bluuebunny/crossref_metadata_2025 huggingface dataset:
Active local noise control in open space
Authors: Guo Jingnan , Pan Jie
Published: July 2002

Local noise control, which creates quiet zones in desired areas, is a practical option of active noise control in open space when the control sources and the primary sources are not able to be very close. In most cases, the local control system attenuates the sound pressure in some areas at the cost of total sound power output increase. As a result, while the control system creates a quiet zone in some areas, it causes the sound pressure to increase in others. Two indicators of control efficiency, quiet zone size and total sound power output, are dependent upon the configuration of the control system. It has been found that for the multichannel control system, there exists a range of optimal configuration of control system, in which the control system can create the largest quiet zone with the lowest increase of total sound power output. Outside this range, the control system either becomes useless in creating large quiet zones, or causes great increase of sound pressure in most areas.
Active noise barrier efficiency improvement using multirate signal processing
Authors: Certic Jelena , Kovacevic Slobodan , Pravica Petar
Published: July 2002

In this paper, implementation of multirate signal processing techniques in an active noise barrier system was considered. Such a modification of a conventional multiple-error filtered-x LMS algorithm is supposed to give improved overall system performance, by separately controlling two different frequency ranges. The control system consists of one detection microphone, three secondary sources, and three error sensors. The primary signal was a random noise signal with a spectrum that coincides a typical road traffic noise spectrum. Locations of components were the ones found to be optimal in our previous work. Computer simulation was developed to compare the attenuation achieved with a control system that uses a multiple-error filtered-x LMS algorithm and the one involving multirate signal processing. Results of the computer simulation confirmed that attenuation is increased using multirate signal processing.
Methods for measurement and manipulation of timbral physical correlates
Authors: Beauchamp James W.
Published: July 2002

Multidimensional scaling calculations based on the results of listening tests comparing musical sounds almost always identify one perceptual dimension which is strongly correlated with a measure of the spectral centroid, whereas other dimensions are less obviously correlated to particular physical parameters. Some parameters which have been suggested as good correlates are attack time, spectral flux, and spectral irregularity [J. Krimphoff et al., J. Phys. IV (C5), 625–628 (1994)]. Also, spectral rolloff, preattack noise, general noisiness, and inharmonicity have been proposed as important factors. Based on time-variant spectral analysis with custom software [J. Beauchamp, Audio Eng. Soc. Preprint No. 3479], these parameters and others can be quantified and manipulated, leading to various applications. For example, synthesis using simplified parameter contours provides stimuli for discrimination testing to reveal listeners’ sensitivities to these parameters. Measurement of spectral differences can be correlated to discrimination results. Equalization of parameters common to two instrument sounds allows listeners to focus on those timbral aspects which are different. Finally, hybrid musical sounds created by interchanging parameter contours between instruments can shed light on timbral perception.
Acoustic response of a thin poroelastic plate
Authors: Horoshenkov Kirill V. , Sakagami Kimihiro
Published: July 2002

The expression for the viscosity correction function in the Attenborough model for the acoustic properties of rigid frame porous media is modified to account for the viscothermal effects in the oscillatory flow in the vibrating frame. The Helmholtz integral equation formulation is used to produce the solution for the sound field reflected from an infinite, thin, porous, elastic plate. The effect of an air cavity behind the plate is considered. A parametric study is performed to predict the effect of variations in the microscopic parameters of the poroelastic plate.
A nondestructive method for measuring the airflow resistance of locally reacting jet engine nacelle components
Authors: Nightingale T. R. T. , Tinianow Brandon
Published: July 2002

As a noise control measure to reduce inlet fan noise of jet engines, the nacelles are often equipped with a locally reacting absorber formed by a thin resistive wire mesh placed over a honeycomb structure. Historically there has been a problem to measure, in nondestructive fashion, the airflow resistance of repaired or refurbished nacelle parts for the purpose of demonstrating OEM compliance. ASTM-C522 is the traditional airflow resistance test method and is destructive, requiring a sample be cut from the specimen and fit into an apparatus where the flow velocity due to a constant pressure drop can be measured. This paper presents the theory and practical considerations of a nondestructive test method to measure the airflow resistance using an ASTM-E1050 impedance tube placed against the wire mesh of the complete specimen. Transfer matrix theory is used to describe the combined impedance of the wire mesh and air cavity. It is shown that at the air cavity resonance frequency the measured system impedance will be that of the wire mesh with the real part being the airflow resistance. Airflow resistance estimates obtained using the presented method and the ASTM-C522 test method are shown to be in excellent agreement.
The limit of absorbing characteristics of folded resonators silencers and ways of its realization
Authors: Starobinski Roudolf , Kergomard Jean
Published: July 2002

