bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Optimization of Catalytic Converters Taking Into Account 3D and Transient Phenomena as an Integral Part in Engine Cycle Simulations
Authors: Wurzenberger Johann C. , Peters Bernhard J.
Published: February 2009

The Discrete Channel Method (DCM) is presented as a new approach to model the transient multidimensional behavior of honeycomb-type catalytic converters. DCM combines a detailed modeling of effects taking place inside individual channels with the description of thermal effects occurring in the entire converter. The model is compared to experimental data measured under adiabatic conditions and to solutions generated by the finite difference method. DCM is applied to simulate the light-off behavior for different exhaust gas compositions under adiabatic and non-adiabatic conditions. The results show the influence of changing gas compositions and of radial heat losses on the performance of catalytic converters and aftertreatment systems. Hence, DCM is an effective and computationally fast method tailored for the integration in the engine analysis tool BOOST but also for stand-alone catalyst simulation.
The Effect of Lubricant Chemistry on Wear and Scuffing of Coated Surfaces
Authors: Cheenkachorn K. , Perez J. M. , Ajayi O. O. , Fenske G. R.
Published: February 2009

This study focuses on the effect of lubricant chemistry on wear and scuffing of coated surfaces. The coated surfaces in the present work include TiAlN, TiN, and CrN in the presence of different lubricants including high-oleic sunflower oil, high-oleic corn oil, fully-formulated sunflower oil, fully-formulated corn oil, and a synthetic base oil. The tests are conducted using the four-ball wear test to study the wear and scuffing properties. The scanning electron microscope (SEM) and optical microscope with MicroXAMR are used to study the wear mechanism. The study shows that coatings do not affect the friction coefficient at severe test conditions. However, some coatings, TiN and CrN, improve the wear properties even in base fluids without additives. All coatings improve the scuffing properties and increase the contact severity index. The vegetable-based lubricants perform comparably to commercially available synthetic lubricants.
An Experimental and Computational Investigation on the Pre-Heating of Fuel to Improve Cold Starting of Diesel Engines
Authors: Gambhir Gurpreet S. , Abata Duane L. , Michalek Donna J.
Published: February 2009

This paper describes the effect of elevated fuel temperature on cold starting operability in compression ignition engines. This study was based on the hypothesis that in a cold start condition, fuel heated to a temperature higher than the surrounding ambient air before it enters the combustion chamber would improve cold starting. Experiments on heating the injector and the fuel before the injection event were performed in a cold room facility with ambient temperatures varying from −20 degrees to 20 degrees Celsius. A computational analysis of the injector was conducted using Star-CD to more fully understand the physical phenomena involved and help explain results obtained from the experiment. Results indicated that fuel heating does affect the efflux velocity, Sauter mean diameter and the lifetime of a fuel droplet. Droplet break-up time and spray penetration are not much affected. Computational and experimental results were within 30% of each other. Results of this work should be useful in the design of improved cold starting methods of diesel fueled engines.
CFD Analysis of Engines: An Advanced Approach Based on Codes Dynamically Coupled
Authors: De Vita Angelo , Di Angelo Luca , Andreassi Luca
Published: February 2009

An advanced approach to evaluate the gas flow in internal combustion engines has been carried out. It is based on an interactive procedure which dynamically couples one-dimensional (1D) and three dimensional (3D) computational fluid dynamics codes. Direct feedback between the codes has been assured allowing 3D fluid flow effects to be fed back into the 1D system. A cycle-by-cycle convergence of results in the data exchange sections has been guaranteed. The capability of describing physical phenomena increases and some numerical problems, as the reflection of pressure waves on the 3D grid boundaries, can be avoided. The procedure has been applied to a simple test case and to a typical engine application where 3D effects are not negligible: flow field definition within an air box for race cars. The procedure has proven effective and could be easily adapted for further different applications.
A Learning-Machine Based Method for the Simulation of Combustion Process in Automotive I.C. Engines
Authors: Anguita Davide , Rivieccio Fabio , Canova Marcello , Casoli Paolo , Gambarotta Agostino
Published: February 2009

