bluuebunny/crossref_metadata_2025 huggingface dataset:
Rating noise—The experience of the computer industry
Authors: Warshawsky Marc , Hellweg Robert D. , Pei Hsien-sheng (Jason)
Published: July 2002

With the general consensus of practicing noise control consultants that the two different sets of criterion curves for evaluating room noise contained in ANSI S12.2-1995 [room criterion (RC) and balanced noise criterion (NCB)] should be replaced with a single set of criterion curves, the authors believe that lessons can be learned from the computer industry, especially in accounting for noises with abnormal characteristics. This industry realizes that the noise emissions from their products should be compatible with the acoustical requirements of the environment in which the products are installed. The types of computer products cover a wide range with respect to functionality, size, sound power level, and spectral and temporal characteristics of their emissions. The rooms in which these products are installed also cover a wide range, including many types with significantly different levels of acceptable noise. In addition to using A-weighted descriptors (sound power level to describe product emissions and sound-pressure level to describe room noise levels), the computer industry has recognized the need to take into account and to characterize abnormal features of the noises, such as prominent discrete tones (ECMA-74-1996 or ANSI S1.13), tonal modulation or beating, and impulsive or fluctuating sounds. This paper presents some of these experiences from the computer industry in the context of establishing room noise criterion curves. [See NOISE-CON Proceedings for full paper.]
Experimental demonstration of an acoustic time-reversal mirror in the ocean
Authors: Kuperman William A. , Hodgkiss William S. , Song Hee Chun , Akal T. , Ferla C.
Published: July 2002

A time-reversal mirror (TRM) was implemented in an experiment conducted in the Mediterranean Sea in April 1996. The experiment utilized a vertical source–receiver array (SRA) spanning 77 m of a 125-m water column with 20 sources and receivers and a single source/receiver transponder (SRT) colocated in range with another vertical receive array (VRA) of 46 elements spanning 90 m of a 145-m water column located 6.3 km from the SRA. The TRM demonstration consisted of transmitting a 50-ms pulse from the SRT to the SRA, digitizing the received signal, and retransmitting the time-reversed signals from all the sources of the SRA. The retransmitted signal was then received at the VRA. An assortment of runs were made to examine the structure of the focal point region and the temporal stability of the process. The process was extremely robust and stable. Iterative enhancement of the focusing process was also demonstrated by a ‘‘ping-pong’’ exchange of a pulse between the transponder and the TRM.
Radial magnetic topology for dynamic loudspeakers
Authors: Telesky Ted R. , Shaw Neil A.
Published: July 2002

Magnetic topologies for loudspeakers have remained essentially unchanged since the conversion from electrodynamic to dynamic magnetic structures. By utilizing the magnetic technology developed for long-stroke linear actuators, a neodymium magnet circuit was developed by dynamic loudspeakers that uses a radially charged magnetic topology. Benefits of this topology include large linear travel, low distortion, and high-power handling. The topology is also inherently shielded. The technology has been successfully demonstrated in dynamic cone-type direct radiator transducers that range in size from 2 to 18 in. in diameter.
Josephson acoustic radiation in superfluid 4He: Towards a quantum mechanical pressure standard
Authors: Backhaus Scott , Packard Richard E.
Published: July 2002

Below 2.2 K, 4He is a superfluid that exhibits nearly dissipationless flow for velocities less than a well defined critical velocity. For flow through submicron apertures, the superfluid begins to dissipate energy at the critical velocity by the creation and motion of individual quantized vortices across the aperture. Using a recently developed pressure control technique, a constant pressure drop, ΔP, is applied across the aperture. This causes the vortices to cross the aperture at a Josephson frequency given by fj=(m4ΔP)/(ρh) where m4 is the mass of a helium atom and h is Plank’s constant. The periodic vortex crossing causes the superfluid velocity in the aperture to oscillate and emit acoustic radiation at fj. This sound source will radiate a total power of 10−21 W into freespace. Radiation from the vortex motion has been detected using a 1/4 wave resonant detector and a novel cryogenic microphone. This phenomena could lead to a frequency based pressure standard where the frequency is determined by quantum mechanics. [Work partially supported by the Office of Naval Research and NASA.]
Intimate ’96: Shallow water tomography in the Sea of the Condemned
Authors: Coelho Emanuel , Jesus Sergio , Stephan Yann , Demoulin Xavier , Porter Michael B.
Published: July 2002

As is well-known, the tidal force of the moon and the sun can cause notable changes in the sea level. Besides this so-called barotropic effect, the tidal force also drives internal waves in a daily rhythm. Thus, the internal wave spectrum is often dominated by a single component with perhaps 10 km from crest to crest. This ‘‘internal tide’’ tends to propagate toward shore and has its greatest height near the shelfbreak. As this tide propagates it modulates the surface duct and its acoustic signature is often seen in data. The Intimate ’96 experiment (conducted off the coast of Portugal) was specifically designed to acoustically image the internal tide with an eye toward a more precise understanding of its structure and acoustic impact. A towed source emitted chirps every 8 s for several days and the chirps were received on the SACLANTCEN portable array. The data show a textbook multipath structure with early refracted paths followed by some 30 distinct bottom and surface echoes which shift with the internal tide. The acoustic and oceanographic interpretation of this data will be discussed.
Perfectly matched layers for acoustic waves in viscous media: Applications to underwater acoustics
Authors: Liu Qing-Huo , Tao Jianping
Published: July 2002