The folded resonance silencer is a version of 1/4-wave resonator having a very compact shape. They are usually used for suppressing of narrow-band and discrete frequency noise. The sets of resonators tuned to adjacent frequencies can be successfully used for a wide frequency band as well. The general theorems governing the behavior of these resonators are represented in this report. The limits of the muffling characteristics of the resonators and the ways of its realization are investigated on their base. It is shown that the potential muffling ability of a folded linear resonator is 1.2 dB less than for a Helmholtz resonator. However, taking into consideration the possibility of increasing the neck’s cross-sectional area, they are more effective at high sound levels because of the higher quality factors. It is shown also that with the help of coupling folded resonators the resonance effects can be created in the frequency band wider than two octaves. These peculiarities make the use of the folded resonators very interesting in noise control systems.
Reminiscences on bubble dynamics and cavitation
Authors: Strasberg M.
Published: July 2002

A review of various topics in cavitation and bubble dynamics discussed with Hugh Flynn, most of them still containing unsolved details. Among these are rectified diffusion of gas into pulsating bubbles and the effect of surface films; thermal rectified diffusion and the associated temperature rise; parametric shape oscillations of bubbles and the failure to observe resonances; the threshold conditions for cavitation, the cause for the persistence of the required nuclei, and the effect of a temporary static pressure increase on the nuclei; the dynamics of an individual cavity growing and collapsing in a compressible liquid and the associated internal pressure and radiated sound; and the cavitation noise radiated by cavitating propellers.
Susceptibility of silicon wafers to acoustic microcavitation damage
Authors: Madanshetty Sameer I. , Chandran Jogesh B.
Published: July 2002

Acoustic methods are being increasingly used in semiconductor processing. Given the increase in circuit densities being implemented on semiconductor chips the requirements for particulate contamination tolerance are becoming more stringent. The semiconductor industries road-mapped specifications for 1998, 0.25 μm feature size require control of all particulate contaminants larger than 0.08 μm. Fine cleaning of post CMP wafers is currently being done by using the megasonics process. The cleaning effectiveness depends on the strength of the acoustic fields used. In using high-intensity, high-frequency acoustic fields it is crucial to ensure that the surface of the silicon wafer does not suffer any damage due to cavitation. This paper assesses the damage potential of semiconductor wafers to acoustic microcavitation. Acoustic microcavitation is brought about by low megahertz acoustic fields giving rise to micron size bubbles that live a few microseconds. In exposing a surface to continuous waves one could obtain cavitation effects in an average, overall sense; the details of nucleation, evolution of inertial events, however, get glossed over. Both, pulsed and cw insonification were studied. Experimental measurements of the thresholds for cavitation damage of semiconductor wafers will be presented.
Enhanced ray theory
Authors: Maltsev Nikolai E.
Published: July 2002

The numerical implementation of standard ray theory faces two intrinsic difficulties, the infinite value of the field at caustics and the nonlinear boundary value problem for computation of eigenrays—rays which connect source and receiver. In an earlier work [N. E. Maltsev, J. Math. Phys. 35, 1387–1389 (1994)], a nontraditional approach was developed to treat the caustics problem. This report describes a procedure of embedding a nonlinear boundary value problem for eigenrays into the space of a higher number of dimensions, where it becomes an initial value problem for a new system of equations, differential equations for eigenrays. These two enhancements of the ray theory produce a regular method of computation of the field anywhere in the media, including shadows, for harmonic and pulse sources with all physical attributes of rays, such as arrival times and angles.
Estimation of forward-propagated ultrasonic fields in layered fluid media
Authors: Ha K. L. , Kim M. J. , Zhang W. Y. , Ye S. G. , Gong X. F.
Published: July 2002

The forward propagation of two-dimensional ultrasonic fields through layered fluid media was investigated theoretically by the angular spectrum method combined with the Rayleigh–Sommerfeld diffraction theory and experimentally by measurement of the fields using a precise scanning system with a needle-point hydrophone. Two types of transmitting transducers, one of which is a plane and the other of which is a concave type with the same frequency and the same aperture, were used. In theoretical analysis fields of incidence on a boundary of layer were calculated by the Rayleigh–Sommerfeld diffraction theory and those of transmission throughout the boundary were obtained by applying the angular spectrum method to the fields of incidence and considering the spatial-frequency-dependent transmission coefficients on each boundary. The optimum angular range and the spatial sampling interval could be obtained by supposing the virtual boundaries in the homogeneous medium of water and its appropriateness was confirmed experimentally. It was shown that the forward-propagated fields which could be estimated theoretically agreed reasonably with the measured data in two kinds of simple layered media with one or two boundaries.
Particle trajectories in a drifting resonance field separation device
Authors: Handl Bernhard , Gröschl Martin , Trampler Felix , Benes Ewald , Woodside Steven , Piret James
Published: July 2002