In automotive applications problems related to management and diagnostics play an important role to improve engine performance and to reduce fuel consumption and pollutant emissions. In the design of control systems the use of theoretical models for the simulation of engine behaviour proved to be very useful, and it is apparent from the literature. However, since automotive engines have become very complex plants, their modelling requires a comprehensive description of the behaviour of many processes and components. Combustion process has a strong influence on performance and emissions, but its theoretical description can be hardly combined with the requirements of control-oriented models (especially as regards “real-time” applications). Two simplified theoretical models are proposed in the paper, based on a thermodynamic and a simplified approach respectively. In the first case a single-zone method was followed with the introduction of an apparent heat release rate (HRR) described as a superposition of two Wiebe functions. Coefficients of these burning functions are estimated by means of Learning Machines (LM), i.e. Support Vector Machines (SVM), trained from experimental data and then embedded in a Simulink® block. In order to make calculation time shorter, a simpler and faster model based on the application of SVM was defined to describe combustion process. Starting from experimental data, the proposed SVM was trained and implemented in a Simulink® block to evaluate exhaust gas temperature and bmep directly from engine operating parameters. Both blocks were defined to be easily embedded in engine simulation models for control-oriented applications. Results were promising for both models, showing very short computation time. A comparison of theoretical outputs with experimental data is reported in the paper, together with an application of both calculation procedures to a comprehensive model of a modern automotive turbocharged Diesel engine.
Investigating the Effects of Turbulence Inducement on Diesel Engine Combustion and Emission Characteristics
Authors: Senthilkumar K. R. , Gopalakrishnan K. V. , Mehta Pramod S.
Published: February 2009

In the present work, the effects of inducing in-cylinder turbulence through bluff bodies or internal jets are experimentally investigated on a direct injection diesel engine. The bluff bodies are placed horizontally across the piston cavity in the form of rods or rods wound with thin wire in different arrangements. The jet turbulence is introduced by holes on the piston crown, allowing a tangential entry of the working fluid into the piston cavity along the direction of swirl. The changes in performance, emission and combustion characteristics of the engine, due to these arrangements, are analyzed. In general, horizontal bluff bodies do not result in significant advantage in fuel economy and smoke levels, but some reduction in NOx concentration is observed. More importantly, it is observed that the internal jets introduced through the tangential holes showed improvement in the engine brake thermal efficiency and exhaust smoke level with a marginal increase in NOx concentration.
TCA: MAN B&W Diesel’s New Turbocharger Generation
Authors: Bartholoma¨ Klaus
Published: February 2009

MAN B&W Diesel’s proven NA/S and /T9 turbocharger generation has been successfully in the market for approximately 10 years. Early in 2000, MAN B&W Diesel decided to meet the increased demands of the engine manufacturers by developing a new turbocharger generation. The investigations of the two prototype TCA77 turbochargers were already started in the middle of 2001 on the burner rig test bed and afterwards on the engine. This abstract gives an overview about the development targets and shows the TCA turbocharger programme. The design details are explained with special attention to the design features of the compressor, the turbine and the bearing concept. This paper explains MAN B&W’s new containment safety concept applied to the TCA generation and shows the results of the investigations with regard to noise emissions and efficiencies.
Engines Benefit From Automotive Technology
Authors: List Helmut
Published: February 2009

With intense competition today among builders of large engines the drive to improve technology and reduce engine cost has accelerated. Leading large engine builders have always developed their own techniques to do this. A huge investment has been made in the last 10 years by the automotive industry to further develop technology and large engine builders are now benefiting from these advances. Use is also being made of the longer experience of the automotive engine builders in developing electronics and in meeting emissions legislation. We look at how these techniques are being adapted for marine, locomotive and power generation engines and at the benefits they are bringing. Examples are described from analytical software development, common rail FIE, in cylinder measurements and reliability engineering to production engineering, engine health monitoring and alternative fuels. Further market demands and more stringent regulations are considered because they will force ever more development in an ever reducing time scale. Shorter engine test times are essential. Other ways are being developed to ensure competitive performance and reliability. Future developments in response to these demands are predicted and the effects these may have on large engine design are assessed.
Dynamic Simulation of a Wind Farm With Variable Speed Wind Turbines
Authors: Muljadi E. , Butterfield C. P.
Published: February 2009

Wind power generation has increased very rapidly in the past few years. The total U.S. wind power capacity by the end of 2001 was 4,260 megawatts. As wind power capacity increases, it becomes increasingly important to study the impact of wind farm output on the surrounding power networks. In this paper, we attempt to simulate a wind farm by including the properties of the wind turbine, the wind speed time series, the characteristics of surrounding power network, and reactive power compensation. Mechanical stress and fatigue load of the wind turbine components are beyond the scope this paper. The paper emphasizes the impact of the wind farms on the electrical side of the power network. A typical wind farm with variable speed wind turbines connected to an existing power grid is investigated. Different control strategies for feeding wind energy into the power network are investigated, and the advantages and disadvantages are presented.
A Wind Tunnel Study of Heat Transfer Over Complex Terrain
Authors: Pantoya Michelle , Shifflett Kenneth , Oler Walter , Burton William
Published: February 2009

