bluuebunny/crossref_metadata_2025 huggingface dataset:
Absolute intensities of acoustic shadow zone arrivals
Authors: Van Uffelen Lora , Worcester Peter , Dzieciuch Matthew
Published: May 2008

Qualitative observations from bottom-mounted US Navy SOSUS receiving stations in the North Pacific reveal anomalously deep acoustic arrivals at travel times directly corresponding with timefronts expected to have turned much higher in the water column. The vertical structure of these shadow zone arrivals was studied during SPICEX, a long-range propagation experiment conducted from June to November 2004 in the North Pacific, utilizing moored sources 500 and 1000 km distant from two vertical line array receivers, which together virtually spanned the full ocean depth. Comparison of the measured absolute intensities of shadow zone arrivals with Monte Carlo parabolic equation simulations suggest that the amount of internal wave scattering associated with the standard Garrett-Munk (GM) internal wave spectrum is not adequate to account for the extent of scattering into the acoustic shadow evident in the experimental data, suggesting either that the GM spectrum is not an appropriate representation of the internal wave field or that some other mechanism, such as oceanic spice, may be also be contributing to the scattering.
Performance analysis of GARCH based DOA estimation in SONAR
Authors: Amiri Hadi , Amindavar Hamidreza , Kamarei Mahmoud
Published: May 2008

In this paper we propose a new source localization method using additive noise modeling based on Generalized Autoregressive Conditional Heteroscedasticity (GARCH) time-series. In an actual application such as underwater acoustics, the measurement of additive noise in a natural environment shows that noise can sometimes be significantly non-Gaussian and nonstationary, and therefore, signal processing algorithms that are optimized for Gaussian noise, may degrade significantly in this environment. GARCH models are feasible for heavy tailed PDFs and time varying variances of stochastic process and also has flexible forms. We use a more realistic GARCH(1,1) based noise model in the Maximum Likelihood Approach for the estimation of Direction-Of-Arrivals (DOAs) of impinging sources. In the performance analysis of the method, we examine the suitability of the proposed method in a passive sonar using simulation methods with cramer-rao bound (CRB) and perturbaion appraoch such as gain, phase and sensors positions errors.
Scattering from rotationally-symmetric objects using only free space Green's functions
Authors: Abawi Ahmad , Porter Michael B.
Published: May 2008

To compute scattering from an object, one has to solve the wave equation and impose the appropriate boundary conditions on the surface of the object. For objects for which the wave equation can be separated, like cylinders, spheres and spheroids, this problem can be solved analytically. For more general objects, methods like the finite element or boundary element techniques can be employed. The use of free space Green's functions offers another method for computation of scattering from a general-shaped object. This method, which is known as the method of field superposition or the virtual source technique, can be used to impose the appropriate boundary conditions on the surface of the object by using free space Green's function with complex amplitudes. These amplitudes are determined from a matrix equation that results when boundary conditions are imposed. In this paper we apply this technique to compute scattering from rotationally symmetric objects. These objects can be homogeneous solids or shells, filled with a homogeneous fluid. The versatility and robustness of the method is demonstrated by applying it to various objects in free space and in a waveguide.
A multistatic synthetic aperture sonar to detect a cylinder lying on a rough interface: experimental results
Authors: Herve Caroline , Sessarego Jean-Pierre , Guillermin Régine , Schmitt Françoise , Daout Franck
Published: May 2008

Monostatic Synthetic Aperture Sonar (SAS) are high resolution systems for target imaging which are now of common use in the underwater acoustics domain. The objective of this work was to analyse what kind of information should be obtained from a multistatic SAS system. This idea has been applied in radar but very few works exist in the underwater acoustics domain. The applications could be detection and identification of buried mines or mines lying on the seabed and divers detection for harbour protection. These applications deal with the problem of target detection and identification near a rough surface. To show what can be obtained with a multistatic SAS processing, we have performed an experiment with a circular cylinder of 1 cm diameter lying on a rough interface made of sand grains of 1 mm diameter. Measurements were performed in a tank with both a multistatic and a monostatic SAS systems. The signal used to insonified the target area was a short impulse with a 2 MHz central frequency which corresponds to a ka about 40. Images of the cylinder in presence of clutter have been reconstructed with the matched filtering algorithm from monostatic and multistatic acquisitions and have been compared.
Gold Medal of the Acoustical Society of America
Authors: Bell-Berti Fredericka , Zhang Yang , Iverson Paul
Published: May 2008

The Gold Medal is presented in the spring to a member of the Society, without age limitation, for contributions to acoustics. The first Gold Medal was presented in 1954 on the occasion of the Society's Twenty-Fifth Anniversary Celebration and biennially until 1981. It is now an annual award.
Room acoustics prediction based on multiple linear regressions and artificial neural networks
Authors: Ribeiro Maria , Martins Fernando
Published: May 2008

