bluuebunny/crossref_metadata_2025 huggingface dataset:
Forensic Engineering Case Studies of Machinery Product Designs
Authors: Thornhill R. Joe , Ramirez Ciro N. , Long Clarence L.
Published: June 2008

Engineering case studies of two product liability lawsuits involving accidents with machinery are presented. The studies focus on the design, manufacturing, and marketing of these products and related legal issues. In the first case study a person riding on the access/egress step of a construction machine was injured when the step failed. Although the step had been damaged prior to the accident, the plaintiff alleged that the step design was defective, and this issue was further confused because the manufacturer had changed the design before the accident. The warnings on the machine and in the manual were adequate, but the judge ruled that neither the injured party’s behavior nor the manufacturer’s warnings could be discussed before the jury. In the second case study, a person was scalded by hot water and steam when he disconnected the inlet hose to a large sprinkler of the type used on a sports field. The product had a foreseeable design defect which directly contributed to the accident. There were also marketing and warning issues because no comprehensive manual was provided which adequately covered the integration of the subassemblies used in the product.
Critique: Drain Cover Standard ASME/ANSI - A112.19.8M-1987 (1996) Case Study — Steering Wheel
Authors: Barnett Ralph L. , Poczynok Peter J.
Published: June 2008

The current ASME/ANSI standard for pool/spa drain covers is relied upon as an effective guideline for drain system safety by pool industry practitioners, state building code commissions, the Consumer Product Safety Commission, the National Spa and Pool Institute, and a myriad of pool safety sophisticates. In fact, it is a license to kill. To demonstrate its shortcomings in the dawn of its next revision, an ordinary steering wheel is shown to satisfy the current standard while exposing bathers to every known fatal drain cover scenario. The paper raises a new issue: ASME, ANSI and pool professionals may all be in legal jeopardy.
NIOSH AutoROPS Latch and Release Mechanism: Second Generation
Authors: McKenzie E. A. , Etherton J. R.
Published: June 2008

Approximately 132 agricultural tractor overturn fatalities occur per year (Myers and Snyder, 1993). The use of rollover protective structures on farm tractors (ROPS), along with operator seat belt use, is the best known method for preventing these fatalities. One impediment to universal ROPS use, however, is low clearance situations, such as orchards and animal confinement buildings. To address the need for ROPS that are easily adapted to low clearance situations, the Division of Safety Research (DSR), National Institute for Occupational Safety and Health (NIOSH), developed a prototype automatically deploying, telescoping ROPS (AutoROPS). The NIOSH AutoROPS consists of two subsystems. The first is a retractable ROPS that is normally mounted to the tractor axle and latched in its lowered position for day-to-day use. The second subsystem is a sensor that monitors the operating angle and rate of roll on two axes of the tractor. If an overturn condition is detected by the sensor, the retracted ROPS will deploy and lock in the full upright position before ground contact. This paper discusses the second generation design of the latch and release mechanism (LRM) for the NIOSH AutoROPS and recommends key areas for future surveillance and design research to best facilitate reduction in farm rollover fatalities.
Commercial Tree Chipper: The Leg Pull-In Hypothesis
Authors: Brickman Dennis B.
Published: June 2008

This paper addresses a commercial mobile tree chipper with a mechanical infeed system that is manually fed. The purpose of this paper is to show that tree branches and brush presented to a disc chipper through the infeed hopper will not pull an erectly standing operator’s leg off the ground and into the feed wheels given the conditions set forth in this test program. In order for an erectly standing operator’s leg to contact the feed wheels, it is necessary for the leg to be pulled off the ground and over the bottom leading edge of the infeed hopper. Experiments demonstrate that the operator’s leg is pulled up against the lower leading edge of the infeed hopper and lodges there during pull-in scenarios using a winch, cable, and rope attached to the operator’s ankle. Two safety devices, an infeed extension pan and a safety control bar are explored in this paper.
Forklift Mounted Self Dumping Hoppers
Authors: Barnett Ralph L. , Ferrone Christopher W.
Published: June 2008

A safety device is proposed that will enable the operator of a sit-down rider forklift to discharge a self-dumping hopper while seated at the control station. Dumping proceeds without ground personnel which removes them from traffic flow and protects them from impacting loads that overspill the hopper, roll, bounce, or are accidentally discharged from the hopper. Just the right amount of rearward mast tilt is normally required to overcome the latching resistance of heavily loaded forward biased hoppers without becoming relatched when the trip lever is released. The associated trial and error balancing procedure is eliminated together with any need for muscling the latch rod. Unlatching poles are no longer used for elevated dumping.
Promoting Accident Prevention by Combating Fatigue
Authors: Cohen Mandi
Published: June 2008

