bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining dynamic viscoelastic properties without time-temperature shifting
Authors: Madigosky Walter M. , Lee Gilbert F. , Niemiec Jan M.
Published: May 2008

A novel unbiased procedure to analyze dynamic mechanical data of rheologically simple viscoelastic polymers by modeling the data with the Havriliak and Negami (HN) equation is described. The real and imaginary parts of the HN equation are used to solve for the global frequency-time dependent parameter (ωτ) for all the data thereby uniquely determining the time- temperature shift function. Displaying the experimental data in the form of a wicket or Argand diagram provides initial estimates for the HN parameters. An unbiased error analysis is performed to minimize the difference between experimental and calculated complex viscoelastic values. Finally the characteristic relaxation time, τb> <0>, is determined by minimizing the error between the calculated data and experimental data at the reference temperature  <0> . Using this procedure, the complete master curve is generated without the need for overlapping frequency data and the procedural error and operator bias associated with time-temperature shifting is eliminated. The technique can also generate a complete frequency spectrum from isochronal temperature scans such as those obtained from a torsion-pendulum, rheovibron or a Dynamic Mechanical Analyzer (DMA) apparatus, which is not otherwise possible.
Velocity dispersion analysis of acoustic scattering wave from elastic shells
Authors: Zhengliang Cao , Shuanping Du , Shihong Zhou , Weihua Cong
Published: May 2008

In recent years the analysis of velocity dispersion of circumferential waves (or surface waves), excited by an incident plane wave to an elastic cylindrical or spherical shell, has theoretically provided valuable insight into the underlying mechanisms of scattering. In the present study, an approach of velocity dispersion analysis on acoustic scattering wave is advanced for the data induced by a spectral bandwidth signal. The method, based on a signal processing technique in time-frequency domain, is examined with simulating waveforms scattered from an elastic spherical and cylindrical shell respectively by linear frequency-modulated signal. In addition, the forward scattering waves of an elastic cylindrical shell filled with fluid is obtained by a line horizontal array in laboratory waveguide, and the results of velocity dispersion is compared with that of theoretical calculation. [Work supported by the National Natural Science Foundation of China (Grant No. 10704068)]
Measuring attenuation and velocity within unconsolidated lacustrine sediments, using high-resolution seismic data
Authors: Pinson Luke J. , Henstock Timothy J. , Dix Justin K. , Bull Jonathan M. , Best Angus I.
Published: May 2008

We present estimates of in-situ compressional-wave attenuation and velocity within the uppermost 30 m of unconsolidated lacustrine sediments within Lake Windermere (U.K.), using high-resolution seismic data acquired with Boomer and Chirp sources. The wide frequency bandwidth of the Chirp source allows attenuation to be examined over a frequency range of approximately 2-9 kHz, and by using a spectral ratio technique incorporating robust re-weighted least squares regression, the apparent quality factor of sediments can be accurately and precisely determined. A 60 m multi-channel streamer used with the Boomer source allows interval velocities between target reflectors to be obtained. Models relating quality factor to mean grain-size distinguish between coarse grain-dominated and clay-dominated sediments. The interval velocities improve the classification of the sediment sequences to clays, laminated silts & sands, and coarse sand and gravel deposits. The results are evaluated against geological and core data.
Efficient time reversal by Lanczos iterations
Authors: Oberai Assad A. , Feijoo Gonzalo R. , Barbone Paul E.
Published: May 2008