Berenger’s perfectly matched layer (PML) has recently been proved to exist for elastodynamic equations [Chew and Liu, Schlumberger-Doll-Res. Rep. (1995)]. This fictitious material absorbs all waves with an arbitrary incident angle and an arbitrary frequency without giving rise to any reflections. Therefore, when used as an absorbing boundary condition (ABC) at the computational edge in a finite-difference method, the PML provides orders of magnitude higher absorption than other existing ABCs. In this work, the PML is further extended as an ABC for a finite-difference simulation of acoustic waves in viscous media. For such attenuative media, an additional term involving the time-integrated wavefield is introduced to account for the coupling between the attenuation from the PML and the normal viscous attenuation. This ABC is highly effective in absorbing outgoing waves at the computational edge even when a dipping interface intersects the outer boundary. This new material ABC is ideal for parallelization on multiprocessor computers. The algorithm is validated by analytical and numerical solutions. Various two- and three-dimensional numerical simulations will be shown to demonstrate the applications in underwater acoustics and other areas. [Work supported by a Presidential Early Career Award for Scientists and Engineers through EPA and by Sandia National Laboratories.]
Measuring the frequency-dependent attenuation in highly lossy material using spread spectrum ultrasound
Authors: Gordon Grant A.
Published: July 2002

Broadband signals are commonly used in ultrasonic spectroscopy to measure the frequency-dependent attenuation characteristics of lossy solid media. As compared with narrow-band signals, broadband signals are preferred since they do not require tedious frequency scanning and extensive data reduction efforts. By using spread spectrum techniques to design signals with given bandwidth and temporal characteristics, the overall accuracy and resolution of ultrasonic spectroscopy can be improved. An expression for ultrasonic attenuation is developed and compared with the traditional analysis approach to illustrate the improved accuracy of the new technique. Experimental results obtained using a direct sequence modulation system will also be presented for the attenuation spectra of various lossy solids.
The effect of word-final phonemes on spoken word recognition
Authors: Miner Caroline S. , Fowler Carol A. , Rueckl Jay G.
Published: July 2002

Three experiments tested subjects’ ability to recognize spoken words based on word-final phonological information. Experiment 1 replicated the finding [A. Salasoo and D. B. Pisoni, J. Memory Lang. 24, 210–231 (1985)] that when presented with phonological information incrementally beginning from word-offset (backward gating), subjects correctly identified spoken words in the absence of word-initial phonemes. Additionally, experiment 1 demonstrated that acoustic neighborhood size is a significant predictor of recognition probability for both forward and backward gated words. In experiment 2, word-initial and word-final acoustic word fragments were used as primes in a crossmodal identity priming task with a naming response. Both word-initial and word-final primes significantly facilitated subsequent naming reaction times. Experiment 3 replicated experiment 2 using an associative priming paradigm. The results are interpreted from a connectionist perspective. [Work supported by NICHD.]
Acoustics of the khaen: The Laotian free-reed mouth organ
Authors: Fetzer Casey A. , Cottingham James P.
Published: July 2002

The khaen is constructed with free reeds mounted in bamboo pipe walls inside a carved wooden windchest. Each reed of the khaen sounds for both directions of air flow (inhaling and exhaling). The reed vibration is strongly coupled to the pipe resonance, and the reed will sound only if a small hole near the reed is closed, causing the resonant frequency of the pipe to be near that of the reed. For some examples of khaen made in northeastern Thailand, variations in frequency and sound spectrum with blowing pressure have been studied, with both positive and negative blowing pressures considered. The relationship between frequency of reed vibration and pipe length has been studied to determine the range of pipe length over which the reed can be made to sound, as well as the amount of frequency shift associated with changes in resonance frequency of the pipe. A comparison is made with a previously reported result that the sounding frequency of the reed-tube combination is higher than the natural resonance frequencies of either the reed or the pipe taken alone. [L. E. R. Picken, C. J. Adkins, and T. F. Page, Musica Asiatica 4, 117–154 (1984).]
A comparative database of salient architectural features: Performance spaces and houses of worship
Authors: Brooks Christopher
Published: July 2002

A set of salient architectural features for the interior volumes of houses of worship and performance spaces was selected. These features include volume, height, length, width, number of audience seats, type of plan, and predominant material. The buildings were chosen to illustrate a broad range of types within these two categories; well-known examples are included as benchmarks. Data were taken from the literature and entered into a database. With a descriptive statistics program, these data can be inspected from various perspectives. The purpose of this study is to allow a designer to enter features of a proposed design, and by inspection to get a sense of where the design lies in relation to existing buildings. For instance, a proposed church may have important similarities with an existing concert hall. Future plans include access to drawings and acoustical measurements (if available) for each building included, and posting on the World Wide Web with forms for collecting new data.
Consonant discrimination in noise with earplugs and muffs in combination
Authors: Abel Sharon M. , Spencer Deborah L.
Published: July 2002

