bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study on resistance and noise reduction of low functional surfaces hydrophobic coatings
Authors: Zhang Lin , Jiang Ting
Published: May 2008

The object moves in viscous fluid will accepting two kinds of resistance, one kind is the friction drag that the fluid applied to the object directly, another kind is the pressure drag that because of separating the fluid and taking from, and this drag force can create the flow noise. On theoretical aspect, this article analyses the relation between physical properties of the material and flow resistance and flow noise. The conclusion is that the surface material has the effect of reducing the flow resistance and noise because of its experimental on reducing the mutual action between fluid and solid surface under given conditions. On experimental aspect, use the gravitational low noise water tunnel test condition and adopt torpedo model, many times have the test on the drag and noise reduction of the torpedo model under diversity flow rate, have coating and not coating situation. Indicate by analysis that the low surface energy dewatering coatings used in experiment have the certain drag and noise reduction effect under the high flow rate, and with the flow rate power-up, the effect of the drag and noise reduction becomes better and better.
Tidal Effect of Reciprocal Sound Propagations at the Experiment in Hashirimizu Port
Authors: Ogasawara Hanako , Nakamura Toshiaki , Mori Kazuyoshi , Mizutani Koichi
Published: May 2008

Acoustical monitoring method could monitor wide area such as ocean because it can spatially measure the measurement object with a few sensors. It is important to monitor ocean structure changes for understanding global climate changes and for controlling aquatic resources. We investigated sound propagation characteristics using sound propagated data measured at Hashirimizu port of Yokosuka, Japan in August 2006 and 2007. The experimental area was very shallow water with the average depth of 5 m and travel distance of 110 m. M-sequence signal alternately propagated every 30 seconds from each bank side. Water depth change caused by tide affected received signal amplitude traveled with the frequency of 12 kHz and 80 kHz. It was also confirmed from simulated sound pressure by FDTD method through the change of assumed water depth. Furthermore, water temperature fluctuation could be confirmed from the travel time changes.
Modeling ocean reverberation under short pulse conditions
Authors: Weinberg Henry
Published: May 2008

The Comprehensive Acoustic System Simulation (CASS) is a standard model for predicting ocean reverberation. However, the current version, CASS V4.1, is known to have theoretical and numerical difficulties when investigating short pulse lengths. This is due to two model requirements: (1) the time increment for sampling reverberation should not exceed the pulse length; and (2) the range increment for sampling the environment should not exceed half the sound speed-pulse length product. Unless these requirements are met, certain phenomena, such as time splitting, may not be accurately modeled. In addition, the predicted results may have an unrealistic step function appearance. On the other hand, very small time and range increments often lead to excessive computational requirements. A simple modification to CASS V4.1 appears to have relaxed the current increment requirements substantially. The range increment must still be small enough to sample environmental features, but not to the extent dictated by small pulse lengths. Although the modification is based on a well known mathematical method for accelerating convergence, its success in modeling reverberation was unexpected.
Diffraction modeling in acoustic radiance transfer method
Authors: Siltanen Samuel , Lokki Tapio
Published: May 2008

The room acoustic radiance transfer method is a solution to recently presented room acoustic rendering equation which formulates the mathematical basis for all the ray-based (geometrical) room acoustic modeling algorithms. The basic acoustic transfer method gives as accurate results as the state-of-the-art commercial room acoustic modeling software. However, the basic method still lacks, e.g., diffraction modeling and modeling of complex reflections from surfaces. In this paper we discuss different diffraction modeling methods in the light of the acoustic radiance transfer method. The problems as well as benefits of each diffraction modeling method are summarized to understand which one of them can be implemented together with acoustic radiance transfer. Finally, some implementation examples are given.
Analysis of room transfer function and reverberant signal statistics
Authors: Georganti Eleftheria , Mourjopoulos John , Jacobsen Finn
Published: May 2008

For some time now, statistical analysis has been a valuable tool in analyzing room transfer functions (RTFs). This work examines existing statistical time-frequency models and techniques for RTF analysis (e.g., Schroeder's stochastic model and the standard deviation over frequency bands for the RTF magnitude and phase). RTF fractional octave smoothing, as with 1/3 octave analysis, may lead to RTF simplifications that can be useful for several audio applications, like room compensation, room modeling, auralisation purposes. The aim of this work is to identify the relationship of optimal response smoothing (e.g., as in complex smoothing) with respect to the original RTF statistics. More specifically, the RTF statistics, derived after the complex smoothing calculation, are compared to the original statistics across space inside typical rooms, by varying the source, the receiver position and the corresponding ratio of the direct and reverberant signal. In addition, this work examines the statistical quantities for speech and audio signals prior to their reproduction within rooms and when recorded in rooms. Histograms and other statistical distributions are used to compare RTF minima of typical “anechoic” and “reverberant” audio speech signals, in order to model the alterations due to room acoustics. The above results are obtained from both in-situ room response measurements and controlled acoustical response simulations.
The scanning and voxellisation of complex 3D objects for incorporation within finite difference time domain based acoustic prediction
Authors: Drumm Ian
Published: May 2008

