 187 m. These results have practical implications for the design of ultrasonic devices that could be used for repelling clupeids from power plant intakes and dams, as well as for the design of ultrasonic pingers that may reduce dolphin bycatch without affecting the catch of clupeids. [Work supported by NSF.]
Morphological responses of fish to low-frequency sound
Authors: Clark Joseph A. , Young Jane A. , Bart Amrit N. , Zohar Yonathan
Published: July 2002

Results of an earlier study [Clark et al., J. Acoust. Soc. Am. 100, 2709(A) (1996)] suggested that low-frequency vibrations could have a positive effect on the growth rate of fingerlings grown in tanks. This talk describes a more extensive study with a larger sample of fish (640 Tlapia Nilotica grown in four control tanks and four treated tanks) for a longer period of time than the previous six week period. The control tanks were mildly acoustically quieted with foam rubber tank coatings that are normally applied to reduce heat conduction into the tanks. The treated tanks were excited continuously with shakers in the frequency range of 30–60 Hz for the duration of the test. Average weight and length versus time for fish in treated and control tanks were measured at 3 week intervals. Differences in the two groups and their possible causes are discussed.
Changes in acoustic impedance of marine sediment covered with liquid pollutants
Authors: Harms Henning , Matuschek Rainer , Mellert Volker
Published: July 2002

Acoustic properties of porous material are slightly changed by a coating layer, which is thin compared to the acoustic wavelength. These changes affect mainly the spherical wave reflection coefficient at grazing incidence. The phase change of a surface wave component is observed and enables the easy detection of the thin layer by measuring the interference of direct and guided surface waves. This method is investigated for screening observations in order to monitor liquid pollutants on marine sediment. Since sediment is usually not plain but more or less irregularly grooved, the coating by liquid pollutants will occur in patches. Laboratory experiments are carried out with rough surfaces of sediment to investigate the sensitivity of detecting an average change in impedance. The results are compared with a numerical model incorporating Biot theory [Tooms et al., J. Acoust. Soc. Am. 93, 171–181 (1998)], which was successfully applied to model experimental data of plain sediment (Harms et al., 134th meeting of ASA). Since the rough surface produces a significant backscattering, the liquid patches are detectable in the backscattered signal as well. Experimental results of this contribution are presented and the possibility of using this method for monitoring purposes discussed. [Work supported by German Ministry of Technology BMFT.]
Optimal acoustic parameters for induced hyperthermia from focused MHz ultrasound: Phantom measurements with fluid flow and bubble activity
Authors: Holt R. Glynn , Roy Ronald A.
Published: July 2002

The effective coagulation of flowing blood by ultrasound, or acoustic hemostasis, is a complex process that encompasses several physical, biophysical, and biochemical facets. Motivated by this ultimate goal of efficient and predictable hemostasis, we have undertaken a series of laboratory experiments on a variety of phantoms insonified by 1-MHz focused ultrasound at MPa amplitudes. The goal of the present study is to quantify and characterize the physical response of a viscous, particulate-laden Newtonian flow to high-intensity focused ultrasound (HIFU). Experimental hyperthermia in a tissue/flow phantom as a function of acoustic parameters (pulse width, duty cycle, amplitude), flow parameters (volume flow rate, vessel size, flow geometry), and bubble content in the flow phantom is investigated. Spatiotemporally resolved temperature measurements in the flow and surrounding tissue phantom are reported. Time permitting, visualization of the modified flow due to acoustic streaming and radiation pressure will be undertaken to correlate flow events with the hyperthermia results. [Work supported by DARPA.]
High-intensity ultrasound for dewatering of slurries
Authors: Elvira-Segura Luis , Rodriguez-Corral German , Riera F. de Sarabia Enrique , Gallego-Juarez Juan A.
Published: July 2002

Dewatering is a process in which the water is removed from a product without changing its phase. Fine particle slurries are difficult to dewater and several processes such as filtration and centrifugation are conventionally applied. These processes, which are efficient to remove free water, are ineffective in removing water from interstitial spaces. High-intensity ultrasound can be used to assist conventional filtration processes in order to increase the rate of dewatering. Particularly, the application of ultrasonic energy has shown to be useful as a postfiltration process, once the free water has been removed. In this paper a new system is presented in which the combination of vacuum filtration and ultrasonic energy results in very efficient dewatering of very fine slurries constituted by particles sized between 0.1 and 10 μ. The system is based on the application of direct coupled ultrasonic energy to the cake formed on the surface of a ceramic vacuum filter by means of specially designed plate transducers. The obtained results demonstrate that the application of ultrasound significantly increases the interstitial water removal and, consequently, it diminishes the energy consumption of the whole process (dewatering and drying).
Model experiments on the evaluation of the cement bond with ultrasonic pulse-echo techniques
Authors: Qiao Wenxiao , Du Guangsheng , Chi Shihong
Published: July 2002

