bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic variability in the vowels of female and male speakers.
Authors: Henton Caroline
Published: October 2005

When vowel formant values for female and male speakers are normalized and plotted in an F1–F2 space, it is striking that the quadrilateral spaces for the females are uniformly larger than those for the males. Data will be presented from seven languages and dialects, including three dialects of English, which indicate that, all other things being equal, female speakers appear to produce vowels in a manner that is more phonetically explicit than males do. It is particularly in the F1 dimension that the females’ quadrilaterals extend beyond the males’; it may be inferred that female speakers articulate vowels with a more open mouth than males do. Can one expect that speakers with a higher F0 automatically have a larger vowel space? Are females making more of an effort to keep vowels distinct, and potentially contribute to greater intelligibility? Or do females over-articulate, avoiding reduced or centralized forms, as a result of social expectations to be conservative ‘‘guardians’’ of the language? Acoustic and sociophonetic answers to such questions will be offered. In addition, data will be presented from three dialects of English which show that female speakers are not uniform in their behavior: some females merge vowels more often than males do, while other female populations appear to differentiate the same vowels more systematically. The perceived social prestige of an accent is offered as one explanation for these disparate directions of change.
Durational effects of prosodic structure in spontaneous spoken French.
Authors: Cedergren Henrietta J. , Levac Louise , Perreault Hélène
Published: October 2005

The relation between segmental timing variability and prosodic structure in Montreal French is investigated. Twenty-four minutes of data extracted from recordings of spontaneous conversations using a balanced corpus of eight speakers differentiated according to sex, age, and social class were measured on digital spectrograms. An auditory analysis was used to categorize the basic prosodic structure of the speech corpora. Four levels of prosodic organization were established: syllabic units, metrical feet, accentual groups, and intonational phrases. A linguistic analysis was used to determine the distribution of deleted vowels. This study investigates the role of two types of durational effects in utterances: local effects and global effects. The multiple layering of temporal effects is examined by means of a statistical analysis of syllable durational variability. It is shown how the distribution of vowel deletion follows from the interaction of effects in the temporal implementation of prosodic domains. [Work supported by SSHRCC.]
Recovery of auditory threshold following exposures to a pure tone and white noise.
Authors: Young I. M. , Lowry L. D. , Menduke H.
Published: October 2005

Recovery from temporary threshold shift (TTS) was measured for a subject with normal hearing following exposures to a continuous pure tone 1000 Hz and white noise. The intensity of the exposure tone was 123, 117, and 110 dB SPL and the exposure duration was 21, 10, and 10 min, respectively. The intensity and duration of exposure to white noise were 123 dB SPL and 30 min. Automatic audiometer was used to obtain TTS and recovery at a frequency 1500 Hz measured from 1 min to 51 days, 6 days, and 23 h after exposures to 1000 Hz. For white noise, TTS and recovery were measured from 1 to 25 min. Results indicated that, (1) there was steady progression of recovery to pre-exposure threshold, and (2) recovery was neither a simple linear nor monotonic process. These results were compared with our previous study of TTS and recovery obtained at various frequencies following exposures to pure tones 250 and 1000 Hz.
Time domain processing in mid-frequency structural acoustics.
Authors: Baggeroer A. B. , Schmidt H. , Fricke J. R. , Bondaryk J.
Published: October 2005

The processing and analysis of high-frequency scattering and radiation experiments have naturally been performed in the time domain, with the sources being short duration transients. This is due to the fact that the scattering and radiation from structural features are easily separated and identified in the time domain. In low-frequency experiments the acoustic wavelengths are large compared to the structure and the structural details in particular. Therefore the analysis and processing have here been naturally performed using frequency domain modal approaches. The mid-frequency regime (ka≂5–20) provides a transition zone where none of the traditional processing approaches are particularly suitable. Thus, the duration of transients in this regime is longer than the travel time across the structure, making direct time separation of individual arrivals impossible. However, this is a problem encountered in other areas involving wave propagation, including underwater acoustics and seismology. Here a number of high-resolution processing schemes have been developed over the last couple of decades, capable of isolating individual scattering and radiation events, in turn allowing for identification of scattering ‘‘hot-spots,’’ etc. Here, state-of-the-art frequency and time domain signal processing is reviewed, and the merits of the various approaches are discussed. Examples will be given illustrating the use of such high-resolution time domain processing schemes in mid-frequency structural acoustics.
Isolated feature extraction from composite short pulse scattering data for a thin submerged elastic plate.
Authors: Kapoor Tarun , Felsen Leopold B.
Published: October 2005