This paper presents techniques developed to incorporate complex 3D objects within the author's own finite difference time domain based acoustic prediction software application. Using a combination of 3D laser scanning, ray based voxellisation and a least pth norm based filter design approach to emulate the absorption profiles of non-rigid boundaries; complex objects can be incorporated into a variety of FDTD based acoustic prediction scenarios. The paper will evaluate the success of the approach and explore its application. Of particular interest is the emulation of furniture, people, acoustic modifiers and other complex non planer structures within room acoustics predictions.
Measurement of room-to-room airborne sound insulation with an access floor in a dwelling unit of condominium
Authors: Koga Takashi
Published: May 2008

It is preferred covering a wooden access floor on the concrete floor for condominium apartments in Japan. The access floor usually installed after every partition in each dwelling unit. If access floor and ceiling were done before partition, one can obtain accuracy of construction and reduce waste material. Therefore, one can provide building more green. But, there is concern that may deteriorate sound insulation because of flanking path through under the access floor. On the other hand, there is also another dominant flanking path irrespectively to these construction methods: via doors leading into hallway. A number of field measurements of sound insulation were done with opening/closing doors to evaluate the flanking transmission via the doors. These results show that the doors affect especially in high frequency, but not significant in low-mid frequency. Next, the sound transmission performances of access floors and ceilings measured at laboratory are compared with direct sound transmission through wall itself. As a conclusion, field measurement results show that this construction method difference less affect to airborne sound insulation performance.
Enhancement of impact sound insulation for “Gründerzeit-Häuser” build around 1900 during refurbishment using concrete-wood composite floors or suspended ceilings
Authors: Bednar Thomas
Published: May 2008

During refurbishment of Viennese buidlings that have been erected around 1900 an important aspect is to enhance the impact sound insulation of the old wooden floors. Usually the floors are wood beam floors and the uppermost floor is a massive wooden floor called Dippelbaumdecke. Two important measures are taken to increase the impact sound insulation to achieve the minimum requirement of LnTw<=48⩽dB. The paper describes the design of an optimal suspended ceiling to avoid additional measures and as an alternative the impact of an additional thin concrete floor on top of the Dippelbaum-floor to achive minimum floor heights. As the thin concrete floor has a much larger area than the rooms below the measured results showed a big influence of concrete floor area on the impact sound level.
Sound insulation properties of building elements, considering the frequency range below 100 Hz
Authors: Muellner Herbert , Frey Anna , Humer Catrin
Published: May 2008

The constantly increasing standard of comfort in general and the rising number of apartment buildings in lightweight mode of construction directed the focus of research to the sound insulation properties of timber frame and massive wood element buildings. The complaints of the residents of terraced houses and multiple dwellings in lightweight buildings mainly concern noise events characterised by dominant low frequency. This problem regards airborne sound insulation as well as impact sound insulation. Based on empirical data the comparison of the sound insulation properties of the building elements investigated shows the specific problem of each category of construction mode in the frequency range below 100 Hz. The typical sound insulation characteristics regarding the low frequency range are discussed in the light of the current applied sound insulation requirements as well as in relation to the problem to comply with the resident's apperception of sound insulation quality.
Acoustic analysis of the framework and walls stage in the construction of a housing block
Authors: Ballesteros Maria Jesus , Quintana Samuel , Fernandez Marcos D. , Ballesteros Jose A. , Rodriguez Laura
Published: May 2008

The noise in the construction process is one of the main environmental and industrial noise sources. There are no specific regulations in several European countries for assessing such kind of noise, neither reference indexes for its evaluation. Therefore, the limits adopted are those for environmental and industrial noise, although they do not take into account the intrinsic characteristics of this noise. A measurement procedure has been stated for assessing the noise in building sites in which, the most appropriate indexes for this noise have been analyzed and used to derive the acoustic characteristics of the framework and walls stage. This stage is considered as one of the most annoying in the construction process of a housing block.
A geometric acoustics simulation proposal for curved geometry
Authors: Van Der Harten Arthur , Calamia Paul
Published: May 2008

Current methods for acoustical simulations based on geometrical acoustics are designed to ascertain the properties of rooms using models comprising large flat polygons. Typically these same methods are used on models of spaces with curved surfaces in which the curves are approximated using planar facets. In such cases, errors are introduced in the simulation when the infinitely varying normal of a curve is replaced with a finite number of piecewise constant normals, one for each facet. NURBS - nonuniform rational B-splines - offer an alternative geometric representation that allows curves to be represented with precision. Using Rhinoceros, a commonly used NURBS-based CAD program, as a platform for an acoustic simulation tool for models of both NURBS and polygon geometry, we can begin to discover whether it is possible to conceptualize a geometrical acoustics method that is more accurate for curved surfaces. This talk will cover the implementation and early testing of an acoustic-simulation plug-in for Rhinoceros.
The nanomechanics of mechanosensory neurones in vivo
Authors: Windmill James F. , Pook Victoria G. , Robert Daniel
Published: May 2008