Room acoustic quality is known to be dependent on several objective variables that are expected to be well correlated with subjective impressions of the room acoustics as judged by musical experts. Although subjects have different preferences and overall judgments are based in different criteria, it can be said that listeners in their subjective evaluation would give preference to reverberance, clarity, intimacy or spaciousness attributes. In this study, reverberance and clarity, expressed respectively by T30/EDT and C80 objective values, were predicted by multiple linear regression and artificial neural networks using normalized original data and principal components as dependent variables. The results obtained by these approaches were compared with predicted values using a computer simulation program based on the physics of ray-tracing and with measured data. Room acoustical quality was also evaluated based on preferred values as suggested by some researchers.
Minimum BRIR grid resolution for dynamic binaural synthesis
Authors: Lindau Alexander , Maempel Hans-Joachim , Weinzierl Stefan
Published: May 2008

Binaural synthesis of acoustical environments is based on binaural room impulse responses (BRIRs) measured with a certain grid of spherical coordinates separated by angles of typically between 1° and 15°. The resulting spatial resolution defines the size of the BRIR database as well as the duration of its measurement. Perceptual evaluations of datasets with a different spatial resolution using HRTFs (anechoic case) have been reported from. Most of these studies use the localization performance of listeners as a criterion; a more sensitive measurement for slight degradations in audio quality can be expected from a criterion-free comparison of datasets with different angular grids. Thus, to determine the minimum grid resolution required for dynamic binaural synthesis a listening test was performed. Following an adaptive 3AFC procedure, the spatial resolution of a recorded BRIR dataset was gradually lowered from a maximum of 1°/1° resolution until audible artefacts were introduced. This was done for a sound source located at 0°/0° presented with dynamical auralization in two degrees of freedom. To test for interaction effects the thresholds were derived independently for azimuth and elevation. The datasets used were acquired in an anechoic environment and in two rooms of different size and reverberation time.
Optimum Room Acoustic ComfortTM (RACTM) can be achieved by using a selection of appropriate acoustic descriptors
Authors: Svensson Carsten , Nilsson Erling
Published: May 2008

In order to create an optimum Room Acoustic ComfortTM (RACTM) in rooms it is important to consider a variety of different acoustic descriptors. These descriptors must match and facilitate for wanted human qualities such as ability to concentrate, reduced stress, clear speech etc. In this process it is important to consider the people, what they do (the activity) and what room they will be in. Today, when designing ordinary rooms from an acoustic perspective, mainly reverberation time (T20) is utilised - both in practice but also in building regulation and standards. Reverberation time (T20) only describe the later part of the decay curve, and therefore only partly mirror the wanted acoustic reality. Thus, based upon a large number of acoustic measurements, we suggest a "cocktail" of acoustic descriptors for ordinary rooms in buildings like schools, offices, health care premises etc. These descriptors have to cover both early and late decay, sound levels and speech quality. Our suggestions are Speech Clarity (C50), Speech Transmission Index (STI), Early Decay Time (EDT), Reverberation Time (T20) and Strength (G). Moreover, in open and long spaces we also suggest the acoustic descriptors Rate of Spatial Decay (DL2) and Excess of Sound Pressure Level (DLf).
The directivity of the forced radiation of sound from panels and openings including the shadow zone
Authors: Davy John L.
Published: May 2008

This paper presents a method for calculating the directivity of the radiation of sound from a two dimensional panel or opening, whose vibration is forced by the incidence of sound from the other side. The directivity of the radiation depends on the angular distribution of the incident sound energy. For panels or openings in the wall of a room, the angular distribution of the incident sound energy is predicted using a physical model which depends on the sound absorption coefficient of the room surfaces. For an opening at the end of a duct, the sound absorption coefficient model is used in conjunction with a model for the directivity of the sound source in the duct. For angles of radiation approaching 90 degrees to the normal to the panel or opening, the effect of the diffraction by the panel or opening, or by the finite baffle in which the panel or opening is mounted, is included. A simple empirical model has been developed to predict the diffraction of sound into the shadow zone when the angle of radiation is greater than 90 degrees to the normal to the panel or opening. The method is compared with published experimental results.
An Application of Time-Reversal Acoustics to Sound Insulation Measurements in Buildings
Authors: Lee Doheon , Cabrera Densil
Published: May 2008

This paper considers the possible application of time reversal acoustics (TRA) to airborne sound insulation measurements in buildings. In TRA, an array of transducers is set up to form a time-reversal 'mirror' or 'cavity'. Using this array, the sound radiated from an initial source is collected and refocused spatially and temporally, thereby being reproduced at the initial source position with high signal-to-noise ratio (S/N). Most previous studies of TRA have been conducted underwater with ultrasonic sound sources, with only a few in the audible range in real buildings. The technique is best suited to non-dissipative systems, raising the question of whether any advantage could exist for transmission between rooms. This study applies TRA experimentally in the audible range using maximum length sequence signals for transmission between two rooms. Comparison is made between conventional measurements (with and without impulse response deconvolution) and TRA in terms of effective S/N and apparent level difference between the rooms. Substantially greater S/N is achieved using TRA, but the interpretation of measurements is not straightforward, and the technique is much more demanding than conventional measurements.
Repeatability and reproducibility of field noise isolation testing
Authors: Loverde John , Dong Wayland
Published: May 2008