Previous research shows that when the transducer is immersed in slurry, it is nearly impossible to determine the cement bond quality of the interface between the cement annulus and formation (Interface II) using the ultrasonic pulse-echo technique. Because strong reflection occurs at the interface between the slurry and casing, most of the portion of the pulse energy is reflected back. In this paper, methods of cement bond evaluation are studied in four different model experiments, in which the transducer is contacted closely to the casing. In these experiments, no matter whether the ultrasonic pulses are normally or obliquely incident to the casing, obvious signals corresponding to the Interface II are observed. Considering the practical implementation of the technique, a thin steel plate is inserted between the transducer and casing. The reflection signal can still be achieved. The model experiments indicate that the transducer-contact-casing system can eliminate the influence of the slurry, improve the ratio of signal-to-noise, evaluate the interface between the casing and cement (Interface I), and determine the cement bond quality of the Interface II if the Interface I is well bonded.
Optical detection of leaky-Rayleigh waves at air–solid interfaces
Authors: Adler Laszlo , Mattei Christophe , de Billy Michel , Quentin Gerard
Published: July 2002

Due to the difficulties associated with ultrasonic generation and detection in air in the megahertz region, air-coupled nondestructive evaluation has only recently been explored. In this work, a shear transducer is mounted directly over the edge of a solid specimen so that it can generate a bulk mode in the interior of the solid as well as a Rayleigh wave along the surface. A recently developed optical heterodyne interferometer proved to be sensitive to the leaky-Rayleigh wave in air more than a centimeter away from the solid surface. Results of velocity and attenuation measurements of leaky-Rayleigh waves for several solids will be presented. The technique can also be applied to plates to measure leaky-Lamb velocity and attenuation in air. This method can be used for low optical reflectivity solid surfaces: Thus it can be extended for noncontact nondestructive evaluation applications.
High-resolution spectroscopy of the Lamb modes of a plate near normal incidence
Authors: Durinck G. , Thys W. , Izbicky J. L. , Rembert P.
Published: July 2002

Using a high-resolution digital oscilloscope and advanced datahandling plate modes near normal incidence, other than those identified by Lamb, were studied. This search was led by the complex roots of the dispersion relation for a plate in water. Solutions with a complex wave number component in the propagation direction indeed reveal near normal incidence the existence of plate modes no one has ever observed to our knowledge. In this paper experimental results are presented at the cutoff frequencies of the S1 and S2 modes of a 1.5-mm-thick aluminum plate, and at the cutoff frequencies of the A1 and A2 modes of a 1.5-mm-thick glass plate. The extra resonance predicted by the theory is resolved by looking at the time history of the radiating plate. This is done either by displacing the time window far into the free emission regime or by displacing the receiving transducer in the propagation direction.
Psychoacoustic development in humans and the effects of otitis media on psychoacoustic development
Authors: Hall Joseph W. , Grose John H.
Published: July 2002

Psychoacoustic measures of auditory development in children with normal hearing and fluctuating conductive hearing losses reveal several general trends. First, processing efficiency is usually reduced in young children: they require higher SNRs and are less sensitive to AM. However, underlying mechanisms may be mature: derived measures of frequency selectivity, TMTF time constants, across-frequency processing (CMR and the processing of multiple modulations), and binaural processing (MLD for broadband maskers and sensitivity to off-midline stimuli) are adultlike by age 5. Nevertheless, key differences remain: across-frequency processing in children is less tolerant of asynchronies than in adults and, for narrow-band maskers, young children have poor binaural masking release, a result which is not due simply to perceptual similarities between signal and masker. A second general trend is that deficits in function due to early conductive hearing loss are not permanent, although the duration of abnormal performance appears to be strongly associated with the specific function being measured. Basic measures of CMR recover by approximately six months but the processing of multiple modulations takes longer. The MLD may take several years to recover. Interpretations of these findings in terms of CNS strategies for analyzing peripheral information will be presented. [Work supported by NIH NIDCD.]
The influence of barrier edge treatments
Authors: Möser Michael
Published: July 2002

