bluuebunny/crossref_metadata_2025 huggingface dataset:
Perception of American English /r/ and /l/ by Mandarin speakers: Influences of phonetic identification and category goodness
Authors: Tsao Feng-Ming , Hall Michael , Eyraud Richard , Kuhl Patricia K.
Published: July 2002

Studies in speech perception show a perceptual magnet effect for listeners which is characterized by shrunken perceptual distances near excellent exemplars of phonetic categories and stretched distances near poor exemplars. This study extended this work by examining the influence of Mandarin speakers’ phonetic identification and category goodness on their perception of American English /r/ and /l/. Eighteen /ra/ and /la/ tokens were used that varied F2 and F3 frequencies. Listeners identified stimuli as Mandarin /u/, /m/, or /l/, provided goodness ratings for them, and rated the similarity of all stimulus pairs. Multidimensional scaling analyses of similarity ratings exhibited that the perceptual ‘‘map’’ for Mandarin speakers differs substantially from that of American speakers [Iverson and Kuhl, J. Acoust. Soc. Am. (1996)] listening to the same stimuli. The results indicate that (1) Mandarin speakers perceived /u/ and /l/ in the space, (2) perceptual distance was shrunk near the best exemplars of phonetic categories and stretched near the category boundary, (3) variations of F2 were more important than F3, and (4) individual differences in /l/ identification corresponded to a degree of shrinking near the best exemplars of the /l/ category. Results indicate that listeners use their native-language representations in the perception of a non-native language.
A software teacher for acoustical measurements
Authors: Tokola Ila , Karjalainen Matti , Rahkila Martti
Published: July 2002

The huge development in computer technology has made it tempting to use computers in acoustics education. QuickSig, an object-oriented Common Lisp based signal processing environment has been used for acoustical measurements. It provides an excellent means to present graphics and handle signals, and it is easy to program for educational purposes as well. A Simple Loudspeaker Measurement Program is a Computer Based Education (CBE) application for self-studying of acoustical measurements. The application deals with free-field measurements of loudspeakers and related theory. The measurements are actually made with the program and genuine results are achieved each time. The software teacher interactively helps the student to obtain results that make sense and monitors the progress with multiple-choice questions. The results can also be saved for post-processing. The main difference between this application and on-line help systems in measurement packages is that the teacher emphasizes learning of acoustical measurements, not the measurement software itself! On the other hand, with this application, the students do real measurements, including the loudspeaker and microphone setup in an anechoic chamber, unlike most self-study CBE applications. Furthermore, the application can be used also by engineers, technicians, etc. for assisted measurements.
Design and development of PC-IMAT
Authors: Schuler John W. , Korman Murray S.
Published: July 2002

NPRDC has been tasked to provide empirical evidence of effective instructional strategies for the acquisition of conceptual knowledge under the project name PC-IMAT (Personalized Curriculum for Interactive Multisensor Analysis Training). The domain to be investigated and demonstrated includes those concepts required for the successful planning and execution of antisubmarine warfare (ASW), specifically, the conceptual knowledge underlying the prediction of sound transmission paths and detection ranges. Navy-standard models which are used in fleet SONAR prediction systems are available to support the learners’ conceptual understanding of the elements of the oceanographic environment which affect acoustic propagation. To date, these models are employed in a microcomputer based, stand-alone delivery architecture in both a linear interactive courseware (ICW) format and in modules suitable for independent exploratory learning. Midshipmen taking SP411 (Underwater Acoustics and Sonar) are currently using PC-IMAT to help investigate what are the effective instructional strategies which convey understanding of a complex multivariate domain (like ray trace or propagation loss models). Research on ‘‘scientific visualization’’ (to enhance comprehension and retention) and student feedback will also be used to help develop and evaluate other training materials including beamforming, reverberation, target motion analysis, and scattering. [Work supported by ONR.]
Measuring and modeling the effect of source distance in head-related transfer functions
Authors: Huopaniemi Jyri , Riederer Klaus A. J.
Published: July 2002

Efficient modeling of human spatial hearing by digital filter approximations of head-related transfer functions (HRTFs) is the key technology in 3-D sound processing. It is well known that the HRTF bears the major static localization cues, the interaural time difference (ITD), and the interaural level difference (ILD) that are functions of frequency and the incident angle of arrival. The effect of source distance has, however, often been neglected in HRTF models. In this paper, a method for efficient distance-dependent HRTF modeling is presented, which is based on both theoretical and empirical data. HRTF measurements on eight human subjects and one dummy head were carried out at two source distances, 2 and 0.65 m. It has been argued in the literature that the distance changes mainly affect the ILD, whereas the ITD remains approximately constant. Based on this finding, which was also supported by the measurements performed in this study, a filter structure that models the ILD change as a function of distance was derived. The results of this study are applicable to many near-field listening applications.
Parabolic equation modeling with the split-step Fourier algorithm in four dimensions
Authors: Tappert F. D.
Published: July 2002