Time reversal methods have seen many applications in underwater acoustics, medical ultrasound, nondestructive evaluation, and several non-acoustics applications. Techniques to target and/or locate individual scatterers are based upon using iterative time-reversal. From a mathematical perspective, iterative time reversal is akin to the power method of extracting eigenvectors of the scattering operator. As such, standard iterative time-reversal inherits the limitations of the power method. For example, iterative time-reversal converges slowly in the presence of multiple scatterers of similar strength and has difficulty identifying weaker scatterers. On the other hand, Lanczos iterations surmount these difficulties, and tend to converge faster than the power method, even when the latter works well. In this contribution we show how Lanczos iterations can be adapted to time-reversal iteration. This allows the strongest eigenvectors of the scattering operator to be measured with greater accuracy and in many fewer iterations than required by standard time-reversal. We describe how this algorithm may be implemented in a practical situation and build a new time-reversal method around it. We apply this method to some numerical examples to demonstrate its effectiveness and compare its performance with the more traditional time-reversal iterations.
Application of the Mode Matching Technique to Fluid - Solid Layered Acoustic Problems
Authors: Sertlek Hüseyin Ö. , Aksoy Serkan , Bolükbas Deniz , Akgün Sevgi
Published: May 2008

An application of Mode Matching technique for analyzing interactions between range dependent fluid-solid layers in two dimensional cylindrical coordinates is presented by using Normal Mode method. The transmission loss for fluid-solid medium with semi-infinite bottom layer is calculated for range-dependent bottom profiles. The bottom solid half space is divided independent vertical regions due to different bottom parameters for simulation of the real acoustic environment. The transition between the independent vertical regions is ensured by using Mode Matching technique with Normal Mode method. The attenuation of acoustic wave modes in a range dependent two layered fluid-solid medium due to absorption of the lower semi-infinite solid layer is calculated. In order to validate the obtained results in the sense of Transmission Losses, Parabolic Equation program (RAM) is used for different transition cases. The good agreement is found between the results which can be used for realistic Sonar simulators.
Backscattering From Scale Models of Elastic Ocean Bottoms with Power-law Roughness
Authors: Soukup Raymond J. , Kunz Edward L. , Canepa Gaetano , Simpson Harry J. , Summers Jason E.
Published: May 2008

Rough surface analogs to ocean bottom interfaces with two contrasting power-law roughness spectra were fabricated from slabs of PVC. A tank experiment with a nearly monostatic geometry and transmitted signals in the band 100-300 kHz was performed, with the source and receiver positioned to produce acoustic interactions on multiple locations on the surfaces. Models of scattering strength and the received time series, using deterministic and stochastic representations of the surface, are used to verify the predicted dependence of the scattering, with emphasis on the sub-critical angle (< 50 degrees grazing) region, where the predicted difference in scattering strength due to the contrast in roughness between the two fabricated surfaces is on the order of 10 dB. The numerical models employed were perturbation theory, a second-order small-slope calculation using the power-law roughness parameters, and a fourth-order small-slope calculation using the actual grid of heights as an input. The experimental effort also focused on the near-critical angle region where the predictions of the numerical models differed markedly. [Work supported by ONR and NURC.]
Shallow-water tank experiments and model comparisons over range-dependent elastic bottoms
Authors: Collis Jon M. , Collins Michael D. , Simpson Harry J. , Soukup Raymond J. , Siegmann William L.
Published: May 2008

A series of tank experiments has been conducted in order to obtain high quality data for acoustic propagation in shallow-water environments with elastic bottoms. Such problems can now be solved accurately with the parabolic equation method, which is being used for comparisons with measured transmission loss. Results from the initial experiment with a flat or sloped slab of PVC demonstrated both benchmark quality agreement between computed solutions and data, and the necessity of accounting for elasticity in the bottom [J. M. Collis, et al., JASA 122]. This paper will present results of a second experiment, conducted in the same manner as the first, but modified to allow for variable bottom slopes. Time series were collected at 100-300 kHz on horizontal arrays for two source positions. Parabolic equation solutions for treating variable slopes, using coordinate transformation methods of mapping and axis rotations, will be benchmarked against the new data. [Work supported by the Office of Naval Research.]
Benchmarking of computational scattering models using underwater acoustic data from a corrugated wax slab
Authors: Calvo David C. , Canepa Gaetano , Soukup Raymond J. , Kunz Edward L. , Sessarego Jean-Pierre , Rudd Kevin
Published: May 2008