The ability to detect and process sound is a sense particularly important in many animals, including insects, playing a key role in predator, prey and mate detection. Acute hearing, both in the sense of extreme sensitivity to sound and sharp frequency selectivity, relies on the active participation of auditory mechanoreceptors. In insects, active auditory mechanics was first demonstrated in mosquitoes, whereby auditory sensitivity is enhanced by the action and reaction of mechanosensory neurones to sound-induced vibrations. The mosquito's auditory neurones can generate motions that mechanically drive the antenna and tune it to biologically relevant sounds. The mechanosensory neurones are capable of detecting exquisitely small mechanical displacements, down to 100 picometres. In the mosquito's Johnston's organ (300 μm in diameter) there is a high density of these neurones (16 000 units). The mechanical response of the mechanoreceptors was measured in vivo using an atomic force microscope, in response to stimulation of the external antenna. The work establishes the link between the previously measured non-linearities of the mosquito's antennal vibrations and the nanoscale mechanics of the mechanosensory neurones.
The acoustic field on the melon of echolocating Atlantic bottlenose dolphin (Tursiops truncatus)
Authors: Au Whitlow W. , Houser Dorian S. , Finneran James J. , Dankiewicz Lois , Lee Wu-Jung , Moore Patrick W.
Published: May 2008

An array of five broadband suction cup hydrophones were placed on the melon of two bottlenose dolphins to determine where on the melon the echolocation beam emerges and to examine how signals in the acoustic near-field relate to signals in the far-field at 1 m. Four different array geometries were used: a linear one with hydrophones arranged along the midline of the melon between 2.8 and 3.7 cm apart, and two around the front of the melon at 1.4 and 4.2 cm above the melon-rostrum crease and one across the melon in certain locations not measured by other configurations. The beam axis was found to be close to the mid-line of the melon, approximately 5.4 cm above the melon-rostrum crease for both animals. The signal path coincided with the low-density, low-velocity core of the melon supporting the melon hypothesis postulated many years ago by Kenneth Norris. Slight asymmetry in the signal was found with higher amplitudes on the starboard side of the melon. Although the signal waveform measured on the melon appeared distorted, when they were mathematically summed in the far-field while preserving the relative time of arrival, the resultant waveform matched that measured by the hydrophone located at 1 m.
Acoustic localization of two distinct blue whale (Balaenoptera musculus) subspecies in the South-West Indian Ocean
Authors: Samaran Flore , Adam Olivier , Motsch Jean-François , Cansi Yves , Ruzié Gérard , Guinet Christophe
Published: May 2008

Analysis of one year of acoustic signal recordings from the five permanent autonomous hydrophones of the International Monitoring System in the South-West Indian Ocean reveals low frequency with high intensity calls produced by two blue whale subspecies. The “Antarctic” or “true” blue whale (B. m. intermedia) calls and the “Madagascar-type” Pygmy blue whale calls (B. m. brevicauda) were automatically detected through the matched filtering method. The potential movements were investigated by using the time difference of arrival (TDOA) of calls to assess the bearing of the sound source. The fully range dependent parabolic equation code (RAM - range-dependent acoustic model) and the PMCC code (progressive multi-channel correlation) are applied to estimate the range between our system and the vocalising animals. Our results show that (1) the variation of call number revealed two distinct patterns of seasonal whale occurrences and (2) the distances from the hydrophones to the blue whales reached up to 50 km. Tracking whales is possible when whales are concentrated of the hydrophone array.
AFM and BSEM: Novel approaches to the Basilar Membrane
Authors: Ketten Darlene R. , Dimitriadis Emilios K. , Chadwick Richard S. , Mountain David
Published: May 2008

For over a half century, researchers have probed cochlear biophysics with increasingly sophisticated technologies. Recently, we brought two new approaches, atomic force microscopy (AFM) and backscatter electron microscopy (BSEM), to bear on the question of how basilar membrane structural variations affect mechanical responses. Hemi-cochleae and basilar membrane segments were obtained from rat, guinea pig, and gerbil ears by temporal bone microdissection. Hemi-cochleae in PBS or formalin were imaged in a hydrated, uncoated state (VP wet mode) in Petri dishes mounted on boutons using an Hitachi S3400 N-1 SEM. Membrane segments were excised, trimmed of laminae and ligament remnants, and mounted on polylysine/albumin-coated glass for AFM imaging and force measurements. Both BSEM and AFM data indicate two distinct regions consistent with softer ground substance separating relatively stiff, ordered fiber bundles oriented radially in pectinate regions. Fibers and bundles ranged 0.3 to 1 μm in diameter with elasticity values, based on a Hertzian contact model, in the hundreds of kPa range, consistent with mixed elastin and collagen. Greatest variations occurred in matrix spacing, suggesting differences are attributable largely to packing density. Middle turn ground substance spacing averaged 1.5 μm, consistent with previously reported values (Naidu and Mountain, 2007; Fung, 1993).
Ultrasonic production and reception in frogs: Lessons from Asia
Authors: Narins Peter
Published: May 2008