Fully range-dependent 3-D (with coupled azimuths) single-frequency PE/SSF models have existed for many years, and 2-D (vertical plane at fixed bearing) wide-angle broadband PE/SSF models have existed for even longer. By combining these, a 4-D (three space dimensions plus time) PE/SSF model has been developed that runs on a desktop computer. This model is exactly reciprocal if ocean currents are omitted, and is exactly energy conserving if absorption is omitted. Examples of model predictions, projected onto two dimensions, are displayed for shallow water propagation. In a situation where ray chaos due to variable bathymetry is strong, plots of intensity as a function of travel time and bearing at fixed depth and range are especially interesting. [Work supported by ONR.]
Role of the acoustic advisors in the design of the Tokyo International Forum
Authors: Yamamoto Teruji , Tachibana Hideki , Jaffe Christopher
Published: July 2002

The Tokyo Municipal Government appointed two acoustical advisors to review the acoustic design criteria developed for the Tokyo International Forum, Dr. Teruji Yamamoto and Dr. Hideki Tachibana. This paper describes the role of acoustic advisors on such a large project and show how they were able to assist the design team throughout the design and construction of the complex. Items to be covered include: process of design competition, acoustic requirements, process of acoustical design, outline of construction; and acoustical check during and after construction.
On spatial variability of room acoustics measures
Authors: Nielsen Johan L. , Halstead M. Miklin , Marshall A. Harold
Published: July 2002

The use of high-energy measurement signals combined with digital multichannel recording and postprocessing leads to a highly efficient collection of impulse responses in concert halls. During measurements in two similar concert halls, the Christchurch Town Hall, New Zealand, and the Hong Kong Cultural Centre (both described in companion papers), responses were collected in all seats in some areas and in different positions in some single seats, in addition to the usual sampling of all areas. An omnidirectional loudspeaker source was used, and the measurements were repeated in several source positions. The distribution of various parameters in these areas are compared to the results for the whole hall. Based on this comparison the use of mean and standard deviation as measures of location and spread for the parameters is discussed, and the variation of parameters with varying source locations is demonstrated. Approaches toward the reduction of parameter sensitivity to insignificant details in the early sound field are briefly discussed and illustrated using the measured data.
Estimation and analysis of acoustic parameters of ancient churches for concert performances
Authors: Ottonello Tiziana , Dassori Enrico , Trucco Andrea
Published: July 2002

This paper presents a study on the propagation of musical sound, where occasionally concert performances are held. The five selected churches were built in Genoa between the eleventh and the seventeenth century. The analysis was aimed at the computing of acoustic parameters (e.g., reverberation time, early decay time, initial decay gap, speech trasmission index, definition index), based on structural modeling and computer simulation (RAMSETE software) as well as experimental texts. Analysis of results showed that romanic churches generally provide better acoustic characteristics. Furthermore, acoustic not standing modifications (e.g., absorbing panels, curtains) were designed in order to make the ob-served acoustic parameters comparable with those observed in a typical concert hall. This work was developed in the framework of a project aimed at creating new music halls using the existing old buildings, generally dedicated to other aims.
Relationship between speech transmission index and easiness of speech perception in reverberatory fields
Authors: Sato Hiroshi , Yoshino Hiroshi , Nagatomo Muneshige
Published: July 2002

When evaluating speech intelligibility in rooms, the Tri-syllable articulation test is used as one of the standard indicators in Japan. Sometimes there are differences between auditory impression and the score of the articulation test. So the psychological scale values of easiness of speech perception (ESP) were measured by experiments, which indicated differences between ESP and articulation scores and a good correlation (R=0.9) between ESP and speech transmission index (STI) in reverberation. The purpose of this paper is to point out relationships between the condition of sound field and ESP. The first of two experiments in this study was done in reverberatory fields. Sound-pressure level (SPL) of direct sound, direct sound to first reflection ratio (D/R), initial delay time, frequency characteristics of reverberation, and reverberation time (RT) were varied. The other experiment was done in simulated fields of actual auditoriums. The result of the first experiment shows D/R and RT has alarge effect on ESP and while varying D/R, the correlation between ESP and STI is not good (R=0.6). The second experiment indicates that when the sound source is on the center of the stage, the correlation between STI and ESP is 0.8; and a different tendency is found while using the sound reinforcement system.
Investigation of the speech intelligibility in the dome space
Authors: Inoue Satoshi , Katoh Masahiro , Sugino Kiyoshi , Imaizumi Hiroyuki
Published: July 2002