Maximizing wind energy resources requires a detailed understanding of atmospheric flow behavior over complex topography. The objective of this research is to examine unstable flow behavior over a three-dimensional topographic model, representative of mesa terrain that is common in West Texas. The goal is to develop an understanding of how unstable atmospheric conditions caused by surface heating affect boundary layer flow patterns in the natural environment. This objective was accomplished by experimentally monitoring transient thermal behavior of narrow band liquid crystals over a scaled model. Photographic data was collected as the heated model was subjected to a cooler flow field. The transient isotherms result from cooling as the model is exposed to flow in an atmospheric boundary layer wind tunnel. Results suggest that flow patterns associated with unstable conditions can be explained by increased wind speeds on the lee side of a mesa followed by vigorous mixing causing increased cooling rates around the mesa sides. The results could be used to improve the accuracy of numerical atmospheric flow models, assess the feasibility of developing wind turbine sites, and increase the knowledge-base in order to advance wind energy forecasting techniques.
Output Power Correlation Between Nearby Wind Power Plants
Authors: Wan Yih-Huei , Milligan Michael , Parsons Brian
Published: February 2009

The National Renewable Energy Laboratory (NREL) started a project in 2000 to record long-term, high-frequency (1-Hz) wind power output data from large commercial wind power plants. Outputs from about 330 MW of wind generating capacity from wind power plants in Buffalo Ridge, Minnesota, and Storm Lake, Iowa, are being recorded. Analysis of the collected data shows that although very short-term wind power fluctuations are stochastic, the persistent nature of wind and the large number of turbines in a wind power plant tend to limit the magnitudes and rates of changes in the levels of wind power. Analyses of power data confirm that spatial separation greatly reduces variations in the combined wind power output relative to output from a single wind power plant. Data show that high frequency variations of wind power from two wind power plants 200 km apart are independent of each other, but low frequency power changes can be highly correlated. This fact suggests that time-synchronized power data and meteorological data can aid in the development of statistical models for wind power forecasting.
Summary of the Delft University Wind Turbine Dedicated Airfoils
Authors: Timmer W. A. , van Rooij R. P. J. O. M.
Published: February 2009

This paper gives an overview of the design and wind tunnel test results of the wind turbine dedicated airfoils developed by Delft University of Technology (DUT). The DU-airfoils range in maximum relative thickness from 15% to 40% chord. The first designs were made with XFOIL. Since 1995 RFOIL was used, a modified version of XFOIL, featuring an improved prediction around the maximum lift coefficient and capabilities of predicting the effect of rotation on airfoil characteristics. The measured effect of Gurney flaps, trailing edge wedges, vortex generators and trip wires on the airfoil characteristics of various DU-airfoils is presented. Furthermore, a relation between the thickness of the airfoil leading edge and the angle-of-attack for leading edge separation is given.
Computation of Modal Aerodynamic Damping Using CFD
Authors: Bertagnolio F. , Gaunaa M. , So̸rensen N. N. , Hansen M. , Rasmussen F.
Published: February 2009

This work focuses on the numerical evaluation of aerodynamic damping for a wind turbine rotor. A finite beam element code is used to describe the structure. Two types of aerodynamic models are compared. Firstly, two engineering semi-empirical dynamic stall models implemented in the structural code for modelling the aerodynamic forces are applied. Secondly, a Navier-Stokes flow solver has been coupled to the structural model. Test cases involving a two-bladed wind turbine rotor are computed. The aerodynamic damping is determined for the two first eigenmodes of the structure. A comparison study of the results highlights the discrepancies between the different models.
Statistical Analysis of Inflow and Structural Response Data From the LIST Program
Authors: Nelson Luke D. , Manuel Lance , Sutherland Herbert J. , Veers Paul S.
Published: February 2009

The Long-Term Inflow and Structural Test (LIST) program is gathering inflow and structural response data on a modified version of the Micon 65/13 wind turbine at a test site near Bushland, Texas. Data from 491 ten-minute time data records are analyzed here to determine the dependency of fatigue and extreme loads on inflow parameters. Flap and edge bending moment ranges at a blade root are chosen as the structural response variable, z. Various parameters related to the inflow (including, for example, primary parameters, the mean and standard deviation of the hub-height horizontal wind speed, and secondary parameters, Reynolds stresses, vertical shear exponent, etc.) are each considered in an inflow parameter vector, x. Time series for the structural response, z, are processed in order to obtain a structural response parameter, y, where in separate statistical studies, y is taken to be either an equivalent fatigue load or an extreme load. This paper first describes a procedure by which the important “dependencies” of y on the various variables contained in the inflow parameter vector, x, may be determined considering all the available data. These dependencies of y on x are then recomputed using only the data with above-rated mean wind speeds (taken to be approximately 13 m/s). The procedure employed is similar to other previous studies, but we do not bin the data sets by wind speed since dependencies in one wind speed bin may be different from those in other bins. Also, our procedure, in sharp contrast to previous studies, examines each inflow parameter in the vector, x, in a sequential analysis, rather than by using multivariate regression.
Reducing the number of vocal fold mechanical tissue properties: Evaluation of the incompressibility and planar displacement assumptions
Authors: Cook Douglas D. , Nauman Eric , Mongeau Luc
Published: February 2009