Among the vertebrates, only microchiropteran bats, cetaceans and some rodents are known to produce and detect ultrasonic (US) frequencies for the purpose of communication and/or echolocation, suggesting that this capacity may be restricted to mammals. We have recently provided the first evidence of ultrasonic communication in an amphibian - the concave-eared torrent frog, Amolops tormotus (Ranidae) from Huangshan Hot Springs, China. Males of A. tormotus produce diverse birdlike melodic calls with pronounced frequency modulations that often contain spectral energy in the US range. Acoustic playback experiments conducted in the animal's natural habitat confirmed that the audible as well as the US components of an A. tormotus call could effectively evoke males' vocal responses. Electrophysiological recordings from the auditory midbrain confirmed the US hearing capacity of these frogs and that of a sympatric species facing similar environmental constraints. This extraordinary upward extension into the ultrasonic range of both the harmonic content of the advertisement calls and the frog's hearing sensitivity is likely to have coevolved in response to the intense, predominately low-frequency ambient noise from local streams. Supported by NIH grant DC-00222.
A brownian energy depot model of the basilar membrane oscillation
Authors: Kim Chul Koo
Published: May 2008

Response of a living basilar membrane (BM) is significantly different from that of the cadaver and is known to be essentially active. The best candidate for a generator of the active force in mammals is the outer hair cells. By employing the outer hair cells as the energy depot, we newly propose an interactive energy depot model for the basilar membrane. In this model, the nonlinear responses and the spontaneous basilar membrane oscillation are obtained. In the regime of small vibration, this model is reduced to the well-known Hopf bifurcation model. Our model suggests two-fold roles of the outer hair cells in hearing: an amplification for a weak stimulation and a protection for a strong stimulation.
Synchrony and neuromechanical sensitivity in the mosquito hearing organ
Authors: Jackson Joseph C. , Robert Daniel
Published: May 2008

Sound detection is a fundamental tool for many biological organisms to sense their environment. Sensing the particle velocity component of sound waves has led to the evolution of exquisitely sensitive auditory organs: small oscillators that are driven resonantly by the sound field. The sound detection threshold is often indistinguishable from Brownian motion. To achieve such low thresholds, the mammalian cochlea incorporates active mechanisms, adding energy to the sound oscillations, and so enhancing sensitivity and selectivity. Mosquito antennae are also endowed with active auditory mechanics. Males use these highly sensitive external antennae to detect the flight sound of females. Sound-induced oscillation of the antenna stimulates thousands of mechanosensory neurones. The antenna exhibits dynamic responses remarkably similar to vertebrate auditory systems: self-oscillation and amplitude-dependent bandwidth both occur. They also exhibit hitherto unseen nonlinear responses including mid-level amplification and hysteresis. The mechanisms for these effects are thought to derive from ciliary motility in the mechanosensory neurones. We show that synchronization in the motile neurones generates large stable coherent forces that provide the antenna with its nonlinear response characteristics. Synchronization ensures a coherent neuronal output, improving signal fidelity. Finally, coherent force modifies the dissipation of antennal energy, changing the bandwidth and enhancing sensitivity.
Changes in structure of Redwing's (Turdus iliacus) local dialect in time
Authors: Osipova Ludmila
Published: May 2008

The question of the period of existance of a local dialect is yet to be answered. Were there a changes in time-and-frequency parameters of dialects with time? If there were, what parameters had changed? On the basis of original data for 2005 - 2007 period, and archives of Department of Vertebrate Zoology of Saint-Petersburg State University, the history of local dialect of Redwing (Turdus iliacus) from Saint-Petersburg's outskirt (Peterhof) was investigated.The archive contains recordings of local dialects of Peterhof for 1960-1991 period. Until now, the longest period of local dialect observation for this species did not exceed 10 years (Bjerke, 1981). In observed period of 48 years several changes were found. Number of elements in phrase, it's duration, frequency modulation of all elements, their configuration, duration and frequency range. The major changes occurred to the first element of song. It is gradual reduction with time is obvious.
Optimization of the characteristics of receiving echoes by free-flying echolocating bats, revealed by onboard pulse-echo recordings
Authors: Hiryu Shizuko , Shiori Yu , Hosokawa Tatsuro , Riquimaroux Hiroshi , Watanabe Yoshiaki
Published: May 2008

