bluuebunny/crossref_metadata_2025 huggingface dataset:
Internal combustion engine noise analysis and production using a novel multipulse excited time series modeling technique.
Authors: Amman Scott A. , Das Manohar
Published: October 2005

Automobile manufacturers have learned that customers have well-defined notions as to what an automobile engine should sound like for the various vehicle segments (luxury, sportscar, economy, etc.). Therefore, it is advantageous to model and synthesize various types of engine sounds for customer evaluation. Much work has been done in the area of speech modeling and synthesis based on physical assumptions of human speech production. The intent of this paper is twofold. First discussed are the similarities and differences between speech and engine noise modeling and synthesis problems. Second, application of techniques learned for speech synthesis to that of automotive noise production is demonstrated. Early models of speech production used periodic pulse excitation in a linear predictive coding (LPC) framework. This technique is used to synthesize engine noise. It is then compared to that of a new suboptimal multipulse method proposed by the authors. It is hoped that this paper will pave the path for a better understanding of the relationship between the two systems so that much of the work performed in speech analysis and production can be applied to the analysis and synthesis of automotive internal combustion engine sounds.
Active control of sound radiated from an open-ended duct using sound intensity.
Authors: Kang S.-W. , Kim Y.-H.
Published: October 2005

Sound intensity based active control for the reduction of sound radiated out of the duct exit is studied experimentally as well as theoretically. The active intensity control strategy is derived based on the relation of the exterior sound field out of the duct exit and interior sound field of the duct. One of the features of the active intensity control strategy is that the control performance can be maintained regardless of the sensor location, compared with the conventional local sound-pressure control methods at either interior downstream or exterior field position. Simple numerical examples are demonstrated to compare the acoustic characteristics of the active intensity control scheme with the other control strategies. For a more practical comparison with the conventional sound-pressure control strategy, an experiment, based on a time-domain adaptive filtering with an intensity sensor filtered-x LMP (least-mean-product) algorithm, is performed. From the experimental results, it is shown that the exterior sound field is much more observable by sensing the active intensity than by sensing the sound pressure. It is also demonstrated that the active intensity control performances are superior to the sound-pressure control ones.
Acoustics of American reed organs.
Authors: Cottingham James P.
Published: October 2005

The instrument that has come to be called the ‘‘American’’ reed organ shares with its relatives the accordion, concertina, and harmonica the use of free reeds, but differs from its reed organ cousin, the harmonium, in the use of a vacuum exhauster rather than a pressure bellows to drive the reed vibration. The acoustical properties of the instrument are summarized along with the results of some recent experimental studies. These investigations have explored variations in properties of both the reed vibration and the resulting sound as a function of pressure. Effects of airflow rate, and reed cell dimensions have also been studied. Both live and recorded musical examples are provided.
Techniques for defining clarinet reed quality via computerized light transmission analysis.
Authors: Payne James M.
Published: October 2005

A basic and well-recognized problem in clarinet and saxophone (single-reed) performance is maintaining consistency in high-quality generation and manipulation of tones. This generative process, involving reed, mouthpiece, and the player’s embouchure, produces the instrumental ‘‘voice’’ of the performer and is fundamental to artistic communication. Playing skill and a well-designed mouthpiece cannot overcome the liability of poorly vibrating arundo donax, the natural material used in reed manufacture. Inconsis- tency in quality leads professionals to spend as much as $2500 per year on reeds and to perform on relatively few of those purchased. Highly skilled performers agree that the identification of fine performance reeds cannot be accomplished by visual inspection. Trial by playing is the customary means of determining quality and one must purchase reeds before these trials can be made. Even these carefully selected reeds degrade and become unplayable after approximately 10–20 h of performance. Computerized light transmission analysis (TRACOR) has proven to be of value in determining performance characteristics of clarinet reeds.
Handmaking clarinet reeds: New tools accelerate the process.
Authors: Anderson Timothy
Published: October 2005

The vast majority of clarinetists worldwide (professionals, students, and amateurs) perform on commercially manufactured reeds. However, a number of performers, including many professionals, maintain that commercial reeds can never match the high quality of reeds handmade from tube by the performer. For clarinetists this time-consuming practice was once standard procedure and still is with double-reed performers (oboe and bassoon). This reed-maker supports the position that the best reeds are produced by the performer. Recently, tools have become available that accelerate the process of making one’s own clarinet reeds. Using some of these tools a reed will be fashioned from arundo donax tube during the presentation and its sound will be demonstrated.
I Clarinetti Virtuosi: Chamber ensemble of the Ohio State University.
Authors: Pyne James , Stimpert Elisabeth
Published: October 2005

The clarinet ensemble continues to emerge as a capable vehicle for art performance. It can, more than any other family of wind or brass instruments, closely reproduce the range, flexibility, and homogeneity of the string ensemble. These characteristics will be briefly discussed and demonstrated using the individual instruments of the clarinet family from contra-bass to piccolo clarinet including basset horn, a favorite instrument of Mozart. I Clarinetti Virtuosi are clarinet performance majors at The Ohio State University, graduate students and undergraduate seniors. They will perform a variety of works that display the wide range of musical and virtuosic capability of the ensemble.
International activities in the use, standardization, and regulation of hearing protection.
Authors: Berger Elliott H.
Published: October 2005

