bluuebunny/crossref_metadata_2025 huggingface dataset:
The comparative analysis of two solutions of Pekeris boundary problem
Authors: Zlobina Nadezhda , Kasatkin Boris
Published: May 2008

The solution of the reduced Pekeris boundary problem, satisfying to the generalized radiation condition on an impedance interface is obtained. Mode part of the solution is presented by series expansion on the total system of regular normal waves, of generalized normal waves and of leakage normal waves. The principle of the continuous continuation of the obtained solution in physical half-space with validity of boundedness condition is formulated. Expansion of the solution on physical half-space in a class of generalized functions is constructed. The obtained generalized solution includes canonical series expansion on the set of eigenfunctions of both conjugate operators corresponding an initial not self-conjugate boundary problem, the associated eigenfunctions of a waveguide with two soft boundaries, the associated eigenfunctions of a waveguide with upper soft boundary and lower rigid boundary and a set of spherical components. Results of the comparative analysis of the classical solution and generalized solution are given.
Tank experiments of sound propagation over a tilted bottom: Comparison with a 3-D PE model
Authors: Korakas Alexios , Sturm Frederic , Sessarego Jean-Pierre , Ferrand Didier
Published: May 2008

We present results of tank experiments of long-range acoustic propagation over a wedge-shaped oceanic bottom. Previous work investigated the propagation of broadband pulses in a range-independent configuration showing good agreement between experimental results and model predictions [Korakas et al., Proceedings of UAM 2007 (Heraklion, Crete, Greece, 25-29 June 2007)]. As a follow-up, preliminary experiments were carried out considering a tilted bottom. Non-negligible 3-D effects were observed and proved to compare favorably with numerical predictions obtained running a parabolic equation based code [Sturm et al., Proceedings of UAM 2007]. In the present work we continue the investigation of the wedge-like environment. Additional series of experimental measurements are performed. Received signals are recorded on a very fine spatial grid. Then, the measured data are processed using matched field processing. In our inversion algorithm, the replica are provided by a fully three-dimensional parabolic equation code. The technical aspects of the inversion procedure used (e.g., CPU time) are discussed.
Architectural and acoustic restoration of the 'Benevento' Roman Theatre
Authors: Maffei Luigi , Iannace Gino , De Gregorio Leda , Palmieri Umberto
Published: May 2008

Acoustics as well as the extraordinary architecture are substantial part of the heritage of ancient Greek and Roman theatres. These archaeological areas are more often used for classical and modern performing activities but to emphasise the original acoustics, restoration of the original shape, reconfiguration of the space and introduction of new technologies and materials may be needed. These activities must happen taking into account the "International Charter for The Conservation and Restoration of Monuments and Sites" as main tools defining conservation, use and maintenance guidelines in matter of discipline for ancient performing places. This paper presents some proposals for the stage reconstruction of the Benevento Roman Theatre and examine the associated effects on the theatre acoustics. Design proposals, minded to preserve the place authenticity, improving the acoustics and keeping intact the surrounding atmosphere for spectators, are the result of archaeological data, contemporary performances requirements, state of the art in matter of stage setting design. Acoustic field prediction is based on numerical models and auralization aiming to reproduce the real listening conditions.
On the Acoustics of the Underground Galleries of Ancient Chavín de Huántar, Peru
Authors: Abel Jonathan S. , Rick John W. , Huang Patty P. , Kolar Miriam A. , Smith Julius O. , Chowning John M.
Published: May 2008

Chavín de Huántar is a monumental World Heritage archaeological site in the Peruvian highlands predating Inca society by over 2000 years. The importance of site acoustics is suggested by distinctive architectural features, notably an extensive network of underground galleries used in part for ritual purposes. The labyrinthine galleries are arranged in a series of small rectangular alcoves off narrow corridors. Here we focus on measuring and modeling the acoustics at Chavín to understand the implications of auditory experiences within the galleries as related to the site's role in developing religious authority. Acoustic measurements and models of a site can be used to archive site acoustics, estimate the acoustics of inaccessible or alternative site architectures, and reconstruct original site acoustics; they may also be used to corroborate aspects of rituals suggested by other archaeological data. Preliminary acoustic measurements at Chavín show a short reverberation time, dense and energetic early reflections, and a large lateral energy fraction. The short reverberation time would enable rhythmically articulated group performance using Strombus shell trumpets found onsite. The early reflections would provide strong acoustic reinforcement and consistent resonances for participants in gallery alcoves. The wide soundfield would envelop participants, contributing to the ritual experience.
The marvellous sound world in the 'Phonurgia Nova' of Athanasius Kircher
Authors: Tronchin Lamberto , Durvilli Ilaria , Tarabusi Valerio , Mastromatteo Galia
Published: May 2008