Drifting resonance field (DRF), a new method for the separation of particle/fluid suspensions is introduced. Unlike particle filters using ultrasound-induced coagulation, the DRF method only utilizes the primary acoustic radiation force to achieve the separation effect. This is done by cyclically switching the driving frequency of the DRF resonator between consecutive resonances, causing a directed motion of the particles and thus concentrating the particles in a certain region of the separation volume. Trajectories of polystyrene spheres (approximately 12 microns in diameter) suspended in distilled water have been measured in a prototype DRF resonator, varying the number of the utilized resonance frequencies and the acoustic power input. The measured particle trajectories are compared to computer simulations based on the same process parameters as used in the experimental setup, showing a high correspondence between experimental and simulated data. Both experiments and simulations prove the high potential of the DRF method for separation technology. A promising field of application is the up-scaling of acoustic cell retention systems recently introduced in animal cell culture, potentially yielding higher flow-through rates. The presented results are a valuable basis for design and process parameter optimization of future DRF separation devices.
Simulation of ultrasound propagation in a thermally turbulent fluid using Gaussian beam summation and Fourier modes superposition techniques
Authors: Lhuillier Christian , Fiorina David , Berton Jean-Luc , Juve Daniel
Published: July 2002

The CEA (French atomic agency) develops ultrasonic devices for the control and the inspection of Fast Breeder Reactors. The ultrasonic pulses propagate in a liquid which may be turbulent. To predict or interpret the effects of a homogeneous isotropic thermal turbulence, a numerical model has been implemented. Independent realizations of random thermal field are generated by superposition of random Fourier modes. For each realization the complex pressure field is calculated by the Gaussian beam summation method. Statistics over the set of realizations provide an estimation of the variance of time of flight and intensity fluctuations. Simulations have been performed with a point source. When the level of fluctuations is small, the model yields results which are in a good agreement with the analytical solutions given by Chernov and Rytov. When the level of fluctuations grows, it predicts correct evolutions. Multiple eigenrays are well predicted and calculations in time domain with a pulsed source show multiple transmitted signals or modifications in the signal shape.
Integrating monaural and binaural spectral information
Authors: Akeroyd Michael A. , Summerfield Quentin , Foster John R.
Published: July 2002

When speech is presented at a different lateral position to an interfering noise, analyses of both intensity and interaural differences can recover parts of the speech spectrum. It would thus be advantageous if listeners could integrate these two types of information. Their ability to do so using two-formant vowel-like stimuli was tested. A diotic white noise was modified by either increasing the intensity of two 1-ERB-wide bands by 6 dB (‘‘monaural’’ condition), by interaurally decorrelating those two bands (‘‘binaural’’ condition), or by increasing one band’s intensity but interaurally decorrelating the other (‘‘mixed’’ condition). Four center frequencies were used—250, 650, 950, and 1850 Hz—and combined in pairs to create four vowels: 250–950, 250–1850, 650–950, and 650–1850. Both bands must be detected to distinguish these stimuli. Identification performance was significantly above chance in all conditions but best in the monaural condition. It was as good in the mixed condition as in the binaural condition. Performance in the mixed condition was better than predicted form performance when only a single band was presented, and thus it could not be due to listening to the bands individually. These results indicate that listeners can integrate monaural and binaural evidence of speech spectra.
Modulation masking in a speech recognition task for normal-hearing and hearing-impaired subjects
Authors: van der Horst Rene
Published: July 2002

The effect of masking in the modulation domain was determined in a consonant recognition task. It is known from psychoacoustical experiments [T. Houtgast, J. Acoust. Soc. Am. 85, 1676–1680 (1989)] that modulation detection can be masked by another modulation. An experiment was designed that tries to verify whether detection of the modulations in a speech signal is essential for speech recognition. The goal of this experiment was to determine whether stochastic modulations can mask the modulations in a speech signal and disturb speech recognition as effectively as filtering out speech modulations [R. Drullman et al., J. Acoust. Soc. Am. 95, 1053–1064 (1994)]. The masker used was a stochastic narrow-band signal with minimal inherent fluctuations. The masker signal was, in every critical band, multiplied with the speech modulations. Several masking conditions were created with different bandwidths and center frequencies. The center frequencies were all lying in the region of modulation frequencies which are important for speech (4–20 Hz). Normal-hearing subjects and subjects with sensorineural hearing loss participated in the experiment. The confusion matrices were analyzed by means of multidimensional scaling techniques. The results of the two groups of subjects will be compared with the results obtained with a psychoacoustic model.
Categorical loudness perception in normal and hearing impaired subjects
Authors: Rawool Vishakha W.
Published: July 2002

This study compared categorical loudness perception in three subject groups: young (22–24 years) normal, older (43–60 years) normal, and older (60–80 years) hearing impaired (thresholds between 50 and 70 dB SPL at the test frequencies). Eleven subjects were included in each group. The subjects were asked to judge the loudness of warbled tones (2 and 4 kHz) presented at various sound-pressure levels in the following categories: not audible, very soft, soft, comfortable, loud, and very loud. The sound-pressure levels were calibrated for each individual ear. The multivariate analyses of variance was performed on the very soft, soft, comfortable, and loud variable. Average SPLs obtained in each category were used for the analyses. The results showed significant differences in the young normal and the hearing impaired groups in loudness perception across the four categories. No significant differences were apparent in the young normal and older normal groups. The older normal and the older hearing impaired groups differed across all the loudness categories except for the ‘‘loud’’ category where no significant differences were apparent. [Work supported by a Bloomsburg University grant for Research and Disciplinary Projects.]
Across-channel sensitivity to temporal asynchrony in cochlear implantees
Authors: Carlyon Robert P. , Geurts Luc , Wouters Jan
Published: July 2002