Prevention of hearing loss due to noise exposure often means one thing—the consistent and correct use of hearing protection. Since noise-induced hearing loss has been identified as one of the leading occupational diseases and injuries, there are millions of workers worldwide in need of, or already currently wearing, hearing protection. How well they utilize the products they are provided, as well as the extent and quality of government enforcement activities, is influenced, in part, by the standards and regulations that govern the testing and labeling of such products. As such, this paper will summarize current international standards on testing, labeling, and performance of hearing protectors as well as reviewing field performance and anecdotal observations pertaining to actual use. Attention will focus on ISO, CEN (Community on European Normalization), and Australian activities, as well as on a new draft ANSI standard (S12.6-199X) pertaining to the laboratory measurement of the real-ear attenuation of hearing protectors, and on the efforts of the National Hearing Conservation Association Task Force on hearing protector effectiveness to craft recommendations for the labeling of hearing protection devices sold in the U.S.
Hearing hazard from the noise of air bag deployment.
Authors: Price G. Richard , Rouhana Stephen W. , Kalb Joel T.
Published: October 2005

Recent studies have questioned the adequacy of current noise standards for intense impulses, especially those with large low-frequency content, a category which includes air bag deployments. Unfortunately, almost no tests have been done with real ears and air bag impulses. Such data are also needed for development of theory and validation of our hearing loss model [G. R. Price and J. T. Kalb, J. Acoust. Soc. Am. 90, 219–227 (1991)]. Therefore, 32 anesthetized cats positioned at the driver and passenger locations in a pickup truck were exposed in pairs to one air bag deployment (electrically initiated). Hearing was tested at 1, 2, 4, 8, and 16 kHz by evoked-response audiometry before exposure, immediately after, 1 month, and 6 months later. Exposure conditions included doors open, compartment closed, and closed compartment sealed with tape; seven exposures to passenger bag only and nine to driver and passenger bags. Pressures at inboard ears ranged from 167- to 173-dB peak and B durations from approximately 50–150 ms, with unweighted energies as high as 4000 J/ m2 (or 8 h LEQA=95.5 dB). All ears showed significant hearing losses immediately, averaging 60-dB threshold shift at 4.0 kHz which resolved to an average PTS of 37 dB.
Modeling auditory hazard from impulses with large low-frequency components.
Authors: Price G. Richard , Kalb Joel T.
Published: October 2005

In order to validate the model of hearing hazard from intense sounds [G. R. Price and J. T. Kalb, J. Acoust. Soc. Am. 90, 219–227 (1991)], hearing loss data have been sought from impulse noise exposures which extend the range of exposures already examined with the model. One such impulse (reported in Price et al. at this meeting) is that produced by air bag deployment, which contains a mixture of high-frequency energy often superimposed on a low-frequency pedestal, reaching peak pressures near 170 dB and with B durations of 150 ms. The model’s predictions for firearms impulses in the same intensity region correlated well with actual threshold shifts [Price et al., J. Acoust. Soc. Am. 97, 3343 (1995)]; however, the hazards calculated with the air bag impulses were generally too large. Examination of the data suggested that middle-ear muscle activity needs to be accounted for, that corrections for the angle of incidence of the wavefront are needed, and that the existing model included too much damping for large displacements of the middle ear.
Acoustic nonlinearity and radiation pressure in ultrasonic bioeffects.
Authors: Rudenko Oleg V. , Sarvazyan Armen P.
Published: October 2005

Most of the biomedical applications of ultrasound are based on the use of focused ultrasound with a high concentration of energy in the focal region and, respectively, with significant contribution of nonlinear phenomena in ultrasonic bioeffects. The main objective of the current paper is to provide a clear understanding of basic phenomena in nonlinear acoustic fields of focused ultrasound, and to derive simplified equations that would enable physicists and engineers to optimize parameters of biomedical devices for particular applications. Special attention is paid to the contribution of acoustic nonlinearity to the second-order quantities, such as radiation pressure and temperature rise in ultrasonic fields in tissues. Based on asymptotic methods recently developed in nonlinear acoustics, analytical solutions of the equations for the radiation force induced in a dissipative medium are considered. The relationships between parameters of acoustic field and characteristics of biological tissues are quantitatively analyzed. Possible roles of nonlinear acoustic phenomena and ultrasound radiation force in various features of interaction of ultrasonic waves with biological media are discussed.
Effects of ultrasound on binding of tissue plasminogen activator to fibrin.
Authors: Sidiqi Farhan , Braaten Julie V. , Francis Charles W.
Published: October 2005