Athanasius Kircher, Jesuit, was born in Geisa, Thüringen, in 1608. He spent a large amount of his life in Rome, where he died in 1680. He was active in many different topics, ranging from geology to philosophy. He was the author of many books at his time, among all the Musurgia Universalis, written in 1650, and the Phonurgia Nova, of 1673. Whilst the Musurgia Universalis gathered a wide attention also in recent years, the Phonurgia Nova, which means " a new method of sound production", was only recently rediscovered. In this paper the original Latin version of the Phonurgia Nova, which comprises two different books, i.e. the "Phonosophia nova" and the "Phonosophia anacamptica", is analyzed. The first book deals with the influence of music in the human being, whereas the second book analyses the sound propagation in enclosure. This book reveals some interesting acoustic apparatus for sound production and propagation, as the "tuba stentorophonica" (the loud trumpet), the "statua citofonica" (the talking statue). Some of these phonic apparatus are described, analyzed and commented.
Acoustics of Unique Baroque Theatre in Český Krumlov
Authors: Dolejsi Jana , Slavko Pavel , Pouzar Ladislav , Rychtarikova Monika
Published: May 2008

The castle theater in the Český Krumlov is a unique historical site in Europe which represents a valuable example of a theater with Baroque scenes from the late 18th century. It was preserved with exceptional completeness and authenticity since it has never burned, and during the last two centuries it was not modernized. The baroque period must be understood as a universal style with many methods of expression which act in harmony, and the individual elements must complement each other and be interconnected to produce an effective unit. It was a challenge to experimentally prove these relationships and connections in as wide context as possible (i.e. relations between the architecture, contemporary scene lighting, perspectives and proportions, roomacoustic properties, contemporary musical interpretations and vocal techniques, placing of the orchestra and other. According to musicians, actors and audience is this theatre known as a hall with excellent acoustic condition. However, no room acoustic measurements were performed in the theatre in the last century. This article report on results from the acoustical measurements and simulation in the main hall of the theatre which help us to understand which acoustical values people find pleasant in the room of this character.
Assessment of strong reflections in ancient theatres: Spatial information from parallel measurement data
Authors: Rodonò Giuseppe , Gullo Marco , La Pica Armando , Vinci Vincenzo
Published: May 2008

The sound field in ancient open-air theatres shows a finite time-response in a transient. The structure of the time-response depends on geometrical characteristics of the theatre and source-receiver position: upon geometry dimension of the stage area its possible to observe nearly strong reflections and quantify the associated delay time. Sampling the theatre space with a single microphone does not allow any directional information on the sound field but the parallel use of more microphones and software post-processing could add spatial information. Dataset consists of four syncronized impulse response measured along a radial direction in the theatre plan for differents source positions. A directional receiver system based on a post-processing method has been implemented and applied to measurement data. The obtained experimental results are reported and discussed.
Analysis of the impact of sound diffusion in the reverberation time of an architectural space - A proposal for the characterization of diffusive surfaces using scale models
Authors: Garay-Vargas Elisa , Rodriguez-Manzo Fausto E.
Published: May 2008

The acoustic quality of architectural spaces has been related directly with the reverberation phenomenon, in order to understand more about sound in architecture, this proposal tries to conclude how diffusion acts on the reverberation time. The fact that architects deal with absorption coefficients and change the reverberation time by playing and designing with materials, opens a door to the possibility of new ways of architectural design, knowing how simple or complex and even natural diffusion surfaces will act in space. Several examples of the use of diffusion and reverberation in architectural spaces can be found in buildings like the Jewish Museum from Daniel Libeskind or the Therme Vals from Peter Zumthor, the use of big surfaces of concrete in the first and uneven surfaces in the second, transform each of these places in one with very interesting sound qualities. To create spaces like these we can take diffusion as a design argument but, How will certain diffusive surfaces influence on the reverberation time of an architectural space? To answer this question it is necessary to experiment with scale models measuring the reverberation time, and not the diffusion itself.
Predicting the acoustics of historic Istanbul Tunnel: Simulation, calculation methods and geometrical details
Authors: Bal Kocyigit Filiz , Senturk Sertan
Published: May 2008

The Istanbul Tunnel, which was designed and constructed by Eugene Henry Gavand at 1875 is the 3rd. Metro and 2nd underground railway system in the world after Washington Metro (1868). In this paper, the acoustics of the Istanbul Tunnel are investigated. This is a special case which sets up a challenge to these prediction methods. The shape of the tunnel and therefore focusing the sound, reverberant wall, and therefore fluctuation effect demands high accuracy in predicting the early reflections. The energy dissipates quickly in this type of enclosures and there is little masking effect of the reverberation. Another aspect that has been shown to give very different results in this case study is the geometrical detailing of the models. When the Istanbul Tunnel is compared with modern metro systems; nowadays railway systems are controlled by modern electronic and mechanical system, but in the 19th century these electronic systems were not available. A solution could be found with the shape of the building. The aim of this paper is to clarify some of the problems that can arise in this type of constructions, and give guidelines for how they can be overcome / avoided. Another objective is to emphasize that room acoustic computer simulations although very useful, need careful consideration about the underlying calculation methods.
The engineering method of sound field control for amplifications in sports arena
Authors: Peng Jian , Peng Zhao
Published: May 2008