Five post-lingually deafened users of the LAURAflex cochlear implant detected temporal asynchronies between two 400-ms, 100-Hz trains of 40-μs biphasic pulses, applied to two ‘‘target’’ electrode pairs. The pulses in the signal stimulus of each 2IFC trial were delayed by between 0.3 and 4.8 ms on either the basal or apical target, relative to those on the other target. The pulses in the standard stimuli were nearly synchronous, containing a 0.1 ms-delay to the electrode whose pulses were not delayed in the signal. All listeners performed substantially above chance over a wide range of delays. Four were more sensitive to basal delays than to apical delays; one showed the opposite trend. Presenting a ‘‘masking’’ 1000-Hz pulse train to electrode(s) between the two targets did not substantially affect the results. This finding, combined with the wide (6–10 mm) separation between the targets suggests that performance was not mediated by neurons responding to both target electrodes. Rather, it is argued that they represent a genuine sensitivity to differences in timing between discrete auditory channels.
Fuzzy structure, initial problem. Poincare theorem
Authors: Rybak Samuil A.
Published: July 2002

A system consisting of a master structure—an oscillator, coupled with a number of oscillators, distributed in some frequency range—is considered. The master oscillator is initiated by a delta-function pulse, and damping is neglected. The energy flows from the master structure to the fuzzy system, the amplitude of its oscillations falls exponentially, and the amplitudes of fuzzy system oscillators are exponentially growing. This means that asymptotically the master structure becomes silent and the fuzzy oscillators have the maximum of their amplitudes. After the time T, depending on the full number of degrees of freedom, the picture almost fully returns back. But the time T becomes infinite when the number of oscillators is infinite (when their distribution is continual, for example). If at an arbitrary time one changes the signs of the velocities of the full system of oscillators, the phase trajectory turns back strongly the same way, because the system is conservative. The path tracing of the pole, which is originating in the integral describing the influence of the fuzzy system of oscillators on the master oscillator, is the same as usual, but the sign of the index of the exponential attenuation changes and the system goes to the initial state, with amplitude growing exponentially. [Work was partially supported by the Russian Foundation of Basic Research.]
Testing two information taxonomies in Spanish
Authors: Toledo Guillermo Andrés
Published: July 2002

Two information taxonomies, i.e., in the first experiment, New/Given distinction and, in the second experiment, three cognitive categories of the mental representation of referents: activation, semiactivation, inactivation differences [W. Chafe, in Tomlin Coherence and Grounding in Discourse (John Benjamins, Amsterdam, 1987), pp. 21–51 and K. Lambrecht, Information Structure and Sentence Form (Cambridge U.P., Great Britain, 1994), pp. 1–1161 have been explored in Argentinian Spanish. In the first experiment, semispontaneous materials were recorded from communicative interactions between three male speakers, one female speaker, and the listener. Brand-New plus New (Inferrable) versus Given (Textually Evoked) items were selected for acoustic analysis. In the second experiment, activation, semiactivation, and inactivation states encoded in semispontaneous discourses were taken from interactions between three male speakers and the listener. In both experiments, tonal prominences were studied through intonational contours on pairs of contrasted items: natural values and data transformed through logarithmic z-score normalization. Results in the first experiment indicated a relevant tonal encoding in new items. Findings in the second experiment have shown higher prominences correlated with inactive states, lower prominences with active and semiactive states.
Coarticulation in CV syllables: A locus equation and EPG perspective
Authors: Tabain Marija
Published: July 2002

Stop, nasal, and fricative consonants of Australian English were paired with a wide variety of vowel monophthongs to form CV syllables which were placed in a carrier phrase. The EPG and acoustic data were obtained from four female speakers producing these phrases. Locus equations [Lindblom, Acoust. Soc. Am. 35, 1773–1781 (1963)] were generated from the acoustic data, and coarticulation indices [Farnetani, Speech Production and Speech Modelling, edited by Marchal and Hardcastle (1990), pp. 93–130] were calculated from the EPG data. The coarticulation indices were compared with the slope values from the locus equations [Krull, PERILUS 10, 87–108 (1989)] in order to determine the degree of coarticulatory resistance for a given consonant phoneme as measured in the articulatory and acoustic domains. Results suggest that the greatest degree of coarticulation is shown in the labial and velar consonants, and less in the apico-alveolar consonants. The least degree of coarticulation is shown by the lamino-postalveolar consonants /S Z/. These results agree with data from Australian Aboriginal languages and with results presented by Recasens for Catalan [J. Phon. 12, 61–73 (1984); 19, 177–192 (1991)].
Ranking the pitches of concurrent vowels
Authors: Paschall D. Dwayne , Assmann Peter F.
Published: July 2002