Employees are increasingly working the nightshift or increased overtime. Many employees are operating systems while fatigued. Fatigue is induced by a number of factors, but most often it is caused by lack of sleep. Individuals who work late at night, longer than normal shifts, or random shift times may be prone to errors in attention, decision-making, and response to pertinent information. These errors lead to accidents. There are several simple methods to dramatically reduce the effect abnormal working hours has on the body. Fatigue is beginning to be recognized as a contributing factor in accidents, however more can be accomplished. Methods can be applied by both the employee and employer to prevent accidents from occurring as a result of fatigue. This paper will focus on methods of reducing the risk of human error in the workplace and address countermeasures used to reduce fatigue thus promoting a safer working environment.
Application of Annealed Cable for Vehicle Arresting Barriers
Authors: Kemper Bart
Published: June 2008

Transportation and traffic managers have had to deal with increased liability issues regarding containing vehicles during impact with protective barriers. Today’s security environment has a heightened need for means of stopping vehicles in controlled manner for security and liability purposes. Using strain energy absorption via annealed steel cables has proven to be a commercial success. Gated vehicle barrier applications using this mechanism range from safely stopping runaway vehicles at railroad crossing in compliance with National Cooperative Highway Research Program (NCHRP) Report 350 to stopping a potential attacker at an industrial plant in compliance with Nuclear Regulation (NUREG) CR-6190. This paper will examine different applications of this mechanism for controlling vehicle impact, analyze the nonlinear interactions at work, and develop operating parameters for using annealed steel wire rope for these applications.
Multi-Scale Strain Measurements of a Particulate Composite Material
Authors: Liu C. T. , Smith C. W. , Ravichandran G.
Published: June 2008

In this study, the strain fields on two different length scales in a particulate composite material containing hard particles embedded in a rubbery matrix were investigated, using two different techniques. The experimental results were analyzed and are discussed.
Computational Process Simulation and Energy Parameter Analysis From Mechanical Deformation of Aerospace Alunimum Alloys
Authors: Fragomeni James M. , Venugopal Giridhar
Published: June 2008

Many systems that work on the processing of energy can be modeled in terms of that energy. The energy that is given to the system may be stored or dissipated in the form of heat. It was proposed to extend this concept to attainment of critical level of stored energy and/or dissipated energy for occurrence of buckling of a metal column under compressive loading. The fact that Energy Factor Parameter (E.F.P.) computed from the experimental true stress-true strain values, suddenly decreased and approached value close to zero indicated either buckling and/or softening, but deviated with the E.F.P. computed from the theoretical true stress and true strain values. The 7050-T7451 (Al-Zn-Mg-Cu-Zr) and Al-Li-Cu aluminum alloys in longitudinal and transverse grain orientations were compression tested for mechanical properties of yield strength, buckling strength, strength coefficient, strain hardening exponent. Correlation between ratio of buckling strength and yield strength with aging time for preaged ASTM compression specimens was established. The compression deformation of aluminum alloy 7050 was modeled using finite element analysis, with the experimental testing parameters and the database in the software package.
Uncertainties caused by source directivity in room-acoustic investigations
Authors: San Martín Ricardo , Arana Miguel
Published: June 2008

Although deviations in the measurement of acoustic parameters should be lower than the subjectively perceivable change in the corresponding parameter measured, this study reflects that directionality of sound sources could cause wide audience areas to break away from this criterion at high frequencies, even when using dodecahedron loudspeakers which meet the requirements of the ISO 3382 standard. The directivity of four different acoustic sources was measured and the influence of its accurate orientation spatially quantified in five enclosures for speech and music. By means of simulation software, the number of receivers affected by uncertainties greater than difference limens was established.
Frequency discrimination learning in children
Authors: Halliday Lorna F. , Taylor Jenny L. , Edmondson-Jones A. Mark , Moore David R.
Published: June 2008

Psychoacoustic thresholds of pure tone frequency discrimination (FD) in children are elevated relative to those of adults. It has been shown that it is possible to improve FD thresholds in adults, following a single (subhour) training session. To determine whether FD thresholds in children may be improved by training and, consequently, reduced to adult levels, 100 normally hearing 6-to11-year-old children and adults received ∼1h of training on a FD task at 1kHz. At the start of training, a quarter of all child participants had FD thresholds that resembled those of naïve adults (adult-like subgroup). Another quarter achieved thresholds that were adult-like at some point during training (trainable subgroup). For the remainder (nonadult-like subgroup), thresholds did not reach those of naïve adult listeners at any point in the training session. Subgroup membership was linked to the influence of three factors—age, nonverbal IQ, and attention. However, across subgroups, learning was found not to generalize to either a different standard frequency (4kHz) or a variable (roving) presentation paradigm. The results indicate that it is possible for some children to achieve FD thresholds comparable to those of naïve adults, either natively or after limited training.
Influence of supraglottal structures on the glottal jet exiting a two-layer synthetic, self-oscillating vocal fold model
Authors: Drechsel James S. , Thomson Scott L.
Published: June 2008