The paper deals with the reduction of the sound field in the shadow region behind barriers by means of an attached body at the edge of the screen. The reflecting attributes of the barriers hatpiece are described by a locally reacting impedance. The considerations start with a repetition on the diffraction at ideal soft and hard bodies to demonstrate the governing principle of tangential power transport parallel to their surface: The impedance must be chosen in such a way that the tangential intensity near the edge is lowered, such turning the incoming power to ‘‘undangerous’’ directions. Subsequently, the differences due to finite impedances are discussed. The physical principles are demonstrated in a computer animation of the sound fields for the different cases. Theoretical computations give considerable improvement of the level reduction in the shadow zone for not too small angles of diffraction. They are compared with measurement results and practical applications are discussed.
Wave propagation in a wavy fiber–epoxy composite material: Theory and experiment
Authors: Kim Kwang Yul , Zou Wei , Sachse Wolfgang
Published: July 2002

In this paper analytic formulas are developed for the ray path and travel time of a ray propagating in a wavy fiber–epoxy composite material and calculate them for rays initiating at various points with wave normals of differing directions. The arrival times observed by using various combinations of pointlike sources and pointlike detectors are found in good agreement with those predicted by the theory of geometrical acoustics.
Focusing and steering through absorbing and aberrating layers: Application to ultrasonic propagation through the skull
Authors: Tanter Mickaël , Thomas Jean-Louis , Fink Mathias
Published: July 2002

The time-reversal process is applied to focus pulsed ultrasonic waves through the human skull bone. The aim here is to treat brain tumors, which are difficult to reach with classical surgery means. Such a surgical application requires precise control of the size and location of the therapeutic focal beam. The severe ultrasonic attenuation in the skull reduces the efficiency of the time reversal process. Nevertheless, an improvement of the time reversal process in absorbing media has been investigated and applied to the focusing through the skull [J.-L. Thomas and M. Fink, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43, 1122–1129 (1996)]. Here an extension of this technique is presented in order to focus on a set of points surrounding an initial artificial source implanted in the tissue volume to treat. From the knowledge of the Green’s function matched to this initial source location a new Green’s function matched to various points of interest is deduced in order to treat the whole volume. In a homogeneous medium, conventional steering consists of tilting the wave front focused on the acoustical source. In a heterogeneous medium, this process is only valid for small angles or when aberrations are located in a layer close to the array. It is shown here how to extend this method to aberrating and absorbing layers, like the skull bone, located at any distance from the array of transducers.
Physiological studies of the precedence effect in the inferior colliculus of the kitten
Authors: Litovsky Ruth Y.
Published: July 2002

The precedence effect (PE) is a perceptual phenomenon that reflects listeners’ ability to suppress echoes in reverberant environments. The PE is not present at birth and appears only several months postnatal. Recent physiological studies have demonstrated correlates of the PE in the central nucleus of the inferior colliculus (ICC) of adult animals. The present study extended the same techniques to search for similar correlates in the ICC of kittens during the first postnatal month. Stimuli consisted of pairs of clicks or noise bursts presented from different locations in free field or with different inter-aural differences in time (ITD) under headphones, with an inter-stimulus-delay (ISD) between their onsets. Results suggest that a physiological correlate of the PE, i.e. suppression of responses to the second source, is present as early as 8 days postnatal, and occurs at similar ISDs to those recorded in adult cats. Suppression in kitten neurons varies with stimulus level, duration, and azimuthal position, in a similar manner to that in adult neurons. The age at which correlates of the PE in the kitten can be found precedes the age at which kittens can localize sound sources effectively, and presumably before the age at which they would demonstrate the PE behaviorally. Thus, the neural mechanisms that might be involved in the first stages of processing PE stimuli may be in place well before the behavioral correlate develops.
Measurements of the two-frequency mutual coherence function for sound propagation through a turbulent atmosphere
Authors: Havelock David I. , Stinson Michael R. , Daigle Gilles A.
Published: July 2002