When two vowels are presented simultaneously, listeners can label them more accurately if their fundamental frequencies differ, and under some conditions they can report which vowel has the higher pitch. In this study the interaction of fundamental frequency and binaural cues on judgments of the relative pitches of concurrent vowel pairs is examined. On each trial listeners were told which vowels were presented and were asked to indicate which vowel was on the higher pitch. The first vowel had an F0 of 140 Hz and the second vowel was either 1, 2, 4, or 8 semitones lower or higher than the first. When the fundamental frequency difference was small (1 semitone), the ability to rank the pitches of the two vowels was near chance level, and dichotic presentation provided little advantage over monaural presentation. With monaural presentation performance improved gradually with increasing F0 difference, reaching a maximum near 80% correct at +8 semitones. When the stimuli were presented dichotically there was a dramatic improvement between 1 and 2 semitones and performance was near 100% with larger F0 differences of 4 and 8 semitones. The interaction of F0 differences and binaural cues places important constraints on models of concurrent vowel segregation.
An exemplar-based model of silent-center syllable perception
Authors: Winters Stephen , Johnson Keith
Published: July 2002

Rakerd and Verbrugge [J. Memory Lang. 26, 558–563 (1987)] suggested that the perception of silent-center syllables—CVC syllables with the middle 60% of the vowel edited out and replaced with silence—had to involve some form of speaker normalization. Crucial to their argument was their subjects’ ability to perceive cross-gender hybrids of such syllables. Rakerd and Verbrugge reasoned that even modest accuracy in perceiving these hybrids entailed some sort of normalization of the disparate acoustic qualities of male and female voices in order to derive one perceptual whole. Rakerd and Verbrugge’s study has been replicated in order to test the ability of a computationally implemented exemplar model to perceive silent-center syllables. Exemplar-based modeling utilizes no ‘‘speaker normalization’’ as such, but, nonetheless, the model in this study approximated the performance of human subjects in perceiving silent-center syllables correctly. The model’s performance on the important ‘‘hybrid’’ case was almost identical to subjects’ responses. These results suggest that the human ability to perceive silent-center syllables does not necessarily entail some process of speaker normalization in speech recognition. [This material is based upon work supported under a National Science Foundation Graduate Fellowship and NIDCD Grant No. R29-DC01645-06.]
The time course of learning: Neurophysiologic changes during speech training
Authors: Tremblay Kelly L. , Kraus Nina , McGee Therese , Zecker Steve
Published: July 2002

The ability of normal-hearing adults to identify and discriminate novel speech sounds improves with training. Neurophysiological changes associated with this improvement include increased duration and area, as well as shortened onset latency, of the mismatch negativity (MMN) [N. Kraus et al., J. Cog. Neurosci. 7, 25–32 (1995); K. Tremblay et al., J. Acoust. Soc. Am. 102, 1–12 (1997)]. The MMN is a passively elicited, preattentive, auditory event-related potential that reflects auditory discrimination and echoic memory [R. Naatanen et al., Acta Psychol. 42, 313–329 (1978)]. To date, little is known about the time course of neurophysiological change and the manifestation of learning. The present study examined the time course of perceptual learning and its relation to changes in the MMN with the expectation that cortically evoked potentials could provide insight into the biological processes underlying perceptual learning and serve as a clinical tool for evaluating change during efforts of (re)habilitation in the communicatively impaired. Specifically, it was found that neurophysiological change is apparent in the MMN preceding behavioral improvement. This suggests that auditory training alters the neural activity that provides the necessary coding of the speech stimuli and those changes are later integrated into functional behavior.
Two-dimensional measurement of acoustic properties of tissue using 3 to 50 MHz ultrasound
Authors: Hachiya Hiroyuki , Ohtsuki Shigeo , Tanaka Motonao
Published: July 2002

Application of ultrasound has been expanded in the medical field and used widely for diagnosis. Acoustic properties such as the sound speed of a bulk wave in biological tissues are important parameters for quantitative characterization of living tissues. But the relationship between ultrasonic characteristics and pathohistological changes in tissues is poorly understood. To investigate the relationship, we have proposed a high-precision noncontact measuring method of acoustic properties of tissues using 3- to 50-MHz ultrasound. In this method, the travel time of sound through the sample, and the difference in travel times from the transducer to the rigid reflector with and without the sample are estimated based on frequency-time analysis which does not require physical contact of ultrasonic probes to living or freshly excised tissue specimens. The components of multipath propagation in tissues are decomposed in a frequency complex plane. The travel time and the time difference are estimated using all waveform information; rms error of sound speed is less than 3 m/s. Two-dimensional measurement of acoustic properties in rat and human tissues is performed using the noncontact measurement method. The relation between the acoustic properties change and the physical structure change in tissues is getting clear.
Dynamic flow quantitation with spatial orientation guided digital color Doppler imaging: In vitro validation and initial in vivo experience
Authors: Li Xiang-Ning , Jong Jing-Ming , Hausken Trygve , Dunmire Barbrina , Goldman Bryan , Leotta Daniel F. , Beach Kirk W. , Martin Roy W.
Published: July 2002