Measured time series for underwater acoustic scattering from a 30 cm x 30 cm x 5 cm wax slab with a two-dimensional corrugated (rippled) surface are compared with simulation results. The experimental geometry and directionality of the sensors allowed for ensonification of the rippled surface and the appearance of shadowing effects at low grazing angles. The acoustic source transmitted impulses at 200-800 kHz (wavelengths between 0.75-0.19 cm). The height and spacing of the ripples were 0.3 cm and 3 cm, respectively, and the slab had negligible shear speed and a measured attenuation. We simulate the experiment with the following methods listed in increasing levels of physical accuracy and computational cost: Kirchhoff Approximation (KA), Second-order Small-Slope approximation (SSA2), the Wide-angle On-Surface Radiation Condition method (WOSRC), a Pseudo-differential Impedance Operator method (PIO), a 2-domain Integral Equation method (IE-2DOM), and an Elastodynamic Finite Integration Technique (EFIT). The range of techniques allowed us to examine effects such as reflections off the interior bottom or ends of the slab and the effectiveness of the asymptotic (KA/SSA2) and pseudo-differential (WOSRC/PIO) methods for cases that include shadowing. (Work sponsored by ONR and NURC.)
Sound resonance in prehistoric times: A study of Paleolithic painted caves and rocks
Authors: Reznikoff Iegor
Published: May 2008

Caves have natural properties of resonance: some parts sound very well, the sound lasts for some seconds or gives several echoes, some other parts have a dull resonance or no resonance at all. It is extremely interesting to compare in a given cave the map of the most resonant locations with the map of the locations of the paintings: are there correlations between resonance and paintings? We have studied many Paleolithic caves in France in which the answer was remarkably positive; stated shortly: the more resonant the location, the more paintings or signs are situated in this location. Here are presented some studies and results in the caves of Isturitz and Oxocelhaya in Pays Basque and in some other caves. Some considerations are given about the resonance - pictures relationship in open spaces with prehistoric painted rocks. Bibliography I. Reznikoff: Prehistoric Paintings, Sound and Rocks in Studien zur Musikarchäologie III: 2nd International Symposium on Music Archaeology, Sept. 2000, ed. E. Hickmann, Berlin, Rahden, 2002, 39-56. The Evidence of the Use of Sound Resonance from Palaeolithic to Medieval Times, Archaeoacoustics, C. Scarre & G. Lawson ed., University of Cambridge, Cambridge, 2006, 77-84. On Primitive Elements of Musical Meaning, www.musicandmeaning.net, JMM 3 (Invited papers), 2005.
Assessment of Acoustical Characteristics for Historical Baths (Hammams)
Authors: Aydin Asuman , Tavukcuoglu Ayse , Caliskan Mehmet
Published: May 2008

Comprehensive studies are necessary to better understand the original acoustical characteristics of historical baths (hammams) in order to discover the historical technologies establishing acoustical properties in these structures and keep their proper functioning for long periods of time. The study was conducted on five historical Turkish hammams, belonging to the Ottoman period. Their acoustical performances were examined in terms of basic acoustical parameters, such as, reverberation time, early decay time, clarity, lateral fraction, sound transmission index. The 3D computer modelling and acoustics simulation were done for each structure by "ODEON combined 8.5". Their audio performance was evaluated by taking into consideration of the volume, materials use and environmental conditions. The analyses were done for the case of the unoccupied condition while one of the structures, Sengul Hammam in Ankara, was analysed both for non- and fully-occupied conditions. The joint interpretation of the results was done in order to define the acoustical features of the hammam structures. The potentials for improving the acoustical performance of interiors were also discussed. The use of 3D computer modeling and acoustical simulation, adapted for the case of historical hammam structures, provided a good opportunity for the assessment of their acoustical performance on quantitative basis.
The mridangam: A study of the history and acoustics of an ancient South Indian drum
Authors: Krishnamurthy Rohan , Hempe Ian , Cottingham James
Published: May 2008