Robust interpretation of observables in acoustic scattering data from submerged elastic structures requires decomposition of composite effects into interacting isolated effects, each of which is matched as well as possible to the relevant wave dynamics. Having selected what one believes to be an observable-based parametrization (OBP), one may then proceed to process the data so as to link the observable features with the wave objects that synthesize them. This strategy is applied here to two-dimensional scattering of a line-force-excited short pressure pulse by a submerged thin elastic plate of finite width. The database is generated numerically by a time domain (TD) finite difference code, with observers located on a line parallel, and exterior to, either side of the plate. The selected OBP involves hybrid combinations of ray acoustic geometrically reflected and edged diffracted fields, with coupling to the supersonic (leaky) compressional mode in the plate, and with collective responses due the multiple interactions between the plate edges. The TD processing is built around auxiliary numerical problems that involve a semi-infinite plate and an infinite plate which, respectively, isolate single-edge diffraction and geometrical reflection. By subtracting these numerically from the composite data, one may isolate the TD edge diffraction coefficient, the leaky mode detachment coefficient, and other OBP quantities. The processing is also performed in the radon transformed time-slowness domain. [Work supported by ONR.]
Ray acoustic formulation of sound wave scattering from submerged cylindrical thin elastic shells with endcaps.
Authors: Ho J. M. , Felsen L. B.
Published: October 2005

Cylindrical shells with endcaps of various types are useful prototypes for a class of submerged elastic structures of current interest period. In the mid- and high-frequency ranges (ka≳3, where ‘‘a’’ is the radius of the cylinder), ray acoustics offers a physical-based methodology for computing the scattered signature. Restricted to thin shell dynamics, hemispherically capped cylinders are investigated by combining results from our previous studies of infinite cylindrical and full spherical shells [Felsen etal., J. Acoust. Soc. Am. 87, 554–569 (1990); J. M. Ho and L. B. Felsen, J. Acoust. Soc. Am. 88, 2389–2414 (1990)]. Rays from arbitrarily incident plane waves are traced to the cylinder and give rise there to geometrically reflected and phase matched shell guided supersonic wavefields, each with its own distinct trajectories. The surface guided fields follow helical paths on the cylindrical portion, which are smoothly matched to great circle paths on the hemispheres, and are turned back there toward the cylinder at a pitch-dependent caustic. The total field is synthesized by the sum of all possible ray paths, traversing the structure azimuthally and longitudinally, which reach the observer. Quantitative expressions are obtained by including ray field launching, detachment, and propagation coefficients. Attention is also given to conical endcaps and to conical sections with smoothly joined spherical caps. [Work supported by ONR.]
Can the loudness function determine the shape of the Weber function?
Authors: Hellman William S. , Hellman Rhona P.
Published: October 2005

A recent model relating measures of loudness and intensity discrimination [W. S. Hellman and R. P. Hellman, J. Acoust. Soc. Am. 87, 1255–1265 (1990)] is shown to reveal that the near threshold slope of +1 obtained for the loudness function requires the near threshold slope of the Weber function for intensity discrimination to be −1. This result is consistent with psychophysical intensity discrimination measurements for pure tones and broadband noise, as well as with theoretical considerations which predict that the Weber function should have a slope of −1 as the detection threshold is approached [N. F. Viemeister, Auditory Function, 213–241 (1988)]. The model also generates the overall shape of the Weber function over a suprathreshold range of sound pressure levels up to 80 dB. Empirical examples are provided. [Partially supported by the Rehab. R. & D. Service of the VA.]
Selective attention to loudness, ignoring pitch.
Authors: Melara Robert D. , Marks Lawrence E. , Yamagishi Noriko
Published: October 2005

Perceptual and decisional separability between the dimensions of loudness and pitch were evaluated in discrimination procedures in which subjects focused on loudness and ignored variation in pitch. In one task, subjects decided on each trial whether a test signal was the same as or different from a referent in loudness. Results showed that subjects were unable to ignore changes in pitch, even though it was in their best interest to do so. Both sensitivity and bias were affected adversely by irrelevant pitch. In a second task, analogous to Garner’s speeded classification task, subjects decided on each trial whether a single signal was loud or soft, ignoring trial-to-trial changes in pitch. Under these conditions the dimensions were separable, both perceptually and decisionally; subjects’ classification performance was optimal, in the sense that they could ignore pitch completely when it varied orthogonally with loudness, but could integrate pitch when it correlated with loudness. Taken together, the results indicate that successful auditory selective attention is task dependent. The concept of separability is apparently not general to a pair of dimensions, but specific to the conditions under which selective attention is tested.
Modal analysis of a Korean bell.
Authors: Rossing Thomas D. , Perrier Alexis
Published: October 2005

Large temple bells have been cast in Korea for more than 1200 yr. Most Korean bells have a circular area, called a dangjwa, which provides a convenient striking point, and a sound pipe, called a eumtong, at the top. The asymmetry due to the dangjwa and the ornamentation gives rise to mode doublets and results in a slow beating, which is carefully controlled and considered to be an important characteristic of Korean bell sound. The vibrational modes of a small Korean bell have been studied, using holographic interferometry and modal analysis with impact excitation. The vibrational modes are somewhat different from those of carillon bells, tuned church bells, and handbells previously studied [see N. H. Fletcher and T. D. Rossing, ThePhysicsofMusicalInstruments (Springer-Verlag, New York, 1991), Chap. 21]. No (m,l*) modes are observed. Mode doublet splittings range from 1% to 9%. The fundamental (2,0) mode decays much more slowly than the higher modes of vibration, and thus determines the pitch of the bell. [A.P.’s visit was supported by a grant from Ecole Nationale Superieure des Telecommunications.] a)Student intern from Ecole Nationale Superieure des Telecommunications, Paris.
Geographic representation of noticeability of aircraft noise in Grand Canyon National Park.
Authors: Fidell Sanford , Sneddon Matthew , Smyth John , Pearsons Karl
Published: October 2005