This paper discusses the engineering method of sound field control for amplifications in sports arena, which includes the selection, assembly and adjustment of the loudspeaker system. It also includes the site characteristics of the sports arena, as well as the relations between the loudspeaker and the site. Through the measurements of the rated sensitivity and maximum noise power, the loudspeaker system can be determined as distributed or central system, linear or plane array. With the adjustments on parameters such as the directivity D(Θ)and the directivity factor Q, the loudspeaker system will be able to effectively control the sound field during amplification process and to achieve better sound quality in sports arena. Besides determining the effective engineering method for sound field control in the amplification process, this paper also considers the acoustical characteristics of sound sources and coupling effect in the sound field.
Simulation of the reverberation time of an existing architectural space using a 1:10 scale model
Authors: Gonzalez-Rodriguez Luz Del Carmen , Rodriguez-Manzo Fausto E.
Published: May 2008

Recently the science of acoustics has been reconsidered and valued more than just a tool concerning physics, telecommunications, and music. It is now an important topic of research for the acoustic comfort of places where people work and live, and it is also considered as an essential issue for the physical and mental health of human beings. Sound has to be integrated as a design concept in architecture, but architects need tools for understanding more the way to reach not only good acoustics but also good architectural design. It has been proven that physical scale models are very useful for the prediction of the acoustical behaviour of rooms, therefore this process is analyzed and studied at the Acoustic Design and Analysis Laboratory of the UAM-Azcapotzalco in Mexico City, in order to promote further investigations that provide useful data for the design of architectural spaces as well as the design of sound control devices. This paper shows the work of a master degree thesis where the main objective is to present the measurements of reverberation time taken in an existing room compared with those taken in the physical scale model of the same room.
Translating acoustics into architecture
Authors: Wetherill Ewart A.
Published: May 2008

Ever since Wallace Clement Sabine's first presentation to the American Institute of Architects in 1898, a substantial gap has often existed between available information on building acoustics and its successful application to the design of buildings. Experience over at least the past 40 years suggests that one of the reasons for this has been the difficulty of adapting construction methods, that were selected to meet other criteria, to satisfy specific acoustical conditions. In a complex project it is important that requirements for individual spaces be identified and resolved early in the design process so that they can be integrated successfully into the overall building design. This paper discusses a procedure that has been found very convenient for establishing acoustical requirements during the schematic design and transferring recommendations efficiently for inclusion in the construction documents. The information is compiled in a book-style format for ease of distribution and for fast reference at any time in design and construction.
Variable Source-Directivity Using Dodecahedron-Loudspeakers
Authors: Behler Gottfried K. , Pollow Martin
Published: May 2008

For room-acoustical measurements dodecahedron loudspeakers are commonplace to achieve a uniform directivity. Therefore all transducers are fed with the same signal. If the signals for the twelve transducers are individually adjustable, the variation of amplitude and phase offers the possibility to achieve a predefined directivity. The goal is to calculate the twelve frequency dependent amplitude- and phase-coefficients for any given directivity with the least possible error. A simple approach like superposition unfortunately does not reveal a correct result, since all transducer interact with each other. The decomposition of spherical functions into spherical harmonics, however, leads to an analytic solution for the prediction of the sound radiation. The acoustical components - like sound pressure and sound velocity - are split up into weighted, orthogonal base functions which can be combined in a way that the mutual coupling between different membrane vibrations is respected. Under these conditions complex filter transfer functions, individually optimized for each one of the twelve transducers can be computed with respect to the target directivity function. Different approaches for the optimization procedure are discussed. Besides the more theoretical approach measurements with a real multichannel system are shown.
High sound pressure models for microperforated panels backed by an air cavity
Authors: Tayong Rostand , Dupont Thomas , Galland Marie-Annick , Leclaire Philippe
Published: May 2008

When submitted to relatively high sound pressure amplitudes, Micro Perforated Panels (MPP) are influenced by certain effects, which are non negligible (vibration of the panel, end radiation and also proximity of the perforations). A model of the total impedance of the MPP is derived from the sum of the contributions of each effect in the case of relatively high sound pressure. The effect of end radiation is supposed to be independent of the propagation inside the apertures. The model is applicable for low Mach numbers. In order to validate the models, various steel MPP specimens were built with different aperture diameters, interstices (distance between two near apertures) and thickness sizes. The experimental method consists in measuring the acoustical pressure before the specimen and the velocity at the aperture entrance. The experimental setup is based on the use of an impedance circular tube. A loudspeaker capable of delivering high sound pressure is used as a source. The excitation is a white noise in a frequency range between 500 Hz and 5000 Hz and the detection is performed with microphones. The comparison between measurements and simulations for the impedance and absorption coefficient is done and discussed.
Swept Sine against MLS in room acoustics with music signals as background noise
Authors: Paulo Joel P. , Bento Coelho J. Luis
Published: May 2008

