bluuebunny/crossref_metadata_2025 huggingface dataset:
Violin bridge-hill to radiation: The energy trail
Authors: Bissinger George
Published: October 2013

Simultaneous experimental modal and acoustical analysis in an anechoic chamber was used to track energy flow through quality-rated violins to clarify the link between the mechanical motions at a driving point on the G-corner of the bridge, and subsequent radiation from the violin. The 0–4-kHz range covered included a broad hump near 2.4 kHz in driving point mobility generally labeled the bridge-hill and thought to be related to violin quality and radiativity (and sound). The bridge-hill enhancement showed up successively in the averaged mobility of the bridge, at the bridge feet, and over the corpus; a corresponding peak was also seen in the radiativity, indicating that enhanced radiation accompanied enhanced bridge motion. All bridge motions except low-frequency rigid-body motions were complex, and generally showed some semblance of rocking motion at higher frequencies. No evidence was observed for any bridge resonance separate from string or corpus resonances, although most bridges showed a complex squat mode near 0.8 kHz (not accompanied by enhanced radiation) that is likely an out-of-plane bending mode falling far below the rocking mode. Bridge-hill magnitude was not found to correlate well with violin quality, or averaged corpus mobility, or averaged radiativity.
Guitar radiation—resonant and nonresonant
Authors: Lyon Richard
Published: October 2013

The sound radiation from a guitar contains about 50 fundamental semitones and about 200 harmonics. The resonant modes of the guitar body are insufficient in number and of insufficient bandwidth to support all of these frequencies, so some frequencies are coincident with resonances and some are not. It is the purpose of this paper to discuss the role of resonances as they occur in the guitar top, sides, and back in affecting the radiation. Conjectures about the role of the nonresonant radiation in the attack of the sounds and the hearing mechanism on the perception of the sound are presented in a tentative manner.
The low-frequency resonances of harp soundboxes
Authors: Waltham Chris , Kotlicki Andrzej
Published: October 2013

The harp soundbox is a thin shell coupled directly to the strings. The sound board at the front is usually solid, but at the back are holes for access to the tethering points of the strings. As with other plucked instruments, the most important resonances for sound production tend to be those at low frequency, and these often involve the coupling of the whole soundbox to the air inside, and also to other parts of the harp structure. The low-frequency resonant structure of small folk harps and a full-size concert harp has been investigated, and results will be presented here. The instruments used, a tap hammer and accelerometer, were made in the laboratory from inexpensive materials, and their manufacture and calibration will also be discussed.
Airborne ultrasound enters the ear through the eyes
Authors: Lenhardt Martin
Published: October 2013

Musical spectrum above 20000 Hz has been demonstrated to influence human judgments and physiology. Moreover airborne ultrasonic noise has been implicated in hearing loss, tinnitus, and other subjective effects such as headaches and fullness in the ear. Contact ultrasound, i.e., with a transducer affixed to the skin of the head/neck, is audible; assumed by bone conduction. However, lightly touching the soft tissues of the head, avoiding bone, can also produce audibility. When contact ultrasound is applied to the head, energy from 25 to ∼60 kHz can be recorded from the closed eyelid, with care to avoid sensor contact with the orbit. If the same frequency band of noise is passed through a transducer in from of the eye, with just air coupling, the same response is again recordable on the head. An acrylic barrier between the eye and the transducer eliminates the response. Once airborne ultrasound exceeds the impedance mismatch of the eye it readily propagates through the soft tissues of the eye and brain via one of the fluid windows (end lymphatic, perilymphatic or vascular) to the cochlea. The eye fenestration explains how people can detect airborne ultrasonic components in music and develop ear effects from airborne ultrasonic noise.
Separation of piano tones into tonal and broadband components
Authors: Keane Martin
Published: October 2013

Few studies have proposed simple objective methods to evaluate the quality of piano tones. Recordings of both sound and vibration of six pianos (two grands and four uprights) were analyzed. The results suggest an objective measure for piano tone quality. A method is given for splitting recorded tones into tonal and broadband components. The broadband vibration was found to be more intense in the upright pianos than in the grand pianos, this is due to differences in the construction of the keybed. There was no such difference found in the tonal component. These results suggest the hypothesis that a smaller broadband component correlates with higher quality in piano tones.
Polyphonic pitch detection and instrument separation
Authors: Bay Mert , Beauchamp James W.
Published: October 2013