A novel geographic representation of the noticeability of aircraft noise that accounts for topographic relief has been constructed in a distributed computing environment. A regular grid of points spaced at 300-m intervals was superimposed over Grand Canyon National Park. Starting from digital elevation model data, GRASS geographic information system software running on a Sun workstation determined line-of-sight transects from each surface grid point to points on a complex system of aircraft flight paths. An acoustic propagation model based on algorithms of the U.S. Army Tank-Automotive Command’s ADRPM-7 software was then exercised on networked VAX and Butterfly computers to predict 1/3-octave-band aircraft noise levels produced by operation of a fleet of aircraft at each grid point. Bandwidth-adjusted signal-to-noise ratios were then calculated and returned to the Sun for construction of a new GRASS map layer of noticeability levels for the park. The new map can be color coded, draped over terrain contours, and rendered in perspective views for visualization purposes.
Loss factor height–width tradeoffs for viscoelastic materials.
Authors: Hartmann Bruce , Lee Gilbert F. , Lee John D.
Published: October 2005

It is observed empirically that the height of the dynamic mechanical shear loss factor peak in a viscoelastic material is inversely related to the width of the peak (as a function of frequency). There is a question of whether this observation represents a fundamental limitation of nature or whether some new material might be found with a peak that is both high and broad. Starting with a single relaxation time model and progressing to the Havriliak–Negami model, the tradeoffs between height and width are pointed out. These analytical models confirm that the empirical observations represent fundamental limitations that high peaks are narrow and low peaks are broad. The height of the peak is maximized as the material approaches a single relaxation time. The width is maximized by minimizing the ratio of the relaxed modulus to the unrelaxed modulus and by minimizing the asymmetry of the relaxation. For realistic values of the parameters, a loss factor peak height of 2 can have a width of no more than about 3 decades. Conversely, a relaxation with a width of 8 decades can have a loss factor peak height of no more than 0.5.
Viscoelasticity of crosslinked gels.
Authors: Adolf Douglas , Martin James E.
Published: October 2005

The damping characteristics of a crosslinked polymer are determined by its viscoelastic properties. Yet the loss mechanisms of networks have not been fully understood. It is shown that insight into network behavior can be gained from studies of how viscoelasticity evolves during the curing process. In addition, the peculiar viscoelasticity of the incipient gel (the polymer exactly at the gel point) is shown to offer unique damping characteristics. Experimental studies on an epoxy system show that the evolution of structure prior to the gel point follows the predictions of percolation and that the divergence of the bulk viscosity and the power law behavior of the dynamic shear moduli, G’∼G‘∼ωΔ, at the gel point follow the predictions of a dynamic scaling theory. A new superposition principle (time-cure superposition) holds for the linear viscoelastic responses at different extents of reaction in the critical regime both before and after the gel point. From the master curve beyond the gel point, the divergence of the inverse equilibrium modulus and the terminal relaxation time are shown to obey the theoretical predictions as well. In addition, an intriguing relationship exists between the relaxation time spectra of a network at the gel point and in the fully cured state. Measurements of the dynamic shear moduli of several epoxy and siloxane networks, with equilibrium moduli varying by four orders of magnitude, show G‘∼ωΩ at all extents of reaction past the gel point, where the network viscoelastic exponent Ω remains at the incipient gel value Δ. This surprising correspondence suggests that chemical networks possess some remnant of the fractal structure of the incipient gel. [Work supported by the U.S. DOE under Contract No. DE-AC-04-76DP00789.]
Specific property of sound field and computer simulation in a hemianechoic room.
Authors: Cai Biao , Wang Jiqing
Published: October 2005

This paper is based on the calculative method used in a former paper [J. Wang and B. Cai, J. Acoust. Soc. Am. 85, 1206–1212 (1989)]. With the help of a computer, the calculations of the sound field of a point source in a hemianechoic room show that the results are related to the height of the point source from the ground. Uncertainty of the interference field of direct sound and the first reflected sounds of pure tone is often greater than the requirements in ISO 3745. Authors computed the sound power level of the machine and the directivity factor of the point source (suppose the sound source has an omnidirectivity) with computer simulation. The systematic error of the sound field is greater than the requirements in ISO 3745. The results agree with the experiments. In accordance with simulated results, several kinds of ISO 3745 testing methods of the machine’s sound power level were discussed.
A first experimental comparison between the Schroeder’s backintegration method and a new method based on sound intensity for measuring reverberation time.
Authors: Stanzial Domenico , Carletti Eleonora
Published: October 2005