The reliability and precision of test measurements and methods are generally described in terms of repeatability and reproducibility. ASTM standards define and quantify these terms for noise isolation test methods in both laboratory and field conditions. Understanding these as reproducibility and repeatability of the measurement method, the authors extend the concept to the reproducibility and repeatability of a wall or floor/ceiling assembly design. Multiple instances of a floor/ceiling assembly on a multi-family residential project built by the same contractors is an example of design repeatability, while the same assembly design constructed on different projects is an example of design reproducibility. In a previous paper [LoVerde and Dong, J. Acoust. Soc. Am. 122, 2955 (2007)], definitions were suggested for field repeatability and reproducibility for Field Impact Insulation Class testing. Test data is presented to quantify the field repeatability and reproducibility of several assembly designs, which are compared to laboratory values. Field and laboratory repeatability and reproducibility of airborne noise isolation for a partition assembly are also examined.
Vocal Learning in Pinnipeds: A Model System for Human Speech Evolution
Authors: Fitch William T. , Schusterman Ronald J. , Reichmuth Colleen , Spasikova Marija , Mietchen Daniel
Published: May 2008

Vocal learning is limited to a small subset of vertebrates: including birds (songbirds, parrots, hummingbirds), and mammals (humans, cetaceans, pinnipeds, and probably elephants and bats). Intriguingly, in most of these species, vocal production involves functionally or mechanistically novel systems: the avian syrinx, the nasal bursae in odontocetes, and ultrasonic echolocation in bats. The novel neural circuitry that evolved to control these systems may provide a "preadaptation" for vocal learning. Only two known vocal learners - humans and seals - definitely use the standard vertebrate vocal production system (larynx and vocal tract). Our studies of vocal production in harbour seals verify a surprisingly human-like vocal production system, and the critical question remaining is what neural mechanisms underlie the control of the Phoca vocal system, and whether such "human" specializations as direct cortico-ambiguual connections are also found in seals. Pinniped investigations also open the door to molecular exploration of the genetic bases for neural innovations. In addition to these mechanistic questions, we discuss evolutionary questions. What functional forces might select for vocal learning in aquatic mammals? One hypothesis is that selection for control of breathing may provide a preadaptation for enhanced cortical vocal control, explaining its prevalence in marine mammals.
Sound production by pinnipeds can be modified by contingency learning
Authors: Schusterman Ronald J. , Reichmuth Colleen
Published: May 2008

In contrast to terrestrial mammals, pinnipeds (seals, sea lions and walruses) have remarkable flexibility in the ways that they can learn to use and modify their amphibious sound emissions. The experiments that we will describe are drawn from captive studies which show that changes in sound production can occur as a result of contingency learning, using food as positive reinforcement. A range of specialized physiological and anatomical adaptations appear to play a critical role in controlling sound production in pinnipeds. These adaptations include breath-holding and buoyancy mechanisms, as well as fine muscular control of the mouth, lips and tongue that may be used primarily in feeding. The manipulation and modulation of air flow through these components of the vocal tract and associated super-laryngeal filters appears to be susceptible to some of the same reinforcing consequences that are routinely used to establish reliable control over motor behaviors, such as flipper waving, in operant conditioning contexts.
Air and bone conduction evoked potential audiometry in the northern elephant seal
Authors: Houser Dorian S. , Crocker Daniel , Finneran James J.
Published: May 2008

Elephant seals (Mirounga angustirostris) are the largest and most aquatic of the pinnipeds, spending up to eight months of the year at sea diving to depths as great as 1600 m. The pinna is absent in the elephant seal and the middle ear cavity and auditory canal are lined with a cavernous tissue, both of which are likely adaptations to deep diving. Elephant seals demonstrate a greater sensitivity to low frequency sounds than do other pinnipeds and an overall greater sensitivity to underwater sound than to airborne sound. The relative importance of sound conduction pathways in the elephant seal is undetermined, although it has been speculated that bone conduction pathways are important to underwater hearing in this species. To compare the sensitivity of the elephant seal to both air and bone conducted stimuli, auditory evoked responses were recorded in seals exposed to signals presented through headphones and via a bone vibrator. In comparison to airborne stimuli, bone conduction methods provide an opportunity to more effectively study sensitivity to low frequency sounds, but are challenged by a lack of reference equivalent threshold sound pressure levels. Future efforts should compare bone conduction and direct field audiometry results obtained within the same individual.
Variation in pup vocalisations and mother-pup behaviour between harp seal whelping patches: effects of climate or geography
Authors: Van Opzeeland Ilse Catharina , Corkeron Peter J. , Risch Denise , Stenson Gary B. , Van Parijs Sofie
Published: May 2008