In order to investigate the acoustical characteristics of an underground dome (2 320 m3), objective and subjective properties were tested and the mutual relationship of them was examined. Then to improve the speech transmission quality there, some simple absorption treatments were given. A series of experiments, carried out under different acoustical conditions, has confirmed the effects of the treatment. The main results are as follows: (1) In the dome space without absorption treatment, the differences of some objective measures and subjective responses (speech intelligibility) were great in places where observation was made, e.g., RASTI value was distributed over a range of 0.17–0.59. (2) It is indicated that the speech transmission quality was high at the observation points where the energy, arriving in the first 0.06 s after the arrival of the direct sound, is predominant, and others are almost low. (3) Among the physical measures, EDT, early/late-arriving sound energy ratio, ts (at 1 kHz octave-band), and RASTI were correlated well with speech intelligibility. (4) Rubber tiles on the floor, 12-m cotton canvas hung from the ceiling, and glass wool board were found to be effective in decreasing reverberation time and diffusing the sound. Also, this treatment was useful in improving the speech intelligibility remarkably.
Disruption of contrast agents for monitoring blood flow
Authors: Fowlkes J. Brian , Rhee Richard T. , Sirkin David W. , Carson Paul L.
Published: July 2002

An experimental system is being developed for controlling the flow of ultrasound contrast agent to create abrupt changes in contrast levels in tissues. Such changes can be used to monitor blood flow through bolus passage and to identify specific feeder vessels. Focused ultrasound (2.25 MHz) has been used to interrupt the flow of the contrast agent MRX-115 (ImaRx Pharmaceuticals, Tucson, AZ) in a tube (6 mm diameter, average velocity of 9.45 cm/s) using short bursts 20 cycles in duration with a pulse repetition frequency (PRF) of 0.75–6.0 kHz. Peak rarefactional pressures (PRP) for effective disruption of contrast agent were only 0.6–1.2 MPa. This corresponds to mechanical indices (MI) of 0.4–0.8 and intensity values which are well within the recommended limits for diagnostic ultrasound, up to 90% of contrast agent signal was eliminated and positive boluses were produced by turning the field off and on. Similar results have been achieved with a 1.8-MHz in vivo system in a rabbit model. Therefore the potential exists to use common diagnostic ultrasound to produce contrast disruption suitable for short bolus production. [Work was supported in part by the U.S. Army under Grant No. DAMD17-94-J4144.]
Determination of the noise attenuation of hearing protectors by numerical modeling of the outer ear
Authors: Gerges Samir N. V. , Bavastri Elizabete Y.
Published: July 2002

This paper will address the important practical issues of hearing protectors, used in industry, to protect the workers from high noise levels. Comments on the difficulties for the measurements of hearing protector’s noise attenuation is discussed. A new work on the numerical modeling of the outer ear canal, considering the eardrum acoustic impedance, using the finite elements (FEM), infinite FEM for the quantification of the noise attenuation of the protectors is presented. This numerical model considers the geometry of the outer ear, outer ear canal, and the eardrum acoustic characteristics. This numerical model can serve as a quick and low cost tool for the optimization of the protector project and the investigation of the effect of different parameters such as protector insertion, effect of leakage, materials, and others on the protector noise attenuation.
Piezoelectric transducer for a hearing aid using PZT thin film
Authors: Yasui Hidehiko , Kurosawa Minoru , Morita Takeshi , Kanda Takefumi , Higuchi Toshiro
Published: July 2002

A piezoelectric transducer using a PZT thin film deposited by a hydrothermal method was fabricated for the investigation of ability for an earphone. The PZT material can produce sounds efficiently from an electrical signal. The thin film technology is suitable for the fabrication of a small transducer which is worn in the ear. Especially, the hydrothermal method has merits such as thick film fabrication and possibility of deposition on a round surface. Therefore we can design and fabricate a diaphragm for a small earphone which produces a high enough sound-pressure level for people who have an obstacle for hearing ability. The fabricated transducer had a bimorph construction. The base material was titanium foil 20-μm thick. Both sides of the titanium, PZT thin films 10-μm thick were deposited. The diameter of the transducer was 6 mm. We investigated the ability of the fabricated transducer. Displacement amplitude of the transducer was about 0.9 μm per 5 V driving voltage below the resonance frequency.
Results of human studies with linear and nonlinear earplugs: Implications for exposure limits
Authors: Dancer Armand L. , Hamery Pascal J-F.
Published: July 2002

Soldiers equipped with linear and nonlinear earplugs have been exposed to large impulses (weapon noises) and audiometric tests have been performed just before and after the exposures. In particular, new nonlinear perforated earplugs (allowing speech communication, detection and localization of acoustic sources) which have been developed at the French–German Research Institute of Saint-Louis are efficient for repeated exposures up to 187-dB peak when they are well fitted [Johnson and Patterson (1996) personal communication]. From various TTS studies it is concluded that: (i) the peak pressure attenuation (measured with a specially designed ATF) grossly underestimates the protection afforded by the earplugs when used in conjunction with the classical criteria for weapon noises (CHABA, MIL-STD, criterion of Pfander, criterion of Smmorenburg). The risk corresponding to an exposure to a slow rise-time impulse (i.e., under an earplug) is much lower than the risk corresponding to an exposure to an impulse of the same peak pressure with an instantaneous rise time, (ii) the LAeq8 attenuation values based on objective insertion loss measurements (ATF) give in most exposure conditions a good evaluation of the auditory hazard, but in some other cases they still underestimate the efficiency of the hearing protectors.
Nonlinear propagation of laser-generated acoustical pulses in granulated media
Authors: Naugolnykh Konstantin , Esipov Igor , Matveev Konstantin , Zosimov Viktor
Published: July 2002