The incompressibility and planar displacement assumptions were used to reduce the number of independent tissue parameters required for the characterization of a structural model of the vocal folds. The influence of these simplifying assumptions on the vibratory properties of the model was investigated. The purpose was to provide estimates of the error introduced by these assumptions. The variability in human tissue properties was accounted for through systematic variation of several material parameters. The modal properties of a vocal fold structural model were computed with each assumption and, in turn, were relaxed to determine their respective effects. The results indicated that the incompressibility assumption introduces little error. Errors introduced by the planar displacement assumption were found to depend on the ratio of the longitudinal stiffness and the transverse stiffness. Criteria for determining the compatibility of tissue property values from independent studies are also presented.
Effects of shear waves on boundary-coupled vector sensors
Authors: Smith Kevin B.
Published: February 2009

The impact of the acoustic properties of a solid medium on the response of an acoustic vector sensor placed at the boundary between water and the solid is examined. In particular, the components of the vector field both normal and tangential to the boundary are studied. It is shown that the component of the velocity tangential to the boundary is affected by the introduction of shear in the solid medium, which leads to amplitude and phase discontinuities across the boundary. Such discontinuities can lead to mismatches between the vector sensor components that interfere with common, coherent processing techniques. Implications for ocean bottom- and hull-mounted examples are provided.
Effect of internal resistance of a Helmholtz resonator on acoustic energy reduction in enclosures
Authors: Yu Ganghua , Li Deyu , Cheng Li
Published: February 2009

The effect of internal resistance of a Helmholtz resonator on acoustic energy reduction in an enclosure and the multimodal coupling-based Helmholtz resonator design are investigated. Using the analytical solution of a resonator-enclosure interaction model, an energy reduction index is defined in a frequency band to optimize the resonator resistance. The dual process of energy dissipation and radiation of the resonator is quantified. Optimal resistance of the resonator and its physical effect on the resonator-enclosure interaction are numerically evaluated and categorized in terms of frequency bandwidths. Predictions on the resonator performance are confirmed by experiments. Comparisons with existing models based on different optimization criteria are also performed. It is shown that the proposed model serves as an effective design tool to determine the internal resistance of the resonator in order to achieve sound reduction in the frequency band enclosing acoustic resonances.
Low probability of detection underwater acoustic communications using direct-sequence spread spectrum
Authors: Yang T. C. , Yang Wen-Bin
Published: February 2009

Direct-sequence spread spectrum is used for underwater acoustic communications between nodes, at least one of which is moving. At-sea data show that the phase change due to source motion is significant: The differential phase between two adjacent symbols is often larger than the phase difference between symbols. This poses a challenge to phase-detection based receiver algorithms when the source or receiver is moving. A pair of energy detectors that are insensitive to the phase fluctuations is proposed, whose outputs are used to determine the relationship between adjacent symbols. Good performance is achieved for a signal-to-noise ratio (SNR) as low as −10dB based on at-sea data. While the method can be applied to signaling using short code sequences, the focus in this paper is on long code sequences for the purpose of achieving a high processing gain (at the expense of a low data rate), so that communications can be carried out at a low input SNR to minimize the probability of detection (PD) by an interceptor. PD is calculated for a typical shallow water environment as a function of range for several source levels assuming a broadband energy detector with a known signal bandwidth.
Modeling a surface-mounted Lamb wave emission-reception system: Applications to structural health monitoring
Authors: Moulin Emmanuel , Grondel Sébastien , Assaad Jamal , Duquenne Laurent
Published: February 2009

The work described in this paper is intended to present a simple and efficient way of modeling a full Lamb wave emission and reception system. The emitter behavior and the Lamb wave generation are predicted using a two-dimensional (2D) hybrid finite element–normal mode expansion model. Then the receiver electrical response is obtained from a finite element computation with prescribed displacements. A numerical correction is applied to the 2D results in order to account for the in-plane radiation divergence caused by the finite length of the emitter. The advantage of this modular approach is that realistic configurations can be simulated without performing cumbersome modeling and time-consuming computations. It also provides insight into the physical interpretation of the results. A good agreement is obtained between predicted and measured signals. The range of application of the method is discussed.
Binaural signal detection, overall masking level, and masker interaural correlation: Revisiting the internal noise hypothesis
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: February 2009

This study provides data concerning the characteristics of internal noise that limits binaural detection at 500Hz under “pulsed” masking conditions and evaluates whether the parameters of such internal noise depend upon masker/signal duration. A single-interval adaptive procedure was employed to measure NoSπ detection thresholds as a joint function of the level of broadband masking noise and masker/signal duration. Sπ detection thresholds were also measured as a joint function of the interaural correlation of the masker and masker/signal duration. Findings include : (1) changes in Sπ thresholds taken either as a function of diotic masker level or as a function of masker interaural correlation are independent of masker/signal duration; (2) 500-Hz “quiet” So and Sπ thresholds yield a masking-level difference of −2.0; (3) reductions in thresholds with increasing duration are similar regardless of masker level. Analyses indicate: (1) the presence of stimulus-independent, interaurally-negatively-correlated, additive internal noise and stimulus-dependent internal noise having a level proportional to that of the external masker while being independent of masker/signal duration; (2) that NoSπ thresholds taken as a joint function of masker/signal duration and masker spectrum level are, quantitatively, well described by taking into account effects produced by the combination of internal and external noises.
Evaluating roadside noise barriers using an annoyance-reduction criterion
Authors: Nilsson Mats E. , Andéhn Mikael , Leśna Paulina
Published: February 2009