An array of 32 microphones spanning 675 m of range was used to measure the frequency coherence for pulse signals propagating through atmospheric turbulence near the ground. Frequency coherence is the correlation between the fluctuations in received signals of different frequencies as expressed through the two frequency mutual coherence function evaluated at the same point in space and time. The experiments were conducted for frequencies between 200 and 1000 Hz under both downward and upward refracting propagation conditions. Measurements and theory are shown to be in good agreement for line-of-sight propagation. In the acoustic shadow region the frequency coherence bandwidth shows a strong dependence on mean frequency. The effects of refraction and diffraction, which cause wandering in the pulse arrival time and broadening of the pulse width, respectively, are clearly distinguished. The measurements provide experimental characterization of signal fluctuations for sound fields propagating outdoors. They are important for acoustic remote sensing and detection applications and for the validation of theoretical and numerical developments in sound propagation modeling.
Extracting modal wave numbers from data collected in range-dependent environments
Authors: Kessel Ronald T.
Published: July 2002

Properties of the seafloor affecting sound propagation can be inferred from the horizontal wave numbers of bottom-interacting modes of sound propagation. To this end, the modal wave numbers can be extracted from the harmonic sound field recorded by a single hydrophone, when either the source or hydrophone are towed at constant depth, giving in effect a well-sampled synthetic aperture array. This method has been used to determine the bottom properties in a range-independent environment, by first applying a Hankel transform to get a representative wave-number spectrum in which the wave numbers of the dominant modes feature prominantly [S. D. Rajan et al., J. Acoust. Soc. Am. 82, 998–1017 (1987)]. In range-dependent environments, however, the modes vary owing to changes in bathymetry and seafloor properties, making it impossible to speak of a single set of range-independent modal wave numbers as the Hankel transform method requires. In this paper, a phase demodulation technique is derived from the adiabatic mode model of sound propagation whereby range-dependent wave numbers can be extracted from data collected in range-dependent environments using the same experimental setup as in range-independent environments.
Masking of tones by harmonic complexes in the budgerigar (Melopsittacus undulatus)
Authors: Dent Micheal L. , Dooling Robert J. , Leek Marjorie R. , Summers Van
Published: July 2002

Birds frequently show psychoacoustic abilities remarkably similar to those of humans in spite of considerable differences in auditory structure and function. Harmonic complexes constructed in positive and negative Schröeder phase are differentially effective as maskers in humans, even though they have essentially identical temporal envelopes and long-term spectra [V. Summers and M. R. Leek, Hear. Res. 118, 139–150 (1998)]. Because these masking differences are believed to be closely tied to cochlear mechanisms in mammals, investigations of Schroeder-phase masking in birds might reveal the contributions of particular auditory structures to complex sound processing in both species. To this end, three budgerigars were trained by operant conditioning and tested using the method of constant stimuli to detect pure tones masked by Schroeder waveforms. In parallel testing, two human listeners showed more masking by the negative than by the positive Schroeder waveforms. However, none of the birds showed greater masking by the negative than the positive waves, and in some cases the positive waveform was the more effective masker. These results may reflect structural differences underlying the traveling wave in these two species, as well as a difference in active processing in avian versus mammalian cochleas. [Work supported by NIH DC00198.]
Segmental and prosodic effects on coda glottalization
Authors: Huffman Marie K.
Published: July 2002

Glottalization is a common property of coda t’s in American English. Previous work [J. Pierrehumbert, Proc. CLS 2, 232–256 (1994)] found coda glottalization to be affected by following segmental context. This paper examines segmental and prosodic contextual factors as they condition the occurrence of glottalization on ‘‘voiceless’’ stops [p] and [t] in English. Following Pierrehumbert’s methodology, audio recordings were made of discourse fragments containing open-ended lists, which minimize phonation changes associated with low pitch. To test the effect of segmental context, various sounds were placed in the onset of the second member of compounds such as ‘‘kite maker’’ and ‘‘suit fitter.’’ To test the effect of prosodic context, these list items were compared with single word list items, as in ‘‘color, height, make,...’’ with a phrase boundary after the coda consonant. For coda [t], glottalization is more common before sonorants, and is affected little by a following phrase boundary. In contrast, coda [p] is less frequently glottalized, and is more sensitive to context. Glottalization is more frequent before sonorants, without an intervening phrase boundary. Thus, the strength of segmental and phrasal context effects in determining the occurrence of glottalization depends on the target segment. [Work supported by NSF.]
Experimental study of the target undershoot model using acoustic and ‘‘articulatory’’ data
Authors: Pitermann Michel , Ciocea Sorin
Published: July 2002