A new method based on the experimental evaluation of the energy transfer function of an enclosed space from sound intensity measurements has been experimentally compared with the well-known method of measuring reverberation time due to Schroeder [M. R. Schroeder, J. Acoust. Soc. Am. 37, 409–412 (1965)]. The measurements of active and reactive sound intensity were carried out by a B&K 2133 real time frequency analyzer and the reverberation time was computed using the built-in reverbBack user defined function over a pressure input multispectrum. As the transfer function is simply related to the reverberation time through an Eyring-like formula [D. Stanzial, J. Acoust. Soc. Am. Suppl. 1 88, S185 (1990)] the comparison gives a first experimental confirmation of the intensimetric approach to reverberation time evaluation.
Adaptation to transformed auditory localization cues in a hybrid real/virtual environment.
Authors: Shinn-Cunningham Barbara , Durlach Nat , Held Richard
Published: October 2005

The ability of humans to adapt to intermodal discrepancies is an important factor in the design of virtual environments. In the present study, azimuthal localization cues were altered (to magnify azimuthal differences near zero degrees) relative to real proprioceptive, visual, and vestibular cues. Subjects were alternately tested and trained in hybrid real/virtual environments where auditory stimuli were synthesized (using a PC, Convolvotron, and electromagnetic head tracker) to be at one of 13 discrete positions marked by real lights. Testing consisted of identifying the azimuth of virtual sound sources without relevant visual feedback or significant head motion. During training, a virtual sound from one of the positions was gated on with the light at that position, and subjects turned their heads to face the composite stimulus. Further identification experiments involving modified experimental procedures, as well as minimum-audible-angle discrimination experiments, were performed to help clarify the results. Preliminary findings on resolution, bias, and identification will be briefly overviewed. [Work supported by AFOSR, Grant 90-200.]
New standards at NIST based on digital techniques.
Authors: Bell Barry A.
Published: October 2005

The ability to accurately characterize the linearity, effective bits, step response, and other properties of analog-to-digital converters (ADCs), waveform recorders, and high-speed digitizers is critical in many measurement applications, including some electroacoustical ones. Test methods and techniques have been developed at NIST for evaluating the performance of high-resolution (up to 18 bits), high-accuracy (to 2 ppm) ADCs and digital-to-analog converters (DACs), as well as 4- to 12-bit high-speed (up to 500 Msamples/s) ADCs, typically used in sampling oscilloscopes and waveform recorders. Several of these NIST-developed methods have been incorporated in the recent IEEE Std. 1057 Trial Use Standard for Digitizing Waveform Recorders (July 1989). Precision DACs having small linearity errors can be used to provide reference electrical waveforms. By using a pair of such DACs, a 2-Hz to 50-kHz audio frequency phase angle calibration standard was developed at NIST that demonstrated the feasibility of generating dual sinusoidal waveforms with a relative phase difference resolution of about 2-mdeg and an accuracy of better than 10 mdeg. With careful attention to the fidelity of each step in the waveform, a dual-DAC approach for interleaving the small steps of the output waveform has formed the basis for an rms ac voltage standard with a frequency range from less than 1 Hz to 50 kHz, good to an overall rms uncertainty of 20 ppm.
Application of dynamic signal analyzers to selected electroacoustical measurements.
Authors: Nedzelnitsky Victor
Published: October 2005

Modern dynamic signal analyzers incorporating a variety of digital signal processing techniques and excitation source types are now sufficiently accurate to be used in many precision measurement situations for which much more labor-intensive methods previously have been necessary. Such use typically requires well-designed analyzers for which individual electrical components and system performance have been well characterized, and may require performing the same type of measurement several times with different choices of analyzer setup parameters, involving different tradeoffs among measurement uncertainty components. Validation of analyzer measurement results by comparison with results of established techniques is often necessary. These analyzers also can provide new ways to examine the individual influences of some measurement uncertainty components that have been notoriously difficult to quantify. Such components include those attributable to imperfections in anechoic chambers, and to unwanted scattering and diffraction effects of instrument structures. Specific examples to be considered include preliminary measurements of free-field phase characteristics at low frequencies in the large NIST anechoic chamber, and the effects of chamber imperfections and of slight standing waves between opposing microphone diaphragms during free-field calibration by reciprocity at essentially normal incidence in the small NIST anechoic chamber at frequencies up to 100 kHz.
Measuring hearing-aid performance with complex signals.
Authors: Kates James M.
Published: October 2005

New test procedures are being developed for hearing aids based on the response to complex test signals. The tests are motivated by the need to better describe the response of a hearing aid to a speechlike stimulus, since conventional measurements, such as pure-tone sweeps, are often inadequate in showing the behavior that will occur under conditions of actual use. The hearing-aid response typically includes both linear and nonlinear behavior, and both need to be described. Measurement techniques that will be discussed include the use of speech-shaped noise to measure frequency response, the use of bias tones to help determine the frequency response of a nonlinear device such as an automatic gain-control (AGC) circuit, the use of coherence to measure nonlinear distortion, and the use of recorded speech to measure the effects of adaptive signal-processing circuits.
Optical techniques applied to underwater surface scattering measurements.
Authors: Suiter H. R.
Published: October 2005