To investigate the mechanism of ultrasound-enhanced fibrinolysis, the effect of ultrasound on binding of tissue plasminogen activator (t–PA) to fibrin was examined because t–PA–fibrin interactions are important in determining the rate of fibrinolysis. A novel system to quantitate t–PA–fibrin interactions was developed in which radiolabeled, active site blocked t–PA flowed through a fibrin gel at constant rate and temperature, and specific binding was determined by monitoring incorporation of radiolabel. Exposure to 1-MHz ultrasound to 2 W cm2 resulted in no significant change in the kD of t–PA binding to either cross-linked or noncross-linked fibrin. Ultrasound, however, significantly increased the Bmax, and the molar binding ratio increased in the presence of ultrasound from 1.85 (mol t–PA/mol fibrin) to 2.54 (mol t–PA/mol fibrin) for noncross-linked fibrin and from 1.19 (mol t–PA/mol fibrin) to 1.43 (mol t–PA/mol fibrin) for cross-linked fibrin. Ultrasound resulted in no significant changes in binding of t–PA to fibrin monomer in the same system. It is concluded that exposure to ultrasound increases binding of t–PA to polymerized fibrin, possibly by exposing additional binding sites in the polymer which are inaccessible in the absence of ultrasound.
Ultrasound increases fluid permeation in fibrin gels and reversibly disaggregates large fibers.
Authors: Braaten Julie V. , Sidiqi Farhan , Carstensen Edwin L. , Francis Charles W.
Published: October 2005

Since ultrasound accelerates fibrinolysis and since transport of enzymes into clots is an important determinant of the rate of fibrinolysis, the effect of ultrasound on fluid permeation through fibrin gels in vitro was examined. Gels of purified fibrin were prepared in plastic tubes, and the rate of pressure-mediated fluid permeation was measured. Exposure to 1 MHz ultrasound at 2 W cm−2 and duty cycle of 5 ms on, 5 ms off resulted in a significant (p=0.005) increase in flow through the gel of 29.0±4.2% (mean±SEM). The increase in flow was intensity dependent and not due to heating or fragmentation but was reduced by degassing, suggesting a role for cavitation. Scanning electron microscopy was used to examine potential effects of ultrasound on fibrin structure, which is the primary determinant of flow resistance. Fibrin gels were fixed and prepared for microscopy before, during, and after exposure to 1-MHz ultrasound at intensities from 4 to 8 W cm−2. Ultrasound caused a significant (p<0.000001) increase in fiber density and decrease in fiber diameter which was reversible when ultrasound was switched off. These results indicate that ultrasound exposure can induce a significant reversible change in fibrin structure and fluid permeation that could contribute to the ultrasonic enhancement of fibrinolysis.
Determination of velocity and attenuation of shear waves using broadband pulse technique.
Authors: Wu Junru
Published: October 2005

The ultrasonic spectroscopy (broadband pulse) technique was applied to simultaneously measure phase velocity and attenuation coefficient of shear waves in a solid in the megahertz frequencies. This technique is an extension of the ultrasonic spectroscopy technique currently used in determining dispersion of longitudinal waves. Sources of error in measurements including diffraction loss and nonlinear distortion will be discussed. [Work supported by Hewlett–Packard Co.]
Quality characterization of an electrical solder point.
Authors: Ezzaïdi Mohamed , Moudden Ali , Decultot Dominique , Maze Gérard
Published: October 2005

The Lamb waves are guided modes which propagate in a plane layer. The Ai antisymmetric and Si symmetric (i=1,2,...) Lamb waves have an infinite phase velocity in low frequencies (cutoff frequencies), and the phase velocity limit, in high frequencies, is equal to the velocity of the shear wave in the isotropic solid material. The thickness resonance of an elastic plate normally insonified by an ultrasonic plane wave is related to the cutoff frequencies. From these resonance frequencies, the plate thickness can be easily deduced. In this presentation, a focused ultrasonic transducer with a large bandpass to characterize an electrical solder point between two steel sheets is used. This solder is abundantly used to manufacture cars. An experimental ultrasonic pulse method (pulse-MIR) allows us to plot acoustic spectra. The solder is placed in the focal spot of the beam. The transducer can be moved in a parallel direction to the surface of the sheet steel. Many time signals are recorded along a diametrical line with a small step. For each time signal a spectrum is computed. The results are shown with a graphical software. The false color images allow us to evaluate the solder quality.
Experimental study of Lamb waves having a negative energy velocity in a thin plane plate immersed in liquid.
Authors: Eudeline Yannick , Duflo Hugues , Duclos Jean
Published: October 2005

Lamb waves having a negative energy velocity have been theoretically predicted; they are called negative waves for short. This word is used if the phase velocity is in the opposite direction to the energy velocity. When a plate is immersed in a liquid, this phenomenon still occurs. These waves become leaky as their energy is being reradiated into the liquid. Any negative wave has the same limit frequency as a Lamb wave, and the same label with a prime (′) sign (i.e., S2−S2′). Some common solids were studied: duralumin, stainless steel, brass, and glass. The negative waves were generated (as Lamb waves are) by a tone burst bulk wave and observed after propagation over the plate by translating one of the transducers in order to receive the negative waves. The existence of several negative waves was proved; especially the A3′ glass wave which can be observed quite easily. When the frequency × thickness product decreases, several properties were observed in accordance with the theory: (i) the absolute value of energy velocity increased and reached a maximum near the cutoff frequency, (ii) the attenuation increased. A time-frequency study follows which enables the calculation of the energy velocity.
Scattering of an obliquely incident wave by a transversely isotropic cylinder.
Authors: Honarvar Farhang , Sinclair Anthony N.
Published: October 2005