The assumptions of geometric shape and uniform velocity profile prohibit the use of conventional Doppler methods for volume flow quantification with irregularly shaped nonvascular passages in space. A flow quantification method that integrates a three-dimensional (3-D) position and orientation sensing system with digital color Doppler imaging approach has been developed. Methods: The optimized ultrasound system settings were predetermined using a static, laminar flow model. The instantaneous flow rate was measured by the integration of the area-velocity product with angle correction. Initial in vivo studies quantified gastric emptying on five healthy volunteers 10 min after ingestion of a 500-ml meat soup, postprandially. Digital Doppler images were obtained continuously covering a transpyloric flow episode, immediately following the 3-D scan of the passage. The flow direction was derived from 3-D reconstruction using the centroids of two short-axis views. Results: In vitro validation showed the Doppler flow rates were within 10% for reference flow rates ranging from 6 to 30 ml/s. The average gastric emptying lasted 0.75 s with 3.0 ml in volume. Conclusions: With appropriate instrument settings, orientation determined digital Doppler can be used for the quantification of gastric emptying with adequate accuracy. This method minimized the angular ambiguity and geometric assumptions.
Assessment of vascular dialysis access with Doppler
Authors: Beach Kirk W. , Paun Marla , Ahmad Suhail , Meissner Mark , Hickman Robert , Fauser Laurie
Published: July 2002

Shunts between the arterial and venous systems are created to provide the blood flow required for hemodialysis. These shunts, created with interposed grafts or fistulas, often fail unexpectedly due to occluding thrombi. Such cases require surgical repair of the existing shunt or new shunt creation at an alternate site. Measuring pressure in the venous dialysis needle at a fixed flow rate is a standard method of surveillance. The method is not as effective as required because there is too much measurement variability. The variability is probably due to variability in placement of the dialysis needle. Neither ultrasonic duplex scanning nor x-ray angiography is viable for surveillance because the cost is too high. A simple ultrasonic Doppler method of measuring the change in flow between the dialysis needles as the dialysis pump is started and stopped can be used to compute the resistance of the graft during each dialysis. The cost is minimal, therefore making Doppler surveillance feasible. In addition, this method could be used to control the dialysis pump rate to an optimized value.
A comparison of hydrophone calibration by free-field reciprocity and by optical interferometry
Authors: Robinson Stephen P. , Preston Roy C.
Published: July 2002

As the national standards laboratory in the UK, the National Physical Laboratory has established two primary standard methods for the free-field calibration of hydrophones. In the frequency range 500 kHz to 20 MHz, the primary standard is realized using optical interferometry; in the range from 5 to 500 kHz, it is realized by the method of three-transducer spherical-wave reciprocity. Although the ranges of the primary standards are defined as above, both methods can be used in the frequency range 200 kHz to 1 MHz, enabling a comparison to be undertaken between these two independent methods. The comparison was made by calibrating reference hydrophones using both methods and comparing the results. In general, the results agree to within ±0.4 dB or better, well within the combined uncertainties of the methods. In this paper, a comparison of results is presented and a discussion given of the major sources of uncertainty in the methods.
Tracking the frequency components of musical tones based on global waveform fitting
Authors: Ding Yinong
Published: July 2002

A novel approach to estimating sinusoidal parameters of musical tones is presented. The proposed algorithm uses a combined quadratic polynomial phase sinusoid and residual signal model, and a waveform fitting criterion, as opposed to the traditional energy fitting one as employed by short-time Fourier transform-based approaches. The proposed algorithm obtains sinusoidal parameters by minimizing the squared difference between the original and the synthesized musical tones. The signal synthesis is implemented implicitly and the synthesis errors are taken into account while the sinusoidal paremeters are estimated. A number of different phase models proposed for music analysis and synthesis are reviewed and their pros and cons are identified. This analysis justifies the use of the proposed signal model. Experiment results for the analysis and synthesis of a variety of musical instrument tones such as piano, trumpet, french horn, flute, and violin are given to demonstrate the accuracy and effectiveness of the proposed algorithm. A VLSI architecture for sinusoid synthesis using the parameters obtained from the proposed algorithm is also given to provide a complete solution to the parametric modeling-based music analysis and synthesis.
Nonlinear dynamics of bubbles with surfactants
Authors: Apfel Robert , Chen Xiaohui , Ketterling Jeffrey
Published: July 2002

Hugh Flynn pioneered many aspects of cavitational phenomena. He even got a patent on the idea that large bubble collapse could be used for inertially induced thermonuclear fusion. Some researchers currently working in the area of sonoluminescence are asking the same questions. One of the key requirements for confining the energy in the collapse of a bubble is maintaining spherical symmetry. Instabilities, such as Rayleigh–Taylor and Kelvin–Helmholtz, can compromise this requirement. Therefore it is useful to examine the role of surfactants in conferring stability on the collapse of bubbles. Codes that have recently permitted the description of superoscillations of liquid drops with surfactants in air [e.g., Apfel et al., Phys. Rev. Lett. 78, 1912–1915 (1997)] can be applied to the case of a bubble in a liquid. Of particular interest are insoluble surfactants, such as bovine serum albumin, which do not reduce the surface tension that much, but which greatly increase the surface damping. The role of damping in discouraging or delaying instability of collapsing bubbles in an acoustic field will be presented. [Work supported in part by NASA through Contract No. 958722 managed by the Jet Propulsion Laboratory.]
Giant resonance in the dynamics of small bubbles
Authors: Akhatov Iskander Sh. , Ohl Claus-Dieter , Mettin Robert , Parlitz Ulrich , Lauterborn Werner
Published: July 2002