The acoustical properties of the South Indian drum, the mridangam, were studied. The barrel-shaped mridangam has been described in ancient Hindu scriptures and depicted in cave paintings and temple sculptures. With a claimed antiquity dating back to the Vedic period, it is the principal percussion instrument in South Indian classical music and dance and possesses unique tonal properties. The mridangam is comprised of three primary parts: The tonal head (valanthalai), the bass head (thoppi), and the central shell (kattai), to which the two heads are traditionally fastened by leather rope. Measurements of modes and mode frequencies were made on traditional drums, as well as on drums where the heads were remounted using a new and user-friendly design. Measurements of drumhead vibration and sound spectra were also made when the drumhead was excited by a skilled player using standard strokes. The frequencies of the first few modes of the tonal head were found, as expected, to be tuned approximately harmonic. Practical performance variables, including effects of altering mounting tension and coupling between the drumheads, were also studied. Results from the study will be followed by a practical demonstration of the instrument.
Binaural enhancement of speech intelligibility metrics
Authors: Deux Florent , Kleiner Mendel
Published: May 2008

Efficient methods of quantifying speech intelligibility are needed for designing and understanding functional architectural spaces. All current measures of speech intelligibility are based on monaural impulse response, which excludes consideration of important binaural aspects of human hearing, including dereverberation and decoloration. Acquisition of binaural data has increasingly become common practice, using dummy heads or in-ear microphones, making the development of binaural intelligibility measures especially timely. The need for such a measure is illustrated by calculations of speech transmission index (STI) with a single energy-based impulse obtained through combination of binaural data channels. Each method of combination produces significantly different STI values that illustrate the impact of orientation and location on intelligibility calculations. The relationship between such estimation variation and subjective experience must be studied to determine the research direction for a much needed, uniquely binaural speech intelligibility measure. The aim of this research is then to provide a guide to be used in comparing values obtained by the various methods. The project will then involve measurements of psychoacoustic metrics for speech intelligibility by objective methods as well as determination of speech intelligibility by subjective methods using tests with binaural recording and playback listening.
Perception of teachers and pupils to the acoustics of classrooms
Authors: Loro Carmen L. , Zannin Paulo Henrique Trombetta T.
Published: May 2008

The present survey has evaluated the acoustic characteristics of classrooms built as modular classrooms. The study has focused on the background noise, reverberation time, noise insulation and interviews with teachers and pupils. The acoustic comfort of classrooms in a Brazilian public school has been evaluated through interviews with 62 teachers and 464 pupils. Acoustic measurements have revealed the poor acoustic quality of the classrooms. The walls between the classrooms and the corridor have permanent ventilation openings on glassy bricks. The measured weighted apparent sound reduction index (ISO 140-4; ISO 717-1) for the wall, with a door and glassy brick, was R'w = 17 dB. The low value of the weighted apparent sound reduction index R'w= 17 dB contributes significantly to the noise transmission from one room to the other, contributing to the elevated levels of background noise inside the classrooms. Interviews with teachers and pupils have shown that the main noise sources noted in the classrooms originate inside the school: voices of students and of the teacher of the neighboring classroom.
The noise control in laboratories and health areas: A keyword in order to pratice biosafety
Authors: Ribeiro Valle Macedo Marta
Published: May 2008

The noise control in laboratories and health areas: a keyword in order to pratice biosafety Marta Ribeiro Valle Macedo Coordenação de Saúde do trabalhador, Fundação Oswaldo Cruz, Av. Brasil 4365, Manguinhos-Rio de Janeiro, Brasil, CEP.21040-360 The environmental noise control is an increasing preoccupation at the international level in order to observing the effects on the human health. At the outdoor environment or in habitations, in work places and health areas, these effects are verified, as mentioned by World Health Organization (1995; 1999) and in rich bibliography about this subject. In areas with biological and chemical risk, where the development of activities need of great concentration, noise is a stressor agent and causes direct and indirect effects on the human health as well as affecting the intelligibility of the speech, the performance of activities and causing work accidents. However, the exposition to the main sound sources found in laboratories and hospitals located at the Fundação Oswaldo Cruz (Fiocruz), a Brazilian health institution, could have been avoided if some noise control measures had been employed. This paper presents the main situations observed at the evaluation devoloped during 2007, in 744 environments of work and shows how environmental noise comes interfering at the workers performance in Fiocruz.
Influence of the conservation state of the facade elements as a variable of prediction of acoustic insulation to airborne sound
Authors: Meza Leonardo
Published: May 2008