Harp seals breed in pack-ice, a substrate which can vary substantially between whelping patches depending on differing environmental and oceanographic conditions. This study demonstrates clear site differences in pup vocalizations and mother pup behaviour between Northeast (Greenland Sea) and Northwest (Canadian Front) Atlantic harp seal populations. Classification trees showed a distinctive split between Front and Greenland Sea pup vocalisations. No clear sex differentiation in vocalizations was present for pups at the Front; 42% (n = 12) of male and 38% (n = 13) of female calls could be attributed to a given individual. In the Greenland Sea, 55% (n = 42) of female vocalisations were attributed to individuals compared with only 8% for males (n = 47). In addition behavioural observations of mother pup pairs were conducted (Front, n = 58; Greenland Sea, n = 78). Greenland Sea pups were found to nurse more, and were more alert than Front pups. Female attendance patterns also differed between sites: females at the Front were more likely to attend their pups than those in the Greenland Sea. This marked difference in female presence between sites could have several origins such as variability in ice conditions, predation pressure, or female condition.
Adjoint modeling for Acoustic Inversion based on an Adjoint Parabolic Equation
Authors: Papadakis John S. , Flouri Evangelia T.
Published: May 2008

In this paper the acoustic propagation problem is modeled by the wide angle parabolic equation and the bottom boundary condition is in the form of a Neumann to Dirichlet map. We formulate the inversion as an optimal control problem, the control parameters being the sound speed in the water and the sound speed, density and attenuation in the bottom. Using the adjoint operator to the wide angle parabolic equation, an inversion scheme is derived for the acoustic parameters of the water column and the bottom region. The optimization approach used is the method of steepest decent. Several test cases are exhibited.
Modeling of "anomalous" velocity dispersion in trabecular bone: effect of multiple scattering and of viscous absorption
Authors: Haiat Guillaume , Lhémery Alain , Padilla Frederic , Laugier Pascal , Naili Salah
Published: May 2008

Speed of sound is now widely used in the clinic to assess bone strength and susceptibility to fracture. Therefore, much effort has been spent on the understanding of ultrasonic wave propagation in trabecular bone, which is an attenuating composite material in which negative values of velocity dispersion have been measured, but remain poorly explained physically. In this work, the physical determinants of velocity dispersion are described with a 2D homogenization model of the wave propagation in trabecular bone. The medium is assumed to be constituted of infinite viscoelastic cylinders (trabeculae) immersed in a saturating viscoelastic matrix (marrow). The coupling between multiple scattering and absorption phenomena allows the computation of phase velocity and of dispersion as a function of bone properties. Negative values of velocity dispersion are predicted, in good agreement with experimental results obtained in phantoms mimicking trabecular bone. In trabecular bone, mostly negative but also positive values of velocity dispersion are predicted, which spans within the range of values measured experimentally. Scattering effects are responsible for the negative values of dispersion whereas the frequency dependence of the attenuation coefficient in bone marrow and/or in the trabeculae is shown to induce an increase of dispersion.
Experimental and numerical investigation of ultrasonic transmission through the skull bone and associated temperature rise
Authors: Pernot Mathieu , Bossy Emmanuel , Muller Marie , Boué Christine , Aubry Jean-François , Tanter Mickael , Fink Mathias , Boccara Albert-Claude
Published: May 2008

The feasibility of transcranial high-intensity focused-ultrasound (HIFU) therapy within the brain relies on the ability to transmit ultrasound through the skull bone at relatively high ultrasound power. Absorption of ultrasound through the skull bone may cause important temperature rises, and is therefore an important parameter to control. Ultrasonic measurements have shown that the ultrasound beam undergoes a significant attenuation when propagating through the skull, with values on the order of 10 to 20 dB/cm/MHz. To predict temperature rise from such values, it is fundamental to weigh the relative role of absorption to the total ultrasonic attenuation (scattering + absorption + specular reflection). In this work, two types of numerical simulations and experiments are performed to investigate this relative role. Through-transmission of 1 MHz ultrasound was performed numerically using a 3D Finite-Difference Time-Domain (FDTD) algorithm coupled to a 3D bone model obtained from high-resolution synchrotron microtomography, and compared to experimental measurements obtained with the same bone sample. Temperature rises were numerically simulated using the 3D bone model coupled to the heat equation, and compared to infrared thermography obtained experimentally while high-intensity ultrasound was propagating through the sample.
Ultrasound simulation in the distal radius using clinical high-resolution CT images
Authors: Kaufman Jonathan J. , Le Floch Vincent , McMahon Donald J. , Luo Gangming , Cohen Adi , Shane Elizabeth , Siffert Robert S.
Published: May 2008