A synthetic two-layer, self-oscillating, life-size vocal fold model was used to study the influence of the vocal tract and false folds on the glottal jet. The model vibrated at frequencies, pressures, flow rates, and amplitudes consistent with human phonation, although some differences in behavior between the model and the human vocal folds are noted. High-speed images of model motion and flow visualization were acquired. Phase-locked ensemble-averaged glottal jet velocity measurements using particle image velocimetry (PIV) were acquired with and without an idealized vocal tract, with and without false folds. PIV data were obtained with varying degrees of lateral asymmetric model positioning. Glottal jet velocity magnitudes were consistent with those measured using excised larynges. A starting vortex was observed in all test cases. The false folds interfered with the starting vortex, and in some cases vortex shedding from the false folds was observed. In asymmetric cases without false folds, the glottal jet tended to skew toward the nearest wall; with the false folds, the opposite trend was observed. rms velocity calculations showed the jet shear layer and laminar core. The rms velocities were higher in the vocal tract cases compared to the open jet and false fold cases.
Computing the far field scattered or radiated by objects inside layered fluid media using approximate Green’s functions
Authors: Zampolli Mario , Tesei Alessandra , Canepa Gaetano , Godin Oleg A.
Published: June 2008

A numerically efficient technique is presented for computing the field radiated or scattered from three-dimensional objects embedded within layered acoustic media. The distance between the receivers and the object of interest is supposed to be large compared to the acoustic wavelength. The method requires the pressure and normal particle displacement on the surface of the object or on an arbitrary circumscribing surface, as an input, together with a knowledge of the layered medium Green’s functions. The numerical integration of the full wave number spectral representation of the Green’s functions is avoided by employing approximate formulas which are available in terms of elementary functions. The pressure and normal particle displacement on the surface of the object of interest, on the other hand, may be known by analytical or numerical means or from experiments. No restrictions are placed on the location of the object, which may lie above, below, or across the interface between the fluid media. The proposed technique is verified through numerical examples, for which the near field pressure and the particle displacement are computed via a finite-element method. The results are compared to validated reference models, which are based on the full wave number spectral integral Green’s function.
Acoustic characteristics of English lexical stress produced by native Mandarin speakers
Authors: Zhang Yanhong , Nissen Shawn L. , Francis Alexander L.
Published: June 2008

Native speakers of Mandarin Chinese have difficulty producing native-like English stress contrasts. Acoustically, English lexical stress is multidimensional, involving manipulation of fundamental frequency (F0), duration, intensity and vowel quality. Errors in any or all of these correlates could interfere with perception of the stress contrast, but it is unknown which correlates are most problematic for Mandarin speakers. This study compares the use of these correlates in the production of lexical stress contrasts by 10 Mandarin and 10 native English speakers. Results showed that Mandarin speakers produced significantly less native-like stress patterns, although they did use all four acoustic correlates to distinguish stressed from unstressed syllables. Mandarin and English speakers’ use of amplitude and duration were comparable for both stressed and unstressed syllables, but Mandarin speakers produced stressed syllables with a higher F0 than English speakers. There were also significant differences in formant patterns across groups, such that Mandarin speakers produced English-like vowel reduction in certain unstressed syllables, but not in others. Results suggest that Mandarin speakers’ production of lexical stress contrasts in English is influenced partly by native-language experience with Mandarin lexical tones, and partly by similarities and differences between Mandarin and English vowel inventories.
A magnetic resonance imaging-based articulatory and acoustic study of “retroflex” and “bunched” American English /r/
Authors: Zhou Xinhui , Espy-Wilson Carol Y. , Boyce Suzanne , Tiede Mark , Holland Christy , Choe Ann
Published: June 2008

Speakers of rhotic dialects of North American English show a range of different tongue configurations for /r/. These variants produce acoustic profiles that are indistinguishable for the first three formants [Delattre, P., and Freeman, D. C., (1968). “A dialect study of American English r’s by x-ray motion picture,” Linguistics 44, 28–69; Westbury, J. R. et al. (1998), “Differences among speakers in lingual articulation for American English /r/,” Speech Commun. 26, 203–206]. It is puzzling why this should be so, given the very different vocal tract configurations involved. In this paper, two subjects whose productions of “retroflex” /r/ and “bunched” /r/ show similar patterns of F1–F3 but very different spacing between F4 and F5 are contrasted. Using finite element analysis and area functions based on magnetic resonance images of the vocal tract for sustained productions, the results of computer vocal tract models are compared to actual speech recordings. In particular, formant-cavity affiliations are explored using formant sensitivity functions and vocal tract simple-tube models. The difference in F4/F5 patterns between the subjects is confirmed for several additional subjects with retroflex and bunched vocal tract configurations. The results suggest that the F4/F5 differences between the variants can be largely explained by differences in whether the long cavity behind the palatal constriction acts as a half- or a quarter-wavelength resonator.
Enhancement, adaptation, and the binaural system
Authors: Šerman Maja , Semal Catherine , Demany Laurent
Published: June 2008