Laser generation of high-intensity broad frequency band acoustical pulses in different fluids and their propagation in water-saturated cobalt-manganese crust (CMC) samples are investigated. Acoustic pulses of amplitude up to 3 MPa and duration about 1 s are generated in water, oil, and benzene by the action of CO2 on a laser pulse. The propagation of the short acoustic pulses through the water-saturated CMC samples is considered. The complexity of the CMC structure leads to specific nonlinear acoustical features of the process—nonlinear distortion of the acoustic pulse and amplitude-dependent attenuation. Abnormal sound attenuation in the high-frequency band is observed with low-energy probing sound pulses. This effect could be connected with the sound energy capture and its localization as oscillating modes of the structure. This effect vanishes with increasing intensity of the probing pulses, apparently due to the changes in crust structure. At the same time, specific nonlinear distortion of the sound pulse takes place—increasing of the acoustic pulse amplitude leads to decreasing of the negative phase of the passed acoustic pulse. [Work supported in part by Russian Fund for Fundamental Research.]
Evidence of prenatal hormonal effects on the auditory system
Authors: McFadden Dennis
Published: July 2002

There are marked sex differences in a number of behavioral and physiological measures of the auditory system. Evidence is accumulating that some of these sex differences exist at birth and are attributable to the magnitude of prenatal exposure to androgenic hormones, such as testosterone. A generalization emerging from this evidence is that greater prenatal androgen exposures lead to greater masculinization of these auditory responses. At this point, little is known about the modes of action of androgens on developing cochelear structures, but because the degree of masculinization of otoacoustic emissions (OAEs) appears to parallel the degree of masculinization of other brain structures and behaviors, OAEs appear to have the potential to be a valuable, noninvasive window onto the processes of prenatal development and sexual differentiation. Examples of this potential will be discussed. [Work supported by NIDCD.]
Realization of the Cremer admittance of silencer linings with passive absorber elements
Authors: Mechel Friedel P.
Published: July 2002

L. Cremer has shown that the maximum attenuation in a lined duct is obtained when the solution of the characteristic equation lies in the first branch point of that equation. This condition specifies a surface admittance of the lining, the Cremer admittance. Much effort was undertaken in the Institute of Professor Cremer, later directed by Manfred Heckl, to realize this admittance. It will be shown how a computer program can find the material and dimension parameters of a lining with Cremer admittance, after a suitable principal construction was conceived (e.g., multilayer porous absorber, or Helmholtz resonators, etc.). The potentials and the principal limitations of a lining with a Cremer admittance will become visible.
Intergestural coordination adjacent to multiple prosodic boundaries
Authors: Byrd Dani
Published: July 2002

Recent work has demonstrated that progressively larger prosodic boundaries result in increasing amounts of lengthening for consonant gestures both preceding and following the boundary. This experiment extends these findings by considering kinematic data collected with a magnetometer to determine if: (1) vowel gestures demonstrate lengthening patterns comparable to those of consonant gestures due to adjacent prosodic boundaries, and (2) the relative timing or intergestural coordination between consonant and vowel gestures is affected by adjacent boundaries. Eighty tokens were recorded for each of three speakers using magnetometry for a /...amə(♯)mi.../ sequence with five differing boundary conditions: (1) no boundary, (2) a simple word boundary, (3) a boundary between elements in a list, (4) a vocative name boundary, and (5) an utterance boundary. Durations of the bilabial closings and openings, duration of the vocalic tongue raising movement from [a] to [i], and temporal latencies between the pre- and post-boundary [m]’s and the [i] articulation were determined. All subjects demonstrated lengthening of the vocalic tongue raising for larger boundaries, although they differed in whether the lengthening was more pre- and post-boundary. Furthermore, two subjects had no systematic changes in relative /♯CV/ timing, but one subject showed relatively later vocalic peak velocities for larger boundary conditions. [Work supported by NIH.]
Nontraditional acoustic features of focus
Authors: Bunnell H. Timothy , Hoskins Stephen R. , Yarrington Debra
Published: July 2002

Natural productions of the sentence ‘‘Bob bought Bogg’s box’’ in which focus was varied over each of the four words of the sentence were altered to produce prosodic cue neutralized versions. The alterations were applied singly and in all possible combinations to form eight experimental versions of each original sentence (the original and seven cue-neutralized versions). The original sentences as spoken by eight talkers and their cue-neutralized versions were presented to listeners with the task of identifying the focused item in the sentence. Results indicated that (a) overall, F0 cues were more important than either amplitude or duration cues in signaling focus, (b) the importance of amplitude and duration cues was greatly enhanced when F0 cues were neutralized, and (c) in many cases, identification of focus remained above chance after all three acoustic features were neutralized. The present study reports analyses of the residual acoustic features which continue to convey focus when amplitude, duration, and F0 are neutralized. [Work supported by NIDRR and the Nemours Research programs.]
The relationship between spectral properties and perceptual evaluation of hypernasality in children with cleft palate—vowel /i/
Authors: Kataoka Ryuta , Zajac David , Mayo Robert , Warren Donald , Okabe Kaoru
Published: July 2002