The overall objective of this research is to develop an ultrasonic method for non-invasive assessment of the distal radius. The specific objective of this study was to examine the propagation of ultrasound through the distal radius and determine the relationships between bone mass and architecture and ultrasound parameters. Twenty-six high-resolution peripheral-CT clinical images were obtained from a set of subjects that were part of a larger study on secondary osteoporosis. A single mid-section binary slice from each image was selected and used in the 2D simulation of an ultrasound wave propagating from the anterior to the posterior surfaces of each radius. Mass and architectural parameters associated with each radius, including total bone mass, volume fraction, trabecular number, and trabecular thickness were computed. Ultrasound parameters, including net time delay (NTD), broadband ultrasound attenuation (BUA), and ultrasound velocity (UV) were also evaluated. Significant correlations were found between NTD and total bone mass (R2 = 0.92), BUA and trabecular number (R2 = 0.78), and UV and trabecular bone volume fraction (R2 = 0.82). The study shows that ultrasound measurements are correlated with bone mass and architecture at the distal radius, and thus ultrasound may prove useful as a method for non-invasive assessment of osteoporosis and fracture risk.
Guided ultrasound wave propagation in cortical bone with microstructure using the gradient elasticity theory
Authors: Vavva Maria G. , Protopappas Vasilios C. , Gergidis Leonidas N. , Charalambopoulos Antonios , Fotiadis Dimitrios I. , Polyzos Demos
Published: May 2008

Ultrasonic characterization of bone has been largely based on the linear theory of classical elasticity. However, the classical theory cannot adequately describe the mechanical behavior of materials with microstructure. In such materials, the stress state has to be defined in a nonlocal manner by employing theories, such as those proposed by Cosserat brothers, Mindlin (gradient elastic theory) and Eringen. In this study, we adopt the simplest form of gradient theory (Mindlin FormII) to model the cortical bone's microstructural effects in a macroscopic framework. The frequency characteristic equations are analytically derived for a bone plate (4mm thick, density 1.5 g/cm3, bulk longitudinal velocity 4107 m/s). The plate is assumed free of stresses, as in the classical Lamb problem, and free of double stresses. The volumetric strain gradient energy coefficient, g (a measure of internal length), is equal to 10-4 and 10-5 m, i.e. of the order of the osteons size. The velocity dispersion curves of guided waves are numerically obtained using root-finding techniques and compared with those of the Lamb waves. It is shown that microstructure affects mode dispersion by inducing both material and geometrical dispersion. In conclusion, bone models with microstructure can contribute to the interpretation of in vivo measurements.
Investigation of the porous network as a determinant of the overall stiffness of cortical bone: Mori-Tanaka model vs. ultrasound propagation
Authors: Baron Cécile , Grimal Quentin , Talmant Maryline , Laugier Pascal
Published: May 2008

Assessing the effect of porosity on stiffness in cortical bone remains an important issue that has already been addressed with several models. The originality of the present work is to compare two models of cortical bone: one uses a realistic porous network (voxel 20 microns) reconstructed from synchrotron radiation tomography; the other considers cylindrical pores aligned in a single direction. In the first case, overall elastic properties are evaluated indirectly by means of finite difference time domain simulation of ultrasound bulk wave propagation at 1 MHz. In the second model, effective elasticity is calculated by means of a Mori-Tanaka scheme based on Eshelby solution for cylindrical inclusions with ellipsoidal cross section. Overall properties were evaluated with the two methods for 18 porosity values, each corresponding to a reconstructed bone volume. The diagonal stiffness coefficients of the overall bone material estimated with the two methods compared well. Results for the stiffness coefficient in the longitudinal bone direction are indistinguishable, which indicates that the detailed geometry and distribution of the pores have a negligible effect on the longitudinal stiffness. For the other stiffness coefficients, the Mori-Tanaka method slightly overestimates the stiffness compared to the wave propagation evaluation.
Numerical modelling and in-vitro studies of ultrasound signal loss across fractures in cortical bone mimics
Authors: Humphrey Victor F. , Dodd Simon P. , Gheduzzi Sabina , Cunningham James L. , Miles Anthony W.
Published: May 2008

The propagation of 200 kHz ultrasonic waves along cortical bone mimics and across a simulated fracture has been investigated using a Finite Difference numerical model. The first arrival signal (FAS) transit time and peak amplitude have been calculated as a function of range at 200kHz in order to help understand the factors that determine the propagation across a fracture. The variation in the amplitude of the first peak of the reradiated wave is studied as a function of the gap width and shape. The results compare well with experimental measurements made in vitro using an axial transmission technique on cortical bone mimics and bovine cortical bone samples. The effects of various stages of the healing process have also been considered by introducing different fracture geometries into the plate model. Changing the geometry to an external callus with different mechanical properties causes the signal loss across the fracture to reduce significantly. The most significant changes are observed to occur from the initial inflammatory stage to the formation of a callus and in the remodelling stage after a significant reduction in the size of the callus has taken place.
From frequency to time domain: Signal features and physical characteristics for resonant acoustical systems
Authors: Rodriguez Samuel , Gibiat Vincent , Guilain Stephane , Lefebvre Alain
Published: May 2008