While the scattering of a plane acoustic wave from a solid isotropic cylinder has been extensively studied for the past several decades, very little has been investigated regarding scattering from anisotropic cylinders. In this paper, the mathematical formulation for the scattering of a plane acoustic wave incident at an arbitrary angle α on an infinite transversely isotropic cylinder is developed. The normal mode solution is based on decoupling of the SH wave from the P and the SV waves. The resulting partial differential equations have closed-form solutions and the scattered pressure field can be calculated at any point outside the cylinder. The solution degenerates to the well-known simple model for isotropic cylinders in the case of very weak anisotropy. The validity of the mathematical model is verified first by applying it to the familiar case of an isotropic aluminum cylinder. The model is then applied to a transversely isotropic cylinder generated by perturbing various elastic constants of the isotropic aluminum cylinder. The manner in which these perturbations affect each of the Rayleigh, Whispering Gallery, and longitudinally guided wave modes is shown to be consistent with elasticity theory and modal shapes of these resonances. Some experimental results are also presented.
Diffuse field decay curvature for material characterization.
Authors: Burkhardt John
Published: October 2005

A new quantitative technique is proposed for determining both the concentration and spatial extent of viscous dissipation in dynamic systems. When dissipation is distributed unevenly within a system, nonexponential response decays can result within certain frequency ranges. Unlike typical exponential decays that carry volume averaged information about the strength of dissipation, nonexponential decays carry information about both the strength and distribution of dissipation in the system. Two parameters describe the nonexponential decay process and can be directly related to the strength and spatial extent of the dissipation. It is proposed that fitting observed nonexponential decays to the predicted model may provide a method for the nondestructive determination of both the extent and severity of dissipation causing defects in materials. The presented work concentrates on acoustic systems and provides a test of the proposed concept. Theoretical predictions are presented and compared with numerical experiments to determine the effectiveness of the proposed approach.
Effects of modulator phase for comodulation masking release and modulation detection interference tasks.
Authors: Richards Virginia M. , Buss Emily
Published: October 2005

Three experiments evaluated the joint effects of target/masker frequency separation and modulator phase on modulation detection interference (MDI) and comodulation masking release (CMR). The tasks were (a) detection of the sinusoidal amplitude modulation (SAM) of a tone, (b) discrimination of changes in modulation depth of a SAM tone, and (c) detection of a tone added to a narrow band of noise. Thresholds were obtained for either the target alone, or the target presented with two maskers. The target frequency was 1500 Hz. The maskers were above and below the target at frequency separations ranging from 1/3 to 2 oct. The maskers were either tones or maskers appropriate for the task (SAM tones or noise). For nontonal maskers, the masker envelopes were either coherent or random with respect to the envelope at the target frequency. Substantial individual differences were obtained. When the tonal maskers led to only modest masking, effects of target/masker envelope randomization tended to occur for frequency separations less than an octave. The results suggest a dependence on interactions within a single, relatively broadband analyzer. [Work supported by NIH and Univ. Penn. Research Foundation.]
Altered temporal and spectral patterns produced by cochlear implants: Implications for psychophysics and speech recognition.
Authors: Shannon Robert V. , Zeng Fan-Gang , Wygonski John
Published: October 2005

Cochlear implants produce highly unnatural temporal and spatial (tonotopic) patterns of neural activation in the auditory system, and the patterns may vary considerably from patient to patient. In spite of these abnormal patterns, psychophysical measures of temporal processing are relatively normal in patients with cochlear implants and brainstem implants. A high level of speech recognition is possible with only three bands of modulated noise [Shannon et al., Science 270, 303–304 (1995)]. What parameters of the peripheral activity pattern are critical for the transmission of speech pattern information? Four-band speech processors were constructed which reduced the spectral information in speech to four, amplitude-modulated noise bands. Variations were constructed that altered the location, spectral extent, overlap, and amplitude compression of the four noise bands relative to the original speech. Manipulations of the band overlap and the cut-off frequencies dividing the bands had relatively little effect on speech recognition. However, amplitude compression and the tonotopic misalignment of noise bands with the speech cues resulted in severe reductions in speech recognition. These experiments and the performance levels of present cochlear implant patients demonstrate that normal temporal information and considerable speech information can be received with relatively poor tonotopic selectivity. [Work supported by NIDCD.]
The index of interaural correlation: Accounting for binaural detection across center frequency.
Authors: Bernstein Leslie R.
Published: October 2005