An acoustic lens was used as a collimator to measure periodic surface backscattering. Techniques to align and focus the acoustic lens are described. The performance is evaluated in the context of classical lens aberration theory and was checked experimentally. Using these methods, an experimenter is able to measure high-frequency backscattering in a constrictive tank environment without interference from target edges or concern that far-field conditions are being compromised. Limitations on the method are discussed. [Work supported by ONR.]
Acoustic related senior projects in Electrical Engineering at Utah State University.
Authors: Wheeler Paul A.
Published: October 2005

With the increase in acoustic research in the Electrical Engineering Department at Utah State University comes an increase in the number of acoustic related senior projects. This poster presentation will display several of the senior projects performed. These include such projects as: (1) sound system design software for matching sound system equipment to different performance environments; (2) analog audio synthesizer designs; (3) design of active crossover networks; and (4) audio amplifier/equalizer designs. Including acoustic-related senior projects in the electrical engineering curriculum allows students to apply the theory learned in classes to real-world experiences. It increases a student’s interest in the field of acoustics and prepares new engineers for employment in the audio industry.
A back-propagating ray technique for source localization.
Authors: Lu I-Tai , Voltz Peter
Published: October 2005

This paper reports on a novel source localization scheme in the time domain consisting of the following two steps: (1) use advanced signal processing techniques to sort out the ray arrivals, including their arrival direction and arrival times; and (2) back propagate these rays to their source region by a ray tracing algorithm. Some key advantages of this approach are: (1) Localization ambiguity is minimized by utilizing ray travel times as well as path convergence. (2) Ray tracing is a very efficient propagator in range-dependent environments. (3) The approach does not require full-wave matched-field processing and the required knowledge about the environment is minimized. (4) Phase ambiguity is eliminated by employing the group delay of arriving wave packets. (5) Ray chaos can be avoided simply by excluding chaotic rays from the backpropagating procedure. [Work supported by ONR.]
Acoustic parameters of nasal utterances in the hearing-impaired and normal-hearing speakers.
Authors: Chen Marilyn
Published: October 2005

One of the more prevalent abnormalities in the speech of the hearing-impaired that contributes to reduced intelligibility is inadvertent nasality. From acoustic analysis of the speech of hearing-impaired children, the presence of an extra pole-zero pair between the first and second formants and reduced first formant prominence characterize spectra of nasalized vowels. The difference between the amplitude of the first formant and the amplitude of the extra peak, A1–P1, was a measure that correlated with listener judgments of the degree of vowel nasalization. To obtain further validation of these parameters as measures of nasalization, A1 and the pole-zero spacing were systematically manipulated in synthetic utterances. Perceptual experiments with synthesized, isolated static vowels [i], [i], [o], and [u] showed that both parameters contributed to the perception of nasality. Another perceptual experiment with a number of synthesized words (of the form bVt) gave results indicating somewhat different relative importance of the two parameters. Correlation of A1–P1 with the average nasality perception judgments of ten listeners was found for both groups of stimuli. [Work supported in part by NSF and NIH.]
Resolution of part-word repetitions by stutterers: A temporal-spectral study.
Authors: Viswanath N. S. , Beardsley Amy Neel
Published: October 2005

Forty stuttering events on words beginning with /k/ and 17 with /g/ obtained from five adult male stutterers were examined from the pause before the first fragment to the eventual fluent production of the word. Spectrographic measurements made using CSL (Kay) included: duration of stuttering events, duration of pauses in stuttering events, duration of each fragment and its component parts if any (frication, aspiration, vowel), spectra of the release burst, and spectra of the following vowel at three predefined points on LPC signal. The findings were: 83% of events were composed of one or two fragments, fragments in /k/ plosive environments less frequently had vowels following release (18%) than fragments in /g/ environments (50%), pauses were short (77% under 200 ms) and may reflect articulatory closure duration rather than linguistic processes, and peak values of burst spectra did not progressively approximate those of fluent productions in two-fragment stuttering events. These and other results highlight the variable nature of articulatory processes in the resolution of part-word repetitions and provide constraints for modeling of stuttering events. [Work supported by a USPHS grant.]
Array processing with acoustic measurements at a single point in the ocean.
Authors: D’Spain G. L. , Hodgkiss W. S.
Published: October 2005