An algorithm for polyphonic pitch detection and musical instrument separation is presented. Each instrument is represented as a time-varying harmonic series. Spectral information is obtained from a monaural input signal using a spectral peak tracking method. Fundamental frequencies (F0s) for each time frame are estimated from the spectral data using an Expectation Maximization (EM) algorithm with a Gaussian mixture model representing the harmonic series. The method first estimates the most predominant F0, suppresses its series in the input, and then the EM algorithm is run iteratively to estimate each next F0. Collisions between instrument harmonics, which frequently occur, are predicted from the estimated F0s, and the resulting corrupted harmonics are ignored. The amplitudes of these corrupted harmonics are replaced by harmonics taken from a library of spectral envelopes for different instruments, where the spectrum which most closely matches the important characteristics of each extracted spectrum is chosen. Finally, each voice is separately resynthesized by additive synthesis. This algorithm is demonstrated for a trio piece that consists of 3 different instruments.
Seeing the B-A-C-H motif
Authors: Catravas Palmyra
Published: October 2013

Musical compositions can be thought of as complex, multidimensional data sets. Compositions based on the B-A-C-H motif (a four-note motif of the pitches of the last name of Johann Sebastian Bach) span several centuries of evolving compositional styles and provide an intriguing set for analysis since they contain a common feature, the motif, buried in dissimilar contexts. We will present analyses which highlight the content of this unusual set of pieces, with emphasis on visual display of information.
Advantages and challenges of distributed active vibro-acoustic control
Authors: Frampton Kenneth D.
Published: October 2013

As active control technologies reach their performance limits in large scale systems, many investigators have looked toward decentralized control as a means of expanding the application horizons. Decentralized control is defined here as numerous independent controllers operating on a single system. These decentralized approaches have been shown to be effective, but not as effective as traditional centralized control. In an effort to achieve control performance approaching centralized control while maintaining the scalability benefits of decentralized control, the use of distributed control is considered. Distributed control consists of numerous control processors operating on a system that are capable of communicating with each other over a network. This work discusses the application of distributed active control to vibroacoustic problems. Key elements in distributed control systems will be presented along with the state of each of the key technologies involved. Of particular interest are the limitations in enabling technologies that limit the application of distributed control: namely real-time network communications; distributed control algorithms and design tools; software infrastructure for system management; and other factors. Results will demonstrate that distributed control can perform nearly as well as centralized control, but that it can also be ‘‘scaled up’’ for use in large complex systems.
Development of transparent thin film speaker and its application for active sound transmission control through windows
Authors: Yu X. , Rajamani R. , Stelson K. A. , Cui T.
Published: October 2013

Homes close to airports and highways in major metropolitan areas suffer from serious noise problems. Typically, windows constitute the primary path through which noise enters a home. As an effective method for attenuating low frequency noise, active noise cancellation approach has drawn increasing interest. A small voice coil actuator can be used to vibrate a glass panel and achieve significant reduction in noise transmission at its location. However, global noise cancellation over the entire panel can not be achieved with such a single point actuator. Using multiple voice coil actuators is also not practical, since several actuators on a windowpane would destroy the aesthetics of the window. This necessitates the development of thin film actuators that can provide distributed canceling sound over the entire surface of large sized glass panels. The need of transparence for the windows application poses a great challenge to the development of such thin film actuators. In this paper, transparent thin film speakers are developed, based on the use of carbon nanotubes for conductive films that are coated on polzerized PVDF films. Preliminary experimental results show that the transparent thin film speaker has the potential to be a promising solution for the ANC windows.
Stability analysis of the active control of self-sustained pressure fluctuations due to flow over a cavity
Authors: Micheau Philippe , Chatellier Ludovic , Laumonier Janick , Gervais Yves
Published: October 2013

The addressed problem is to actively control the self-sustained pressure fluctuations due to low Mach number turbulent flow (M<0.1) over a large, shallow cavity in a wing-shaped model. For the studied configuration, the sound pressure is generated by the unstability of the mixing layer [L. Chatellier, J. Laumonier, and Y. Gervais, ‘‘Theoretical and experimental investigations of low Mach number turbulent cavity flows,’’ Exp. Fluids 36, 728–740 (2004)]. An original active device, a vibrating surface located at the trailing edge, and an adjustable narrow-band controller are used to control the self-oscillation: to synchronize and amplify it in open loop, and to attenuate it in closed loop. Experimental data were obtained in the test section of an Eiffel-type wind tunnel. For a free stream at 31 m/s, the SPL measured at 397 Hz in the cavity is attenuated from 118 dB to the ground level at 105 dB with the active control. A complete analysis of the system based on the describing function analysis is presented. The experimental results favorably compare with the prediction of the model; moreover, they allows identification of some parameters, such as the equivalent volume velocity of the unstable mixing layer and its coupling gain with the pressure fluctuation.
Product audit for heavy duty diesel engines in production environment
Authors: Suh Sanghoon , Beresford Jim
Published: October 2013