The purpose of this study was to examine the relationship between spectral characteristics and the perceptual evaluation of hypernasality in speakers with cleft palate. Speech samples from 32 cleft palate patients (average age 9.3 years) and 5 normal subjects (average age 9.4 years) were used in this study. The isolated vowel /i/ produced by each subject was filtered using 16 one-third octave bandpass filters from 200 Hz to 6.3 kHz to obtain a 1/3 octave spectrum. These spectra were normalized using the total power level of the 16 1/3 octave bands. Three sophisticated listeners rated the speech samples using a six-point equal-appearing interval scale. Average spectra obtained from the hypernasal and the normal groups were compared. Spectral characteristics of hypernasality in the vowel /i/ were identified as a rise in power level between the first formant (F1) and the second formant (F2) and a rise in power level of F1. Multiple regression analysis revealed a high correlation (r=0.81) between the averaged perceptual scores and four levels of 1/3 octave bands: the band containing F1, the first, the second, and the fourth bands from F1. [Work supported by NIDR Grant Nos. DE07105 and DE06957.]
The use of random spliced speech for the recognition of familiar voices
Authors: Figueiredo Ricardo M.
Published: July 2002

Various techniques for experimental speech signal manipulation to test recognition of familiar voices have been used, but random spliced speech (RSS) has not been tried. This procedure, which consists of randomly recombining digitally segmented speech signals, offers the advantage of more natural-sounding speech and decreased risk of creating artifacts interfering with perception. Although intelligibility is also destroyed by this technique, RSS preserves the spectral cues related to voice quality, as well as F0 level and range. In the present experiment, various 3.5 s RSS samples of 11 males were presented to 34 listeners, each familiar with only one of the voices. In a recognition task with forced yes/no responses, the index of correct identification was well above chance. An analysis of misindentifications revealed that proximity of F0 means led to more errors than did similarity of long term average spectra. Since speakers with F0 mean less than 2.8 semitones apart were frequently confused, it seems that in such an experimental situation the listeners may be forced to rely on isolated cues, such as F0; this may explain the high number of false identifications, even though the number of false rejections is practically nonexistent.
Multichannel acoustical measurement for sound field mapping
Authors: Gade Svend , Hald Jo/rgen
Published: July 2002

A newly developed sound field mapping method, which uses time-domain holography, is useful for localization, quantification, and ranking of sound generating regions on engines and gearboxes under run-up (i.e., nonstationary) conditions. The technique, which is called nonstationary STSF, requires simultaneous measurement of time histories on a planar surface covering the sound source. Thus subarray scanning as used with the cross-spectral STSF technique cannot be applied and a two-dimensional microphone array with half wavelength microphone separation must be used. Consequences of the need for a full size fixed array system is that it is not feasible for measurements to cover a whole vehicle, except at low frequencies, and for engine measurements a large number of microphone measurement channels is needed to cover a frequency range up to 3 kHz. The technique maps all sound field descriptors in the near field, but not only as a function of physical location but also as a function of time for transient events. Nonstationary STSF allows source attenuation simulations similar to the cross-spectral STSF technique to be performed. The development of TDH is part of the Brite–Euram project PIANO, dealing with new pass-by noise optimization methods for quiet and economic heavy road vehicles.
On fitting functions to data for the percent of a community highly annoyed by noise such as impulsive noise
Authors: Schomer Paul , Hirsch Karl
Published: July 2002

Survey respondents ‘‘highly annoyed’’ (HA) typically are categorized as those responding in the top 30% on an anchored numerical scale or in the top two categories on an adjectival scale. The percent HA typically ranges from 0% to 40%. At higher percents HA (e.g., >15%), the noise stimulus is clear and dominant and the reliability to the percentage values is high. At low percentages, the reliability is low. Some respondents may be annoyed any time they hear a sound. Depending on the number of such respondents, the percent HA can vary greatly on a percentage basis (4% HA versus 2% HA is a change of 100%). Therefore, alternatives to using small percentages HA (e.g., <10%) are considered when fitting transition functions to HA data. One method is to approximate the transition function by three asymptotes. The transition (sloped) asymptote would be fit by the 50% point and the slope when the percentages HA were large. Another way to avoid small percentages HA is to consider the group ‘‘little annoyed’’ or ‘‘happy.’’ This category might include the bottom two categories on a five-point adjectival scale or the bottom 30% on a numerical scale. This paper explores these issues.
Effect of low-frequency content on the rate of growth of annoyance of impulsive sounds
Authors: Fidell Sanford , Pearsons Karl , Silvati Laura
Published: July 2002