The determination of the impulse response or the reflection function of an acoustical system from data expressed in the frequency domain is not immediate. Signal processing from frequency domain to time domain should involve phenomena of large amplitude as oscillations known as "ripple" that does not correspond to any physical phenomenon. The "ripple phenomenon" will be analyzed from both a signal processing and a physical point of view with the help of simple duct acoustic examples. A map designed as a new time-frequency tool helps us to show that it cannot be removed in most cases without the use of processing techniques involving modifications in the computed signal. This work has been developed for the automotive research, but can be applied to musical acoustics or to any field connected with time domain exploration of acoustic cues.
Math and science partnership program in the Upper Cumberland districts of Tennessee
Authors: Darvennes Corinne
Published: May 2008

The Mathematics and Science Partnership (MSP) program by the US Department of Education "is intended to increase the academic achievement of students in mathematics and science by enhancing the content knowledge and teaching skills of classroom teachers. Partnerships between high-need school districts and the science, technology, engineering, and mathematics (STEM) faculty in institutions of higher education are at the core of these improvement efforts." This paper will present efforts in the Upper Cumberland districts of Tennessee to introduce engineering applications to Math and Science teachers in grades 8-12. The science teachers recruited represented the disciplines of Chemistry, Physics, and Physical Science. The 3-year program consisted of summer institutes, as well as bi-monthly Saturday workshops. An overview of the program will be discussed. It will include background information about the Upper Cumberland region, Tennessee content standards related to acoustics, working with teachers, some of the hands-on activities that were used during summer workshops, and the equipment that was provided to the teachers.
The energy flow for a spherical acoustic lens: ray vs. wave methods
Authors: Dean Cleon E. , Braselton James P.
Published: May 2008

A simple classroom demonstration consists of a weather balloon filled with carbon dioxide, a sound source, and a microphone. Since the speed of sound is slower in carbon dioxide than in air at room temperature and pressure, the balloon acts as a positive spherical acoustic lens. The accuracy of ray methods in locating the acoustic focus versus a full blown wave solution approach is probed. This problem presents particular difficulties if the sound source lies in the near field region. The sound emitter is treated as a dipole source equivalent to a rigid oscillating sphere of small size and amplitude of motion relative to the scatterer. The energy flux around the balloon is visualized by both ray methods and by the acoustic Poynting vector field. The geometrical ray results and the acoustic Poynting vector field resulting from the wave solution are compared.
Application of Volterra series to simulate dynamics of a Reissner beam
Authors: Roze David , Hélie Thomas , Bensoam Joël
Published: May 2008

Sound synthesis of strings needs the use of nonlinear models to provide realistic sounds according to the amplitude and the method of excitation (pluck, bow...). In order to include coupling between the different degrees of freedom, the Reissner beam model will be used to simulate nonlinear dynamics of a string. Expression of equilibrium of Reissner beams using Lie groups and algebra allows us to write an exact, simple formulation including nonlinearities due to large strains. This work aims to apply Volterra series method to this formulation in order to perform simulation of a Reissner beam at a given order of nonlinearity. Volterra series requires a rewriting of the model with well-defined boundary and initial conditions and interconnection laws of the series adapted to the variables (vector and matrix). Once the linear part isolated and studied (calculation of the Green function, and therefore of the first kernel), nonlinear terms must be organized to define a recurent relation and solve the kernel equation. Finally, it can be possible to identify a structure of simulation using instantaneous sums and products of outputs of linear filters.
SILENCE(R): A major step towards aircraft noise reduction
Authors: Kors Eugène J.
Published: May 2008

From 2001 up to 2007, SILENCE(R) has focused on the development of aircraft noise reduction technologies. As an European Union project coordinated by Snecma, SILENCE(R) brought together some 50 companies (including Airbus, Rolls-Royce, MTU Aero Engines and Snecma), research centers and universities. The overall budget was 112 million euros. Combined with innovative low-noise operational procedures studied at the same time, SILENCE(R) has achieved an impressive 5 dB noise reduction. This meets the medium-term objective of the European Commission's R&D Framework Programs, and marks a significant advance towards ACARE's research goal of a 10 dB reduction in aircraft noise by 2020. SILENCE(R) carried out successful tests of more than 35 prototypes to check 10 noise reduction technology concepts. These included several advanced low noise fan rotors, as well as components for a complete low-noise nacelle (negatively scarfed intake, "squid" nozzle fitted with high frequency liner), flight tested on an Airbus A320. Flight tests were also carried out on an Airbus A340 with landing gear fitted with aerodynamic fairings.
Passive and active designs for noise and vibrations reduction in aircraft cabins
Authors: Marant Vincent , Reig Fabado Antonio , Aguilera De Maya Juan Luís , Donayre Ramírez José Christian
Published: May 2008