The Swept Sine and the MLS techniques are very popular in room acoustic measurement set-ups. Advantages and disadvantages of both methods have been well investigated and can be found in the literature. However, information regarding the performance of these techniques in the presence of high background music levels is scarce. Since the estimation of the room impulse response is based on the correlation between signals, the likelihood between the test signal and the music contents has an important role on the results accuracy. This paper explores these issues by taking into account the semantic information of the music signals when used as disturbance. The method used for the assessment of the gain between the two techniques consists on splitting each frame in segments and applying a weighting function depending on a likelihood function. The features used for the likelihood function are the rms value of each segment, spectral energy envelope relation, bandwidth and harmonic structure. Several examples are presented for comparison of the performance of the Swept Sine and the MLS techniques. Advantages and disadvantages of each technique are discussed for music signals as noise.
The auditory time resolution in bottlenose dolphins: Behavioral experiments versus auditory evoked potential methods
Authors: Zaslavski Gennadi L.
Published: May 2008

Non-invasive auditory evoked potentials (AEP) methods are now widely used to study dolphins' hearing because some auditory characteristics can be obtained much faster compare to behavioral methods. The bottlenose dolphin auditory time resolution assessed using evoked potentials responses to a double click, amplitude modulated tone and periodic click is generally believed to be around 300 microseconds. This assessment is claimed to be in full agreement with behavioral measurements. The intention of this paper is to reevaluate behavioral results which are believed to support AEP methods in light of numerous behavioral results indicative of the bottlenose dolphin time resolution as high as 20-30 microseconds. We found that as long as there are differences in waveforms, bottlenose dolphins are able to discriminate between very short (as short as a bottlenose dolphin sonar click) signals with identical energy spectra as well as between brief noise signals with random energy spectra. Auditory evoked responses do not reveal any differences between such signals whereas the differences are readily indicated by behavioral responses of the dolphins. The auditory temporal analysis of brief signals in bottlenose dolphins seems to be inaccessible by AEP methods, at least in their present form.
Vocalizations of the Spotted Hyena (Crocuta crocuta): Eliciting Acoustic Variation in Groans
Authors: Theunissen Frédéric E. , Glickman Steve , Page Suzanne
Published: May 2008

Spotted hyenas (Crocuta crocuta) are highly social animals possessing a complex vocal repertoire. Vocal signals of different types correlate with distinct social circumstances. Groans constitute a very large category in the spotted hyena repertoire which is not well understood. Sounds labeled as groans vary in their acoustical quality from more growling sounds to more tonal vocalizations. Groans are also elicited in many different social interactions. To begin to decipher the meaning of these vocal signals, we examined how the variation in the acoustic properties of groans was correlated with experimentally controlled eliciting conditions. Groans were elicited in adult hyenas presented with three objects: unfamiliar spotted hyena cubs, meaty bones, and the empty transport cage used to contain bones or cubs on other trials. Cubs elicited more groans from more adults than other objects but all objects elicited vocal responses. More importantly, discriminant analysis revealed differences in the acoustic characteristics of groans elicited by cubs and those elicited by other objects. Cubs elicited more prolonged and more tonal groans with higher fundamental frequency. Our study shows that groans can be classified into different groups and that these different sounds were produced in different behavioral contexts.
Overview of U.S. Navy Operational Oceanographic Models in Support of Acoustic Applications
Authors: Allard Richard , Barron Charlie , Bub Frank , Coelho Emanuel F. , Cummings James , Fabre J. Pacquin , Helber Robert , Rowley Clark
Published: May 2008

The Naval Oceanographic Office operational global 1/8° Navy Coastal Ocean Model assimilates satellite and in-situ data to produce daily 72-hr forecasts. Output includes 3D fields of temperature, salinity, u- and v-components of ocean currents at standard depth levels, and these support derived fields including sound speed and sonic layer depth. The global model provides initial/boundary conditions for nested regional models, primarily relocatable NCOM. The relocatable NCOM modeling system can be set up quickly for areas of interest, includes river and tidal forcing, and is forced with a high-resolution atmospheric mesoscale model. Local and remote observations are incorporated into the models through the Navy Coupled Ocean Data Assimilation system, which assimilates sea surface temperature data from satellite, ships and buoys, profile data from floats and gliders, xbt's, CTD's, fixed and drifting buoys as well as altimeter-derived sea surface heights and ice concentration. In this presentation we will discuss how the operational ocean models feed into acoustic prediction models and tactical decision aids, the role glider observations will play in the modeling strategy, the use of ensembles to provide improved prediction error estimates and guide new observations, and future plans.
Integrated scheme of rapid environmental assessment for shallow water acoustics
Authors: Le Gac Jean-Claude , Hermand Jean-Pierre , Absil Frans
Published: May 2008