A common indicator of effectiveness for roadside noise barriers is the reduction in A-weighted sound pressure level (LA). The present experimental study considered alternative indicators using an annoyance-reduction criterion. A large number of 8 s experimental sounds were created from binaural recordings conducted at various distances from a highway at a location with a 4.6 m high roadside barrier (barrier sounds) and at a location along the same road with no barrier (nonbarrier sounds). Eighteen listeners scaled the annoyance of the experimental sounds with the method of magnitude estimation. The barrier sounds recorded 10–45 m from the road and nonbarrier sounds recorded 50–200 m from the road were of similar LA. Despite this, the barrier sounds were found to be more annoying than the nonbarrier sounds. The annoyance difference corresponded to approximately a 3 dB increase in LA and was mainly related to the barrier sounds’ higher relative level of low-frequency sound. This suggests that LA reduction may not be a valid indicator of the annoyance reduction caused by a noise barrier. The loudness level (ISO 532B) and a low-frequency corrected sound pressure level (LA∗) were found to be better than LA as indicators of the barrier’s annoyance-reduction efficiency.
Level dominance in sound source identification
Authors: Lutfi Robert A. , Liu Ching-Ju , Stoelinga Christophe
Published: February 2009

Impact sounds were synthesized according to standard textbook equations given for the motion of simply supported, metal plates. In a two-interval, forced-choice procedure, highly practiced listeners identified from these sounds a predefined class of target plates based on their particular material and geometric properties. The effects of two factors on identification were examined: the relative level of partials comprising the sounds and the relative amount of information (given as the difference in d′) each partial provided for identification. In different conditions one factor was fixed while the other either increased or decreased with frequency. The effect on listener identification in each case was determined from a logistic discriminant analysis of trial-by-trial responses, yielding a vector of listener decision weights on the frequency and decay of individual partials. The weights increased proportionally with relative level, but were largely uninfluenced by relative information content—a result exactly opposite to that expected from a maximum-likelihood observer. The dominant effect of relative level was replicated for other sound sources (clamped bars and stretched membranes) and was not diminished by randomizing the relative level of partials across trials. The results are taken to underscore the importance of relative level in the identification of rudimentary sound sources.
Moving microphone arrays to reduce spatial aliasing in the beamforming technique: Theoretical background and numerical investigation
Authors: Cigada Alfredo , Lurati Massimiliano , Ripamonti Francesco , Vanali Marcello
Published: February 2009

This paper introduces a measurement technique aimed at reducing or possibly eliminating the spatial aliasing problem in the beamforming technique. Beamforming main disadvantages are a poor spatial resolution, at low frequency, and the spatial aliasing problem, at higher frequency, leading to the identification of false sources. The idea is to move the microphone array during the measurement operation. In this paper, the proposed approach is theoretically and numerically investigated by means of simple sound propagation models, proving its efficiency in reducing the spatial aliasing. A number of different array configurations are numerically investigated together with the most important parameters governing this measurement technique. A set of numerical results concerning the case of a planar rotating array is shown, together with a first experimental validation of the method.
Age-related differences in the temporal modulation transfer function with pure-tone carriers
Authors: He Ning-ji , Mills John H. , Ahlstrom Jayne B. , Dubno Judy R.
Published: February 2009

Detection of amplitude modulation (AM) in 500 and 4000Hz tonal carriers was measured as a function of modulation frequency from younger and older adults with normal hearing through 4000Hz. The modulation frequency above which sensitivity to AM increased (“transition frequency”) was similar for both groups. Temporal modulation transfer function shapes showed significant age-related differences. For younger subjects, AM detection thresholds were generally constant for low modulation frequencies. For a higher carrier frequency, AM detection thresholds then increased as modulation frequency further increased until the transition frequency. In contrast, AM detection for older subjects continuously increased with increasing modulation frequency, indicating an age-related decline in temporal resolution for faster envelope fluctuations. Significant age-related differences were observed whenever AM detection was dependent on temporal cues. For modulation frequencies above the transition frequency, age-related differences were larger for the lower frequency carrier (where both temporal and spectral cues were available) than for the higher frequency carrier (where AM detection was primarily dependent on spectral cues). These results are consistent with a general age-related decline in the synchronization of neural responses to both the carrier waveform and envelope fluctuation.
Fast volumetric integral-equation solver for high-contrast acoustics
Authors: Bleszynski E. , Bleszynski M. , Jaroszewicz T.
Published: February 2009