A product audit at manufacturing plants has become more important due to the customer’s requirements on product quality. Noise and vibration performance have been a primary concern for gas engines and small size diesel engines. Lately, more interest has been shown by truck manufacturers about engine noise for heavy duty diesel application. It has been regarded that acoustic measurements requires dedicated measurement environment for detailed study. This case study shows that acoustic measurements can be performed at performance cell without any dedicated acoustic treatment at the manufacturing plant to identify some of the noise characteristics with proper preparation. Order tracking and loudness were used to identify two different characteristics related to front gear train in heavy duty diesel engines. In addition, the coordination between technical organization and manufacturing plant for the data acquisition and analysis is discussed.
Hand transmitted vibration measurement using experimentally simulated hand-arm rig
Authors: Kadam Rahul , Johnson Marty , Muract Jorge , Burdisso Ricardo
Published: October 2013

Hand transmitted vibration (HTV) is one of the most common hazards faced by workers in the construction industry. A major source of HTV is hand held percussion tools, such as pneumatically driven chipping hammers and rock drills. This paper presents a new approach to measuring the vibration from these tools using a mechanically simulated hand arm model to which the tools are attached. The simulated hand-arm model has been designed to have similar dynamic characteristics to that of a human hand-arm system. This approach addresses the issue of repeatability as HTV measurements suffer from variability between cases and from user to user. Different percussion tools ranging from a small chipping hammer to a rock drill, from two major construction equipment manufacturing companies, were used to conduct the vibration tests. The goals of these tests were to measure the vibration levels and to determine the most dominant modes of vibration. Comprehensive data analyses of the tests results are presented. Further, the paper discusses potential vibration control methods and expected performance levels.
Consumer oriented product noise testing
Authors: Blomberg Les
Published: October 2013

This paper explores the need for product noise measurements and how best to meet that need in the near future. Currently there is only a small market place for quieter consumer products. This is not because of lack of interest. No one really wants to announce to everyone in their house that they just flushed the toilet, few really want the entire neighborhood to know they are mowing their yard, etc. The small market place is primarily due to a lack of regulations on product noise, a lack of information easily available to consumers about which products are quieter, and market consolidation resulting in fewer manufacturers, most of whom are unwilling to emphasize their quieter products at the risk of eroding sales of their noisier ones (that currently have greater market share). In the absence of the EPA fulfilling its statutory requirement to regulate and label product noise under the Noise Control Act of 1972, and with the unwillingness of most industries to voluntarily publish accurate product noise data, there is a significant role for ‘‘Consumer Oriented Product Noise Testing.’’ This paper explores the Noise Pollution Clearinghouse’s ongoing and planned product noise testing, evaluating its advantages, disadvantages, and limitations.
Case study: The environmental process at Logan International Airport
Authors: Timmerman Nancy
Published: October 2013

For a facility like Logan International Airport in Boston, the Environmental Impact Analysis is performed annually; it is an ongoing activity. The effort is not performed by any one person or any one company. This paper will present the analysis, reporting, and review process for Logan as far as noise is concerned. Examples will be drawn from the 2003 Environmental Data Report (submitted to the Commonwealth of Massachusetts) and from the author’s personal experience.
Using transportation demand models to assess regional noise exposure
Authors: Kaliski Kenneth
Published: October 2013

In the United States, most metropolitan areas run some type of transportation demand model to estimate regional travel patterns, and, to some extent, air pollution. The more advanced of these models accurately represent the geographic contours of the roadways (in contrast to the older straight-line node and link models). This allows an almost seamless integration of these new transportation demand models into noise prediction models. Combined with the locations of individual homes from a separate E911 database, we can readily make estimates of the noise exposure of populations over large areas. In this paper, the regional traffic noise exposure of residences of Chittenden County, VT is estimated and mapped. It was found that 30% of the residences are exposed to noise levels exceeding the WHO sleep disturbance level of 45 dB LAeq(8) and 20% of residences are exposed to levels exceeding the WHO ‘‘serious annoyance’’ level of 55 dB LAeq(16). Maps show noise contours as well as individual homes color coded based on relative day and night noise exposure levels. Measured sound level data are given for particular locations to validate the predictions.
Heavy construction equipment noise study using dosimetry and time-motion studies
Authors: Spencer Ellsworth R. , Yantek David S.
Published: October 2013

Noise-induced hearing loss continues to afflict workers in many occupational settings despite longstanding recognition of the problems and well-known methods of prevention and regulations. Sound levels associated with heavy construction equipment range from 80 to 120 dB(A) and power tools commonly used in construction produce sound levels up to 115 dB(A). The focus of the research was to determine the noise exposures of heavy construction equipment operators while documenting the workers’ tasks, (i.e., hauling, moving, and/or pushing construction material). Time-motion studies were performed at the construction sites and were used to correlate the noise dosage with the work performed by equipment operators. The cumulative dose for the operator was then plotted with references to work tasks, to identify the tasks that caused the greatest noise exposure. Three construction sites were examined and located in the western Pennsylvania and eastern Ohio areas. The types of construction equipment studied included asphalt pavers, backhoes, bulldozers, compaction equipment, excavators, haul trucks, telehandlers, and wheeled loaders. The results showed that bulldozer operators consistently had the highest noise exposures, ranging from a NIOSH REL (Recommended Exposure Limit) dose of 844% to 25836% and an OSHA PEL (Permissible Exposure Limit) dose of 139% to 1397%.
Federal Highway Administration (FHWA) Roadway Construction Noise Model (RCNM)
Authors: Rochat Judith L. , Reherman Clay N.
Published: October 2013