In a previous study [M. Pitermann and J. Schoentgen, 1st ESCA Tutorial and Research Workshop on Speech Production Modeling, 17–20 (1996)], the influence of speaking rate and emphatic stress on formant frequencies and corresponding target estimates were analyzed for the vowels [a] and [ε] in an [i-i] context. Unreached targets were estimated by means of two dynamic and two kinetic models of formant transitions. The results showed that both formant frequencies and target estimates varied with speaking rate and emphatic stress. In the present survey, we analyzed ‘‘articulatory’’ targets for the same corpus in the framework of a vocal tract model. The ‘‘articulatory’’ trajectories were analytically calculated by means of an acoustic-to-articulatory inversion carried out on a six-tube Kelly-Lochbaum model of the vocal tract [S. Ciocea, ‘‘Semi-analytic formant-to-area mapping,’’ Ph.D. thesis (1997)]. Targets were then estimated by means of asymptotes or steady-state solutions of transition models fitted to trajectories of the palatal region. The results suggest that ‘‘articulatory’’ target estimates did not depend on speaking rate, emphatic stress and speaker for a subset of speaking rate and stress pairs. The results will be discussed with respect to possible inversion artifacts and the possibility of target invariance.
A Lloyd-mirror model to estimate the scattering strength of fish near rough ocean boundaries
Authors: Gauss Roger C. , Nero Redwood W. , Wurmser Daniel
Published: July 2002

It is well known that a point scatterer located near the sea surface creates an acoustic dipole and that one near the ocean bottom is in general described by a series of higher-order moments (e.g., a double monopole in the simplest case of a hard, flat bottom). This Lloyd-mirror effect has been coupled with a resonant fish scattering model of Love [R. H. Love, ‘‘Resonant acoustic scattering by swimbladder-bearing fish,’’ J. Acoust. Soc. Am. 64, 571–580 (1978)] to develop a simple model which predicts the backscattering strengths of a variety of fish species known to occur (during at least part of a diurnal cycle) in near-boundary layers. The model is applied to and compared with measurement results from Critical Sea Test 7 (CST-7 Phase 2) to demonstrate that fish can be significant contributors to low-grazing-angle scattering. The general implications of the model are that observed enhancements in backscattering strength over levels predicted by first-order rough-surface scattering theories may, in some cases, be primarily due to backscatter from near-surface fish (rather than from bubbles or the sediment volume). [Work supported by ONR.]
Sound propagation in bubbly liquids, a review and research issues
Authors: Carey W. M. , Roy R. A. , Commander K. W.
Published: July 2002

Sound propagation in bubbly liquids has been studied since the work of Wood (1932). He showed the sonic speed at low frequencies could be calculated for an air bubble–water mixture by use of the mixture density and compressibility. Experimental and theoretical investigations prior to 1985 confirmed his work and provided a basis for the understanding of the sonic speed variation from a low-frequency subsonic region, through a supersonic region, and ultimately to a sonic region at higher frequencies. Renewed interest in the properties of bubbly liquids has resulted from sound scattering from the sea surface, ship’s wakes, and the bubble-related production of underwater sound. Papers have been written on the sound speed variation with frequency, most notably by Commander and Prosperetti (1989), which summarize the dispersive characteristic and methods for the calculation of this characteristic as a function of the bubble size number density spectrum and the acoustic frequency. However, many recently published papers are not consistent with these classical results. It is the purpose of this paper to place contemporary work in perspective by providing a concise theoretical overview. Furthermore, this paper will discuss unresolved research issues of frequency-dependent attenuation factors and dissolution effects. [Work supported by ONR.]
Three organs, three recital halls, three acoustic spaces: Designing the right organ for each project
Authors: Wolff Hellmuth
Published: July 2002

Building organs for concert halls or churches is almost always an exercise in adapting an instrument to a space which was not designed for an organ, neither physically nor acoustically. The author has designed and built four organs in university recital halls and will discuss three of these, one of which is a rare exception: (1) Redpath Hall at McGill University in Montréal—a former lecture hall turned recital hall, due in large part to the addition of a new French-baroque style organ in 1981. Besides a new hardwood floor and air conditioning, no acoustical changes were made to the hall. (2) Stetson Chapel at Kalamazoo College in Kalamazoo, Michigan—a 1930s chapel rebuilt and restored in 1986 and now mainly used as the college’s recital hall. Significant improvements to the room’s acoustics were made, and a three-manual eclectic-design organ installed in 1987. (3) Bales Organ Recital Hall at the University of Kansas in Lawrence, Kansas—a new space built in 1996 exclusively for use of the organ faculty and for organ recitals. A large three-manual French-romantic organ is the centerpiece of this spectacular hall.
Design problems of a concert hall with an organ
Authors: Nagata Minoru
Published: July 2002