To understand complex sensory-motor behavior underlying echolocation by bats, we need to precisely measure acoustic characteristics of echoes that the bats actually listen to during flight. However, it has been technically-difficult to develop a small and light enough microphone set at the position of the bat's ear, and information about the echoes is so far virtually lacked. Here, we have successfully monitored these returning echoes by means of an onboard telemetry microphone mounted on the bats, and we confirmed that the free-flying horseshoe bats compensated for Doppler-shifts by adjusting their call frequency, thus maintaining the echo frequency at constant. Furthermore, we found that the bats also adjusted pulse amplitude with the distance to maintain the echo intensity within the narrow range. Receiving echoes with stable amplitude could help the bats to sustain consistent analysis of successive echoes, and combined frequency and amplitude compensation may be for optimization of successive echoes for target range estimation to control approach and landing. [Supported by a grant to RCAST at Doshisha Univ. from MEXT of Japan: Special Research Grants for the Development of Characteristic Education from the Promotion and Mutual Aid Corporation for Private Schools of Japan and the Innovative Cluster Creation Project.]
First report of burst-pulse vocalizations from white-beaked dolphins (Lagenorhynchus albirostris)
Authors: Simard Peter , Mann David , Gowans Shannon
Published: May 2008

Dolphin vocalizations are generally categorized as tonal whistles or pulsed clicks. Pulsed signals in dolphins are usually associated with echolocation, however an increasing number of species are found to produce burst pulse signals which may be used for communication. Groups of white-beaked dolphins (Lagenorhynchus albirostris) were recorded from a 4.2 m rigid inflatable boat near Halifax, Canada with a hydrophone towed 25 m behind the boat at a depth of approximately 5m, and an M-Audio 24/96 digital recorder (16 bit, 96 kHz). During one 23-minute encounter, 11 burst pulse segments were recorded. Mean burst pulse duration was 0.83s (SD 0.51, range 0.22s - 1.74s). Seven segments with high signal to noise ratios were manually selected for analysis in Matlab. Mean pulse rate was 765 Hz (SD 182.2, range 552 Hz - 941 Hz). These durations and pulse rates are similar to those reported for other dolphin species. These vocalizations were made immediately before the group began actively swimming away from the boat at high speed, suggesting that these vocalizations are used in agonistic encounters as suggested for other species of dolphins. This is the first time burst-pulse vocalizations have been reported in this species.
An opportunistic passive acoustics study of the spatial and temporal distribution and vocal behavior of Blainville's beaked whale (“Mesoplodon densirostris”) in the presence of mid-frequency active sonar
Authors: Moretti David , Morrissey Ronald P. , Dimarzio Nancy A. , Ward Jessica , Jarvis Susan , McCarthy Elena , Izzi Annamaria
Published: May 2008

The effect of mid-frequency active sonar, has increasingly become an issue with navies worldwide. The U.S. navy ranges have been used to develop passive acoustic algorithms and tools to detect, classify, and localize marine mammal vocalizations which have been applied to an opportunistic passive acoustic study of Blainville's beaked whales. Based on Woods Hole Oceanographic Digital Tags (Dtags), these animals are known to produce echo-location clicks only during deep foraging dives. Using passive acoustics detection of vocalizations, foraging groups of animals were isolated and the duration of vocalizations was used as a measure of foraging behavior. The animals' vocal behavior and spatial and temporal distribution were characterized during periods with no active sonar on range. These results are compared to those derived from opportunistic data obtained during multi-ship active mid-frequency sonar operations.
Designing advanced piezoelectric ceramics for novel ultrasonic applications
Authors: Ringgaard Erling , Wolny Wanda W. , Bove Torsten
Published: May 2008

As new applications of medical ultrasound continue to emerge and the development of electronics continues, there is an increased interest in specialised piezoelectric ceramics with optimised properties. With the present level of knowledge about piezoceramics it is possible to design materials combining selected characteristics - although of course the laws of physics prevent changing certain properties independently. The main parameters in the design process are composition modification and controlled porosity. One of the new types of materials developed is especially intended for high-intensity focused ultrasound (HIFU) applications, where the ability to continuously generate high acoustic power should be combined with specifications for electrical impedance matching. Since the first requirement calls for very low dielectric and mechanical losses (hard doping), whereas for typical applications the second one calls for a high permittivity (soft material), a new combination was needed. The new PZT-based materials Ferroperm Pz52 and Pz54 fulfil these requirements and are already being extensively used for HIFU applications. Another example of new materials is the commercial family of porous PZT. The introduction of porosity affects all properties, and by optimising composition and porosity level it is possible to design materials that can replace lead metaniobate-based ceramics for a number of applications.
Combined two frequency array for optoacoustics and acoustics
Authors: Maass Kirsten , Degel Christian , Fournelle Marc , Fonfara Heinrich , Lemor Robert M.
Published: May 2008

A combined transducer for optoacoustics and b-mode ultrasound has to be built according to the specific requirements of both modalities. In order to combine the two tasks in one transducer, we have designed a probe consisting of a PZT array and a PVDF array in a sandwich assembly. The 20 MHz PZT array is a linear array with 128 elements bearing a 150 μm pitch. It operates as a high resolution transmit and receive array for the visualization of geometrical structures in biological tissue. A thin piezoelectric polymer film (PVDF) that is structured as receiving array is superposed to the PZT array. The PVDF array allows to detect the small optoacoustic pressure transients resulting of laser irradiation of small biological structures. Its acoustic impedance of approximately 4-4,5 MRayl allows to use it in a double function as optoacoustic receiving array and matching layer for the PZT array. The combined array is driven by a custom made multichannel read-out system supporting sampling frequencies of 80 MHz and combined imaging with b-mode and optoacoustics. This combined probe integrates the benefits of a high resolution PZT array and gives access to the specificity of optoacoustic signal generation.
Vibration spectroscopy and guided wave propagation data as indicators of structural and mechanical degradation of human bones
Authors: Ogam Erick , Wirgin Armand , Fellah Zine , Masson Catherine , Guillemain Philippe , Gabrielli François , Groby Jean-Philippe , Gilbert Robert
Published: May 2008