The drawback for speech understanding of wearing sound attenuating earplugs and muffs in combination was investigated. Two groups of normal-hearing subjects were tested in backgrounds of low-frequency cable swager and speech spectrum noise, respectively. Consonant discrimination was assessed using the Four Alternative Auditory Feature Test [J. R. Foster and M. P. Haggard, Proc. MRC Inst. of Hearing Res., UK, 9–12 (1979)], in a semi-reverberant chamber that met the specifications of ANSI 12.6-1984. Speech materials were presented free field at a level of 85 dB SPL, in quiet and mixed with noise levels of 80–95 dB SPL. Subjects were tested with the ears unoccluded and fitted with E-A-R foam plugs, Peltor muffs with ANR capability, and the plugs and muffs, with and without ANR operational, in combination. Preliminary results showed that consonant discrimination decreased with S/N ratio. There was no difference due to the protector condition for speech spectrum noise. In contrast, in the low-frequency cable swager noise, subjects showed greater variability in performance across listening conditions, with relatively poorer scores for the combinations. [Work supported by National Defence Canada.]
Musical acoustics: A bridge between physics and music
Authors: Rossing Thomas D.
Published: July 2002

For more than 30 years, I have taught elementary courses in acoustics to students in the liberal arts. Although these courses were designed especially for music students, the subject of musical acoustics has broad appeal to students with a wide variety of backgrounds and with a broad spectrum of professional and vocational plans. One can easily argue that musical acoustics is ‘‘good physics,’’ in that it applies the principles of mechanics, wave motion, thermodynamics, optics, and electricity and magnetism to understanding musical instruments and the way in which musical sound is recorded and reproduced. I have written two textbooks, two reprint books, a book of acoustics laboratory experiments, a book of demonstration experiments, and other suggestions for teaching the science of sound. Some of my experiences and ideas for teaching physics through musical acoustics will be shared.
Multivariate Fourier and wavelet analysis of acoustic backscattering and environmental data from the acoustic surface reverberation experiment
Authors: Williams Neil J. , Monjo Charles L. , Nguyen Hien B. , Deferrari Harry A.
Published: July 2002

Data from the acoustic surface reverberation experiment (ASREX) [Williams et al., J. Acoust. Soc. Am. 97, 3404 (1995)], is analyzed using multivariate Fourier and wavelet techniques to investigate relationships between environmental conditions and observed acoustic surface backscatter at 200, 400, and 800-Hz frequencies. Environmental variables observed included wind speed and direction, wave height, air and sea temperatures, current speed and direction, ambient noise, and various measurements of bubble activity characterized by depth-integrated air volume and e-folding depth. The relative contribution of the environmental parameters to observed backscattering strengths at the various frequencies will be discussed. The analysis techniques will be described, compared, and contrasted. [Work supported by ONR.]
An Arctic acoustic array system: Installation, in situ, repair, and preliminary data analysis
Authors: Sotirin Barbara , Thorleifson Jon
Published: July 2002

Under Project Spinnaker a joint Canadian/U.S. large multiple aperture array was deployed and cabled back to shore under the Arctic ice pack during April 1996 to acquire long-term measurements of Arctic ambient noise. The data collected have been documented and are being distributed to investigators for analysis. As well, the system is planned as a receive station for the joint U.S./Russian Arctic Climate Observations Using Underwater Sound (ACOUS) project. Although batteried for a 3-to-5-year life, in June 1996 the signal from the array terminated abruptly. After detailed analysis of the last recorded data, a repair effort was planned for the Spring of 1997. This paper will describe the anaysis, methods, and outcome of the in situ repair and future use of the deployed acoustic array system. [Work supported by ONR, SPAWAR, and CRAD.]
Echosignal temporal structure from an object of complex form in an irregular waveguide
Authors: Oboznenko E. I.
Published: July 2002

Principal aspects of the problem of sound scattering from an object of complex form (CSO) in a free field and in an irregular waveguide are investigated. The CSOs are prototypes of real artificial submarine objects [I. L. Oboznenko, Complex Shaped Object Detection and Classification (EG&G WASC, Washington, 1995)]. The CSO is represented by a sum of the interacting elements of local reflection (LREs). It is shown that the LREs CSO are partly coherent scattered. In this condition, the CSO is a multipatch object containing glistening points (part of the first Fresnel zone of each LREs). Temporal structure computations of the multipatch echosignals from the four CSO’s models of real constructions have been made within ray approximation in imitation of an irregular waveguide. It is shown that the real signal can vitally distort and exceed the length of the CSO’s echosignal, an irregular waveguide caused by the multipath propagation and the multipatch CSO. This difference is observed by a statistical shift of the CSO along the waveguide direction at a different depth. Some classification indications of the CSO were provoked by scattering in an irregular waveguide.
Synchronic evidence for the historical development of Khmer phonology
Authors: Wayland Ratree , Jongman Allard
Published: July 2002