Within the sixth European Commission framework programme, the main objective of the SEAT project initiated in September, 2006, consists of the development of a radically new concept, where the aircraft passenger comfort is considered at the highest level. Smart reactive seats and an interior environment able to detect on real time physiological and psychological changes in the passenger conditions will be developed. These data will be analysed and the appropriate parameters, like noise and vibration levels, temperature or air ventilation, will be adapted. Moreover, each passenger will be able to create his own configuration, with his personal entertainment and work characteristics. The project is focussed on the questions previous to the integration of the system, that is above all the creation of a more healthy and comfortable travel environment by means of noise and vibration reduction, as well as specific climatic controls. In this paper, the first passive and active designs under development are presented.
An experimental investigation of the measurement uncertainties in the assessment of exposure to noise in a working environment according to ISO 9612
Authors: Nabuco Marco , Fiorini Ana Claudia , Fuchs Gilberto
Published: May 2008

The Brazilian regulation for workplace noise evaluation requires a comparison between the measured noise levels and the noise limits listed on a table. The table establishes the maximum work hours per day for each measured sound level. As in some other countries, the Brazilian table shows limit values with a resolution of 1 dB(A) and considers a 5 dB(A) exchange rate. The measured uncertainty is unknown. The use of type 2 equipment for instance can mean, theoretically, a uncertainty of 3 dB(A). In Brazil it is not possible to estimate the impact of the measurement uncertainty on the costs of compensations paid due to noise exposure. It is also very difficult to assess the number of workers that are receiving unfair compensations or are not receiving any due to inaccurate noise exposition measurements. However it is possible to assure that the amount of money can reach incredible numbers in our country. This paper presents an experimental study of the uncertainty calculated on the ISO 9612 basis for different sound signals, in different workplaces, emitted by different noise sources. The main purpose is to show how important it can be to estimate the uncertainty for each measurement.
A comparison of two active-speaker-detection methods suitable for usage in noise dosimeter measurements
Authors: Lindstrom Fredric , Ren Keni , Persson Waye Kerstin , Li Haibo
Published: May 2008

Measuring noise exposure in a working environment is often done by using standard noise dosimeters. This method is suitable for the evaluation of many working environments. However, in some situations the worker uses his/her voice a large amount during the day, e.g. teachers in a preschool environment. Thus, in these situations regular dosimeter measurements will not correspond to the actual noise exposure. In order to provide correct measurements, methods that can detect when the workers own voice is active are required. This paper presents a study of two such methods originating from voice research; the binaural and the throat microphone methods. The methods are compared using a receiver operating characteristics based method, where the performance is assessed by the Probability-of-failure measure, i.e. the percentage of own voice that the method failures to detect correctly. The evaluation is performed in a lab environment as well as in real field conditions in a preschool. The results of the study show that both methods can be successful in a controlled low noise (<45dBA) environment (Probability-of-failure <0.1% for both methods), while in the preschool environment, the throat microphone method (Probability-of-failure <0.1%) is more suitable than the binaural method (Probability-of-failure >6%).
A comparison of earmuff protection measured in real-world and laboratory conditions
Authors: Kozlowski Emil , Kotarbinska Ewa
Published: May 2008

It has been well known and that noise protection provided by earmuffs in real-world conditions is lower than measured by a laboratory standardized REAT test. In this study, earmuff protection was tested by simultaneous measurement of the LAeq under and outside the earmuffs in 91 industrial workplaces and in the laboratory. In all cases, the LAeq measured under the earmuffs was compared with the level predicted according to the EN 458 standard, by an octave-band method for calculating the A-weighted SPL under the hearing protector. The LAeq levels measured under the earmuffs in real-world conditions were by more than 3 dB(A) and 15 dB(A) higher than predicted by the octave-band method, respectively in 65% and 17% of cases. The main causes of worse protection at workplaces were worn-out earmuffs due to prolonged usage (33%), improper way of wearing earmuffs (15%), or the use of eye-glasses (8%). The data show that attenuation values measured by the REAT method overestimate by 1-5 dB the earmuff protection obtained in real-world conditions. [Work supported by the Polish Ministry of Labour and Social Policy, grants 4.S.03 and 3.S.02].
Impulse and continuous noise reduction of tactical hearing protection systems
Authors: McKinley Richard , Hobbs Brian , Buck Karl , Hudson Dean
Published: May 2008

Tactical hearing protectors are devices designed to protect the wearer from high levels of impulse noise while providing some ambient listening and communication capability. Many of these devices also provide some attenuation of continuous noise. The efficacy of these types of devices depends on the amount of impulse noise protection and continuous noise protection, the quality of the ambient listening capability, and the intelligibility of the speech communication capability. This paper will describe the peak noise reduction of approximately 1 ms duration impulses with peak levels at 165 dB and 195 dB, for several earplugs and earmuffs. The frequency dependent reduction of impulse noise measured using an acoustic test fixture (the French German Research Institute at Saint Louis Head). Generally the data show higher levels of impulse noise reduction with earplugs than with earmuffs. Additionally, continuous noise attenuation was measured using human subjects performing the ANSI S12.6 Real Ear At Threshold (REAT) test. High speed (20k frames/sec) video will show the dynamic motion of typical tactical hearing protection earplugs and earmuffs when stimulated with a 195 dB impulse.
Prediction of impulsive noise waveform under an earmuff worn by a real user
Authors: Mlynski Rafal , Zera Jan
Published: May 2008