Roadway construction is often conducted in close proximity to residences and businesses and should be controlled and monitored in order to avoid excessive noise impacts. To aid in this process, the Volpe Center Acoustics Facility, in support of the Federal Highway Administration (FHWA), has developed a construction noise screening tool. The FHWA Roadway Construction Noise Model (RCNM) is a newly developed national model for the prediction of construction noise. The model is based on the construction noise prediction spreadsheet developed for the Central Artery/Tunnel Project in Boston, MA (CA/T Project or ‘‘Big Dig’’) by Erich Thalheimer of Parsons Brinckerhoff Quade & Douglas, Inc. The CA/T Project is the largest urban construction project ever conducted in the United States and has the most comprehensive noise control specification ever developed in the United States. RCNM incorporates the CA/T Project’s noise limit criteria and extensive construction equipment noise database, where these parameters can be modified according to each user’s needs. Users can also activate and analyze multiple pieces of equipment simultaneously and define multiple receptor locations, including land-use type and baseline noise levels, where RCNM will calculate sound level results for multiple metrics.
Noise and vibration issues in contemporary facilities
Authors: Evans Jack B.
Published: October 2013

Contemporary medical facilities, whether for diagnosis, treatment or research, must accommodate the needs of humans and medical instruments or equipment. With regard to acoustics, the disparate requirements vary from acoustic privacy to freedom from intrusive noise, to vibration control. Medical facilities also grow and change, subjecting occupants to demolition and construction disturbances. Acoustical criteria employed in building designs are often inadequate to control the full spectral range of requirements, although criteria for many conditions do exist. This paper presents interesting problems and conditions that occur in healthcare and research facilities with brief case studies to illustrate them, including construction disturbances, tonal noise affects on patients, privacy, and vibration and low frequency noise affects on medical equipment. Measurement data will contrast ambient versus disturbed conditions. Solution concepts to example problems will be presented with photo or drawing illustrations. Discussion will include typical conflicts, constraints, limitations and compromises. Concluding remarks will suggest application of appropriate and comprehensive acoustical, noise and vibration criteria.
Fast calculations of transient pressure fields produced by spherically focused radiators
Authors: McGough Robert
Published: October 2013

A fast method for calculating the pressure distribution generated by a spherical shell is demonstrated for a pulsed excitation. The integral expression derived for the fast method, which is analytically equivalent to the convolution integral defined for the impulse response, converges very quickly. This rapid convergence reduces the error and the computation time with respect to the impulse response approach. Furthermore, the resulting integral expressions are greatly simplified relative to those obtained with the impulse response approach. Results are computed for a pulsed excitation where the integrals are evaluated with the midpoint rule and Gauss quadrature. Simulation results demonstrate that these expressions achieve smaller errors in less time with Gauss quadrature, whereas the midpoint rule is appropriate for computing transient fields generated by very large spherical shells. [Work supported in part by NIH Grant R01-CA093669.]
Time-space decomposition of the transient pressure field generated by a rectangular piston
Authors: Kelly James F. , McGough Robert J.
Published: October 2013

Exact solutions to the acoustic wave equation for canonical geometries are important for transducer evaluation and as a reference for large-scale simulations of wave propagation. An exact solution for the transient pressure field generated by a rectangular piston is derived. Consisting of a superposition of integrals, this solution avoids the edge singularities associated with earlier solutions. Computational overhead is significantly reduced by applying a novel time-space decomposition technique, whereby the spatial and temporal dependence of the integrand is analytically separated. By evaluating a set of integrals at each point in space, the transient pressure field is synthesized by weighting and summing against a set of time-dependent functions. This decomposition technique, which utilizes spatially band-limited integrands, avoids the artificially large sampling frequencies associated with the standard impulse response approach. Quantitative comparison with the spatial impulse response method is made in terms of maximum error and computation times. At 10% peak error, the time-space decomposition technique achieves a factor of 2 speed-up compared to spatial impulse response. Due to the rapid convergence of the integrals in the new technique, the speed-up increases to a factor of 6.8 at 1% peak error. [Work partially supported by NIH Grant 1R01 CA093669.]
Equivalence of expressions for the radiation force on cylinders and application to elliptical cylinders
Authors: Wei Wei , Marston Philip L.
Published: October 2013