In a test sound consisting of a burst of pink noise, an arbitrarily selected target frequency band can be “enhanced” by the previous presentation of a similar noise with a spectral notch in the target frequency region. As a result of the enhancement, the test sound evokes a pitch sensation corresponding to the pitch of the target band. Here, a pitch comparison task was used to assess enhancement. In the first experiment, a stronger enhancement effect was found when the test sound and its precursor had the same interaural time difference (ITD) than when they had opposite ITDs. Two subsequent experiments were concerned with the audibility of an instance of dichotic pitch in binaural test sounds preceded by precursors. They showed that it is possible to enhance a frequency region on the sole basis of ITD manipulations, using spectrally identical test sounds and precursors. However, the observed effects were small. A major goal of this study was to test the hypothesis that enhancement originates at least in part from neural adaptation processes taking place at a central level of the auditory system. The data failed to provide strong support for this hypothesis.
Dispersion of circumferential waves in cylindrically anisotropic layered pipes in plane strain
Authors: Vasudeva R. Y. , Sudheer G. , Vema Anu Radha
Published: June 2008

Dispersion spectra of circumferential waves along the periphery of circular pipes made of layered anisotropic materials do not seem to be available in literature. This note attempts to partially fill this gap by providing the dispersion spectra in two and three layered cylindrically anisotropic pipes in plane strain motion. The spectra for pipes executing time harmonic vibrations in plane strain condition are obtained as roots of a numerical characteristic equation derived extending a weighted residual method of solution of the governing equations for a single layer pipe [Towfighi et al., J. Appl. Mech. 69, 283–291 (2002)] to a general N layered pipe. The anisotropic elastic coefficients are considered to be independent of position coordinates and the bond condition at interfaces of the layers is assumed to be perfect. Numerical illustrations are presented for two and three layered pipes with anisotropy directions differing in adjacent layers. Increase in curvature of the pipe and inclination of the fiber orientation in the outermost layers to propagation direction are factors that seem to influence the mode number and pattern within the limited examples worked out.
Three-dimensional seismic array characterization study: Experiment and modeling
Authors: Tashmukhambetov Arslan M. , Ioup George E. , Ioup Juliette W. , Sidorovskaia Natalia A. , Newcomb Joal J.
Published: June 2008

In the summer of 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a 21-element marine seismic exploration airgun array of total volume of 0.0588m3 (3590in.3). Two Environmental Acoustic Recording System buoys, one with a desensitized hydrophone, were deployed at a depth of 758m in a water depth of 990m, near Green’s Canyon in the Gulf of Mexico. Shots over a grid were recorded and calibrated to produce absolute broadband (up to 25kHz) pressure-time dependencies for a wide range of offsets and arrival angles in the water column. Experimental data are analyzed to obtain maximum received zero-to-peak pressure levels, maximum received sound exposure levels, and pressure levels in 1∕3-octave frequency bands for each shot. Experimental data are quantitatively modeled by using an upgraded version of an underwater acoustic propagation model and seismic source modeling packages for a variety of ranges and arrival angles. Experimental and modeled data show good agreement in absolute pressure amplitudes and frequency interference patterns for frequencies up to 1000Hz. The analysis is important for investigating the potential impact on marine mammals and fish and predicting the exposure levels for newly planned seismic surveys in other geographic areas.
Eigenvalue equalization filtered-x algorithm for the multichannel active noise control of stationary and nonstationary signals
Authors: Thomas Jared K. , Lovstedt Stephan P. , Blotter Jonathan D. , Sommerfeldt Scott D.
Published: June 2008

The FXLMS algorithm, which is extensively used in active noise control, exhibits frequency dependent convergence behavior. This leads to degraded performance for time-varying and multiple frequency signals. A new algorithm called the eigenvalue equalization filtered-x least mean squares (EE-FXLMS) has been developed to overcome this limitation without increasing the computational burden of the controller. The algorithm is easily implemented for either single or multichannel control. The magnitude coefficients of the secondary path transfer function estimate are altered while preserving the phase. For a reference signal that has the same magnitude at all frequencies, the secondary path estimate is given a flat response over frequency. For a reference signal that contains tonal components of unequal magnitudes, the magnitude coefficients of the secondary path are adjusted to be the inverse magnitude of the reference tones. Both modifications reduce the variation in the eigenvalues of the filtered-x autocorrelation matrix and lead to increased performance. Experimental results show that the EE-FXLMS algorithm provides 3.5–4.4dB additional attenuation at the error sensor compared to normal FXLMS control. The EE-FXLMS algorithm’s convergence rate at individual frequencies is faster and more uniform than the normal FXLMS algorithm with several second improvement being seen in some cases.
Unsupervised bird song syllable classification using evolving neural networks
Authors: Ranjard Louis , Ross Howard A.
Published: June 2008