The different prediction methods of acoustic insulation are based on the acoustic properties of the constituent materials of the buildings, however, they don't usually consider the conservation state as a variable within the prediction, ignoring the natural process of degradation that the material and the construction elements suffer which sometimes are increased by the deterioration due to the use of itself. At this paper, the behavior of some construction elements is analyzed by means of acoustic insulation measurements in-situ, such as windows and its woodwork, which presents in many cases a diminish in the acoustic performance due to the damage and deterioration. Finally, the incorporation of this variable is proposed in future prediction models of acoustic insulation.
In situ evaluation of the vibration reduction index Kij
Authors: Astolfi Arianna , Schiavi Alessandro , Taricco Cristiana , Geroso Simone , Bronuzzi Fabrizio , Savio Andrea
Published: May 2008

As stated in EN 12354-1 and 2 Standards the vibration reduction index Kij is a quantity related to the vibrational power transmission over a junction between structural elements, normalized in order to make it invariant. This quantity allows to quantify the flanking transmission both in air-borne and impact sound insulation between rooms. It is important to underline that the measurement method reported in the EN 10848-1 Standard is only referred to the laboratory measurement, anyway in the Annex E of the EN 12354-1 Standard is indicated that the same methodology is probably useble also in in situ condition. In this work several measurements of the vibration reduction index in situ are reported in order to verify if the methodology is also suitable in uncontrolled conditions as in the field. The measured results are compared with the previsional model results according to the EN 12354-1. In particular the case studies are the T-junctions and the cross-junctions between the ceilings and the vertical walls in some typical rooms in dwellings. From the first experimental results some peculiar building features, influencing the measurement and the calculation data, have been evidenced, expecially with reference to the south European building typologies in brick and concrete.
Reverberation time measuring methods
Authors: Jambrosic Kristian , Horvat Marko , Domitrovic Hrvoje
Published: May 2008

In this paper different well-established methods of reverberation time measurement are compared. Furthermore, the results obtained using these methods are compared to the results provided by some additional methods which could serve as an in situ tool if, for any reason, the reverberation time measurements cannot be carried out using the standardized methods. The methods compared in this paper include the standardized methods (EN ISO 3382:2000), namely the impulse response measured with pink noise, exponential sweep, MLS, but also pistol shots of different calibers, balloon bursts, gated external pink noise, and the B&K filtered burst method. In order to make the comparison, the measurements were performed in four acoustically very different spaces - a rather small and well-damped listening room, a much bigger damped listening room, a rather reverberant atrium, and a large and very reverberant shoebox-shaped room. The results were evaluated according to signal-to-noise ratio criterion as well. Special attention has been given to the influence of room modes on measurement results.
The statistics of plant echoes as perceived by echolocating bats
Authors: Yovel Yossi , Franz Matthias O. , Stilz Peter , Schnitzler Hans-Ulrich
Published: May 2008

To explore the statistics of complex natural plant echoes, we emitted bat-like downsweeps (200-0 kHz) and recorded the echoes of various tree species. A Hilbert transform was used to calculate the envelope of the echoes impulse responses. This corresponds to a one-dimensional representation of the spatial reflector arrangement of the plant. We then calculated the envelope's power spectrum to asses the amount of periodic structures. In control experiments we compared power spectra of a single leaf, a branch and a few branches, and tested the effect of systematically decreasing the leaf density of a plant. On a bi-logarithmic plot, the averaged power spectra of all trees have a sigmoid shape with three approximately linear domains that represent different scales of structure, but differ between species. We hypothesize that the first domain is influenced by the gross skeleton of branches, while the others are associated with smaller scale structures. The control experiments showed a similar dependence between leaf density and power spectrum. Modeling plants as simple three-dimensional textures with stationary statistics was sufficient to predict the characteristics of the spectra. Our findings suggest an interpretable relation between the power spectrum of the echo's envelope and the spatial statistics of the plant.
Modelling of the echo generation process in bat echolocation
Authors: Papadopoulos Timos , Allen Robert
Published: May 2008