Using an appropriate grouping of terms, a radiation force expression for cylinders in a standing wave based on far-field scattering [W. Wei, D. B. Thiessen, and P. L. Marston, J. Acoust. Soc. Am. 116, 202–208 (2004)] is transformed to an expression given elsewhere [F. G. Mitri, Eur. Phys. J. B 44, 71–78 (2005)]. Mitri’s result is from a near-field derivation for the specific case of a circular cylinder. In the usual case, in an ideal lossless media the far-field derivation is not an approximation. The far-field derivation also applies to noncircular objects having mirror symmetry about the incident wave vector. Some general and historical aspects of far-field derivations of optical and acoustical radiation force (going back to 1909) will be noted. Our formulation yields a simple low-frequency approximation for the radiation force on elliptical cylinders by introducing approximations for the partial-wave scattering coefficients of elliptical cylinders first derived by Rayleigh. [Work supported by NASA.]
Time domain evolution of diffuse fields in heterogeneous slabs
Authors: Turner Joseph A.
Published: October 2013

Fundamental studies of elastic wave scattering in heterogeneous media are applicable for problems at several length scales from ultrasonic to seismic waves. The intermediate scattering regime that lies between the single scattering and the diffusion limits is perhaps the least understood. Experiments of elastic wave scattering through a heterogeneous slab have been studied in the time domain using diffusion theory to fit the data. However, numerical solutions of the elastic wave radiative transfer equation (RTE) in the steady state have shown that the conditions for validity of the diffusion limit are only satisfied in the interior of the slab, many mean free paths away from the boundaries. Thus, an examination of the time domain multiple scattering in heterogeneous slabs is important to this class of experiments. The spatial distribution, temporal evolution, and partitioning of the diffuse longitudinal and shear energies are studied as a function of direction and frequency for several types of microstructure including polycrystalline metals and two-phase media using numerical solutions of the RTE. Finally, the ability of a diffusion-type solution to fit RTE solutions is also discussed with applications to inversion of experimental results. [Work supported by DOE.]
Monte Carlo simulations of elastic wave multiple scattering in polycrystalline media
Authors: Ghoshal Goutam , Turner Joseph A.
Published: October 2013

The scattering of elastic waves in polycrystalline media is primarily due to the orientation distribution of the crystal axes of the grains. This scattering may be used to extract microstructural parameters of the material such as grain size and grain texture. In particular, diffuse ultrasonic backscatter measurements have been especially useful for extracting microstructural information. Diffuse backscatter is often modeled analytically under a single scattering assumption. Beyond single scattering, the elastic radiative transfer equation (RTE) governs the evolution of diffuse energy and includes all multiple scattering effects. In this presentation, a rigorous connection between the RTE theory and the backscatter experiments is discussed. Specific solutions are obtained for a specimen excited by a normally incident longitudinal wave. Results are compared with previous backscatter theories. In addition, numerical results are presented using Monte Carlo simulations including various levels of scattering to observe differences between single and multiple scattering solutions. The Monte Carlo solutions are based on the analogy between the RTE and the Boltzmann theory of gas. Relevant applications for materials of common interest are discussed. These results are anticipated to impact ultrasonic nondestructive evaluation of polycrystalline media. [Work supported by U.S. DOE.]
Propagation of elastic waves in hexagonal crystals with fiber texture
Authors: Yang Liyong , Turner Joseph A.
Published: October 2013

Many cold-working processes for polycrystalline metals cause alignment of the grains with a single symmetry axis called fiber texture. The existence of a preferred orientation of the grains has a big influence on the propagation and scattering of ultrasonic waves, which are often used for materials inspection. Knowledge of the wave attenuation of such textured materials is of both theoretical and practical interest to nondestructive testing and materials characterization. In this presentation, the quantitative relations between fiber texture and wave attenuations of hexagonal crystals are presented. The texture is characterized by a Gaussian distribution function that contains a single parameter that governs the transition of the texture from statistically isotropic to fiber texture. Under this assumption, the materials of interest have a varying degree of transverse isotropy representatives of processing conditions. Simple expressions for the attenuations of the three modes of waves are given in a concise representation. Finally, numerical results are presented and discussed in terms of the directional, frequency, and texture dependence. The results presented are expected to improve the understanding of the microstructure evolution during thermomechanical processing. [Work supported by DOE.]
Acoustic performance of a sound attenuating duct utilizing spatially periodic area changes with absorbing material
Authors: Bliss Donald , Danilov Pavel
Published: October 2013