In this paper a detailed acoustic investigation of the difference between clear and breathy phonation types in the Chanthaburi dialect of Khmer is presented. The study of this dialect is of paramount importance since it may prove the only way to quantitatively evaluate the historical claim that Khmer once had contrasting phonation types. Data were collected from five speakers. The phonation types of the vowels were then investigated by means of a variety of algorithms that have been proposed in the phonetic literature, including harmonic-to-noise ratio [HNR; e.g., Wayland et al. (1995)]; H1–H2, where H1 and H2 refer to the amplitude of the first and second harmonic, respectively [e.g., Klatt and Klatt (1990)]; H1−A1, and H1−A3, where A1 and A3 refer to the amplitude of the most prominent harmonic in the region of the first and third formant, respectively [e.g., Stevens and Hanson (1994)]. A comparison of the different metrics will be presented. The results from some analysis methods show that the Chanthanuri dialect distinguishes clear and breathy vowels. The finding that there still is a dialect of Khmer with a phonation−type contrast provides crucial evidence for the historical reconstruction of Khmer phonology.
The relationship between speech information perceived by cochlear implantees in different spectral regions and electrode discrimination
Authors: Henry Belinda A. , McKay Colette M. , McDermott Hugh J. , Clark Graeme M.
Published: July 2002

This study investigated whether the relative amount of speech information contained in specific frequency regions of the speech spectrum differs between implantees and normal-hearing subjects, or between implantees having different speech perception abilities. In addition, the relationship between the amount of speech information implantees perceived in each frequency region and their ability to discriminate adjacent electrodes was investigated. Fifteen subjects using the Nucleus CI-22M implant (SPECTRA-22 processor/SPEAK strategy), and 16 normal-hearing listeners participated. Articulation index procedures were used to measure the amount of speech information perceived in different frequency bands. Results showed that, compared to the normal-hearing listeners, the implantees obtained less speech information in all frequency regions, but more information in the higher, compared to the lower, frequencies. Correlation analysis showed that electrode discrimination and perceivable speech information were correlated in the lower frequency regions, but not in the highest region, suggesting that the perception of speech information in the lower regions requires the ability to discriminate electrodes, while the perception of high-frequency information does not. These findings predict that speech perception may be improved by changing the assignment of frequencies to electrode positions to provide better discrimination of low- to mid-frequency speech information.
Predicting speech intelligibility in noise: The role of factors other than pure-tone sensitivity
Authors: Soli Sigfrid D. , Nilsson Michael J.
Published: July 2002

The ability to communicate with speech in noisy environments is critical in many job settings and occupations. Pure-tone thresholds from the audiogram traditionally have been used to screen individuals who seek employment in hearing-critical jobs. This paper reports on analyses of the relationship between pure-tone thresholds and English speech intelligibility in noise, as measured with the Hearing In Noise Test (HINT) [Nilsson et al., 1993], in a sample of 515 job candidates. The sample was composed of 426 males and 89 females ranging in age from 20 to 50 years, with hearing levels from 0 to 115 dB HL. Subjects were classified into five language categories ranging from native, monolingual English speakers to bilingual speakers of English as a second language. Regression analyses and distributional analyses of the relationship between pure-tone thresholds and HINT scores from four conditions (quiet, noise front, noise right, and noise left) will be reported. These analyses will be used to characterize the range of speech intelligibility in noise among individuals with normal pure-tone thresholds, the prediction of speech intelligibility in noise from pure-tone thresholds, and the relationship of experience with English to speech intelligibility in noise.
Intelligibility of temporal information extracted from narrow-band sentences
Authors: Healy Eric W. , Warren Richard M.
Published: July 2002

Sentences can retain intelligibility when heard through narrow spectral slits even though the fluctuating amplitude envelope within the narrow frequency bands contains little spectral information [K. R. Riener et al., J. Acoust. Soc. Am. 91, 2339(A) (1992); R. M. Warren et al., Percept. Psychophys. 57, 175–182 (1995)]. Other research has demonstrated that intelligibility is retained when broadband speech is divided into contiguous spectral regions and used to modulate the amplitude of corresponding regions of noise [R. V. Shannon et al., Science 270, 303–304 (1995)]. The current report combines aspects of these previous studies and provides information concerning the use of temporal pattern information in various regions of the spectrum: Two noncontiguous narrow bands of speech having various center frequencies were used separately to modulate the amplitude of noises, which were then refiltered to corresponding center frequencies and bandwidths. Despite the absence of spectral information within each of the narrow noise bands, listeners were able to identify many of the 500 keywords in the standard Central Institute for the Deaf sentences. It is concluded that intelligibility can be retained when acoustic information in sentences consists solely of amplitude changes occurring in two noncontiguous bands. [Work supported by NIH.]
Interductile energy transfer of high-frequency pulse propagation in a two-ducted ocean waveguide in the yellow sea
Authors: Sidorovskaia N. A. , Werby M. F.
Published: July 2002