Vibration spectroscopy and guided wave modes analysis of long bones are investigated as tools to assess bone quality or integrity. Two different methods of vibroacoustic experiments are undertaken to determine the health of dry human tibia bones. The first method involves vibratory modes of the bone, excited and measured by piezoelectric transducers and sensors respectively. The measured frequency response is validated using finite element simulation (FES), also used in the inverse problem for retrieval of the bone material properties. The principle of in-plane (IP) and out-of-plane (OP) mode splitting to determine the degree of the damage, that we developed in an earlier study, is applied to classify the bones according to their degree of damage. The second method involves the analysis of the guided wave phase velocities recovered using the reassigned Gabor spectrogram from signals measured along the diaphysis of the tibias. The frequency difference between the peaks of the split modes are then correlated to the phase velocities of the retrieved Lamb modes.
High performance ultrasound arrays assessment through in vitro imaging performance
Authors: Legros Mathieu , Ferin Guillaume , Ratsimandresy Leong , Dufait Rémi
Published: May 2008

Probes are well-known to be a capital element for ultrasound image quality. During design, many parameters can be tuned on the acoustic stack to optimise the electrical, electroacoustical and acoustical performance measurements. But the effects on image quality of these performances are not so well identified. To overcome such a limitation, we developed a quantitative method for image quality assessment. A set of algorithms was developed to assess in vitro images. The goal of this investigation is to link the electroacoustical, acoustical performances and transducer parameters to the imaging performance. Ultrasound test objects were used to quantify the ultrasound images. The acquisition was carried out on a commercial scanner and imaging parameters were set constant in order to benchmark the probes in the same environment. From B-mode images, key parameters such as axial and lateral resolutions, contrast, statistic or metric parameters, and signal to noise ratio are established. Data from transducers, exhibiting different trade-offs on their performances (bandwidth, bandwidth shape, center frequency, elementary directivity) were characterized. Using the algorithms developed, all identified image properties were analysed with regard to these performances. The impact of each electroacoustical parameter on image quality have been identified and discussed.
Modeling of different transducer configurations with combined pseudospectral and finite-difference time-domain methods
Authors: Filoux Erwan , Levassort Franck , Callé Samuel , Lethiecq Marc
Published: May 2008

The numerical simulation of acoustic waves propagating in inhomogeneous media is often achieved using pseudospectral (PS) algorithms, which require few nodes per wavelength to converge, while complex piezoelectric structures are simulated with finite-difference (FD) or finite-element (FE) methods. A combination of the PS and FD algorithms, retaining their advantages, is presented in order to simulate the behavior of various piezoelectric transducers used in ultrasonic imaging with one single model. The theory is exposed and the algorithm is applied to simulate PZT resonators flooded into water. Perfectly matched layers are developed to absorb the mechanical waves at the borders of the computational domain, and space-shifted grids are used to reduce Gibbs phenomenon. The electrical impedance and various physical parameters (displacements, electric potentials) are calculated. Different high frequency transducer configurations have been modeled. In the case of a simple two-dimensionnal plate, described in Cartesian coordinates, the results are satisfactorily compared to those obtained with a commercial FE software. Then, simulations of an axisymmetrical single-element transducer are favorably compared to FE simulations and experimental measurements. The hybrid algorithm is also used to calculate the large radiation pattern of an annular array with little time-processing, which illustrates the efficiency of the method.
Accurate ultrasonic measurement of two-dimensional displacement of heart wall motion for estimation of myocardial regional strain rate
Authors: Honjo Yasunori , Hasegawa Hideyuki , Kanai Hiroshi
Published: May 2008

Methods for imaging of strain rate in the heart wall are useful for quantitative evaluation of regional heart function. We developed a method which can accurately measure the heart wall motion along an ultrasonic beam based on phase changes in rf echoes. However, there are some components in the wall motion which are not along each ultrasonic beam. Therefore, the measurement of motion in the direction perpendicular (lateral) to the beam has been required in addition to that in the axial direction, but some unsolved problems remain in estimation of lateral motion of the wall. In this study, two-dimensional displacement was estimated by 2D cross-correlation between rf echoes. Important parameters, the sizes of a region-of-interest and search region, which determine tracking accuracy, were adaptively optimized by referring to instantaneous wall velocities, in the respective cardiac phases. The correlation coefficient between the lateral displacement estimated by the 2D tracking with optimized parameters in longitudinal-axis view and axial displacement in apical view (corresponding to lateral displacement in longitudinal-axis view) separately and accurately estimated by the 1D phase-based method was 0.93. These results show possibility of this method for accurate measurement of two-dimensional heart motion to assess the regional myocardial strain rate.
Flow-mediated change in viscoelasticity of radial arterial wall measured by 22-MHz ultrasound
Authors: Ikeshita Kazuki , Hasegawa Hideyuki , Kanai Hiroshi
Published: May 2008