An approach for solving volumetric integral equations in acoustics, applicable to problems involving large density contrasts, is described. While the conventional Lippmann–Schwinger integral equations become under such circumstances ill conditioned, the proposed approach reformulates them and casts them into an equivalent system of well-conditioned surface and volume integral equations. The corresponding fast solver [utilizing stiffness matrix compression based on fast Fourier transforms and characterized by O(N log N) solution complexity and storage requirements, where N is the number of unknowns] was enhanced to incorporate the proposed formulation. Features of the solution method and of the solver are illustrated on representative examples of numerically large problems.
Observer weighting of level and timing cues in bilateral cochlear implant users
Authors: van Hoesel Richard J. M.
Published: February 2009

The contribution of binaural level and timing cues available from each pulse in brief electrical pulse trains was determined in a lateralization task using an observer weighting paradigm. Four bilateral cochlear implant users were tested with randomized interaural time delays (ITDs) or, in a separate experimental condition, interaural level differences (ILDs) applied to each pulse at 100, 300, and 600pulses∕s. To examine the effect of cue randomization, weights were also determined for stimuli with a common ITD applied to all postonset pulses. Listeners were further tested for the ability to restart binaural ITD sensitivity at a rate that produced onset dominance by reducing a single interpulse interval in the stimulus. Results showed that the onset always exerted a strong influence. At 100pulses∕s, postonset ITDs and ILDs also contributed strongly. At 300 and 600pulses∕s, contributions from postonset pulses remained substantial for ILDs but were much reduced for ITDs, particularly at 600pulses∕s. Weights were similar with either independent or common ITD cues applied to postonset pulses, indicating that the cue randomization process itself did not affect weights. Restarting of ITD sensitivity at 300pulses∕s by introducing a single reduced interpulse interval was not observed.
Anderson localization of ultrasound in plates: Further experimental results
Authors: Lobkis Oleg I. , Weaver Richard L.
Published: February 2009

Diffuse wave transport is studied in a thick plate with densely machined-in multiple scatterers. As anticipated by theory, energy at short wavelengths diffuses across the structure. Energy localizes at longer wavelengths for which λ∕2π is comparable to the mean free path.
Correction techniques for the truncation of the source field in acoustic analogies
Authors: Martínez-Lera Paula , Schram Christophe
Published: February 2009

The truncation of the source field may induce large overpredictions in the acoustic field computed through acoustic analogies. A comparative study of different correction approaches proposed in the literature is carried out, considering three different techniques: correction terms based on a convection assumption, use of model extensions, and windowing techniques. It is shown that convection-based correction terms need to take into account noncompactness effects of the source field in order to yield accurate results. A modified correction term that includes these effects is derived, and its equivalence to the method of model extensions in the case of purely convected flows is highlighted. Moreover, the performance of different windowing techniques is investigated.
Synchronized spontaneous otoacoustic emissions analyzed in a time-frequency domain
Authors: Jedrzejczak W. Wiktor , Blinowska Katarzyna J. , Kochanek Krzysztof , Skarzynski Henryk
Published: February 2009

A synchronized spontaneous otoacoustic emission paradigm was used to measure the response in time intervals of 80ms following a click stimulus. The responses obtained were decomposed into basic waveforms by means of adaptive approximations using a matching pursuit algorithm. High-resolution time-frequency distributions of signal energy were calculated and showed three types of component: (1) purely evoked of duration less than 5ms, (2) longer lasting and decaying, with exponentially decreasing amplitude, and (3) long lasting and stable. The distributions of the frequencies of components of different durations were similar, with most components falling within the 1–2kHz interval. It is shown that the presence of long-lasting components may influence the estimation of the latency of evoked emissions, especially at higher frequencies where the evoked part has a very short duration.
Frequency response of the skin on the head and neck during production of selected speech sounds
Authors: Munger Jacob B. , Thomson Scott L.
Published: February 2009

Vibrations within the vocal tract during speech are transmitted through tissue to the skin surface and can be used to transmit speech. Achieving quality speech signals using skin vibration is desirable but problematic, primarily due to the several sound production locations along the vocal tract. The objective of this study was to characterize the frequency content of speech signals on various locations of the head and neck. Signals were recorded using a microphone and accelerometers attached to 15 locations on the heads and necks of 14 males and 10 females. The subjects voiced various phonemes and one phrase. The power spectral densities (PSD) of the phonemes were used to determine a quality ranking for each location and sound. Spectrograms were used to examine signal frequency content for selected locations. A perceptual listening test was conducted and compared to the PSD rankings. The signal-to-noise ratio was found for each location with and without background noise. These results are presented and discussed. Notably, while high-frequency content is attenuated at the throat, it is shown to be detectable at some other locations. The best locations for speech transmission were found to be generally common to males and females.
The concept of signal-to-noise ratio in the modulation domain and speech intelligibility
Authors: Dubbelboer Finn , Houtgast Tammo
Published: February 2009