In order to obtain information on the spatial dependence of the underwater acoustic pressure field, the traditional approach has been to deploy a spatially distributed set of hydrophones. However, by use of a Taylor series expansion, the spatial dependence of the sound field can also be obtained from measurements at a single point in space. The purpose of this presentation is to discuss the adaptation of high-resolution array processing algorithms to such single-point measurements. Simulation results will be presented to illustrate the application of Capon’s minimum variance method, the linear prediction method, and the multiple signal classification scheme to measurements in a Taylor series expansion to first order and in an expansion to second order of the pressure field. In addition, a comparison will be made of the high-resolution methods to standard processing (equivalent to the Bartlett method) using actual ocean acoustic data from geophones and hydrophones. Extensions of these techniques to data collected by a receiving system that combines the use of spatially distributed elements with the Taylor series expansion approach will be discussed. [Work supported by ONR and ONT.]
Physics of standing waves in circular underexpanded jets.
Authors: Powell Alan
Published: October 2005

Although the quasiperiodic structure of ideal, slightly underexpanded, round supersonic jets is ‘‘well-known’’ mathematically (Prandtl, 1904; Pack, 1950), its physical nature has lacked some interpretation. The ‘‘diamond pattern’’ is overt in schlieren photographs, the oblique (conical) waves transversing the jet once in distance L= 2R√(M2−1) (M is the Mach number; R is the jet radius). The jet returns to the initial condition of uniform perturbed pressure with reversed sign and slightly reduced amplitude, after distance 2L, with the same sign at 4L, repeating at 4L intervals. The contrast with the two-dimensional case (corresponding distances L and 2L) is attributable to π/4 phase change at the axial focus: The initial step wave emerges as an impulselike wave that has little effect, perse, on the boundary shape when reflected there, becoming a step wave again after the next focus. However, the cell structure has period s=1.640R√(M2−1), corresponding to minima, very nearly, of the jet diameter. Contrasting to square jets, these minima are apparently not associated with any discrete event. [Work supported by the Texas Advanced Research Program.]
Observations on subsonic edge tones.
Authors: Powell Alan , Mascarenhas Noel
Published: October 2005

Discrete tones, sometimes multiple, occur for turbulent jets with exit Mach numbers (M) between 0.14 and 1.0 at nozzle-to-edge distances of 3 ≤ h/d ≤ 55 (d=1 mm), with an 8° wedge. The minimum h/d for discrete tones to occur increases linearly with Mach number for 0.14 ≤ M ≤ 1.0. Broadband tones occur at h/d below this minimum distance. As in the classical edge tone, the frequency of the strongest tone increases proportionally with exit velocity at a constant h/d and is approximately inversely proportional to h/d(f∼h/d−1.1) at a constant exit velocity. Schlieren photographs reveal the asymmetric nature of the jet instabilities and the out-of-phase sound waves on either side of the jet. Up to three continuous stages occur, with frequency jumps between them. Ucon (convection velocity of the jet instability) varies from 0.22 Uexit to 0.45 Uexit (Uexit=fully expanded jet exit velocity) for 0.22 ≤ M ≤ 1.0 and 0.12 ≤Mcon≤0.45, Mcon=Ucon/ca (ca=sound speed). The sound pressure level (SPL) peaks within 1≤h/d≤5 of the minimum h/d. [Work supported by the Texas Advanced Research Program.]
Eberhard Zwicker: The man behind the scientist.
Authors: Zwicker Ulrich Tilmann
Published: October 2005

In order to fully comprehend and appreciate the scientist Eberhard Zwicker, one has to look deeper and try to see the complete colorful personality that he was. Apart from his involvement in science and engineering, he was a dedicated family man, a loving and challenging husband, a wonderful father. He was an avid and very successful gardener and hobby farmer, an accomplished craftsman with a particular passion for working with wood. He was very partial to extended hikes through the Bavarian and Austrian Alps, as well as to taking a thorough look into the heavens as a hobby astronomer, and incessantly dedicated in his boundless love, respect, and interest for all of creation. It was this interaction with nature, and with beings and things in their natural environment, that led him to a particular, generalistic, almost ecological approach in his area of science. Not only was he interested in isolated academic phenomena, but he wanted to know about the general relations with other phenomena involved. Although he was devoted to basic research, which he thought of as irreplaceable, he needed to see practical applications of this research, in particular applications directly beneficial to humankind. Whereas he wanted to see and learn about many things, he also found it most important to see the many sides of those things, the connections, the overall pattern. This wholesome approach, the joy of which he also desired to share via his teaching, is the basis for Eberhard Zwicker’s work, and taking on this approach will give the student of his work much improved insight.
Monitoring microdrilling operations with an intelligent diagnostic system.
Authors: Tansel I. N.
Published: October 2005

Microdrills have a short and unpredictable tool life. It is also very difficult to monitor the condition of the microdrill tip with the unaided eye. In this paper, a new approach is proposed to detect failure of the microdrill with a 0.39-mm diameter. The proposed method measures the thrust force by using a dynamometer and tool displacements with a laser vibrometer. The characteristic features of the data are obtained by modeling the profile of the cutting forces measured by the dynamometer and large variations of the laser vibrometer signals. The encoded data are interpreted to estimate tool condition by using the adaptive resonance theory (ART2)-based neural networks. The proposed approach was tested by using microdrills with a 0.39-mm diameter. After testing, less than 10% error was observed during identification of normal and poor operation conditions (just before breakage, breakage, and drilling with a broken tool) with proper vigilance values.
Application of wavelet transforms for characterizing ultrasonic signals.
Authors: Udpa Satish S.
Published: October 2005