For bubble oscillations under medium and large pressure amplitudes a complicated scenario of bifurcations and coexisting (chaotic) attractors exists. However, for very small bubbles in a very strong sound field the dynamics becomes regular and a new type of strong resonance with a thresholdlike increase in oscillation amplitude occurs [E. A. Neppiras and B. E. Noltingk, Proc. Phys. Soc. London Ser. B 64, 1032 (1951); H. G. Flynn, in Physical Acoustics Vol. 1, edited by W. P. Mason (1964), p. 57; W. Lauterborn, Acustica 20, 105 (1968)]. This phenomenon has a strong influence on many properties of cavitation bubbles. The following aspects are considered: rectified diffusion, stability of the bubble under SBSL conditions, primary and secondary Bjerknes forces, and interpretation of bubble size measurements.
Nonlinear wave propagation in cylindrical air-filled tubes
Authors: Menguy Ludovic , Gilbert Joël
Published: July 2002

Three dimensional conservation laws are reformulated in a dimensionless form for a cylindrical air-filled tube. Three nondimensional numbers therefore appear, and are used to evaluate the order of magnitude of each term. Simplifying leads to two quasi-unidimensional generalized Burgers equations, which take into account both nonlinear phenomena and viscothermal losses. Special attention is paid to the validity of the different approximations we proposed. The method of multiple scales indicates that the interaction between the two opposite propagative waves is noncumulative and remains a local effect. The two Burgers equations are therefore globally independent. A numerical computation in the frequency domain solves the Burgers equations in the case of a stationary wave. The signal is supposed to be known at the two ends of the tube (or impedance instead of signal for one extremity). The computation uses the harmonic balance method to calculate the two opposite propagative waves which makes it possible to verify the right conditions in the two extremities. The signal everywhere in the tube is so pieced together. Some experiments are performed with a siren as source in one extremity, and measurements are compared with theoretical results.
Dependence on waveguide width of elastic convolver efficiency
Authors: Nakagawa Yasuhiko , Kitabayashi Suguru
Published: July 2002

An elastic convolver based on a nonlinear effect in surface acoustic wave (SAW) on a Y-Z⋅LiNbO3 is widely used as a functional device in the area of communication system. Therefore, the efficiency, which is an important parameter for the SAW convolver, is quite low. There have been many reports on electrode structures and convolver materials for improving the efficiency. In this work, theoretical and experimental results are reported for the optimum width of a (Δ=v/v) waveguide which has high convolver efficiency. The theoretical calculation was obtained by using the scalar potential approximation. The efficiency has a peak at a waveguide width of around 1λ. In order to increase the power density multistrip beam width compressors have been used. Performance of a device having a 4-μs waveguide length, a central frequency of 43 MHz and using 10:1 beam width compressors is described. The validity of the theory is proven experimentally, and, therefore, the optimum waveguide width for the convolver efficiency in a conventional elastic convolver is around one wavelength of the input SAW.
Effects of diffraction on the sensitivity of needle-type ultrasonic receivers
Authors: Harris Gerald R. , Gammell Paul M. , Porter Jeffrey M.
Published: July 2002

The low-frequency sensitivity of piezoelectric receivers usually is assumed to be represented accurately by the −3-dB cutoff frequency fco=(2πRiCi)−1, where Ri is the loading (e.g., amplifier) resistance and Ci is the total capacitance. For typical needle-type hydrophones such as used in medical ultrasound exposimetry, fco is less than 50 kHz. However, theoretical studies have shown that diffraction effects at the needle tip can cause a low-frequency rolloff in sensitivity at frequencies much higher than that predicted by this simple electrical model. To examine this effect, broadband frequency response measurements of several needle-type hydrophones were made in the frequency range 0.2–2 MHz. The active sensor material was polyvinylidene fluoride, and needle diameters ranged from a few tenths of a millimeter to approximately 1 mm. In all cases the sensitivity decreased with decreasing frequency, with the −3 dB points all lying above 400 kHz. Such behavior calls the use of these devices into question when accurate knowledge of the pressure waveform is required, particularly with regard to measuring the peak rarefactional pressure in pulsed waveforms displaying significant finite amplitude distortion.
The second harmonic component in the focused sound field diffracted by a straight edge
Authors: Saito Shigemi , Kim Jung-Soon
Published: July 2002