Predicting sound propagation in shallow or very shallow water environments requires that the frequency-dependent acoustic properties be assessed for all components of the waveguide, i.e., the water column, sea bottom and sea surface interface. During the Maritime Rapid Environmental Assessment MREA/BP'07 sea trial in April-May 2007, south of Elba Island in the Mediterranean Sea, an integrated MREA scheme has been implemented to provide a full 4D (3D+T) environmental picture that is directly exploitable by acoustic propagation models. Based on a joint multi-disciplinary effort, several standard and advanced techniques of environmental characterization covering the fields of underwater acoustics, physical oceanography and geophysics have been combined within a coherent scheme of data acquisition, processing and assimilation. The paper presents the whole architecture of the implemented scheme. Based on a preliminary analysis of MREA/BP'07 data, advantages and drawbacks of the approach will be discussed. Ways ahead for further improvement and perspectives are finally drawn.
Statistics of seafloor backscatter measured with multibeam sonar systems
Authors: Penrose John D. , Gavrilov Alexander , Parnum Iain M.
Published: May 2008

A number of theoretical models for seafloor backscatter statistics developed for the recent years show a good agreement with experimental measurements made with sonar systems. However, methods of data collection used in multibeam systems are commonly not taken into consideration when analysing backscatter statistics. Using data collected with a Reson Seabat 8125 system and based on theoretical considerations, it is shown that the seafloor backscatter strength derived from the peak intensity measured as a single value for each beam leads to considerable backscatter overestimation at oblique angles of incidence when the beam footprint is much larger than the insonification area. This occurs because variations of the peak intensity are extreme value distributed, which can be well approximated by the Gumbel distribution. The location parameter of the Gumbel distribution depends on the ratio of the footprint and insonification areas, which results in distorted angular dependence of backscatter strength estimates. On the other hand, the average backscatter strength derived from the integral intensity, i.e. backscatter energy, is a consistent estimate of the actual seafloor backscatter strength. The Gamma distribution is demonstrated to be a good approximation for statistics of the integral intensity, even when the scattering regime is expected to be non-Rayleigh.
Local measurements of the diffusion constant in multiple scattering media: Application to human trabecular bone imaging
Authors: Aubry Alexandre , Derode Arnaud , Padilla Frederic
Published: May 2008

Multiple scattering of ultrasound can occur in trabecular bones. A typical signature of multiple scattering is the coherent backscattering effect, and the average trajectory of a wave undergoing multiple scattering can be characterized by the diffusion constant D. In this work, we present local measurements of the diffusion constant for ultrasonic waves in human trabecular bone, based on near-field observation of the backscattered intensity. The experimental set up consists in an array of programmable transducers placed in front of a slice of bone that we want to image. By achieving Gaussian beamforming both at emission and reception, an array of virtual sources and receivers located in the near-field is constructed. The time evolution of the incoherent component of the intensity backscattered on this virtual array is shown to represent directly the growth of the diffusive halo as (Dt)1/2. A matrix treatment is proposed to separate the incoherent intensity from the coherent backscattering peak. Once the incoherent contribution is isolated, local measurements of the diffusion constant D are achieved around 3 MHz and then a D-map of the bone is built. These measurements are shown to be strongly correlated with the bone mineral density.
Distribution and anisotropy of fast wave speed in the cancellous bone of bovine femur
Authors: Mizuno Katsunori , Soumiya Hiroki , Matsukawa Mami , Otani Takahiko , Takada Masahiko , Mano Isao , Tsujimoto Toshiyuki
Published: May 2008

The ultrasonic longitudinal wave in the cancellous bone is separated into two waves, fast and slow waves [1]. In this study, the relationship between the fast wave speed and the cancellous bone structure is experimentally investigated. A conventional ultrasonic pulse measurement was performed using a PVDF focus transmitter (Custom made, Toray) and a self-made PVDF receiver. Cylindrical specimens of cancellous bone were taken from the head of bovine femur in the distal part, along the three orthogonal directions. The distribution of fast wave speed was obtained by changing the measurement position along the cylindrical axis. The anisotropy of speed was also investigated by rotating the specimens. The structural parameters of each specimen were also measured by X-ray micro CT (MCT-12505MF, Hitachi), which gave us the trabecular length and alignment from MIL (mean intercept length) parameters through TRI/3D-Bon software (Ratoc). We found that the fast wave showed large distribution and strong anisotropy depending on the measurement positions and wave propagation directions in the specimens. The fast wave showed the maximum speed in case of wave propagation along the load direction. Reference [1] A. Hosokawa and T. Otani, J. Acoust. Soc. Am., 101, 558 (1997).
Ultrasonic velocity dispersion in bovine cortical bone
Authors: Haiat Guillaume , Sasso Magali , Naili Salah , Yamamoto Kazufumi , Matsukawa Mami
Published: May 2008