Ultrasonic methods of nondestructive testing (NDT) are used extensively in many applications ranging from detection of cracks in nuclear power plants to monitoring of wear in jet engines. A crucial step in NDT is the solution to the inverse problem, where the ultrasonic reflections are analyzed for extracting information concerning the shape, size, and location of defects. A multiresolution signal analysis technique, based on the wavelet transform of the ultrasonic signals, is described. The basis function or wavelets used in the analysis are generated from a single prototype by dilation/contraction and shifts. This provides the multiscale analysis required in the processing of nonstationary signals. The wavelet transform representation of the ultrasonic waveform is then classified employing a pattern recognition algorithm for characterizing the underlying defect. The effectiveness of the method was verified using a set of experimental signals obtained during inspection of power plant tubing. [Work reported is supported by EPRI under Contract RP 3148-06.]
A novel approach to the solution of inverse problems.
Authors: Udpa Lalita
Published: October 2005

Solution to inverse problems is of interest in many fields of science and engineering. As an example, in the field of nondestructive testing, such solutions offer a tool for automatic defect characterization in materials from transducer measurements. Inverse problems are frequently described by Fredholm integral equations of the form, ∫abk(x,y)z(y)dy=u(x) (c≤x≤d), where u(x) represents the measured data, z(y) represents the source function or system parameters, and k(x,y) represents the kernel of the transformation. The objective is then to solve for the source function from known measurements. This problem is inherently sensitive to the system parameters z, to the shape of the kernel k, and to the accuracy of the measurements u. The paper presents a novel strategy for solving Fredholm integral equations using Hopfield type neural networks. The major advantage of this method is the stability of the solution that comes from the high degree of parallelism and interconnectivity encountered in the neural networks. The algorithm consists of formulating the problem in the form of an error minimization equation. By comparing the error function to the energy function of the Hopfield neural network, the circuit parameters of the network are estimated. Simulation results demonstrating the effectiveness of the approach for obtaining the solution to integral equations are presented.
Parametric ultrasound heating: Theory and modeling.
Authors: Rolt Kenneth D. , Schmidt Henrik
Published: October 2005

Recently, the nonlinear effects of focused ultrasound have been studied to evaluate increased absorption and enhanced heating. These features must be established for safety’s sake in certain ultrasound imaging and hyperthermia applications. One version of nonlinear acoustics in ultrasound that has not been investigated at length is the parametric application, where separate transducers (or arrays) have coincident, simultaneous foci. This forestalls the mutual nonlinear interaction in the near fields and establishes it only in the confocal region; this is worthwhile because this region is where the heating is supposed to occur. Parametric sonars have been known since the 1960s in the transducer, ocean, and nonlinear acoustics fields but have not been ‘‘reinvented’’ in ultrasound. This paper will cast parametric sound in terms of intersecting focused ultrasound, and will show the theory and the results of a brute-force finite difference model which incorporates linear and nonlinear propagation, and heat transfer.
A noninvasive method for measuring muscle filament stiffness using a calibrated glass microneedle.
Authors: Oksanen Markku , Warshaw David M. , Wu Junru
Published: October 2005

Muscle is believed to contract by the relative sliding of actin and myosin filaments as ATP is hydrolyzed. In order to measure the force generated by myosin during actin filament sliding an invitro motility assay has been developed [A. Ishijima etal., Nature 352, 301–306 (1991)] where one end of a single actin filament is attached to a thin glass microneedle and the other end is brought into contact with a myosin-coated coverslip in the presence of ATP. As the myosin tugs on the actin filament, bending of the microneedle occurs and allows the force to be calculated provided its stiffness is known. Recently, the stiffness of a microneedle as small as 0.1 pN/nm was determined in this lab by measuring the Brownian motion of the microneedle in air using a fiber-optic Michelson interferometer and the equipartition theorem. The results of this noninvasive method will be compared with those resulting from other invasive methods. [Work supported by NIH HL45161 and BF Goodrich Simmonds Precision Aircraft System.]
A quasilinear theory of flexible-walled cavity resonators.
Authors: Mast T. Douglas
Published: October 2005

A flexible-walled cavity can be excited into a Helmholtz-like resonance by shearing flow of an incompressible fluid. The mass element is associated with the fluid flowing through the cavity opening; the compliance element is due to the cavity walls. The excitation mechanism involves feedback between the pressure oscillations in the cavity and the unsteady flow in the opening. In this paper, an analytical quasilinear theory of this system is presented. The linear instability of the shear layer, vortex shedding from the upstream edge of the cavity, and structural nonlinearity of the cavity walls are considered. Application is made to the resonance of aneurysms in the bloodstream, incorporating aneurysms’ measured elastic properties and other characteristics of the cardiovascular system. [Work supported by the William E. Leonhard Endowment to the Penn State Univ.]
An impedance model for actively controlled finite waveguides.
Authors: Muehleisen Ralph T. , Swanson David C.
Published: October 2005