The endothelial dysfunction is considered to be an initial step of atherosclerosis. Moreover, it was reported that the smooth muscle, which constructs the media of the artery, changes its characteristics due to early-stage atherosclerosis. Therefore, it is essential to develop a method for assessing the regional endothelial function and mechanical property of the arterial wall. There is an ultrasound-based conventional technique to measure the change in inner diameter of the brachial artery caused by flow-mediated dilation (FMD) after release of avascularization. In this study, the transient change in the mechanical property of the arterial wall was further revealed by measuring the stress-strain relationship during each heartbeat. For this measurement, the minute change in thickness (strain) of the radial artery was measured using the ultrasonic phased tracking method, together with the waveform of blood pressure (stress) which was continuously measured at the radial artery. From in vivo experiments, it has been founded the slope of the stress-strain hysteresis loop decreases due to FMD and the area increase depends on the ratio of elastic modulus and loss modulus (depends on viscosity). These results show a potential of the proposed method for thorough analysis of the transient change in viscoelasticity due to FMD.
Experimental investigation of the scattering of sound by solid spheres in a liquid
Authors: Bach Jason , Declercq Nico F. , Ku David
Published: May 2008

The framework of this investigation is the characterization of spheres in a liquid by means of ultrasound. Experiments are performed to study the effectiveness of the use of bounded ultrasonic pulses in single transmission and in double through transmission to characterize size and shape of spheres. Special attention is paid to the influence of the beam width and frequency in comparison with the size of the sphere. The research is performed by means of a new generation polar c-scan apparatus. In a first step the interaction of sound with a single sphere is studied. In a second step two spheres are studied where one sphere crosses the sound path through the other sphere. Limitations for detection and characterization of spheres depending on their relative position and on the characteristics of the applied ultrasonic pulse are described in detail. The research is performed in the framework of the use of ultrasound for biomedical applications.
Acoustic radiation forces in monitoring of milk composition
Authors: Priev Diana , Ponomarev Victor , Priev Aba
Published: May 2008

High sensitivity of ultrasonic velocity and attenuation to composition and state of milk and other liquid food products is now well established. Unfortunately, existing devices include measurements of the acoustic properties of milk at different temperatures and therefore require waiting for temperature equilibration of the milk when the sample is heated or cooled and cannot be used for real-time monitoring. In this paper ultrasonic particles analyzer of NDT Instruments, AcoMilk-02, used for continuous monitoring of fat globules and somatic cells of raw milk in computerized milking station of cowsheds has been described. This device is based on high intensity standing wave for preliminary separation and concentration of the fat globules and somatic cells by the acoustic radiation forces and low intensity standing wave to measure their content. Testing of analyzer was carried out on 5 cows during one-month period. It was found that milk production level, stage of lactation, and outside temperature have significant influence on the milk composition. Continuous monitoring of milk fat and somatic cells count that typically have high day-to-day variation, provide a much-needed tool for dairy management and for veterinary diagnostic purposes.
Image quality assessment: Vibro-acoustography versus B-mode
Authors: Fatemi Mostafa
Published: May 2008

Vibro-acoustography (VA) is based on conversion of ultrasound energy from high frequency to a low frequency. This conversion, which results from the nonlinear nature of wave equation, gives VA some key advantages over linear ultrasound imaging such as B-mode. Two key features of VA are analyzed: lack of speckle noise, and angle-independency, which is the ability of imaging specular reflectors regardless of their orientation. Both the speckle noise and angle dependency are major artifacts in B-mode. Lack of speckle noise results from the fact that VA images are constructed from the low frequency acoustic signal. Using an acoustical model, it is shown that the random scatterers within soft tissue do not promote speckle noise in VA as they do in B-mode; thus VA generally produces high contrast images. Angle-independency results from the broad beam pattern of the low-frequency acoustic field. A model is constructed describing the amplitude of the acoustic signal versus object orientation angle. It is shown that the signal amplitude is relatively insensitive to object orientation; thus VA may be suitable for imaging specular objects such as implants. It is concluded that VA may be advantageous in applications where speckle noise and angle dependency are of concern.
Viscoelastic properties of myocardium tissue with surface and shear wave methods
Authors: Zhang Xiaoming , Chen Shigao , Urban Matthew , Kinnick Randall , Greenleaf James
Published: May 2008