A new concept is proposed that relates to intelligibility of speech in noise. The concept combines traditional estimations of signal-to-noise ratios (S/N) with elements from the modulation transfer function model, which results in the definition of the signal-to-noise ratio in the modulation domain: the (S∕N)mod. It is argued that this (S∕N)mod, quantifying the strength of speech modulations relative to a floor of spurious modulations arising from the speech-noise interaction, is the key factor in relation to speech intelligibility. It is shown that, by using a specific test signal, the strength of these spurious modulations can be measured, allowing an estimation of the (S∕N)mod for various conditions of additive noise, noise suppression, and amplitude compression. By relating these results to intelligibility data for these same conditions, the relevance of the (S∕N)mod as the key factor underlying speech intelligibility is clearly illustrated. For instance, it is shown that the commonly observed limited effect of noise suppression on speech intelligibility is correctly “predicted” by the (S∕N)mod, whereas traditional measures such as the speech transmission index, considering only the changes in the speech modulations, fall short in this respect. It is argued that (S∕N)mod may provide a relevant tool in the design of successful noise-suppression systems.
The acoustic excitation of air bubbles fragmenting in sheared flow
Authors: Deane Grant B. , Stokes M. Dale
Published: February 2009

An analysis of the acoustic emissions of air bubbles fragmenting in sheared fluid flow is presented. The fragmentation of bubbles into two products only is considered. While the measured pressure amplitude is highly variable, the partition of energy between fragmentation products is highly correlated. The partition of energy between products is, on average, approximately equal irrespective of the relative sizes of the bubble products. This observation suggests that the acoustic excitation mechanism is common to both bubbles immediately prior to fragmentation. A model for the excitation mechanism based on symmetric collapse of the neck of air joining fragmentation products is proposed and found to be sufficient to explain the range of observed bubble pulse amplitudes and the equal partition of energy.
A logistic prediction model for individual allowable noise levels
Authors: Furihata Kenji
Published: February 2009

Annoyance to noise is probably a good measure of the potential for complaint and community action. Each individual’s degree of annoyance to noise cannot be accurately predicted from conventional laboratory studies and social surveys. Therefore, a logistic prediction model for individual allowable noise levels has been developed. In a previous paper [K. Furihata et al., Acta Acust. Acust. 93, 73–83 (2007)], an annoyance scale using the most frequently used annoyance ratings related to noise for community noise assessment in Japan was constructed. The dose-response relationships were obtained by actually listening to sounds in a field situation (1474 subjects) carried out at 14 metropolitan cities in Japan. The logistic prediction model was developed using the logistic regression parameters estimated from each cumulative percentage curve of seven annoyance scale scores based on all data (n=2940). To verify the hypothesis, individual relationships between annoyance and LAeq,(5min) for 24 normal-hearing subjects were constructed using a laboratory experiment. The main conclusion drawn from the results is that if at least one dose-response relation is obtained from each subject, the model can predict whether a sound is annoying or not from its LAeq,(5min) value. Moreover, validation of the model is needed in a field situation.
Source localization from an elevated acoustic sensor array in a refractive atmosphere
Authors: Ostashev Vladimir E. , Scanlon Michael V. , Wilson D. Keith , Vecherin Sergey N.
Published: February 2009

Localization of sound sources on the ground from an acoustic sensor array elevated on a tethered aerostat is considered. To improve estimation of the source coordinates, one should take into account refraction of sound rays due to atmospheric stratification. Using a geometrical acoustics approximation for a stratified moving medium, formulas for the source coordinates are derived that account for sound refraction. The source coordinates are expressed in terms of the direction of sound propagation as measured by the sensor array, its coordinates, and the vertical profiles of temperature and wind velocity. Employing these formulas and typical temperature and wind velocity profiles in the atmosphere, it is shown numerically that sound refraction is important for accurate predictions of the source coordinates. Furthermore, it is shown that the effective sound speed approximation, which is widely used in atmospheric acoustics, fails to correctly predict the source coordinates if the grazing angle of sound propagation is relatively large.
Comment on “Linear and nonlinear frequency shifts in acoustical resonators with varying cross sections” [J. Acoust. Soc. Am. 110, 109–119 (2001)]
Authors: Mortell Michael P. , Seymour Brian R.
Published: February 2009