In a multiducted ocean wave guide, energy may be trapped in each of the ducted regions. For sources suitably placed, energy may be stimulated initially in only one of the ducts when eigenfunctions associated with secondary ducts have negligible overlap with the primary duct. For fixed frequency, no energy is transferred, and although high-angle modes eventually traverse to the secondary ducted region, the energy is not trapped there for monochromatic sources. In reality one must take into consideration a spread of frequencies. Monjo and DeFerarri have noted this effect in collecting and interpreting data. This has led to a very exciting phenomenon, the ‘‘Monjo–DeFerarri effect,’’ which is quite dramatic for the case they studied. The Monjo–DeFerarri effect is a mechanism whereby energy in a lower duct, with the source in the lower duct, may in time transfer energy to an upper ducted region. The energy transport is cyclical, and at suitably high frequencies energy is trapped in the upper channel in discrete time segments. This leads to the arrival of discrete packets of energy in time which are highly localized spatially. These ‘‘precursors’’ arrive in advance of predominant pulse arrivals, and may determine, among other things, the source distance. Here, a study of interductile energy transfer is made for the Yellow Sea. In suitable cases, discrete packets of energy are captured at each high-angle modal contact with the secondary duct. Expressions that predict the arrivals of the upper ducted discrete arrivals, the number in range, the lag time between arrivals, and the lowest frequencies above which this will happen, are presented. [Work sponsored by ONR, NRL, and the University of New Orleans.]
Acoustic field propagation through a shallow water waveguide dominated by internal waves
Authors: Finette Steven , Orr Marshall , Apel John
Published: July 2002

The continental shelf off the New Jersey coast is a site of intense internal-wave activity. The space–time variability of an acoustic field in this shallow-water region was studied using oceanographic measurements along a 42-km track from the SWARM95 [shallow-water acoustics in a random medium] experiment. A sound–speed model based on the KdV equation was developed to include the nonlinear contribution of the internal wave field, with parameters estimated from towed yo-yo ctd data, ship radar images of internal-wavesurface expression and acoustic backscatter images of subsurface internal-wave structure. The linear internal-wave contribution was modeled by an ADCP-derived displacement power spectrum. Bathymetry and sub-bottom parameters were previously estimated from wave-field inversions using chirp sonar surveys. Simulation results are presented for acoustic propagation at frequencies of 224 and 400 Hz using a wide-angle parabolic equation method to compute realizations of the acoustic field. Results include estimates of the intensity fluctuations and coherence for two vertical arrays located at 33 and 42 km from the moored sources. [Work supported by ONR.]
Modeling of broadband time signals in shallow water using environmental inversion
Authors: Nielsen Peter L. , Gerstoft Peter , Bini-Verona Francesco , Jensen Finn B.
Published: July 2002

A numerical modeling scheme is applied to perform broadband environmental inversion by using explosive data acquired in the Mediterranean Sea in May 1997. The area shows a moderate range dependency, and the received time signals from explosive charges cover a frequency band of several kilohertz. The acoustic propagation model is based on a layered normal mode approach, which is capable of efficiently predicting broadband sound propagation in shallow water [Westwood et al., ‘‘A normal mode model for acoustic–elastic ocean environments,’’ J. Acoust. Soc. Am. 100, 3631–3645 (1996)]. This model has been extended to handle range-dependent environments using the adiabatic approximation. Thus calculation of broadband transfer functions from 0 to 10 kHz of range-dependent, shallow-water waveguides can now be done within a few minutes. The combination of the above propagation model and a state-of-the-art global inversion scheme [Gerstoft, ‘‘SAGA user manual 2.0: An inversion software package,’’ SACLANTCEN SM-333 (1997)], makes it possible to perform environmental focusing by optimizing the correlation between the numerical and experimental received time signal at one or more receiver locations. The broadband inversion scheme is introduced to extract the uncertain acoustic parameters in the waveguide, and to assess how accurate broadband signals can be modeled in complex shallow-water regions.
Bubble clouds, velocity distributions, and high-frequency propagation in the Scripps bubble experiment
Authors: Farmer David M. , Vagle Svein , Deane Grant
Published: July 2002

As part of an experiment to determine the distribution and acoustical effects of bubbles near the surf zone, resonators, cameras, a coherent Doppler, and horizontally oriented Doppler sonars were deployed in the vicinity of Scripps Pier. With these instruments, evolution of the waves as they traveled toward the shore were detected and the bubble size distributions, rip currents, turbulence dissipation, and patterns of bubble cloud motion were measured. Propagation tests at 100 kHz along a 230-m path between the end of the pier and the surf were conducted. Bubble size measurements in the surf and on a bottom-mounted frame allowed identification of the spatial evolution of bubble characteristics. The sonar measurements show bubble clouds ejected offshore at discrete intervals and at speeds of ∼0.3 m/s. Pulse propagation into the surf was occasionally completely attenuated by bubble clouds. However, it is interesting that prior to total blocking of the signal the pulse arrival time is delayed, implying an apparent decrease in sound speed. This is unexpected since our frequency (100 kHz) was above the resonance of the dominant bubbles. An explanation is proposed in terms of selective blocking of direct path propagation by bubble clouds. [Work supported by ONR Contracts Nos. N00014-96-C-6030 and N00014-97-1-0288.]
Variation of B/A with 1/c for several liquids
Authors: Hagelberg M. Paul
Published: July 2002