Sound propagation of one-dimensional waves through a duct with spatially periodic area changes has been studied theoretically and experimentally in previous research. The resulting wave behavior is similar to that observed for periodic structures, with Bloch waves, passbands and stop bands. This configuration substantially reduces sound transmission from noise sources having harmonics that fall in the stop bands, while having little effect in passbands. The present study adapts this concept to configurations with dissipative sound absorbing material. The periodically spaced regions of the duct with larger cross-sectional area are partially filled with porous material, so that the open cross-sectional area remains constant throughout the duct. The duct is analyzed as a quasi-one-dimensional system using an approach based on periodic structure theory. The effect of the porous material is to make the propagation wave number in the porous/open subsections complex, thereby changing the nature of the stop and passbands, and providing significant attenuation even in passbands. Results suggest that, for a given amount of porous material, the best attenuation strategy may be to distribute the porous material in periodically spaced subregions rather than in either a single larger volume, or in a uniform distribution all along the duct.
Finite-bandwidth Kramers–Kronig relations for the determination of acoustic group velocity and frequency derivative of attenuation
Authors: Mobley Joel
Published: October 2013

Kramers–Kronig (K–K) analyses of experimental data are complicated by the extrapolation problem, which is concerned with how the unexamined spectral bands impact K–K calculations. In this talk the causal linkages in resonant-type data are demonstrated without extrapolation through acoustic K–K relations for the group velocity and the derivative of the attenuation coefficient (components of the derivative of the complex wave number). Due to their shape-invariant predictions with respect to subtraction constants, these new relations provide stricter tests of causal consistency than previously established K–K relations for the phase velocity and attenuation coefficient. For both the group velocity and attenuation derivative, three forms of the relations are derived. These relations are equivalent for bandwidths covering the infinite spectrum, but differ when restricted to finite spectral windows. Using experimental data from microsphere suspensions, the accuracy of finite-bandwidth K–K predictions for group velocity, and the attenuation derivative are demonstrated. Of the multiple methods, the most accurate forms were found to be those whose integrals were expressed only in terms of the phase velocity, and attenuation coefficient themselves requiring no differentiated quantities.
Quantitative acoustic gas sensing: A two-frequency reconstructive algorithm based on molecular relaxation
Authors: Petculescu Andi , Lueptow Richard
Published: October 2013

Commonly, acoustics-based devices for the sensing and monitoring of fluid media have involved measuring changes in the phase velocity or sound speed. What has been left out is the acoustic attenuation. The nonclassical or relaxational attenuation of sound in fluids arises from the inability of internal molecular degrees of freedom (vibration, rotation, isomerism, etc.) to follow the acoustic fluctuations. Thus, attenuation is directly related to the molecular relaxation times. In traditional laboratory experiments of acoustic relaxation in fluids, one needs to use several acoustic frequencies and vary the ambient pressure over a wide range in order to cover the main relaxation processes. In a sensing device, this would be highly impractical due to time constraints. A novel and unique algorithm is presented that uses only two acoustic frequencies at a single pressure to reconstruct the full frequency dependence of the primary relaxation processes via the effective specific heat, thus enabling a potential sensor to pinpoint the nature and concentration of contaminant molecular species in a host gaseous environment. It will be shown how the algorithm identifies a contaminant of methane in a simulated host atmosphere of nitrogen with accuracy better than 0.5%. [Work supported by NASA.]
Future trends in acoustic gas sensing
Authors: Petculescu Andi G. , Lueptow Richard M.
Published: October 2013

Traditionally, acoustic devices for monitoring gaseous environments have involved measuring the sound speed in the analyzed medium. However, measurements of sound speed alone do not always allow a quantitative analysis of the gas species present in the sensed volume. What has been consistently omitted is the acoustic attenuation. The nonclassical or relaxational attenuation of sound in fluids arises from the inability of internal molecular degrees of freedom (vibration, rotation, isomerism, etc.) to follow the acoustic fluctuations. This feature relates it directly to relaxation times, which are characteristic of the molecular species that are present. Together with sound speed, attenuation can be used to obtain the effective specific heat of the fluid, which is the fundamental macroscopic footprint of all internal relaxation processes characteristic of the gases that form the sensed environment. The purpose of this presentation is to present several trends and challenges in the development of the next-generation ‘‘smart’’ acoustic gas sensors. The operational line of thought, based on physical principles that future intelligent sensors might employ to quantitatively detect and identify contaminant gases leaking into a host environment, is outlined. [Work was supported by NASA.]
Resonant tube spectroscopy of liquids
Authors: Prenzlow Bjorn A. , Tapson Jonathan , Davies Jevon R.
Published: October 2013