Investigations in this laboratory demonstrated that the normalized correlation accounted well for listeners’ performance in binaural tasks utilizing high-frequency stimuli for which the envelopes convey the interaural information. This outcome means that the non-zero mean of the envelopes must be included in the computation of the correlation. Due to peripheral auditory processing analogous to rectification and low-pass filtering, the ‘‘internal’’ representations of auditory stimuli have nonzero means regardless of their frequency. This study evaluated whether the normalized correlation computed subsequent to rectification and low-pass filtering could account for detection data at low and intermediate, as well as high frequencies. In a four-interval, two-alternative task, listeners detected which interval contained a tone (between 500 Hz and 2 kHz) added antiphasically to diotic, 100-Hz-wide, noise (NoSπ). ‘‘Nonsignal’’ intervals contained the tone added homophasically (NoSo). Performance was measured for S/Ns between −30 and +30 dB. For all S/Ns, overall level was 70 dB SPL. Normalized correlation (unlike the correlation coefficient) described performance well, as a function of S/N and center frequency. The parameters of the rectifier and low-pass filter required to describe the data will be discussed. [Supported by research Grant No. 5R01DC0210302, National Institute on Deafness and Other Communication Disorders, NIH.]
Glottal geometry and phonation threshold pressure in a vocal fold physical model.
Authors: Chan Roger W. , Titze Ingo R. , Titze Michael R.
Published: October 2005

The effect of convergent and divergent prephonatory glottal geometries on phonation threshold pressure was investigated using a previously reported physical model of the vocal fold mucosa [Titze et al., J. Acoust. Soc. Am. 97, 3080–3084 (1995)]. Lowest offset phonation threshold pressure in the range of 0.07 to 0.23 kPa was obtained for a rectangular or a near-rectangular glottis (with convergent or divergent angle ≤3°) across different glottal half-widths between 2.0 and 6.0 mm. Phonation threshold pressure for more convergent or divergent glottal geometries was consistently higher. This finding only partially agrees with previous analytical work which predicts a lowest phonation threshold pressure for a divergent glottis [I. R. Titze, J. Acoust. Soc. Am. 83, 1536–1552 (1988) and J. C. Lucero, J. Acoust. Soc. Am. 98, 779–784 (1995)]. The discrepancy between theory and data is likely to be associated with flow separation from a divergent glottis. [Work supported by NIH.]
Effects of driving pressure and recurrent laryngeal nerve stimulation on glottic vibration in an in vivo constant pressure model of phonation.
Authors: Verneuil Andrew , Kreiman Jody , Kevorkian Kevin , Ye Ming , Gerratt Bruce R. , Berke Gerald S.
Published: October 2005

Most in vivo studies of phonation have used constant flow models. However, because the lung–thorax system is better viewed as a constant pressure source, a constant pressure in vivo canine model was developed. In this model, driving pressure and recurrent laryngeal nerve (RLN) stimulation are independent variables, and subglottic pressure (Psub; measured immediately under the glottis), air flow, fundamental frequency (F0), and glottic area are dependent variables. In three dogs, Psub and air flow were measured with constant RLN stimulation and varying driving pressure, and in another condition with constant driving pressure and varying RLN stimulation. Videostroboscopic measures on four animals assessed glottic areas with constant RLN stimulation and varying driving pressure. With constant RLN stimulation, increasing driving pressure had no effect on glottic area, while F0, and air flow increased significantly. Changes in Psub were small in comparison to changes in driving pressure. With constant driving pressure, increasing RLN stimulation increased Psub and F0 and decreased air flow. These findings suggest that Psub during phonation is primarily dependent on RLN activity and associated laryngeal muscular contraction, but not on lung driving pressure. [Work supported by VA Merit Review funds.]
Annealing in a genetic algorithm for task-dynamic recovery from speech acoustics.
Authors: McGowan Richard S.
Published: October 2005

Genetic algorithms, as they have been used for recovery of task-dynamic parameters [R. S. McGowan, ‘‘Recovering articulatory movement from formant frequency trajectories using task dynamics and a genetic algorithm,’’ Speech Commun. 14, 19–49 (1994)], can take some time to converge, which means that expensive function evaluations are necessary to obtain optimum solutions. In previous experiments, each task dynamic- target was always given 6 bits in the chromosome. In the tests reported here, the number of bits in the chromosome string representing target positions was made a function of generation, with the range of the targets remaining constant to see whether an annealing process with ever increasing resolution would speed convergence to a good fitness maximum. Results show that annealing can be helpful in speeding convergence, although not all annealing schedules help. This procedure is related to simulated annealing where the temperature of the search is decreased as the search progresses. It is also related to codebook look-up used in the inverse problem, where vocal tract shapes that produce speech close to that of the data are accessed to initialize a subsequent optimization procedure. [Work supported by NIH Grant DC-01247 to Haskins Laboratories.]
Labial kinematics in stop consonant production.
Authors: Lofqvist Anders , Gracco Vincent L.
Published: October 2005

This study examines kinematic patterns of upper and lower lip movements in bilabial stop production with particular emphasis on events before and during the oral closure. Lip movements were recorded using a magnetometer system. Five subjects participated and produced 50 tokens of the sequences /aCV/, where C was either /p/ or /b/ and V one of the vowels /i, a, u/. Force of labial contact and oral air pressure were also recorded in one subject. The results indicate that at the instant of oral closure, the velocity of both lips was close to peak velocity. They also show that the lower lip continued its upward movement after oral closure. This was reflected in the force of labial contact, which showed an increase in contact pressure after the oral closure had occurred. During the period of lower lip upward movement after the oral closure, the upper lip often showed a corresponding upward movement, suggesting that the lower lip might be pushing the upper lip. These results support the hypothesis that one goal in making the lip closure is a region of negative lip aperture. [Work supported by NIH.]
Lip protrusion movements in normal versus clear speech.
Authors: Perrier Pascal , Perkell Joseph S. , Matthies Melanie L.
Published: October 2005