Evolution of bird vocalizations is subjected to selection pressure related to their functions. Passerine bird songs are also under a neutral model of evolution because of the learning process supporting their transmission; thus they contain signals of individual, population, and species relationships. In order to retrieve this information, large amounts of data need to be processed. From vocalization recordings, songs are extracted and encoded as sequences of syllables before being compared. Encoding songs in such a way can be done either by ear and spectrogram visual analysis or by specific algorithms permitting reproducible studies. Here, a specific automatic method is presented to compute a syllable distance measure allowing an unsupervised classification of song syllables. Results obtained from the encoding of White-crowned Sparrow (Zonotrichia leucophrys pugetensis) songs are compared to human-based analysis.
Categorical dependence of vowel detection in long-term speech-shaped noise
Authors: Liu Chang , Eddins David A.
Published: June 2008

The goal of this study was to measure detection thresholds for 12 isolated American English vowels naturally spoken by three male and three female talkers for young normal-hearing listeners in the presence of a long-term speech-shaped (LTSS) noise, which was presented at 70dB sound pressure level. The vowel duration was equalized to 170ms and the spectrum of the LTSS noise was identical to the long-term average spectrum of 12-talker babble. Given the same duration, detection thresholds for vowels differed by 19dB across the 72 vowels. Thresholds for vowel detection showed a roughly U-shaped pattern as a function of the vowel category across talkers with lowest thresholds at /i/ and /æ/ vowels and highest thresholds at /u/ vowel in general. Both vowel category and talker had a significant effect on vowel detectability. Detection thresholds predicted from three excitation pattern metrics by using a simulation model were well matched with thresholds obtained from human listeners, suggesting that listeners could use a constant metric in the excitation pattern of the vowel to detect the signal in noise independent of the vowel category and talker. Application of the simulation model to predict thresholds of vowel detection in noise was also discussed.
The role of nonlinear effects in the propagation of noise from high-power jet aircraft
Authors: Gee Kent L. , Sparrow Victor W. , James Michael M. , Downing J. Micah , Hobbs Christopher M. , Gabrielson Thomas B. , Atchley Anthony A.
Published: June 2008

To address the question of the role of nonlinear effects in the propagation of noise radiated by high-power jet aircraft, extensive measurements were made of the F-22A Raptor during static engine run-ups. Data were acquired at low-, intermediate-, and high-thrust engine settings with microphones located 23–305m from the aircraft along several angles. Comparisons between the results of a generalized-Burgers-equation-based nonlinear propagation model and the measurements yield favorable agreement, whereas application of a linear propagation model results in spectral predictions that are much too low at high frequencies. The results and analysis show that significant nonlinear propagation effects occur for even intermediate-thrust engine conditions and at angles well away from the peak radiation angle. This suggests that these effects are likely to be common in the propagation of noise radiated by high-power aircraft.
Caustic and anticaustic points in the phonon focusing patterns of cubic crystals
Authors: Wang Litian
Published: June 2008

Phonon focusing patterns are dependent on the existence of concave/saddle regions and acoustic axes in the slowness surface. The main feature of the focusing patterns in cubic crystals can be characterized by the caustic and anticaustic points in the symmetry planes. By applying the Stroh formalism, the caustic and anticaustic points in the symmetry planes are investigated in relation to degeneracies in the Stroh eigenvalue equation. A set of analytical expressions for the locations of the caustic and anticaustic points is derived for cubic crystals.
Vibration activity and mobility of structure-borne sound sources by a reception plate method
Authors: Gibbs B. M. , Cookson R. , Qi N.
Published: June 2008

This paper considers a practical structure-borne sound source characterization for mechanical installations, which are connected to plate-like structures. It describes a laboratory-based measurement procedure, which will yield single values of source strength in a form transferable to a prediction of the structure-borne sound power generated in the installed condition. It is confirmed that two source quantities are required, corresponding to the source activity and mobility. For the source activity, a high-mobility reception plate method is proposed which yields a single value in the form of the sum of the squared free velocities, over the contact points. A low-mobility reception plate method also is proposed which, in conjunction with the above, yields the source mobility in the form of the average magnitude of the effective mobility, again over the contact points. Experimental case studies are described and the applicability of the laboratory data for prediction and limitations of the approach are discussed.
Spatial release from energetic and informational masking in a selective speech identification task
Authors: Ihlefeld Antje , Shinn-Cunningham Barbara
Published: June 2008