The resonant behavior of a fluid-filled piezoelectric tube is studied in an attempt to design a sensor to measure the density, bulk modulus, and viscosity of the sample fluid. It is proposed that the impedance spectrum of the tube over several of its thickness resonances, and the effect of coupling the fluid’s radial modes to these modes, will allow the measurands to be evaluated. The fluid produces several high-Q modes. These couple to the mechanical vibrations of the tube, producing a spectrum with rich modal behavior. In this work, a theoretical model describing the effective acoustic impedance of the fluid is mathematically coupled to that of the empty tube. The relevant governing properties of the piezoelectric tube and the fluid are obtained by optimizing the model with respect to a real spectrum, using an adaptive mutation breeder algorithm. The error between the theoretical and the real spectra for calibrated samples is shown to be small. As a result, the density, bulk modulus, and viscosity of the fluid may be calculated successfully from the features of the measured spectra.
New technology for investigation of photoelastic properties of nontransparent crystals
Authors: Akhmedzhanov Farkhad R. , Meister Lance
Published: October 2013

As is well known, in absolutely transparent crystals an acousto-optical interaction is lacking. In this connection’s greatest interest acousto-optical investigations are presented in optical range, in which the crystal is not transparent. In order to carry out similar experiments, it is necessary to use the crystal with a small light absorption coefficient at applied wavelength. Evidently, the geometry of experiment will be different from that for transparent crystal because the few-millimeters-thick crystal will absorb the incident light completely. The main problem is selection of an appropriate buffer crystal for the investigated crystal that the light beam penetrated into sample by Bragg angle at required frequency. In the present work the measurements of effective photoelastic constant have been done for Si crystal, which is not transparent at wavelength 632.8 nm. The crystal of lithium niobate was used as the buffer crystal because its refractive index (n=2.28) is not far from that for Si crystal. The results of executed investigations have shown the possibility of determination of photoelastic constants in nontransparent crystals by Bragg scattering method. At that rate, the very high intensity of scattered light can be obtained in comparison with that in transparent crystals.
Latest developments of a tire-derived aggregate underlayment to reduce groundborne vibration from light rail transit track
Authors: Wolfe Steven
Published: October 2013

Groundborne vibration reduction for light rail transit (LRT) tracks usually takes the form of some type of soft or special track fastener, or a type of isolation system built under or incorporated as part of the track structure. Two well-known types of track isolation systems are the ballast mat and the floating slab trackbed. A more recent and less-expensive type of track isolation system involves tire-derived aggregate (TDA or shredded scrap tires) used as an underlayment beneath ballast and tie tracks. Field tests have been performed to determine the vibration attenuation and damping properties of TDA for use beneath rail lines and other possible applications. The most recent tests were conducted at an existing LRT system with the trains operating at speed on several sections of revenue ballast and tie track, and where the TDA was installed under ballast and tie rail transit track. Details of the field tests are presented with a focus on the most recent test results, which indicate the performance of the TDA underlayment in comparison with other track isolation methods.
In-service tests of the effectiveness of vibration control measures on the BART rail transit system
Authors: Saurenman Hugh
Published: October 2013

Controlling vibration from new rail transit systems can be quite expensive when the alignment passes through residential areas. However, there is relatively little documented information on how effective different vibration mitigation approaches perform under in-service conditions. This paper presents results of a number of vibration measurements of the different track forms used on the current San Francisco Bay Area Rapid Transit (BART) system including floating slab, resiliently supported half ties, and high-resilience direct fixation fasteners in subways and one section of floating slab used on at-grade tracks. The goal was to obtain data that would improve the predictions of future vibration levels and perhaps lead to more cost effective vibration mitigation strategies for the proposed BART extension to San Jose. The tests show that the floating slabs are performing much as designed, the resiliently supported half ties are less effective than expected, and the high resilience track fasteners are probably performing as expected, although the results are clouded because of severe rail corrugation in the area where the new fasteners were installed. Some unanticipated results are the apparent interaction of the floating slab resonance, the wheel rotation frequency, the bogey dynamics, and vibration propagation characteristics of the ground.
An evaluation of the accuracy of the Federal Transit Administration approved, groundborne noise and vibration prediction model for rail transit systems; a case study for a new subway line using post construction, transit operation measurements
Authors: Carman Richard A. , Reyes Carlos H.
Published: October 2013

The groundborne noise and vibration model developed by Nelson and Saurenman in 1984, now recognized by the Federal Transit Administration as the approved model for new transit system facilities, is entering its third decade of use by engineers and consultants in the transit industry. The accuracy of the model has been explored in the past (e.g., Carman and Wolfe). New data obtained for a recently completed extension to a major heavy rail transit system provides an opportunity to evaluate the accuracy of the model once more. During the engineering design phase of the project, noise and vibration predictions were performed for numerous buildings adjacent to the new subway line. The values predicted by the model were used to determine the need for and type of noise and/or vibration control measures. After the start of transit operations on the new line, noise and vibration measurements were made inside several of the buildings to determine whether the criteria were in fact achieved. The measurement results are compared with the values predicted by the model. The predicted and measured, overall noise and vibration levels show very good agreement, whereas the spectral comparisons indicate some differences. Possible reasons for these differences are offered.
A theoretical-experimental approach for assessing the vibration impact due to vehicular traffic upon the heritage building structures
Authors: Barbaro S. , Barrera G. , Santamaria A. Sansone , Holt Rachael F.
Published: October 2013