A kinematic analysis of midsagittal movement (EMMA) data was performed for upper lip protrusion from [i] to [u] in [iku], [ikku], and [iktku], produced by a speaker of American English. Utterances were embedded in a carrier sentence and spoken in four conditions: normal rate, normal rate and clear, fast rate, fast rate and clear. The results show several regularities across all conditions: (1) the delay between the protrusion onset and the acoustic onset of [u] varies linearly with the vowel-to-vowel duration (VVD), [i]-end to [u]-onset, with a slope of 0.7; (2) the overlap between the protrusion movement and vowel [i] decreases as VVD increases, with no significant differences between conditions for similar VVD values; (3) the relationship between the ratio of maximum velocity (Vmax) to protrusion amplitude (Amp) and the movement duration (T) is constant: Vmax/Amp=c/T; (4) the number of velocity peaks increases linearly with VVD. These regularities suggest that the same control strategy underlies the protrusion gesture, whatever the condition. However, for a given rate, clear tokens were produced with longer VVDs and larger protrusion amplitudes. For similar VVD values, fast clear tokens had larger values of Vmax than normal tokens. [Work supported by NIDCD and NATO.]
Observations of anomalous acoustic penetration into sediment at shallow grazing angles.
Authors: Lopes Joseph L.
Published: October 2005

Buried mines pose a difficult problem for mine countermeasures operations. Mines may naturally bury in coastal waters where wave-induced effects are significant near the bottom. Current techniques for acoustic detection and classification of a buried mine require a high-resolution imaging sonar with bottom penetrating capability. Recently, anomalous acoustic penetration into sediment at shallow grazing angles was observed during a series of experiments which acoustically characterized the shallow water environment. These experiments employed a stationary sonar tower complete with pan and tilt motors. In the initial experiments, backscattered returns from objects of opportunity were recorded; these objects were either partially or completely buried near the water–sediment interface. In a later experiment, buried calibrated retroreflectors and a buried hydrophone were also utilized; the hydrophone was used to measure in-sediment sound-pressure levels. Results of the backscattered returns from the objects of opportunity and calibrated retroreflectors will be presented. Also, the measured in-sediment sound-pressure levels will be compared to the SAFARI (seismic and acoustic fast field algorithm for range-independent environments) code and will be further compared to results reported in the literature. [Work supported by the Office of Naval Research.]
Subcritical penetration of sandy sediments due to interface roughness.
Authors: Jackson Darrell R. , Moe John E. , Thorsos Eric I. , Williams Kevin L.
Published: October 2005

Seafloor roughness can cause acoustic energy to propagate into sediments for ‘‘subcritical’’ incident grazing angles, that is, grazing angles smaller than the critical angle determined by the compressional wave speed. Such effects must be considered in interpreting experimental data on sound penetration into sediments. The sediment is modeled as a fluid supporting only compressional waves and a twofold theoretical approach is used. First, an exact integral equation is solved numerically to obtain the penetrating field in two dimensions. Physical insights are abstracted from these results which are also used to show that perturbation theory is valid for problems of interest. Using perturbation theory, a numerically tractable three-dimensional model is compared to some of the experimental data of Chotiros and colleagues [N. P. Chotiros, J. Acoust. Soc. Am. 97, 199–214 (1995)]. The model and data match well subject to plausible assumptions about roughness statistics. [Work supported by ONR.]
Poroacoustic media.
Authors: Collins Michael D. , Siegmann William L.
Published: October 2005

Some poroelastic sediments have relatively high slow-wave speeds and low shear-wave speeds [N. P. Chotiros, J. Acoust. Soc. Am. 97, 199–214 (1995)]. Wave propagation in these kinds of sediments may be modeled efficiently by neglecting shear waves to obtain the equations of motion of poroacoustic media. With this approach, the number of equations is reduced and numerical implementations may use larger grid spaces. Poroacoustic waves satisfy two coupled equations. Poroelastic waves satisfy three coupled equations for two-dimensional problems (the original formulation involves four equations). The equations of poroacoustics are symbolically identical to the equations of acoustics. The poroacoustic wave equation is a vector generalization of the variable density acoustic wave equation [P. G. Bergmann, J. Acoust. Soc. Am. 17, 329–333 (1946)]. The interface conditions between poroacoustic layers are vector generalizations of the interface conditions between fluid layers. The energy flux integral of poroacoustics is a vector generalization of the energy flux integral of acoustics. The equations of motion are in a form suitable for factoring and solving with parabolic equation techniques. [Work supported by ONR.]
Energy-conservation conditions for poroelastic and poroacoustic waveguides.
Authors: Lingevitch Joseph F. , Collins Michael D. , Siegmann William L.
Published: October 2005