Since useful field studies of the annoyance of high energy impulsive sounds are costly and difficult to conduct, comparatively little is known empirically about community response to high energy impulsive noise exposure. Several attempts have therefore been made to generalize the results of controlled exposure studies of the relative annoyance of impulsive and nonimpulsive noises to community-level analyses. Although such studies have yielded a range of level-dependent growth functions for the annoyance of impulsive sounds, it is commonly observed that the annoyance of impulsive sounds increases more rapidly with level than that of nonimpulsive signals. The findings of a recent set of paired comparison judgments, in which the very low-frequency content of sonic booms was accurately reproduced, suggest that the steep slope of human hearing sensitivity at low frequencies may provide a good account for the common observation, at least for the case of sonic booms. If this is so, then ad hoc ‘‘adjustments’’ to the annoyance of impulsive sounds based on rise time, crest factor, and similar waveform characteristics may be superfluous. [Study supported by U.S. Air Force Air Combat Command.]
Full-scale model investigations into insertion loss of highway noise barriers under different atmospheric conditions
Authors: Hansen Scott D. , Burroughs Courtney B. , Gilbert Kenneth E.
Published: July 2002

The insertion loss of highway noise barriers can change significantly with atmospheric conditions. The insertion loss of a 14×80-ft tongue and groove wooden barrier constructed at the Pennsylvania Transportation Institute test track near State College, PA was measured under different atmospheric conditions. Point sources consisted of pure tones and random noise. Both sources and receivers were held at fixed distances from the barrier. Wind and temperature profiles were estimated from measurements using similarity theory. Measurements were taken as winds varied in both direction and strength for different temperature profiles. Results from parabolic equation model calculations of the propagation over the barrier are compared to the measured data. A statistical analysis of the changes in the insertion loss measurements is performed. This study demonstrates the effects of atmospheric conditions on the insertion loss of the barrier.
Model experiments and predictions of sound field in a downward refracting medium
Authors: Wang Qiang , Li Kai Ming
Published: July 2002

Laboratory experiments are conducted to investigate the diffraction of sound by concave surfaces for both monopole and dipole sources. The cylindrical concave surface in an otherwise homogeneous medium is used to simulate an outdoor situation corresponding to a downward refracting medium. A normal mode solution is developed to predict the sound field diffracted by the curved surface. The analysis is based on a conformal transformation in which a stricter analogy is established. Analytical expressions for dipole sources are deduced directly from that for a monopole source. Furthermore, the normal mode solutions are validated by comparison with that due to the boundary element method. Finally, the experimental results are compared with the normal mode predictions for an exponential sound-speed profile as well as a bilinear sound-speed profile. [Work supported by EPSRC and an Open University Studentship.]
Transient diffraction of a plane step pressure pulse by a hard sphere
Authors: Huang H. , Gaunaurd G. C.
Published: July 2002

Transient diffraction of sound pulses by a sphere is a classical problem extensively studied in acoustics (and in EM) for nearly a century. In spite of this volume of work, a satisfactory treatment of the sound field in the neighborhood of the shadow boundary is not available, and it is still one of the unsolved problems of diffraction theory [see comments in F. Friedlander, Sound Pulses (1958), p. 148]. To our knowledge, no treatment of this case has yet appeared. The modal series solution for this situation is presented here. The time histories of a sufficiently large number of terms of the modal series are accurately computed; a task that is possible today due to the existence of better computers and of more sophisticated computational algorithms. The Cesàro summation method [E. Whittaker and G. Watson, Modern Analysis (1965), p. 155] is used to completely eradicate the Gibbs’ phenomenon effect. This approach yields the diffracted field in the entire space-time domain. In particular, a complete treatment of the diffracted sound field is developed for a hard sphere insonified by a step pressure pulse, including the neighborhood of the shadow boundary where, heretofore, no analytical solution exists.
Prediction of echoes from small targets: Modelization and application to a telemetry problem
Authors: Riffard Cecile , Berton Jean-Luc , Estienne Claude
Published: July 2002

A model for the prediction of echoes from finite dimension transducers and targets was developed on the basis of a formulation published by other authors. The numerical implementation in the context of telemetries on small axisymmetrical targets was validated by comparison with simulation results available in the literature. In the context of telemetry in liquid sodium, the calibration of ultrasonic celerity may be done by measurement of the difference of time of flight between two small targets at given distances. Diffraction effects exist, due to the superposition of delayed contributions of the centers and edges of both the transducer and the target. Thus, the shapes of the echoes of both targets may be different from each other. The study of the resultant error on the difference of time of flight, according to the geometry of the system, constitutes the second part of the paper. The so-called ‘‘diffraction error’’ remains acceptable for a 40-mm transducer illuminating a 30-mm-diam target at normal incidence at 4.5 MHz, even if they are separated by only 300 mm, which is clearly nearer than the far-field limit.
Free and forced vibration of a multisupported string
Authors: Cray Benjamin A.
Published: July 2002