Theoretical models [B. Hartmann, J. Acoust. Soc. Am. 65, 1392–1396 (1979), B. Frank and J. D. N. Cheeke, J. Acoust. Soc. Am. 101, 1184–1186 (1997)] predict that the variation of B/A, the acoustical nonlinearity parameter, with the inverse sound speed 1/c, should be linear or linear with a quadratic term. Confirmation of these models requires experimental data for B/A vs 1/c for individual liquids. Such data will be presented for several liquids including pure water, seawater, mercury, and a number of organic liquids.
Radiation of sound by two concentric free-flooded cylindrical shells excited by a point force
Authors: Kim K. Steven
Published: July 2002

Radiated acoustic pressure fields are obtained when two concentric free-flooded cylindrical shells of finite lengths are excited by a time-harmonic point force. Integral equations are formulated for the two elastic thin shells with simply supported boundary conditions at both ends. Near and far-field acoustic pressures are calculated and effects of acoustic coupling between two shells are discussed.
A combined experimental and numerical method for computing sound radiation from underwater vibrating structures
Authors: Fahnline John B. , Erickson Matthew J. , Capone Dean E. , Hambric Stephen A. , Burroughs Courtney B.
Published: July 2002

Underwater measurements of the radiated sound power from a vibrating structure are conventionally performed either by direct measurements in a large body of water or by reverberation measurements in a water tank. Both methods have inherent drawbacks. Direct measurements in a large body of water require a large scale operation and are relatively expensive. Reverberation measurements are only accurate at high modal densities, and thus a very large tank is required to obtain accurate low-frequency predictions. To avoid both difficulties, a hybrid approach has been devised. Experimental measurements of the vibrations of the structure are taken in a water tank using a scanning laser Doppler vibrometer, where the laser beam is shone onto the submerged structure through an optical quality window. The surface vibration data are then used to derive the specified normal velocity for a numerical calculation of the radiated sound power radiated in free-field conditions. The laser allows dense surface meshes to be defined such that the calculations can be performed to relatively high frequencies. To demonstrate the general accuracy of the calculations, radiation efficiencies are computed for submerged unbaffled plates, and the results are compared to reverberation measurements and to fully numerical predictions.
Does the Rayleigh–Ritz method for vibratory continuous systems actually converge to the analytical eigensolution?
Authors: Ginsberg Jerry H.
Published: July 2002

The Rayleigh–Ritz method for continuous systems uses an N-term series with unspecified coefficients as the trial function for the Rayleigh ratio. Extremizing that ratio leads to N approximate natural frequencies ωj(N), j=1,...,N. The upper bound theorem states that the true values obtained by solving the field equations are such that ωj≤ωj(N). The separation theorem states that adding a single term to the aforementioned series yields new estimates ωj(N+1), j=1,...,N+1, such that the previous ωj(N) fall in the intervals between the new values. Taken together, these theorems constitute a proof that the lower eigensolutions obtained from the Rayleigh–Ritz method should converge to the true eigensolution. However, both theorems assume infinite precision arithmetic. This paper uses the simple case of a cantilever beam to examine the behavior of the Rayleigh–Ritz method with increasing series length. Natural frequencies derived from different classes of kinematically admissible basis functions, drawn from monomials, trigonometric functions, and Bessel functions are examined relative to the upper bound and separation theorems. Most selections fail to yield properly behaved solutions if the series length is extended beyond 10–12 terms. In some cases the eigenvalue solver fails to find real eigenvalues, or to find the correct number of eigenvalues. Some of the basis function sets permit formulating the Rayleigh ratio functional analytically, rather than by numerical integration, but the results are the same. The failure of the method is shown to stem from ill-conditioning that arises as a consequence of similarity in the appearance of higher-order basis functions.
Chair’s introduction to the workshop on basic science at the intersection of speech science and communication disorders
Authors: Bernstein Lynne E. , Weismer Gary
Published: July 2002