A masker can reduce target intelligibility both by interfering with the target’s peripheral representation (“energetic masking”) and/or by causing more central interference (“informational masking”). Intelligibility generally improves with increasing spatial separation between two sources, an effect known as spatial release from masking (SRM). Here, SRM was measured using two concurrent sine-vocoded talkers. Target and masker were each composed of eight different narrowbands of speech (with little spectral overlap). The broadband target-to-masker energy ratio (TMR) was varied, and response errors were used to assess the relative importance of energetic and informational masking. Performance improved with increasing TMR. SRM occurred at all TMRs; however, the pattern of errors suggests that spatial separation affected performance differently, depending on the dominant type of masking. Detailed error analysis suggests that informational masking occurred due to failures in either across-time linkage of target segments (streaming) or top-down selection of the target. Specifically, differences in the spatial cues in target and masker improved streaming and target selection. In contrast, level differences helped listeners select the target, but had little influence on streaming. These results demonstrate that at least two mechanisms (differentially affected by spatial and level cues) influence informational masking.
Comment on “Three-dimensional finite element modeling of guided ultrasound wave propagation in intact and healing long bones,” [J. Acoust. Soc. Am. 121(6), 3907–3921 (2007)]
Authors: Guo Xiasheng , Zhang Dong , Yang Di , Gong Xiufen , Wu Junru
Published: June 2008

Protopappas et al. performed finite element (FE) studies on the propagation of guided ultrasound waves in intact and healing long bones, and found that the dispersion of guided modes was significantly influenced by the irregularity and anisotropy of the bone. A time-frequency (t-f) method was applied to the obtained signals and several wave modes were identified. However, this technique was unable to quantify their observations and provide monitoring capabilities. One possible reason of this shortcoming may come from the inherent disadvantage of the t-f method. The objective of this comment is to demonstrate that it is necessary to combine other techniques with FE simulations for the extraction of significant quantitative ultrasonic features. Individual guided modes in an isotropic pipe have been theoretically examined using the normal mode expansion (NME) method, and many modes that are missed by the t-f analysis have been identified. It is concluded that in order to extract quantitative ultrasonic features, FE simulations should be supplemented by other techniques such as the NME.
Modeling the sound transmission between rooms coupled through partition walls by using a diffusion model
Authors: Billon Alexis , Foy Cédric , Picaut Judicaël , Valeau Vincent , Sakout Anas
Published: June 2008

In this paper, a modification of the diffusion model for room acoustics is proposed to account for sound transmission between two rooms, a source room and an adjacent room, which are coupled through a partition wall. A system of two diffusion equations, one for each room, together with a set of two boundary conditions, one for the partition wall and one for the other walls of a room, is obtained and numerically solved. The modified diffusion model is validated by numerical comparisons with the statistical theory for several coupled-room configurations by varying the coupling area surface, the absorption coefficient of each room, and the volume of the adjacent room. An experimental comparison is also carried out for two coupled classrooms. The modified diffusion model results agree very well with both the statistical theory and the experimental data. The diffusion model can then be used as an alternative to the statistical theory, especially when the statistical theory is not applicable, that is, when the reverberant sound field is not diffuse. Moreover, the diffusion model allows the prediction of the spatial distribution of sound energy within each coupled room, while the statistical theory gives only one sound level for each room.
Measurement of the resonance frequency of single bubbles using a laser Doppler vibrometer
Authors: Argo Theodore F. , Wilson Preston S. , Palan Vikrant
Published: June 2008

The behavior of bubbles confined in tubes and channels is important in medical and industrial applications. In these small spaces, traditional means of experimentally observing bubble dynamics are often impossible or significantly perturb the system. A laser Doppler vibrometer (LDV) requires a narrow (<1mm diameter) line-of-sight access for the beam and illumination of the bubble does not perturb its dynamics. LDV measurements of the resonance frequency of a bubble suspended in a small tank are presented to illustrate the utility of this measurement technique. The precision of the technique is similar to the precision of traditional acoustic techniques.
A mechanism stimulating sound production from air bubbles released from a nozzle
Authors: Deane Grant B. , Czerski Helen
Published: June 2008

Gas bubbles in water act as oscillators with a natural frequency inversely proportional to their radius and a quality factor determined by thermal, radiation, and viscous losses. The linear dynamics of spherical bubbles are well understood, but the excitation mechanism leading to sound production at the moment of bubble creation has been the subject of speculation. Experiments and models presented here show that sound from bubbles released from a nozzle can be excited by the rapid decrease in volume accompanying the collapse of the neck of gas which joins the bubble to its parent.
Energy concentration at the center of large aspect ratio rectangular waveguides at high frequencies
Authors: Cegla F. B.
Published: June 2008

Waveguides in non-destructive evaluation (NDE) applications are commonly of a regular geometry (e.g., circular and ring cross section) for which analytical solutions exist. In this paper, wave propagation in infinitely long strips of large rectangular aspect ratio is discussed. Due to the finite width of strips, a large number of modes exist within the structure. This complicates the analysis and usually discourages the use of strip waveguides in NDE sensors. However, it is shown that among the many modes of a strip, there are some with very desirable properties. This is highlighted by the example of two guided wave modes of a large aspect ratio rectangular strip whose dispersion characteristics approach those of the fundamental modes of an infinitely wide plate at high frequencies. The energy of these modes concentrates in the central region of the strip and decays toward the edges so that the strip waveguide can easily be mechanically attached to other components without influencing the wave propagation. Dispersion curves and mode shapes were derived by using a semianalytical finite element technique and are presented over a range of frequencies. It is shown that selective excitation of both modes is possible in practice and the experimental setup is described.
Phonatory characteristics of excised pig, sheep, and cow larynges
Authors: Alipour Fariborz , Jaiswal Sanyukta
Published: June 2008