An analytic impedance model of a finite waveguide with primary and secondary sources is developed utilizing multiple two-port networks. The acoustic source impedance and the waveguide radiation impedance are included in this model. In addition, a control system block diagram is developed for stability analysis of the physical system. Both the analytic model and the control system diagram are used to derive a closed form solution for an optimal cancellation filter for both feedforward and feedback control systems. The effect of radiation and source impedances on the system resonances and both optimal and suboptimal filters are discussed. Suboptimal control filters are important because all adaptive noise cancellation systems must progress through a suboptimal solution before reaching the least-squared error. During convergence additional system resonances can occur, prolonging the convergence time of the adaptive algorithm. Transfer functions in a waveguide are measured and used to design fixed optimal and suboptimal pole-zero feedforward and feedback filters. The steady-state and transient performance of the filters are compared.
Nonlinear effects in periodic and disordered wave media.
Authors: Maynard J. D. , McKenna M. J.
Published: October 2005

While there has been considerable theoretical and experimental research with quantum and classical wave propagation in linear systems, involving effects of Anderson localization, etc., there has been considerably less research with nonlinear media. A fundamental question is whether or not nonlinear effects destroy Anderson localization. There are about eight theoretical papers that treat this question, and half predict that localization is destroyed, and half predict that it is not. An experiment involving nonlinear acoustic wave propagation in a disordered potential field has been performed, and an unambiguous result has been obtained. Also, measurements of nonlinear wave propagation in a periodic field have been made, and in addition to the expected effects of canting and hysteresis, other novel effects are observed. [Work supported by NSF DMR 9000549 and ONR.]
Spatial evolution of unstable disturbances in a Stokes boundary layer.
Authors: Thompson Charles , Mehta Vineet
Published: October 2005

A model describing the process of transition to chaotic fluid motion in an acoustical field driven in time is presented. It is shown that the unstable disturbances occur locally in space. The region of space where instability ensues is given in terms of a local amplitude conditioned on the basic flow. Subcritical behavior of the energy amplitude is shown to occur near the turning point. The chaotic evolution of disturbances in the streamwise direction is studied. Consideration is also given to the interaction of spanwise Fourier modes. Results for the spatial and temporal structure of the disturbance are given. The nature of the chaotic behavior is described in terms of physical parameters. [Work supported by DOE.]
Pressure fluctuations induced by the nonlinear interaction of ocean surface waves.
Authors: Cox Charles S. , Jacobs David C.
Published: October 2005

Pressure fluctuations caused by the nonlinear interaction of ocean surface waves are, in second order, related to sums and differences of the phases of pairs of surface waves. Terms with frequencies above those of the surface waves result from the sum type. When the sea waves include nearly oppositely directed components these pressure fluctuations arrive on the deep seafloor as acoustic waves (horizontal wave numbers k≤ω/c), at double the frequency of the generating waves, and can couple with Rayleigh waves in the ocean crust [Longuet-Higgins, Philos. Trans. R. Soc. London Ser. A 243, 1–35 (1950)]. At depths between the sea surface and c/ω the horizontal wave-number distribution is broader. Since each wave-number component decreases exponentially with depth, the integrated pressure intensity increases toward the sea surface, approximately inversely as depth squared. This behavior is to be contrasted with pressure fluctuations induced in the sea by microseismic Rayleigh waves from distant sources. Here, the sea surface acts as a pressure release and the intensity of pressure fluctuations diminishes toward the sea surface. Inferences on the magnitude of local generation of microseisms have been made by measurement of pressure spectra over a range of depths. Local generation was dominant when a storm swell was incident on, and reflected by, a steep, rocky shore. Generation was generally weaker when storm waves were incident on a gently sloping sandy shore. [Work supported by ONR.]
Relationship of microseisms and ocean wave climatology.
Authors: Webb Spahr C.
Published: October 2005

Ocean waves have long been recognized as the source of sound in the ocean in the frequency band from 0.05 to 5 Hz. Ocean surface waves from nearly opposing directions interact to excite an elastic wave of much greater phase velocity. Necessarily, the climatology of microseisms is directly related to the climatology of ocean waves. However, the microseism energy propagates as free modes (Rayleigh waves) of the elastic wave waveguide set up by the seafloor and the steep gradient in elastic wave velocities below the seafloor. The propagation of elastic waves within the waveguide is frequency and model dependent. The modes propagate great distances which act to average the ocean wave climate over a large area. The size of this area is frequency dependent and is determined by the e-folding distance associated with attenuation of Rayleigh waves across the ocean. Data from arrays of seismic and pressure instruments in both the Atlantic and the Pacific will be compared to modeling results. The goal is to predict microseism climatology from ocean wave climatology. [Work supported by ONR.]