To analyze the characteristics of the acoustical imaging utilizing higher harmonic components in the focused sound field, the influence of a diffracting edge put into the focal region on the fundamental and second harmonic fields is theoretically and experimentally investigated. A straight rigid edge put normal to the acoustic axis is assumed to diffract a focused Gaussian beam. The second harmonic sound generated both in front of and beyond the edge is taken into account to calculate the diffracted field through the manner using the Green’s function for the governing approximate equation. In the experiment, a knife edge is inserted normal to the sound beam formed by the 1.9-MHz focusing Gaussian source employing a concave piezoelectric transducer with an asteroid electrode. The axial field detected by a needle-type hydrophone as well as the signal obtained with another concave transducer is discussed regarding the amplitudes and phase difference of the fundamental and second harmonic components.
Interactions of pairs of target and context tones based on relative frequency relation and degree of frequency uncertainty
Authors: Neff Donna L. , Wrage Rebecca L.
Published: July 2002

Four normal-hearing listeners completed 2IFC sample-discrimination tasks for frequency, in which they judged which of two tone pairs was drawn from the higher of two Gaussian frequency distributions. The center frequencies of the two target distributions were placed at low (400/500 Hz), middle (1128/1410 Hz), or high (3200/4000 Hz) frequency regions. All distributions were equally spaced and equivariant on a logarithmic frequency scale. Pairs of extraneous (to-be-ignored) context tones were added above, flanking, and below the low-, middle-, and high-frequency target regions, respectively. Across conditions, target and context tones used the same frequency regions, but never occupied the same frequency region within condition. Context tones were fixed in frequency, varied between two known frequencies, or were Gaussian distributed. A level jitter was added to derive perceptual weighting functions across stimuli. The results showed little detrimental effect of fixed-frequency context tones, but large individual differences in the effects of known pairs of tones or tones with Gaussian variation. Weighting functions and patterns of frequency interactions among stimuli will be discussed. [Work supported by NIDCD.]
Effects of tonal masker uncertainty on detection
Authors: Slawinski Elzbieta B. , Scharf Bertram
Published: July 2002

The present study was inspired by results of Allen and Wightman [J. Speech Hear. Res. 38, 503–511 (1995)]. The goal of the present study was to explore the effects of uncertainty of a weak tonal masker (or distractor) on the detection of a tone in noise. The thresholds of three listeners were measured for 1-kHz tone burst (350-ms duration) in broadband noise (300–1800 Hz, at 60 dB SPL). A 2IFC tracking procedure (3 down, 1 up) with six interleaved tracks was used. On each trial, the distractor frequency was selected randomly from six frequencies (525, 800, 925, 1075, 1280, and 1600 Hz) outside of the critical band surrounding the signal. The distractor came on simultaneously with the signal in the signal-plus-noise interval and also at the corresponding moment in the noise-alone interval. The preliminary results indicated that thresholds for the signal increased in the presence of distractors by 3–10 dB, depending on the frequency of the distractors and type of noise. Thresholds were higher for distractors close to the signal frequency, more so in intermittent noise than in continuous noise.
Application of a peripheral model to an attentional filter of missing-fundamental tone
Authors: Miyazono Hiromitsu , Usagawa Tsuyoshi , Ebata Masanao
Published: July 2002

An attentional filter measured by the probe-signal method is compared with the peripheral auditory filter measured by the notch-noise method. The shape of attentional filter is estimated by the roex (rounded exponential) filter model. However, the attention can be given on a frequency without the signal on the actual frequency. In this study, the attentional filter was measured using a missing-fundamental tone which has no energy on an actual frequency. The missing-fundamental tone was produced by a harmonic signal with 13 components from 1000 Hz to 4000 Hz. The fundamental frequency was set to 250 Hz. The psychometric function is measured on various frequencies and the shift of the function from that of control condition is regarded as the effect of the attentional filter. The filter shape is estimated by the roex model and compared with that of the pure tone. In the frequency region apart from the fundamental, the dynamic range of the filter is smaller than that of pure tone. Near the fundamental, the correlation between the measured value by the probe-signal method and the estimated value by the roex filter for the missing-fundamental tone is smaller than that for the pure tone.
Reduction of fluid-loaded ribbed shells to equivalent uniform structures for mid- to high-frequency structural acoustic analysis
Authors: Bliss Donald B. , Franzoni Linda P.
Published: July 2002

The acoustic and vibratory behavior of fluid-loaded shells with ribs and other structural discontinuities is of great interest in naval applications. These structural discontinuities lead to complex phenomena, especially at mid- to high-frequencies where shell wavelengths are shorter than the discontinuity spacing. The methods of homogenization and local/global decomposition can be used to divide this problem into two parts. In the global problem, periodic discontinuities are replaced by an equivalent distributed suspension with slowly varying properties. This problem can be solved much more efficiently than the original problem since all rapidly varying scales have been removed. The local problem is solved separately and independently, except for amplitude information from the global problem. The local problem formulation provides transfer function information that defines the suspension in the global problem. Once the formulation has been developed for a specific structure, the global problem is solved first, and the local solution can be reconstructed afterward. The two constituent parts are then recombined to form a composite solution. As an illustration, this methodology is used to solve for Bloch waves on a structure with identical periodic discontinuities. The application of the theory to nonidentical discontinuities is also explained.