The purpose of this study was to examine the phonatory characteristics of pig, sheep, and cow excised larynges and to find out which of these animal species is the best model for human phonation. Excised pig, sheep, and cow larynges were prepared and mounted over a tapered tube on the excised bench that supplied pressurized, heated, and humidified air in a manner similar to that for excised canine models. Each excised larynx was subjected to a series of pressure-flow experiments with adduction as major control parameter. The subglottal pressure, electroglottograph (EGG), mean flow rate, audio signal, and sound pressure level were recorded during each experiment. EGG signal was used to extract the fundamental frequency. It was found that pressure-frequency relations were nonlinear for these species with large rate of frequency changes for the pig. The average oscillation frequencies for these species were 220±57Hz for the pig, 102±33Hz for the sheep, and 73±10Hz for the cow. The average phonation threshold pressure for the pig was 7.4±2.0cm H2O, 6.9±2.9cm H2O for the sheep, and 4.4±2.3cm H2O for the cow.
Improved scatterer size estimation using backscatter coefficient measurements with coded excitation and pulse compression
Authors: Kanzler Steven G. , Oelze Michael L.
Published: June 2008

Scatterer size estimates from ultrasonic backscatter coefficient measurements have been used to differentiate diseased tissue from normal. A low echo signal-to-noise ratio (eSNR) leads to increased bias and variance in scatterer size estimates. One way to improve the eSNR is to use coded excitation (CE). The normalized backscatter coefficient was measured from three tissue-mimicking phantoms by using CE and conventional pulsing (CP) techniques. The three phantoms contained randomly spaced glass beads with median diameters of 30, 45, and 82μm, respectively. Measurements were made with two weakly focused, single-element transducers (f0=5MHz and f0=10MHz). For CE, a linear frequency modulated chirp with a time bandwidth product of 40 was used and pulse compression was accomplished by the use of a Wiener filter. Preliminary results indicated that improved estimation bias versus penetration depth was obtained by using CE compared to CP. The depth of penetration, where the accuracy of scatterer diameter estimates (absolute divergence <25%) were obtained with the 10MHz transducer, was increased up to 50% by using CE versus CP techniques. In addition, for a majority of the phantoms, the increase in eSNR from CE resulted in a modest reduction in estimate variance versus depth of penetration.
Estimates of compression at low and high frequencies using masking additivity in normal and impaired ears
Authors: Plack Christopher J. , Oxenham Andrew J. , Simonson Andrea M. , O’Hanlon Catherine G. , Drga Vit , Arifianto Dhany
Published: June 2008

Auditory compression was estimated at 250 and 4000Hz by using the additivity of forward masking technique, which measures the effects on signal threshold of combining two temporally nonoverlapping forward maskers. The increase in threshold in the combined-masker condition compared to the individual-masker conditions can be used to estimate compression. The signal was a 250 or 4000Hz tone burst and the maskers (M1 and M2) were bands of noise. Signal thresholds were measured in the presence of M1 and M2 alone and combined for a range of masker levels. The results were used to derive response functions at each frequency. The procedure was conducted with normal-hearing and hearing-impaired listeners. The results suggest that the response function in normal ears is similar at 250 and 4000Hz with a mid level compression exponent of about 0.2. However, compression extends over a smaller range of levels at 250Hz. The results confirm previous estimates of compression using temporal masking curves (TMCs) without assuming a linear off-frequency reference as in the TMC procedure. The impaired ears generally showed less compression. Importantly, some impaired ears showed a linear response at 250Hz, providing a further indication that low-frequency compression originates in the cochlea.
The trapped fluid transducer: Modeling and optimization
Authors: Cheng Lei , Grosh Karl
Published: June 2008

Exact and approximate formulas for calculating the sensitivity and bandwidth of an electroacoustic transducer with an enclosed or trapped fluid volume are developed. The transducer is composed of a fluid-filled rectangular duct with a tapered-width plate on one wall emulating the biological basilar membrane in the cochlea. A three-dimensional coupled fluid-structure model is developed to calculate the transducer sensitivity by using a boundary integral method. The model is used as the basis of an optimization methodology seeking to enhance the transducer performance. Simplified formulas are derived from the model to estimate the transducer sensitivity and the fundamental resonant frequency with good accuracy and much less computational cost. By using the simplified formulas, one can easily design the geometry of the transducer to achieve the optimal performance. As an example design, the transducer achieves a sensitivity of around −200dB (1V∕μPa) at 10kHz frequency range with piezoelectric sensing. In analogy to the cochlea, a tapered-width plate design is considered and shown to have a more uniform frequency response than a similar plate with no taper.
Determination of acoustic attenuation in the Hudson River Estuary by means of ship noise observations
Authors: Roh Heui-Seol , Sutin Alexander , Bunin Barry
Published: June 2008