Wave propagation in range-dependent ocean environments is often treated by dividing the domain into a sequence of range-independent regions. One-way techniques, such as the parabolic equation method, are applied to efficiently solve the wave equation in each region. The reduced order of one-way wave equations limits the number of boundary conditions that may be imposed at the vertical interfaces between regions. This can result in significant errors as well as instabilities. Accurate solutions may be obtained for many problems by a conserving energy flux at the vertical interfaces [M. B. Porter et al., J. Acoust. Soc. Am. 89, 1058–1067 (1991)]. The standard expressions for energy flux are of limited practical use because they are nonlinear. It is possible to obtain equivalent linear conditions by writing the energy flux integrand as a perfect square involving roots of operators. The acoustic case has been resolved and some progress has been made for the elastic case. Problems currently under investigation include energy-flux conditions for poroelastic and poroacoustic media as well as corrections for problems involving different types of layers. [Work supported by the NRC and ONR.]
Low grazing angle scattering by a rough ocean floor.
Authors: Barbone Paul E. , Spivack Mark
Published: October 2005

Low grazing angle acoustic scattering by an irregular ocean floor is considered. The ocean bottom is modeled as a semi-infinite acoustic medium with properties that differ from those of the fluid above. At zero grazing incidence, a flat ocean floor appears acoustically soft. Surface roughness introduces perturbations to both the surface height and the apparent impedance of the interface. This nonuniform limit is examined as a perturbation from a slightly rough pressure release surface. A modified parabolic equation is derived which describes the acoustic amplitude to large distances, and takes into account multiple scattering and radiation into the ocean and bottom. An equivalent formulation will be presented in terms of an integral equation which is solved numerically. Average results as well as results from single realizations are presented. [Work supported by NATO.]
Bottom penetration at subcritical grazing angles by scattering.
Authors: Stephen Ralph A.
Published: October 2005

The physics of sound propagation and scattering is distinctly different between hard and soft ocean bottoms. A hard bottom is defined as having a shear velocity greater than water velocity; a soft bottom has a shear velocity less than water velocity. Geologically hard seafloors consist of igneous rocks such as gabbros and basalts; soft seafloors consist of sediments such as mud and sand. For a soft bottom with sound incident from above, total internal reflection never occurs. For all grazing angles there is always a Snell’s law ray path from compressional energy in the water to shear energy in the bottom. For hard, flat bottoms over homogeneous rock, total internal reflection will occur for grazing angles less than critical. However in this case sound can penetrate the bottom by scattering from surface roughness or volume heterogeneities. Snapshots from time domain modeling by the finite-difference method show that the scattered field consists of wavefronts which are analogous to transmitted compressional and shear body waves. Since the seafloor is rough and laterally heterogeneous over a broad range of length scales, this mechanism could be significant over a broad frequency range. [Work supported by ONR.]
Exposure guidelines for Navy divers exposed to low-frequency active sonar.
Authors: Pestorius F. Michael , Curley Michael D.
Published: October 2005

A 30-month experimental and modeling study was conducted into the effects of low-frequency active (LFA) sonars on Navy divers. 453 dives using 87 subjects were completed with one symptomatic event. A variety of dive equipment, depths to five atmospheres, and three signal waveforms were used. Interim guidance for exposure to LFA signals was issued by the U.S. Navy Bureau of Medicine and Surgery. For exposures to nonimpulsive waterborne sound in the frequency range 160–320 Hz, the following set of parameters did not compromise the safety of a highly trained, fit, and informed diver (diver compromise refers to a diver who could become a casualty or burden to others in an operational setting): A maximum overall SPL of 160 dB for no more than 100 s continuous exposure on a 50% duty cycle, with a cumulative exposure limit of 15 min/dive-day, a total of 9 days of exposure in a 2-week period. SPL is measured at the diver’s location. This guidance is generalizable only to those populations equivalent in medical health and fitness to U.S. Navy divers. [Work supported by U.S. Navy.]
A new multifinger tactual display.
Authors: Tan Hong Z. , Rabinowitz William M.
Published: October 2005

A multifinger positional display, called the Tactuator, was developed to study communication through the kinesthetic and vibrotactile aspects of the tactual sensory system of the hand. The display consists of three independent single-point actuators interfaced (individually) with the fingerpads of the thumb, the index finger, and the middle finger. Each actuator utilizes a disk-drive head-positioning motor augmented with angular position feedback from a precision rotary variable differential transformer (RVDT). A floating-point DSP system provides real-time positional control, using position and derived-velocity feedback. Stimuli from threshold to about 50 dB SL can be delivered throughout the frequency range from near dc to above 300 Hz, thereby encompassing the perceptual range from gross motion to vibration. Actuator frequency and step responses are well modeled as a second-order linear system. Distortion is low allowing delivery of arbitrary stimulus waveforms, e.g., 25-mm low-frequency motion with superimposed high-frequency vibration. System noise and interchannel cross talk are also small. As one example of behavioral performance verification, absolute thresholds measured with the stimulator are in general agreement with reference values. Overall, the Tactuator accurately follows its drive waveforms and is well suited for a variety of multifinger tactual perceptual studies. [Work supported by NIDCD.]
Information transmission with a multifinger tactual stimulator.
Authors: Tan Hong Z. , Durlach Nathaniel I. , Rabinowitz William M. , Reed Charlotte M.
Published: October 2005