In the study of speech perception and production, there is a history of developing, evaluating, and revising models and theories based on data collected exclusively from talkers and listeners judged to be free of communication disorders. Basic research with clinically relevant disorders is sometimes confused with, and dismissed as, clinical/applied research. In other branches of science, including, for example, psycholinguistics and biology, study of clinical disorders is regularly employed as one of the avenues for building and testing more comprehensive theories and/or models, and is viewed as a major source of knowledge concerning the physiological structures responsible for normal processes. The intent of the workshop format is to provide a forum for discussion of the significance of clinical disorders for the scientific areas of speech perception and production. A group of distinguished scientists has been invited: (1) to describe their own work involving disorders in speech production and/or perception; and (2) to comment on scientific, data analytic, philosophical, and pragmatic issues that are specific to the enterprise of incorporating data from clinical disorders into their work and their fields. The organizers encourage the attendance of scientists with and without research involving clinical disorders, as well as students.
Psychophysical studies with two binaural cochlear implant subjects
Authors: van Hoesel R. J. M. , Clark G. M.
Published: July 2002

Psychophysical studies have been completed with two binaural cochlear implant patients. In our earlier studies [van Hoesel et al., J. Acoust. Soc. Am.  94, 3178–3189 (1993); R. J. M. van Hoesel and G. M. Clark, Ann. Otol. Rhinol. Laryngol. Suppl. 106  104, 233–235 (1995)], lateralization experiments showed good sensitivity to interaural amplitudes but poor sensitivity to interaural time delays when compared with normal hearing subjects. In the studies presented here, both temporal and binaural intensity interactions were further explored. Interaural time delay (ITD) perception was investigated using direct measurement of the just-noticeable difference (jnd) in ITD. Both rate and place of stimulation were varied. Binaural rate discrimination was measured and compared with monaural rate perception. Binaural intensity interaction was explored for matched and unmatched place conditions by means of loudness summation and central masking studies. Results showed that ITDs for interaural time delays were large when compared to normal hearing, even when place of stimulation on each of the two sides was carefully matched. The jnds in ITD were similar for stimulation rates from 50 to 200 pps, and increased at 300 pps. Rate difference limens experiments showed similar results for diotic and monaural stimuli, but improved jnds for dichotic presentation at stimulation rates below 150–200 pps. Binaural intensity interactions showed loudness summation effects with both patients, for matched as well as unmatched place conditions. Central masking was also observed with both subjects, although it was not found to be place dependent.
The usage of standard finite element codes for computation of dispersion relations in materials with periodic microstructure
Authors: Åberg M. , Gudmundson P.
Published: July 2002

A method with which standard finite element programs can be used to compute dispersion relations in periodic composites is proposed. The method is applied to two composite microstructures: a two-phase laminate and a fiber composite. The dispersion relations computed for the laminate are compared with a known analytical solution and the agreement is very good. The dispersion relations computed for the fibrous composite are compared with an existing approximate model and experimental results from the literature. The agreement between the approximate model, the experiments, and the computations is very good in the wave guide case and satisfactory for the wave reflect case.
Local admittance fluctuations and the scattering from a cylindrical shell with many internal oscillators
Authors: Bucaro J. A. , Photiadis D. M. , Houston B. H. , Romano A. J.
Published: July 2002

The angular and spectral scattering patterns from local admittance fluctuations, assumed to be caused by the presence of mechanical, dumbbell oscillators attached more or less randomly in the interior of a cylindrical shell, are predicted numerically and compared to the experimental measurements reported by Bucaro et al. [Proc. ASME, Noise Control and Acoustics Division, NCA 22, 87–92 (1996)] and Photiadis et al. [J. Acoust. Soc. Am. 101, 895–899 (1997)]. The numerical results are shown to be in reasonable agreement with what is observed experimentally. It is suggested that scattering contributions from such local admittance fluctuations can be a significant component in the midfrequency scattering patterns of submerged targets of interest. [Work supported by the Office of Naval Research.]
Strategies for computing sound propagation through realistic three-dimensional turbulence
Authors: Di Xiao , Gilbert Kenneth E.
Published: July 2002

For 3-D sound propagation calculations, if computation time were not an issue, it would be straightforward to extend 2-D parabolic equation (PE) models to three dimensions. However, for any 3-D propagation model, computation time is a crucial factor on any personal computer presently available. Hence, in this paper, some computational approaches are discussed that allow one to treat realistic 3-D turbulence in an approximate but physically reasonable way. The computational methods preserve the 3-D statistical properties of the turbulence without generating an unacceptable computational burden. The proposed approaches are outlined and numerical examples are given for sound propagation through meteorologically realistic turbulence fields. [Work supported by DARPA and the Pennsylvania State University Applied Research Laboratory.]
Scattering of pulse signals from fluid-filled elastic shells
Authors: Sidorovskaia Natalia A. , Werby Michael F.
Published: July 2002

The study of the sound scattering from fluid-filled elastic shells has shown a formation of the complicated return structures when scattering from such objects takes place. Preliminary work has suggested that the apparent complicated structure may be resolved in terms of a superposition of standing waves at the interface. Indeed, now, when a new acoustic background has been developed, the coherent vibrational effects may be resolved into patterns that are likely connected with the curved surface analog of Sholte waves on flat plates that are fluid loaded on both sides. Theoretical partial wave studies suggest this, but in order to ‘‘see’’ it in experiment, one must resort to pulse studies and gating methods. This hypothesis is tested by simulating experimental data and employing signal-processing techniques to determine if the effect can be observed in real experiments. [Work sponsored by ONR, the Naval Research Laboratory, and the University of New Orleans.]
Analysis of fluid-driven panels using the energy finite-element method
Authors: Han Fei , Mongeau Luc G. , Bernhard Robert J.
Published: July 2002