The evaluation of cortical bone quality has become possible in clinical practice, but the interaction between a broadband ultrasonic pulse and this complex multiscale medium remains poorly understood. Specifically, the frequency dependence of phase velocity has been sparsely investigated. This study aims at evaluating the determinants of the frequency dependence of phase velocity in bovine femoral cortical bone samples using an in vitro ultrasonic transmission device. Phase velocity is shown to vary quasi linearly in a 1 MHz restricted bandwidth around 4 MHz, which enables dispersion evaluation. Axial dispersion is significantly higher than radial and tangential dispersions. Significant differences in dispersion are obtained according to the anatomical location. The microstructure of each sample is determined using an optical microscope, which allows assessing the dependence of dispersion on the type of bone microstructure. Mostly positive, but also negative values of dispersion are measured. Negative dispersion is obtained mostly in samples constituted of mixed microstructure, which may be explained by phase cancellation effects due to the presence of different microstructures within the same sample. Dispersion is shown to be related to broadband ultrasonic attenuation values, especially in the radial direction. This dependence is compared with results derived from the local Kramers-Krönig relationships.
Effects of bone marrow on the ultrasonic propagation in the cancellous bone - Comparative study on experiment and simulation
Authors: Saeki Takashi , Emura Masahiro , Mizuno Katsunori , Matsukawa Mami , Nagatani Yoshiki
Published: May 2008

Longitudinal ultrasonic wave in cancellous bone separates into fast and slow waves depending on the bone structure. This phenomenon seems useful for the diagnosis of osteoporosis. In this study, we have investigated the influences of soft tissue (bone marrow) in the cancellous bone on the propagation of waves, in order to investigate the mechanism of this phenomenon. First, we have experimentally investigated the temperature dependence of longitudinal wave velocity and attenuation in bovine bone marrow, using a conventional ultrasonic pulse method. We used the ultrasonic wave at 1MHz. Then, we simulated the wave propagation in cancellous bone. For simulation, we used the 3 dimensional elastic FDTD (Finite Difference Time Domain) method. Here, we used the X-ray CT pictures of actual cancellous bone obtained from the head of left bovine femur as the bone model. By changing the velocity and the attenuation values in the soft tissue among trabeculae from those of marrow to the water, we have found the changes in the waveforms of both fast and slow waves. This indicates the changes in both wave properties, due to the properties of soft tissue.
Modeling the ultrasonic scattering in trabecular bone
Authors: Nowicki Andrzej , Litniewski Jerzy
Published: May 2008

Computer simulations conducted to investigate the properties of the ultrasound pulse-echo signal, as it is received on the transducer surface after scattering in trabecular bone was developed. It can be used to yield an ideal environment in which, the effects of various parameters (scatterer mechanical and geometrical properties, scatterers' concentration), the shape of incident wave and experimental conditions influencing the scattering of ultrasonic waves in trabecular bone structure can be examined individually. The Wear's scattering model of a cancellous bone was applied with modifications that allow for changes of mechanical and geometrical properties of individual trabeculae as well as their spatial density variation. The model also enables considering the groups of scatterers with varying mean values, e.g. thick and thin trabeculae of cancellous bone. Also, the real interrogating pulses are considered, thus the pulse shape, the emitted field structure and the frequency transfer function of the transmitting-receiving transducer are applied in simulations. The results proved that the computer simulation is a useful tool for gaining a better understanding of the scattering of ultrasonic waves in biological tissue and has a particular relevance in studying scattering in cancellous bone which may be approximated as a collection of cylindrical trabeculae.
Longitudinal assessment of human bone quality using scanning confocal quantitative ultrasound
Authors: Qin Yi-Xian , Xia Yi , Lin Wei , Cheng Jiqi , Muir Jesse , Rubin Clint
Published: May 2008

Microgravity and aging induced bone loss is a critical skeleton complication occurred particularly in the weight-supporting skeleton, which leads to osteoporosis and fracture. Advents in quantitative ultrasound (QUS) provide a unique method for evaluating both bone strength and density. Using an imaging-base confocal scanning ultrasound diagnostic system (SCAD), the goals of this work were to non-invasively characterize bone quality at proximal femur, and longitudinally monitor effectives of calcaneus bone loss in a 90-day bedrest. QUS scanning was performed at proximal femur (cadaver) and calcaneus (bedrest subjects) regions with QUS images of 80x80 mm2 for hip and 40x40 mm2 for calcaneus. QUS was processed to calculate the ultrasound attenuation (ATT; dB), wave ultrasound velocity (UV), and the broadband ultrasound attenuation (BUA; dB/MHz). Human cadaver proximal femurs have been measured with the SCAD, micro-CT, DXA, and mechanical strength test. Human calcaneus of bedrest subjects were measured using SCAD and DXA in day 0 (baseline), day 60 and day 90. Results demonstrated that QUS measurement has the capability to predict bone BMD, microstructure and mechanical properties in human bone, and indicated significant sensitivity to the progressive change of bone quality, particularly in the trabecular bone region with remodeling activities.
Analytical modeling of piezoelectric ceramic transducers based on coupled vibration analysis
Authors: Aronov Boris
Published: May 2008