This paper examines a simple model: the vibration of an infinite string resting on sets of periodic supports, which are modeled as linear spring-mass-damper systems. The qth set of periodic supports may be offset by a distance xq. These offsets can thus be used to create spatially distributed gratings along the length of the string. Both the free and forced responses are examined, with the objective of gaining an understanding of the vibration response that governs more complicated arbitrarily stiffened elastic structures.
Effects of context-sensitive phonetic variation and lexical structure on the uniqueness of words
Authors: Auer Edward T. , Bernstein Lynne E.
Published: July 2002

Relatively little is known about the optical phonetic speech characteristics to which speechreaders are attuned. However, it is known that phonetic context does affect visual confusability of phonemes. In study 1, behavioral experiments were performed to examine effects of context-sensitive phonetic variation on the visual confusability of consonants and vowels. Hearing and deaf participants identified consonants or vowels presented in carefully constructed sets of nonsense syllables. Vowels were presented in four different consonant–vowel–consonant environments. Consonants and frequently occurring consonant clusters were presented in 14 different disyllabic nonsense words environments. These disyllabic environments varied target consonant position (initial, medial, and final) and target consonant adjacent vowel. Vowel identification was relatively accurate and insensitive to surrounding consonantal context. Consonant identification significantly varied as a function of both position and vowel context. In study 2, computational experiments were performed to assess the importance of patterns of context-sensitive visual confusability on the uniqueness of words in the language. The computational experiments in study 2 provide evidence that choice of a segmental intelligibility model does matter for modeling the uniqueness of words. However, the distribution of words in English substantially preserves lexical uniqueness even when phonetic variability is taken into account. [Work supported by NIH/NIDCD Grant No. DC02107.]
Time variation characterization of a nonstationary time series
Authors: Yen Nai-chyuan
Published: July 2002

The Fourier transform of a nonstationary time series has the difficulty of providing a proper physical interpretation of the signal as the physical attributes and dynamics associated with the time series may consist of several transients that are different in their nature. The time series analysis method developed by NASA [N. Huang et al., ‘‘The Empirical Mode Decomposition and The Hilbert Spectrum for Nonlinear and Nonstationary Time Series Analysis’’ (to be published)] has a unique approach to adaptively break down the nonstationary time series into the sum of several simple mode functions. Each single mode function can then be expressed in terms of an analytical signal whose amplitude and phase can both be varied with time. Those time variations can be related to the abrupt changes associated with dynamic systems. Such a time variation characteristic can be used to observe the occurrence of a transient event even in a nonstationary process. Applications of this technique to observe various types of acoustic signals in noisy environments are discussed.
Measurements of the polarization of sound energy at the mouth of boxes of an Italian opera house
Authors: Stanzial Domenico , Bonsi Davide , Prodi Nicola
Published: July 2002

The measurement of a newly discovered property of sound energy, the polarization [Stanzial et al., J. Acoust. Soc. Am. 99, 1868–1876 (1996)], has been carried out for the first time inside an opera house. Since energy polarization is due to the distributions of wavefronts passing through the measurement point, the analysis of this quantity allows one to obtain a precise picture of the effect of sound reflections at the receiving location. The highly symmetric architectural structure of an Italian opera house has been thus investigated at the opening of some boxes and the energy polarization has been compared with the sightline from each box to the stage. Furthermore, a third octave band frequency analysis in the range 100–5000 Hz has been accomplished that allows the visualization of the frequency-dependent behavior of the reflections’ distribution.
Measurements in an opera house: Comparison between techniques and instrumentation
Authors: Fausti Patrizio , Pompoli Roberto , Farina Angelo
Published: July 2002

In room acoustics, many objective parameters to quantify subjective impression have been introduced. These quantities can be measured using a wide variety of powerful tools and instrumentation. The results can be influenced by the measurement techniques and instrumentation used. Furthermore, the results also depend on the position and condition of the hall in which the measurements are made. With the aim to obtain a procedure to qualify a room acoustically, and in particular an opera house, which gives comparable and reproducible results all over the world, an extensive measurement campaign was made. The procedure takes into account the measurement techniques, the instrumentation, the measurement positions, and the condition of the audience and the stage. Comparisons were made both between different tools (real-time analyzer, DAT, PC-board) and different kinds of acoustic excitation (stationary, impulsive, pseudorandom). Furthermore, comparisons were made in different conditions of the stage and pit (e.g., empty, with the presence of orchestra tools and/or musicians). In this paper the results of the measurement campaign are presented and a proposal is submitted for the discussion.
Bubble generation and dispersion in the surf zone
Authors: Vagle Svein , Farmer David , Deane Grant
Published: July 2002