For the assessment of hearing damage risk caused by impulsive noise, it is important to know the impulse waveform a user is exposed to under the hearing protector. In this study, a complex transmittance of an earmuff was used to predict the waveform under a hearing protector. Earmuff's transmittance was calculated from impulses recorded outside and under the hearing protector, for a real user, as transmittance of the equivalent FIR filter. The transmittance determined in that way was then used to predict the impulse waveforms under the earmuffs produced in response to various outside impulses. Accuracy of predictions was assessed by a comparison of peak SPL, LAeq8, A, C, or D duration of the impulse waveforms calculated and measured under the earmuffs. Results obtained for a real user were compared with the measurements made with the use of an artificial test fixture (ATF, ISO 4869-3). [Work supported by Polish grants R18004304 (MNiSzW) and 3.S.03 (MPiPS)].
Stochastic modeling of the vibro-acoustic behavior of production cars
Authors: Gagliardini Laurent , Durand Jean-Francois , Soize Christian
Published: May 2008

Production cars -as any industrial product- are subject to various causes of variability including process uncertainties or product diversity. Many authors have shown that vibroacoustic problems sensitivity to small uncertainties increases dramatically with frequency until only statistical approaches remain relevant in the high frequency range. Moreover, modeling uncertainties due to numerous model simplifications induce similar dispersion effects on the computed responses. Both kind of uncertainties may be addressed when using a non-parametric stochastic modeling, based on the random matrices theory. Such a modeling, appears to be very practicable for industrial vibroacoustic problems while relying on a strong mathematical background. In a first part, the application of the non-parametric modeling of uncertainties to vibro-acoustics problems will be addressed. Stochastic aspects are controlled by only 7 dispersion parameters that provide most of the dynamic behaviors that can be observed experimentally. A Monte-Carlo simulation is performed to provide converged statistics of the stochastic problem solution. In a second part, the dispersion parameters are identified so that the stochastic model fits experimental data. Frequency Response Functions of 25 production vehicles were measured for this purpose and compared to the computed results in the low frequency range (<200 Hz).
Improved spectrofilter applied to diesel engine noise : combustion and mechanical noise separation
Authors: Pruvost Laurent , Leclere Quentin , Parizet Etienne
Published: May 2008

For engineers working on alternative fuels and diesel engine sound quality, being able to separate combustion noise and mechanical noise would be of prime interest. This separation can be attempted using a spectrofilter (also called Wiener filter) when in-cylinder pressure signals can be recorded. The major drawback of the spectrofilter is its unability to separate correlated sources like combustion and piston slap. An upgraded version of the spectrofilter can be computed. Its computation just requires to consider only the random parts of the engine signals. Actually, considering these random parts artificially uncorrelates the noise sources. Highly correlated signals have been synthesised and successfully separated by the upgraded spectrofilter. When dealing with real-life engine noise, the quality of the separation cannot be judged directly since the signals to separate are unknown. The spectrofilter's causality and stability have been used as criteria to judge its quality. These two criteria both confirmed the superiority of the spectrofilter computed using the random parts of the signals. A synchronous averaging step is required to estimate the signals random parts. This estimation has been found to depend on the phase-locking strategy.
Sound quality evaluation of air-conditioning sounds in a vehicle using psychoacoustic parameters
Authors: Nakasaki Ryota , Ogata Takaharu , Hasegawa Hiroshi , Ozeki Yukio , Onda Masaharu , Kasuga Masao
Published: May 2008

With recent developments of noise reduction technologies from mechanical components of a vehicle, air-conditioning systems become a major noise source in the compartment of a vehicle. To improve quietness in the compartment further, it is important not only to reduce the sound pressure level (SPL), but also to improve the sound quality. In this study, we tried to evaluate the air-conditioning sounds from a viewpoint of sound quality. First, we carried out a subjective evaluation experiment using some evaluation words that represent characteristics of the air-conditioning sounds. As a result of a factor analysis, noting that the air-conditioning sounds can be explained by three factors of "rough," "space" and "refreshing." "Rough factor" has strong correlation with the SPL, however, "space factor" and "refreshing factor" have little correlation with SPL. Next, to investigate parameters that correlate with these factors, we carried out an experiment to evaluate the air-conditioning sounds using the psychoacoustic parameters of loudness and sharpness. As a result, noting that "rough" factor strongly correlates with loudness, "space" and "refreshing" factors correlate with sharpness. This result shows that it is possible to evaluate the air-conditioning sounds a viewpoint of sound quality by using the sharpness that is different from SPL.