The effects of the shape of the container on nonlinear resonant oscillations have been of interest for the past decade. Resonant oscillations in a closed straight tube can contain shocks, but for some tube shapes shock formation can be prevented. How the magnitude of the variation of the shape from a straight tube affects the prevention of shocks is discussed. Criteria to determine whether tuning curves bend right or left are addressed, including that proposed by Hamilton et al. [“Linear and nonlinear frequency shifts in acoustical resonators with varying cross sections,” J. Acoust. Soc. Am. 110, 109–119 (2001)].
The time-reversal operator with virtual transducers: Application to far-field aberration correction
Authors: Robert Jean-Luc , Fink Mathias
Published: February 2009

The decomposition of the time-reversal operator (DORT) is a detection and focusing technique using an array of transmit receive transducers. It can extract Green’s functions of scatterers in a medium. A variant consists in transmitting focused beams (FDORT). It is shown here that the FDORT method can be interpreted as the decomposition of a time-reversal operator between an array of virtual transducers located at the transmit beams’ foci and the physical array. The receive singular vectors correspond to scatterers’ Green’s functions expressed in the physical array while the transmit singular vectors correspond to Green’s functions expressed in the virtual array. The position of the virtual array can be changed by varying the position of the foci, thus offering different points of view. Parameters and performance of some transmit schemes are discussed. Appropriately positioning the virtual transducers can simplify some problems. One application is measuring and correcting aberration in the case of a far-field phase screen model. Placing the virtual transducers near the phase screen transforms the problem in a simpler near-field phase screen problem.
Infrasound induced instability by modulation of condensation process in the atmosphere
Authors: Naugolnykh Konstantin , Rybak Samuil
Published: February 2009

A sound wave in supersaturated water vapor can modulate both the process of heat release caused by condensation, and subsequently, as a result, the resonance interaction of sound with the modulated heat release provides sound amplification. High-intensity atmospheric perturbations such as cyclones and thunderstorms generate infrasound, which is detectable at large distances from the source. The wave-condensation instability can lead to variation in the level of infrasound radiation by a developing cyclone, and this can be as a precursor of these intense atmospheric events.
Mapping unpleasantness of sounds to their auditory representation
Authors: Kumar Sukhbinder , Forster Helen M. , Bailey Peter , Griffiths Timothy D.
Published: February 2009

Certain sounds, for example, the squeal of chalk on a blackboard, are typically perceived as highly unpleasant. This study addressed the question of what aspects of the auditory representation of such sounds are associated with judgments of unpleasantness. Participants rated the perceived unpleasantness of a large number of sounds that included “griding” and other unpleasant sounds. A multivariate partial least-squares (PLS) model was then built to relate the ratings of unpleasantness with an auditory representation derived from a model of processing in the auditory pathway. The “existence region” of unpleasantness in the auditory space of frequency-temporal modulation was determined after the PLS model had been validated by predicting the unpleasantness of novel sounds from the auditory representation. It was observed that the existence region corresponded to spectral frequencies between 2500 and 5500 Hz, and temporal modulations in the range 1–16 Hz.
Beyond the beat: Modeling metric structure in music and performance
Authors: Tomic Stefan T. , Janata Petr
Published: February 2009

Current models for capturing metric structure of recordings of music are concerned primarily with the task of tempo and beat estimation. Even though these models have the potential for extracting other metric and rhythmic information, this potential has not been realized. In this paper, a model for describing the general metric structure of audio signals and behavioral data is presented. This model employs reson filters, rather than the comb filters used in earlier models. The oscillatory nature of reson filters is investigated, as they may be better suited for extracting multiple metric levels in the onset patterns of acoustic signals. The model is tested with several types of sequences of Dirac impulses as inputs, in order to investigate the model’s sensitivity to timing variations and accent structure. The model’s responses to natural stimuli are illustrated, both for excerpts of recorded music from a large database utilized by tempo-estimation models, and sequences of taps from a bimanual tapping task. Finally, the relationship of the model to several other beat-finding and rhythm models is discussed, and several applications and extensions for the model are suggested.
Modeling the dynamic interactions of rolling bearings
Authors: Diniz Guimarães João Henrique
Published: February 2009

This work deals with the generation and propagation of structure-borne sound by the rolling contact in bearings. Rolling bearings are widely used in machines and, in early stages of operation, the interaction of the rough surfaces of races and rolling bodies produces an excitation that will propagate to the surrounding structure. The dissertation presents a model for the determination of the structure-borne excitation due to rolling, using the condition of the surfaces and the dynamics of the rolling movement as input. The model is able to simulate the time evolution of the excitation generated by the bearing that is imposed to the machine. Additionally, this work describes the experimental evaluation of the influence of the path between the point where the excitation is generated (in the bearing) to the point where it is usually measured (on the machine’s housing) using special actuators made of one rolling element. Measurements under running conditions are made for comparisons with cylindrical and spherical rolling bearings. This approach shows that a deeper insight in the understanding of machine vibration can be gained when one tries to model sources and treats the system as a filter that has to be described in order to evaluate the influence of the transfer path. Publisher: Logos Verlag Berlin, 2008; ISBN: 978-3-8325-2010-6.