Considerable interest in the elastic properties of soft tissue has increased in medicine due to their clinical relevance for monitoring various diseases as well as a biomarker for cancer. A recent emerging field is the use of acoustic radiation force for imaging and estimating the elastic properties of tissue. Newly developed imaging modalities include shear wave elasticity imaging, supersonic shear wave imaging, acoustic radiation force impulse imaging, and vibro-acoustography. In these new methods, the shear wave is used to estimate the elasticity of tissue. We have developed a novel surface wave method for noninvasively estimating the elasticity of tissue [X. Zhang et al., J. Acoust. Soc. Am., 122, 2522-2525 (2007)]. In this method, a localized ultrasound radiation force is remotely and noninvasively applied inside the tissue. The surface wave speed is used to estimate the elasticity of tissue. This method has been further developed and applied to estimate the viscoelasticity of animal myocardium tissue. In this abstract, we report our recent results of in vitro studies on animal myocardium tissue. Both the surface wave and shear wave are measured and analyzed. Noninvasive characterization of viscoelastic properties of myocardium tissue may be a very important tool for assessing heart function.
Acoustic radiation force manipulation of PC12 cells In vitro
Authors: Muratore Robert , Szulman Erin , Xu Nina , Simon Melissa J. , Morrison Barclay
Published: May 2008

To understand and prevent brain injuries from head trauma, researchers study mechanically stressed neuronal tissue. To anticipate future application of controllable ultrasonic in-vivo stress, we investigated the effects of acoustic radiation force on in-vitro PC12 cells. Undifferentiated PC12 cells were serum-cultured in DMEM/F12 on poly-L-lysine-coated polystyrene. Some cultures were DAPI stained. The culture plates were placed on an inverted phase-contrast microscope. An f/1.1 ultrasound transducer with a water-filled coupling cone was focused on the culture at a 45-degree angle-of-incidence, and excited with 30-ms 4.7-MHz pulses. Acoustic power was 8 W, and peak pressure was estimated at 300 kPa. Digital images were recorded before, during, and after insonification. Incident-light and fluorescence images revealed three populations: cells that were stationary (apparently outside the effective force field region), cells that elongated about 2 μm under radiation force and returned to approximately their original shapes when the force was removed (apparently adhered to the substrate), and cells that moved about 50 μm with each pulse and did not return (apparently free-floating). We conclude that cell morphology can be influenced reversibly with acoustic radiation force. (Support was provided by the Riverside Research Institute Fund for Biomedical Engineering Research and the Gatsby Initiatives in Brain Circuitry.)
Education for professional career in acoustics
Authors: Burgess Marion , Stead Matthew
Published: May 2008

There is a demand around the world for staff for acoustical consulting companies as evidenced by the “positions available” listings. Companies would ideally like to hire staff with a good engineering, physics or building background plus an understanding of acoustics. Programs of study at University may deal with the principles of acoustics and vibration but there is usually a need for supplementary education and training for new staff in practical applications of those principles. While larger companies may provide this “in house” smaller companies do not have such resources and seek to supplement the basic knowledge with short courses or other educational opportunities. Most of these are available at specific times which may limit their applicability. In this paper we will discuss an approach to address this educational need with a fully flexible distance learning program. The program is loosely based on the UK Institute of Acoustics Diploma program. The modules comprising the program have been developed with the assistance of the senior consultants and from the acoustic consulting industry body. The early experiences with implementing the program will be discussed.
Interdisciplinary teamwork, “Soundscaping”: A pedagogical challenge
Authors: Tro Jan
Published: May 2008

For seven years the Norwegian University of Science and Technology, NTNU, has offered the Master course Interdisciplinary Teamwork (“Eksperter i Team”, EiT). EiT is organized into “villages” (consisting of up to thirty students). The Acoustics Group, NTNU, is in charge of a village named “Soundscaping” mainly dealing with sound design in public areas. The students in each village are divided into teams of five. The team members may represent very different fields of study like history, philosophy, literature, religion, music, electronics, architecture, physics, medicine, chemistry, computer science and more. The paper will discuss aspects of interdisciplinary teamwork training in acoustics and gives visual and sound examples of very different and interesting results and sound products ranging from pure sound art installations and interactive educational programs to talking waste basket and new developed sound absorbers.
Problem based Masters Programme in Acoustics - ten years of experience
Authors: Nielsen Sofus Birkedal
Published: May 2008

The Section of Acoustics at Aalborg University in Denmark has more that ten years of experience in offering a masters programme in Acoustics. The programme provides students with classical and modern aspects of physical acoustics, psychoacoustics and electro acoustics. Also signal processing which today is a major tool in understanding and utilizing of the newest sound technology is a compulsory part of the study. The language is English and the programme is open for all students with the appropriate background. So far half of the students have been non-Danish citizens coming from four continents. The pedagogical concept is problem based learning, with all students organized in groups of 4 - 6 students (having their own group rooms). Each semester has its own theme with relevant courses and suggested projects from the supervisors, industry or the students themselves. The project work is a considerable part of the workload at a semester, one could say that the courses give the theoretical background for the projects which are “learning by doing” with access to the best facilities, rooms and equipment.