The energy method for analyzing piezoelelctric ceramic transducers [B. S. Aronov, JASA, 117(1), 210-220.] is applied to the treatment of transducers with mechanical systems that can be cobsidered as two-dimensional. Analysis is made following the general outline of the theory of coupled vibration in two degree-of-freedom systems and its extention to calculating the resonance frequencies of elastic bodies, as suggested by Gibbe and Blechshmidt [Ann. Physik, Ser. 5, 18, No. 5, 417-485 (1933)]. The approach to the problem is illustrated with examples of piezoelectric rectangular plates, stripes and thin-walled cylinders at various orientations relative to crystallographic coordinate system. For all of the examples the resonance frquencies and effective coupling coefficients are presented as functions of the dimensional aspect ratios. Equivalent electromechanical circuits are introduced that permit calculation of the transducers performance under different loading conditions. Practical recommendations for improving the electromechanical properties of the transducers by use of appropriate aspect ratios are discussed.
Effects of enclosure design on the directivity synthesis by spherical loudspeaker arrays
Authors: Pasqual Alexander Mattioli , Arruda José Roberto , Herzog Philippe
Published: May 2008

Spherical loudspeaker arrays have been used to generate non-uniform directivity patterns. It is known that the poor radiation efficiency of spherical sources and the loudspeaker electroacoustic behavior impose constraints on the directivity synthesis at low frequencies, which are aggravated as the source volume is made smaller. In this work, the effects of the enclosure design on the loudspeaker signal powers are analyzed. Two different approaches have been reported in literature, although quantitative comparisons have not been provided. In the first approach, the drivers share the same enclosure volume and in the second, they have their own independent sealed cavities. Here, an analytical model that takes into account the interior and exterior acoustic coupling is used in order to evaluate the voltages that must feed the array drivers. It is shown that the signal powers can be reduced at low frequencies by letting the drivers share the same enclosure volume. However, this leads to controllability problems, since some natural frequencies of the enclosure are in the operation range of the spherical array. If controllability at natural frequencies is neglected, a simple lumped parameter model of the enclosure presents good agreement with the continuous model, indicating that heavy calculations may be unnecessary.
Acoustical properties characterization of a composite made of SU-8 and nanoparticules for BioMEMS application
Authors: Carlier Julien , Campistron Pierre , Callens Dorothée , Soyer Caroline , Nongaillard Bertrand , Wang Shengxiang , Zhao Xingzhong
Published: May 2008

The photoresist SU-8 (often used in microtechnology) has been acoustically characterized at the frequency of 1 GHz thanks to ZnO transducers. This material will be used to achieve acoustical matching between silicon and water at this frequency and a gain of about 5 dB has been obtained using the combination of this material with a silicon oxyde layer. The acoustical characterization of a composite material made of this photoresist SU-8 doped with nanoparticules (TiO2 for example) is also presented. The aim is to achieve matching layers with specific mechanical impedance around 5 MRay and depending on the nanoparticules concentration. The targeted application concerns the integration of high frequency ultrasonic transducer in Lab-on-Chip for biological cell characterization, especially adhesion properties or biological cells mechanical behaviour. The mechanical impedance and the attenuation of this composite material are characterized around 1 GHz thanks to a standing wave ratio method measuring S11 parameter and extracting the targeted parameters thanks to signal processing.
Consideration on design of the sensitivity in piezoelectric vibratory tactile sensor
Authors: Kudo Subaru
Published: May 2008

The piezoelectric vibratory tactile sensors have been used for measuring the softness and hardness of an object. They make use of changes in the resonance frequency when their vibrating sections are brought into contact with an object. In this study, the sensitivity of the frequency change on the tactile sensors is experimentally considered. The longitudinal-bar-type and the fixed-free-bar type resonators are used as the tactile sensors. Then, the experimental characteristics of the manufactured tactile sensors are shown by measuring the softness and hardness of the test pieces. The differences of the characteristics of the sensitivity are discussed from the viewpoint of the resonance frequency, vibration mode and the dimensions of the resonator. It is clarified that the sensitivity on the tactile sensor is inversely proportional to the mass of the resonator. Moreover, the effects of the resonance frequency change on the tactile sensor by the load force and the additional mass, in case of contacting with an object, are analyzed using the finite element method. The obtained results will be useful for designing the piezoelectric vibratory tactile sensor.
Theoretical Study of Near 3D Sound Field Reproduction Based on Wave Field Synthesis
Authors: Kimura Toshiyuki , Yamakata Yoko , Katsumoto Michiaki
Published: May 2008

It is very important to develop near 3D sound field reproduction techniques in order to realize the ultra-realistic communication such as 3D TV and 3D tele-conference. In this report, the principle of the near 3D sound field reproduction technique using wave field synthesis is defined from Kirchhoff-Helmholtz integral equation and two methods (dipole control method and directional point control method) are proposed. The performance of two proposed methods is studied by computer simulation and it is shown that the dipole control method has good performance and that the directional point control method has good performance if the directivity of loudspeakers is unidirectional or shotgun.
Measurements of head-related transfer function in sagittal and frontal coordinates
Authors: Nakado Takashi , Nishino Takanori , Takeda Kazuya
Published: May 2008