Analysis of sound propagation in a complex urban estuary has application to underwater threat detection systems, underwater communication, and acoustic tomography. One of the most important acoustic parameters, sound attenuation, was analyzed in the Hudson River near Manhattan using measurements of acoustic noise generated by passing ships and recorded by a fixed hydrophone. Analysis of the ship noise level for varying distances allowed estimation of the sound attenuation in the frequency band of 10–80kHz. The effective attenuation coefficient representing the attenuation loss above cylindrical spreading loss had only slight frequency dependence and can be estimated by the frequency independent value of 0.058dB∕m.
Bayesian geoacoustic inversion in a dynamic shallow water environment
Authors: Jiang Yong-Min , Chapman N. Ross
Published: June 2008

This paper presents results for matched field Bayesian geoacoustic inversion of multitonal continuous wave data collected on the New Jersey continental shelf. To account for effects of significant spatial and temporal variation of the water column sound speed, the sound speed profile was represented by empirical orthogonal functions. Data error information for the inversion was estimated from multiple time windows of the data. Inversion results for the sediment sound speeds at three ranges are in excellent agreement with the ground truth.
Effect of ocean sound speed uncertainty on matched-field geoacoustic inversion
Authors: Huang Chen-Fen , Gerstoft Peter , Hodgkiss William S.
Published: June 2008

The effect of ocean sound speed uncertainty on matched-field geoacoustic inversion is investigated using data from the SW06 experiment along a nearly range-independent bathymetric track. Significant sound speed differences were observed at the source and receiving array and several environmental parameterizations were investigated for the inversion including representing the ocean sound speed at both source and receivers with empirical orthogonal function (EOF) coefficients. A genetic algorithm-based global optimization method was applied to the candidate environmental models. Then, a Bayesian inversion technique was used to quantify uncertainty in the environmental parameters for the best environmental model, which included an EOF description of the ocean sound speed.
Human motion analyses using footstep ultrasound and Doppler ultrasound
Authors: Ekimov Alexander , Sabatier James M.
Published: June 2008

Human footsteps generate periodic broadband frequency envelopes of sound due to dynamic friction forces. Also, human body motion when walking is a cyclic temporal process. The individual body parts have different acoustic cross sections and velocities that form unique human Doppler signatures. The paper introduces an approach to analyze this motion using passive and active ultrasound. The passive method employs a narrowband microphone that is sensitive to the sound from footsteps. The active method utilizes continuous-wave ultrasound to measure the Doppler shifted signal from the body appendages. These two methods show time synchronization between Doppler and ultrasonic human footstep signatures.
Nonlinear radial oscillations of encapsulated microbubbles subject to ultrasound: The effect of membrane constitutive law
Authors: Tsiglifis Kostas , Pelekasis Nikos A.
Published: June 2008

The nonlinear radial oscillations of bubbles that are encapsulated in an elastic shell are investigated numerically subject to three different constitutive laws describing the viscoelastic properties of the shell: the Mooney–Rivlin (MR), the Skalak (SK), and the Kelvin–Voigt (KV) models are used in order to describe strain-softening, strain-hardening and small displacement (Hookean) behavior of the shell material, respectively. Due to the isotropic nature of the acoustic disturbances, the area dilatation modulus is the important parameter. When the membrane is strain softening (MR) the resonance frequency decreases with increasing sound amplitude, whereas the opposite happens when the membrane is strain hardening (SK). As the amplitude of the acoustic disturbance increases the total scattering cross section of a microbubble with a SK membrane tends to decrease, whereas that of a KV or a MR membrane tends to increase. The importance of strain-softening behavior in the abrupt onset of volume pulsations, that is often observed with small insonated microbubbles at moderately large sound amplitudes, is discussed.
On the robustness of overall F0-only modifications to the perception of emotions in speech
Authors: Bulut Murtaza , Narayanan Shrikanth
Published: June 2008

Emotional information in speech is commonly described in terms of prosody features such as F0, duration, and energy. In this paper, the focus is on how F0 characteristics can be used to effectively parametrize emotional quality in speech signals. Using an analysis-by-synthesis approach, F0 mean, range, and shape properties of emotional utterances are systematically modified. The results show the aspects of the F0 parameter that can be modified without causing any significant changes in the perception of emotions. To model this behavior the concept of emotional regions is introduced. Emotional regions represent the variability present in the emotional speech and provide a new procedure for studying speech cues for judgments of emotion. The method is applied to F0 but can be also used on other aspects of prosody such as duration or loudness. Statistical analysis of the factors affecting the emotional regions, and discussion of the effects of F0 modifications on the emotion and speech quality perception are also presented. The results show that F0 range is more important than F0 mean for emotion expression.