In past years, a new method of structural analysis has been developed for assessing the vibration impact due to vehicular traffic upon the heritage building structures. This method is based on on the conjuncture among the monitoring of the structure, and the structural identification. The satisfaction of such demands in the case of buildings already realized, above all if ancient, can be prevented by the impossibility to reach to a complete knowledge both of the structural organism and the strength state of maintenance of every component of the building. An exhaustive knowledge would be achievable only applying such methods of investigation to induce heavy troubles to the analyzed manufactured article. From these consideration the idea of the construction of an elementary system is born. An elementary PC model, that is an ideal receiver whose all the mechanical and geometric characteristics are known, has been designed for in situ analysis and excited applying the experimental vibrational levels in order to evaluate the response. A further development is to realize the physical model and execute local experimental campaigns. This operative system has to be transportable and positionable near the source without holding up the traffic nor damaging the measurement site.
The relation between categorical perception of speech stimuli and reading skills in children
Authors: Breier Joshua , Fletcher Jack , Klaas Patricia , Gray Lincoln
Published: October 2013

Children ages 7 to 14 years listened to seven tokens, /ga/ to /ka/ synthesized in equal steps from 0 to 60 ms along the voice onset time (VOT) continuum, played in continuous rhythm. All possible changes (21) between the seven tokens were presented seven times at random intervals, maintaining the rhythm. Children were asked to press a button as soon as they detected a change. Maps of the seven tokens, constructed from multidimensional scaling of reaction times, indicated two salient dimensions: one phonological and the other acoustic/phonetic. Better reading, spelling, and phonological processing skills were associated with greater relative weighting of the phonological as compared to the acoustic dimension, suggesting that children with reading difficulty and associated deficits may underweight the phonological and/or overweight the acoustic information in speech signals. This task required no training and only momentary memory of the tokens. That an analysis of a simple task coincides with more complex reading tests suggests a low-level deficit (or shift in listening strategy). Compared to control children, children with reading disabilities may pay more attention to subtle details in these signals and less attention to the global pattern or attribute. [Supported by NIH Grant 1 RO1 HD35938 to JIB.]
Temporal and acoustic characteristics of Greek vowels produced by adults with cerebral palsy
Authors: Botinis Antonis , Orfanidou Ioanna , Fourakis Marios , Fourakis Marios
Published: October 2013

The present investigation examined the temporal and spectral characteristics of Greek vowels as produced by speakers with intact (NO) versus cerebral palsy affected (CP) neuromuscular systems. Six NO and six CP native speakers of Greek produced the Greek vowels [i, e, a, o, u] in the first syllable of CVCV nonsense words in a short carrier phrase. Stress could be on either the first or second syllable. There were three female and three male speakers in each group. In terms of temporal characteristics, the results showed that: vowels produced by CP speakers were longer than vowels produced by NO speakers; stressed vowels were longer than unstressed vowels; vowels produced by female speakers were longer than vowels produced by male speakers. In terms of spectral characteristics the results showed that the vowel space of the CP speakers was smaller than that of the NO speakers. This is similar to the results recently reported by Liu et al. [J. Acoust. Soc. Am. 117, 3879-3889 (2005)] for CP speakers of Mandarin. There was also a reduction of the acoustic vowel space defined by unstressed vowels, but this reduction was much more pronounced in the vowel productions of CP speakers than NO speakers.
Formant trajectory characteristics in speakers with dysarthria and homogeneous speech intelligibility scores: Further data
Authors: Kim Yunjung , Weismer Gary , Kent Ray D.
Published: October 2013

In previous work [J. Acoust. Soc. Am. 117, 2605 (2005)], we reported on formant trajectory characteristics of a relatively large number of speakers with dysarthria and near-normal speech intelligibility. The purpose of that analysis was to begin a documentation of the variability, within relatively homogeneous speech-severity groups, of acoustic measures commonly used to predict across-speaker variation in speech intelligibility. In that study we found that even with near-normal speech intelligibility (90%–100%), many speakers had reduced formant slopes for some words and distributional characteristics of acoustic measures that were different than values obtained from normal speakers. In the current report we extend those findings to a group of speakers with dysarthria with somewhat poorer speech intelligibility than the original group. Results are discussed in terms of the utility of certain acoustic measures as indices of speech intelligibility, and as explanatory data for theories of dysarthria. [Work supported by NIH Award R01 DC00319.]