Organ music is not common in Japan, which has a poor church-music tradition. Almost all organ concerts are performed in concert halls. This is a major difference from the situation in North America and European countries. Concert halls in Japan are therefore generally expected to also serve as organ recital halls. In order to fulfill the requirements of both concert halls for classical music in general, and organ recital halls in particular, several ideas and devices have been developed and introduced such as movable reflectors, ceilings, partitions, and a reverberation enhancing system using digital signal processing (DSP). The presentation will explain these measures and their effects on the listening experience and discuss the problems involved in carrying out such design work.
Organ acoustics and the concert hall
Authors: Scarbrough Paul H. , Jaffe J. Christopher , Bethards Jack
Published: July 2002

Providing an optimal acoustical environment for a pipe organ requires close collaboration between organ builder and acoustical consultant throughout the design process. Each brings unique and complementary perspectives to this subject. The organ builder offers not only a knowledge of the instrument but often a wealth of practical acoustical experience from a multitude of specific organ installations. The acoustical consultant offers extensive knowledge of acoustical principles as well as an understanding of how these must be interpreted and applied in architectural design. The authors discuss the nature of their design collaboration on recent projects and in the process examine a broad range of issues including: preferred reverberation and frequency response characteristics for organ, the essential balance between reverberation and clarity, ideal placement of the organ within the concert room, differences between spaces dedicated to organ and those that also accommodate instrumental and choral ensembles, and the importance of proper sound isolation and quiet ambient environments. The authors cite relevant aspects of their projects including the Kennedy Center Concert Hall, Severance Hall, the Weidner Center at the University of Wisconsin at Green Bay, and Holzclaw Hall at the University of Arizona.
State of the art of sonic boom modeling
Authors: Plotkin Kenneth J.
Published: July 2002

The fundamentals of sonic boom theory were established and validated in the 1950s and early 1960s. By the early 1970s, these were implemented into practical models. Over the past decade, there have been requirements for design tools for an advanced supersonic transport and environmental assessment of launch vehicles and military aircraft operations. This has resulted in a number of advances in the understanding of sonic boom shock rise times, propagation through turbulence, use of computational fluid dynamics in sonic boom modeling, and analysis of launch vehicle sonic boom including the effect of large underexpanded rocket plumes. This paper reviews the early established theory, the recent advances in theory, and the application of these advances to practical models.
Atmospheric turbulence conditions leading to focused and folded sonic boom wavefronts
Authors: Piacsek Andrew A.
Published: July 2002

A model proposed by Pierce [A. S. Pierce and D. J. Maglieri, J. Acoust. Soc. Am. 51, 702–721 (1971)] to explain the variability of rise times in sonic booms invokes the process of wavefront focusing and folding. Although nonlinear theory applied to a propagating discontinuity predicts that a curved wavefront will always tend to straighten, the finite rise time of a sonic boom permits wavefront folding when the wavefront curvature is sufficiently small [A. A. Piacsek, J. Acoust. Soc. Am. 99, 2539 (1996)]. In the present work, the effect of turbulence is modeled as a rippling of the sonic boom wavefront; two important length scales of this rippling are correlated, via numerical experiments, with wavefront folding. This permits the computation of length and energy scales of atmospheric turbulence associated with the ripple scales of interest and, thus, with folded wavefronts. Additionally, numerical results are shown of the propagation of the positive phase of an N-wave whose wavefront comprises multiple ripples of different length scales. The simulated shock profiles at several propagation distances are compared with representative sonic boom profiles recorded during test flights.
Recent in situ measurements of sediment geoacoustic properties
Authors: Richardson Michael D.
Published: July 2002

Values of surficial geoacoustic properties have been reported for a variety of siliciclastic and carbonate sediment types in coastal environments using direct in situ measurement techniques. Recent measurements in the North Sea have provided detailed profiles of shear wave speed in the upper 30 cm of sediment and increased the meager database of values of shear wave attenuation. These new measurements from North Sea sediments are placed into the context of past measurements and new relationships among sediment physical and geoacoustic properties are presented. Profiles of shear wave speed support theoretical models that predict that the dynamic shear modulus is proportional to the effective stress to the 1/3 power. [Work supported by ONR.]
Diffusion of ultrasound in concrete
Authors: Turner Joseph
Published: July 2002