Energy flow analysis methods have been developed to predict the approximate response of built-up structural-acoustic systems at high frequency. The governing equations of energy flow analysis can be formulated into a finite-element approximation, referred to as the energy finite-element method. In recent investigations, a method has been developed to calculate the power input for energy flow analysis of systems with random, distributed loads. The method uses cross spectra pressure information. The method is intended to allow energy flow analysis and energy finite-element analysis of flow excited panels. Both analytical and experimental verification studies have been done to test the approach for panels excited with distributed pressure loads. The predicted results are excellent approximations of the response.
Acousto-ultrasonic nondestructive evaluation of materials and structures
Authors: Reis Henrique
Published: July 2002

A review of the nature of the underlying rationale of the acousto-ultrasonic methodology is presented. The term acousto-ultrasonics denotes a nondestructive evaluation technique that combines some aspects of acoustic emission methodology with ultrasonic simulation of stress waves. Unlike most nondestructive evaluation techniques, acousto-ultrasonics is less concerned with flaw detection than with the assessment of the collective effects of the various flaws and materials anomalies. Acousto-ultrasonics is primarily concerned with material properties variations, such as the significant reduction in strength and toughness caused by combinations of minor flaw and diffuse flaw populations. Porosity content, and fatigue and impact damage are typical examples of factors that affect material properties variations. Applications of the acousto-ultrasonic approach to the nondestructive testing and evaluation of steel-belted radial truck tires and to other structural systems are presented and discussed.
Optimization of time delay laws for focusing with phased arrays
Authors: Cassereau Didier
Published: July 2002

Recently, phased arrays technology has been greatly improved and represents an efficient tool to focus an acoustic beam in various directions, just changing a time-delay law. Due to the extended dimension of the elements of the array, one major difficulty consists in the optimization of the desired time-delay law. In this paper, PASS (phased array simulation software, developed in the laboratory) is used to illustrate how classical algorithms (average, minimum value, center value) can significantly alter the resulting focal pattern. Then an optimization method based on time reversal is proposed. First, the focal point is replaced by a source and the array measures the resulting field. Then, each channel emits the time reversal of the received signals, thus generating an efficiently focused beam. Finally, a cross-correlation method allows to extract from these signals a time-delay law that is proved to be very efficient and adapted to the expected focal point. Various simulations will be presented to focus the beam through a plane interface separating a fluid and a solid, using two different arrays. It will be shown how classical algorithms fail, while the proposed method based on a time-reversal simulation yields very efficiently focused beams.
Lamb waves generation using embedded piezoelectric elements in composite plates
Authors: Assaad Jamal , Moulin Emmanuel , Delebarre Christophe
Published: July 2002

With the aim of designing nondestructive evaluation and health monitoring systems for composite parts of complex structures (e.g., aircrafts), Lamb waves generated using embedded miniaturized transducers seem to be a very promising technique. Therefore, a cylindrical transducer embedded in a composite host plate has been considered. The electrical impedance of the transducer alone in vacuum and then of the embedded transducer, which allows the identification of the resonance modes, have been obtained by the finite-element method (FEM). Moreover, the displacement fields in the plate, which allow the identification of the type of Lamb waves generated, have been computed at the resonance frequencies. Comparison between the FEM results and the Lamb waves dispersion curves of the host material are in good agreement. Experimental results (electrical impedance, frequency response, and phase velocities) concerning a composite plate specimen containing the same piezoelectric transducer inside it will be shown. A good agreement is generally obtained between numerical and experimental results.
Perception of sequences of octave-related complexes in relation to the tritone paradox
Authors: Ragozzine Frank
Published: July 2002

Shepard [J. Acoust. Soc. Am. 36, 2346–2353 (1964)] has shown that ordered pairs of octave-related complexes are perceived in accordance with proximity. However, in his experiment, proximity-based judgments gradually decreased as intervals approached a tritone. With tritones, Deutsch [Music Percept. 8, 335–347 (1991)] found that listeners perceive half of the pitch-class circle as higher in pitch, and the opposite half as lower. The half heard as higher differs among subjects (the tritone paradox). Deutsch theorized that listeners compare these tritones to a circular pitch-class template, whose orientation with respect to height differs among listeners. The present study examines the perception of octave-related complexes that form intervals of P5/P4 or m3/M6. It was hypothesized that listeners may sometimes use a pitch-class template, rather than proximity, with intervals other than a tritone. Template orientations were determined using Deutsch’s paradigm. Subjects were presented with sequences of tones that traversed the circle of fifths. Perception of these tones was closely related to each subject’s pitch-class template, and not to proximity. Similar, though less pronounced, results were found in a second experiment using an ordered series of m3/M6.