The information transmission capabilities of a multifinger positional stimulator, called the Tactuator, were explored in a series of absolute identification experiments. Variations in the frequency of single sinewave stimuli evoked three relatively distinct perceptual attributes: smooth motion (up to about 6 Hz), a rough or fluttering sensation (about 10 to 70 Hz), and smooth vibration (above about 150 Hz). Multicomponent stimuli were formed by summing sinusoids from each of these three regions, with the intent that frequency (and amplitude) variations within each region could be identified independently. Stimulation was applied to either one of three digits (thumb, index, or middle) or to all three digits simultaneously. For stimulus durations of 500 and 250 ms, information transfer (IT) was 6.6 bits (corresponding to perfect identification of 97 stimuli); at 125 ms, IT was 6.0 bits. Estimates of potential IT rates were obtained by sequencing three random stimuli and (a) having the subject identify only the middle stimulus and (b) extrapolating this IT to that for continuous streams. Estimated IT rates were 13 bits/s, and the optimal stimulus presentation rate was approximately 3 items/s regardless of stimulus duration. This IT rate is roughly the same as that achieved by Tadoma users in tactual speech communication. [Work supported by NIDCD.]
Active noise reduction stethoscopy for lung sounds measurement in loud environments.
Authors: Patel Samir P. , Wodicka George R. , Callahan Matthew G.
Published: October 2005

Auscultation of lung sounds in vehicles such as an ambulance or aircraft is unachievable because of high noise levels. Also, the bandwidths of lung sounds and vehicle noise typically have significant overlap, limiting the utility of bandpass filtering. In this study, a passively shielded stethoscope coupler with one microphone to measure the (noise-corrupted) lung sounds and another to measure the ambient noise was constructed. Lung sound measurements were performed on a healthy subject in a simulated USAF C-130 aircraft environment within an acoustic chamber at noise levels ranging from 80 to 100 dB SPL. Adaptive filtering schemes using a least mean squares (lms) and a normalized least mean squares (nlms) approach were employed to extract lung sounds from the corrupted signal. Up to 25 dB of noise reduction over the 100–600 Hz frequency range was achieved with the lms algorithm, with the more complex nlms algorithm providing faster convergence and up to 5 dB of additional noise reduction. These findings indicate that a combination of active and passive noise reduction can be used to measure clinically useful lung sounds in high noise environments. [Work supported by US Air Force.]
A modal characterization of the ovine head.
Authors: Whitman Teresa A. , Morgan Mark T. , Wodicka George R.
Published: October 2005

Although the vibrational response of the head has been observed to correlate with intracranial pressure when measurements are made directly on the skull [M. Stevanovic et al., Ann. Biomed. Eng. 23, 720–727 (1995)], the effect of the extracranial tissues of an intact head has only been hypothesized. In this study, the modal characteristics of the freely vibrating ovine head under various stages of intra- and extracranial tissue removal were determined. Frequency responses from 20 to 2000 Hz were measured using an accelerometer and impact hammer at 32 sites on 5 intact ovine heads, and after progressive removal of the jaw, intra- and extracranial tissues, and finally on the boiled and dried skull. Intra- and extracranial tissues increased modal damping and decreased natural frequencies. Dried skulls exhibited as many as 5 lightly damped resonances with the lowest occurring around 1 kHz, whereas only 2 heavily damped resonances were evident prior to boiling. The first resonance for the heads at various stages of tissue removal occurred between 200 and 400 Hz and similar mode shapes between heads were found at this lowest resonance as compared by the Modal Assurance Criterion. As natural frequencies increased, the modes became more complex, resulting in dissimilar mode shapes between heads. [Work supported by NSF.]
Measurements of the effect of polypropylene vials on ultrasound propagation.
Authors: Cleveland Robin O. , Averkiou Michalakis A. , Crum Lawrence A. , McAteer James A.
Published: October 2005

Polypropylene vials are commonly used in in vitro experiments to hold cell preparations that are exposed to ultrasound. The vial has an acoustic impedance very close to water, in which case there should be little transmission loss as sound propagates into the vial. Measurements of the acoustic field within polypropylene vials have been carried out using both pulsed medical ultrasound and lithotripter shock waves. It has been found that for certain orientations of the acoustic field and vial there is significant loss of pressure amplitude within the vial. In particular, sound that enters the vial through the round, hemispherical end is attenuated and distorted. Hot and cold spots within the vial are also measured. When the rounded end is replaced with a flat surface very little distortion and attenuation of the waveform occurs. The distortion induced by the round end is apparently due to refraction introduced by the vial—the speed of sound in polypropylene is about 1.7 times that of water. A simple ray analysis indicates the presence of hot and cold spots within the vial in qualitative agreement with observations. These results indicate that cell injury experiments may be dependent on the vial orientation. [Work supported by NIH and the ASA Hunt Fellowship.]