The propagation and scattering of ultrasound in concrete is discussed. The heterogeneous composition of concrete causes the ultrasound to scatter considerably. In the limit of many scattering events, the ultrasonic energy density in bars of concrete is shown to evolve in accordance with a one-dimensional diffusion equation. The ultrasonic diffusivity and dissipation are measured experimentally over the frequency range of 100 kHz to 2 MHz. Such frequencies are well above typical frequencies used for concrete inspection. The diffusivity, which is a measure of the microstructure, is shown to correlate with the strength of the concrete. This technique also allows the true dissipation from viscoelastic effects in the cement to be assessed directly. It is anticipated that the use of these higher frequencies will result in new techniques for characterizing material properties and damage in concrete structures. [Work supported by the Nebraska Research Initiative.]
Backscattering and grain noise in random elastic media, beyond the single scattering model
Authors: Weaver Richard L.
Published: July 2002

Specific intensity, or energy per solid angle per area per time, is the appropriate dependent variable for the study of the transport of ultrasonic energy in a random heterogeneous solid. An integro-differential equation (the radiative transfer equation, or RTE) governs its dependence on time and space and propagation direction. The solutions that have been obtained are, however, arguably irrelevant for the experimental configurations in which a phase sensitive transducer of finite aperture is used. Such transducers are not sensitive to specific intensity per se. In this work it is shown that the RTE must be modified for the case of a finite aperture piezoelectric transducer. While the RTE governs the propagation of specific intensity between successive scatterings, the propagation from the source to the first scattering, and from the last scattering to the receiver, is governed by a more complicated process. It is found that specific intensity is not the appropriate quantity and that the Wigner distribution (in space and wave number, and in time and frequency) of the source and receiver beam patterns is needed. These modifications are discussed and an example presented in which the backscattered signal in a focused transducer includes both single and multiple scattering.
Rayleigh to the Internet: Sources for demonstration experiments
Authors: Rossing Thomas D.
Published: July 2002

Ideas for demonstration experiments in musical acoustics come from many sources: books, journals, conferences, even the Internet. The author will share his favorite sources as well as some of his favorite demonstrations.
An audible demonstration of low-frequency sound propagation in bubbly water
Authors: Roy Ronald A. , Wilson Preston S. , Carey William M.
Published: July 2002

Bubbly liquids have long held our attention as a novel medium for acoustic propagation, with nonlinear, dispersive, and attenuative properties that eclipse those present in either the gas or fluid phase alone. For example, when driven at frequencies that are well below the bubble resonance frequency, the material exhibits both high compressibility and high density. This unusual combination results in a mixture sound speed that can range as low as 100 m/s, far less than that of either the air or the water alone. This remarkable effect will be demonstrated by bubbling air through a vertical water-filled tube. The air injection process results in a broadband noise that drives the tube in its fundamental length mode. The frequency of this mode is audible, and scales with the mixture sound speed. By varying the flow rate of air (i.e., the void fraction), it is possible to vary the sound speed and thus control the pitch associated with the tube resonance. Knowledge of this resonance frequency and the length of the tube allows us to determine the mixture sound speed, which can then be compared with theory. [Work supported by ONR.]
From the speed of light to the speed of sound to chaos: Demos for all occasions.
Authors: Korman Murray S. , Tobin John V. , McMahon Kathryn M.
Published: July 2002

In 1676, the Danish astronomer Olaf Roemer discovered variations in the periods of the four known satellites of Jupiter. The periods of these satellites can be determined by means of their eclipses, i.e., the times at which they enter Jupiter’s shadow in the sunlight. Roemer found that the periods increased when the earth moved away from Jupiter and decreased when the earth moved towards Jupiter, and he concluded that it must take a finite amount of time for light to traverse the diameter of the earth’s orbit. From knowledge of the earth’s orbit (at that time), he computed the velocity of light to be 227 000 km/s—the first evidence for a finite speed of light. One can explain the result using the Doppler effect and bring it to life using sound waves. Let the satellite become a stationary source of sound and place a distant microphone on a radius arm that is allowed to rotate (or orbit). Using Doppler shift versus time information, the speed of sound is ultimately determined. We will then shift gears, and present an apparatus which displays a compass needle going from simple harmonic motion to chaotic behavior in a periodically reversing magnetic field.