3D sounds can be generated by using a head-related transfer function (HRTF), which is defined as the acoustic transfer function between a sound source and the entrance to the ear canal. Since HRTF depends on a subject and the sound source direction, many HRTF measurements were conducted. In most case, HRTFs were measured in horizontal coordinates. However, HRTF measurements in other coordinates are also useful. In previous researches, HRTFs measured in sagittal coordinates were used to investigate the relation between spectral cues and vertical angle perception. Although HRTF measurement in frontal coordinates is rarely conducted, there is an advantage to measure HRTFs densely in the front and rear where sound localizations are very sensitive. Therefore, we measured HRTFs for about 2,300 directions in sagittal and frontal coordinates and constructed a database. The measurements were conducted in a soundproof chamber with two head-and-torso simulators (B&K 4128 and KEMAR). The HRTF database can be downloaded at http://www.sp.m.is.nagoya-u.ac.jp/HRTF/ .
A New Sound Field Reproduction Method Based on the Spatial Covariance
Authors: Takahashi Yoshinori , Ando Akio
Published: May 2008

This work investigates a sound field reproduction method based on the sound field statistics. The covariance among recorded multi-channel signals might represent the relative relationship and the mutual magnitude characteristics between each point in the sound field that time invariant. The author Y. Takahashi et al. proposed a reproduction method minimizing the difference in the spatial covariance between the original and reproduced sound fields [19th ICA, RBA15-012]. We call the method "SOund field Reproduction method based on the sPAtial Covariance (SORPAC)". However it has not been clarified that the theoretical background and the characteristics in listening. The SORPAC doesn't require the information of sound source locations and transfer functions. In this work, we described the reproduction theory of SORPAC in frequency domain. And we showed the relationship between SORPAC and the general wave surface control. Then we confirmed that the SORPAC is able to reproduce the sound source direction without the wave surface control. As a application of SORPAC, we demonstrated a multi-channel contents down-mixing experiment and evaluated the result from the binaural-listening point of view.
Education software for numerical acoustics
Authors: Dazel Olivier
Published: May 2008

Numerical computations tools and scientific computing programs are more and more used by acousticians. This induces that higher education institutions have to include numerical techniques in their programs. Several general aspects should be considered while designing such courses; they are the initial level of the students, their ability with mathematics and/or physics and the aim of the formation. Particular aspects on the choice of a type of software and the methodology need also to be studied. This talk will detail these aspects around the numerical courses at Université du Maine in Le Mans (France) whose formations ranges are from sound and vibration technicians to PhD students. Some typical examples and numerical tools will be presented to illustrate the purpose.
A computer model to study the properties of guided waves
Authors: Lowe Michael J.
Published: May 2008

The author's research group has a specialist interest in developing guided wave techniques for the Non Destructive Testing (NDT) of structures. Guided waves travel along the structure and so can be used to inspect large lengths or areas very much faster then the traditional point-by-point ultrasonic methods. The development of these inspection methods requires careful study and understanding of the properties of the guided waves. To address this need, the author's team has created a general purpose modelling tool. This can model waves in waveguides consiting of an arbitrary number of layers which can be flat or cylindrical, elastic or damped, isotropic or anisotropic solids, or perfect or viscous fluids, and can be immersed in a fluid or embedded in a solid. The primary output of the program is the dispersion curves, that is the frequency-velocity relationships of any modes which could travel in the structure. The program also predicts the attenuation of the modes, caused by leakage into surrounding materials or by material damping, and the mode shapes The presentation will explain the basis of the modelling tool and illustrate the way in which it can be used to understand the guided waves.
Extracting Reed Control Parameters Using Acoustic Measurements and Inverse Filtering
Authors: Smyth Tamara R. , Abel Jonathan
Published: May 2008

The control of virtual musical instruments often relies on either a specially-developed controller on which the performer has usually not gained sufficient virtuosity to play musically, or an existing multipurpose general controller with control parameters not always easily, or intuitively, mapped to the synthesis parameters of the virtual instrument being performed. A response to this problem is to obtain control information from a musical performance where the performer uses an instrument with which s/he is sufficiently familiar. In this work, we incorporate a previously developed measurement technique to transform a measured clarinet signal into a sequence of pulses corresponding to the reed displacement as a function of time. The measurement technique, shown to obtain accurate reflection functions from various tube structures, is used to obtain a filter modeling the bore and bell of the wind instrument used in the performance. The "reed pulse" waveform is then isolated by inverse filtering the measured clarinet signal. The characteristics of this residual waveform, which evolve with the performer's control of the instrument, may be extracted and remapped to the synthesis parameters of a physical model.