A combination of horizontal Doppler imaging, underwater microphotography, and in situ acoustical measurements are used to examine wave propagation, wave breaking, bubble cloud formation, and dispersion in the surf zone near Scripps Pier. Wave breaking is interpreted in terms of the evolution in wave properties between the end of the pier and a sensor tripod mounted in the surf zone. The position of the breaking zone is tracked from sharp discontinuities in the horizontal imaging sonar. Bubble size distribution is measured both photographically and with an acoustical resonator. From time to time the imaging Doppler sonar shows bubble clouds moving offshore from the surf. The observations provide a framework for model analysis of bubble generation, advection, and dispersion in the surf zone.
Void fraction and bubble distributions near surf zones
Authors: Su Ming-Yang
Published: July 2002

Extensive measurements of void fraction and bubble size density due to wave breaking both inside and outside surf zones were made by the Naval Research Laboratory during two joint experiments sponsored by ONR: the Scripps Bubbles/Acoustics Experiment at Scripps Institution of Oceanography, March 1997, and the Sandy Duck ’97 Experiment at the Army CERC Field Research Facility, Duck, NC, Sept.–Oct. 1997. Using a new technique that employs swing bar void fraction staffs anchored on the sand bottom, the new data show very strong tidal effects on the vertical distributions of void fraction. Data will also be presented on the temporal evolution of bubble size density (radius =15–1200 μ) during local storms. Finally, some new results on direct correlation of acoustic noise intensity using a hydrophone with co-located void fraction measurement will be presented.
Tomographic reconstruction of evolving bubble fields in the Scripps Pier bubble experiment
Authors: Rouseff Daniel , Henyey Frank S.
Published: July 2002

The Delta Frame, designed and operated by NRL-SSC, was a major component of the 1997 Scripps Pier shallow water bubbles experiment. The frame supported two sources and eight receivers. Acoustic travel time and attenuation were measured at eight frequencies between 39 and 244 kHz over the resulting 16 intersecting ray paths. Paths ranged in length from 2.5 to 8.6 m. For a given transmission sequence, the measurements at a particular frequency can be combined using tomography to yield a quantitative cross-sectional image of the ensonified region. By generating images for successive sequences, the temporal evolution of the medium can be visualized. A tomography algorithm [D. Rouseff and F. S. Henyey, J. Acoust. Soc. Am. 101, 3032 (1997)] is applied to the Delta Frame data. The images are produced for time periods during the experiment where the bubble field was probed by other independent measurements. Tomography results are compared to the other measurements. [Work supported by ONR.]
A novel approach for obtaining bubble dissolution measurements at sea
Authors: Costa Russell , Roy Ronald A. , Commander Kerry W. , Johnson Victor B. , Colbert Andrew C.
Published: July 2002

A hybrid system for measuring the dissolution of gas bubbles in an oceanic environment was developed utilizing the Coastal Systems Station’s Light Scattering Bubble Counter (LSBC). The LSBC independently measures flow velocity and bubble size, and is capable of distinguishing bubbles from particulate matter. In the hybrid system, the dynamic range of the LSBC measurements is 50 μm to about 300 μm in radius. The system is filled at depth (30 feet maximum without internal pressurization) and initially purged of all free gas. Pneumatically controlled valves are used to establish a closed recirculating system in which a flow can be generated in either direction using a large-volume peristaltic pump driven at low-volume velocity. Clear air is forced through a ceramic fritted disk to create the initial bubble population. This bubbly mixture is recirculated through the system at a nominal flow rate of 22 l/min, which corresponds to a velocity of 30 cm/s through the LSBC aperture. The bubble radii are continuously measured using the LSBC, resulting in time-dependent bubble size distributions. These distributions are used to estimate bubble dissolution rates for the size range indicated. [Work supported by ONR.]
Acoustic liver cauterization: A potential tool for bloodless surgery
Authors: Martin Roy , Vaezy Shahram , Hilton Scott , Caps Michael , Kaczkowski Peter , Keilman George , Carter Steve , Chandler Wayne , Mourad Pierre , Beach Kirk , Crum Lawrence
Published: July 2002

Liver surgery is hampered by the difficulty in controlling hemorrhage, particularly the slow oozing from injured hepatic surfaces. Conventional cauterizing fails in this situation. Bleeding from incisions made in animal livers using high-intensity focused ultrasound (HIFU) by volume cauterizing along the surface of the incision has been successfully stopped. The question arose: Could bleeding be avoided during surgery by precauterizing a thick surface around a region to be resectioned prior to the actual resectioning? The livers of anesthetized rabbits (4) and pigs (3) were treated in this manner under a protocol approved for animal studies at the University of Washington. Two HIFU transducers (3.3 and 3.5 MHz focused at 3.5 and 5.5 cm, respectively) were used for the treatment. Cauterized strips around a region appeared white. The tissue to be resectioned was removed by cutting along the distal border of the strips. No oozing from the liver parenchyma was observed. Bleeding occurred only in the larger vessels (>2 mm inside diameter) present in the cauterized region. Since these size vessels are easily ligated the method appears to be clinically feasible. Survival studies are needed to learn about the possibilities of rebleeding after abdominal closure or unknown healing difficulties.