Very few studies exist that attempt to model the detailed shape of the echoes generated by real targets in bat echolocation. The modelling becomes even more complicated when one attempts to take into account the specific acoustic characteristics of the bat as a source and receiver. Hence, the exact physical acoustics basis that underpins the target detection and classification capabilities demonstrated by bats remains a largely open research question. We use previously published work on real target echo measurement (Simmons and Chen, JASA 1989) as a starting point but modify their experimental method in a way that allows the incorporation of the bat's source and receiver characteristics in the modelling. Furthermore, we compare our measurements with analytically predicted results and show good agreement. We discuss how our experimental method can be used for the prediction of the binaural signals that constitute the actual input to the bat's auditory system during echolocation.
The simulation of bat-oriented auditory processing using the experimental data of echolocating signals
Authors: Kim Su Yeon , Allen Robert , Rowan Daniel
Published: May 2008

There are various approaches to understanding the echolocation phenomenon of bats. A part of the echolocating process is assessed here by determining what acoustic signal a bat's ears receive during echolocation. It is simplified in an experimental rig to measure the reflections from objects in different horizontal angles which represents a sound localisation task in bats. It has been assumed in this study that the remarkable echolocating ability of bats, which is not shown in the most other mammalian species, is achieved by their different physical shape of head and ears, and specialised auditory processing of echolocating signals. In human studies in terms of sound localisation, physical characteristics are usually modelled as a head-related transfer function (or HRTF) and gammatone filter banks are widely used to simulate auditory processing in the cochlear. A modified filterbank is used here to represent the auditory processing in bats and combined with the experimental data of object reflections. Bat HRTFs will be used subsequently to determine the acoustic reflections at both ears.
Steady streaming near model cod otoliths
Authors: Kotas Charlotte , Rogers Peter H. , Yoda Minami
Published: May 2008

Typical fish distinguish sounds at about 10-1000 Hz with particle motions as small as 0.1 nm and angular separation near 10° using their ears, which contain dense, bony otoliths weakly suspended in endolymph and tissue. The otoliths oscillate relative to incident sound, inducing flows in the surrounding fluid which are in turn sensed by the hair cells on the overlying macular membrane which project into the groovelike sulcus on the otolith. These fluid flows are then sampled by the hair cells and ''heard'' by the fish. The irregular geometry of the otolith shapes the flow patterns. The hair cells, which are organized into different ciliary orientation groups on the macula, preferentially sample the flow patterns along their axes. The steady component of the fluid motion near enlarged models of an actual cod otolith oscillated at 2--20 Hz along different directions was studied in the vicinity of the hair cells using phase-locked particle-image velocimetry (PIV) and pathline visualizations. The possible relationship between the flow patterns and hearing capabilities is discussed. Although the oscillation amplitudes studied are much larger than those for underwater sound, evidence suggests that the flow patterns are amplitude independent. [Supported by ONR.]
Passive Acoustic Detection and Monitoring of Schools of Herring
Authors: Hahn Thomas R. , Thomas Gary L.
Published: May 2008

Passive acoustic detection and monitoring of various marine fishes has recently received much attention in the literature. It has been recognized that passive acoustic techniques have the potential to complement traditional active acoustic surveys and to significantly increase their overall efficiency, if the acoustic signatures of the considered species are well understood. In this paper, the potential of passive acoustic techniques is explored for the specific case of Pacific herring (Clupea palassii). It is demonstrated that schools of herring can acoustically be detected by observing the sound of coordinated bubble release, triggered, e.g., by predator activity. This sound not only has identifiable features that can be exploited for determining the presence or absence by simple means, but could also carry abundance and size information. Work supported by ONR and the NMFS via the PWSSC.
High-frequency multibeam echosounder classification for rapid environmental assessment
Authors: Siemes Kerstin , Snellen Mirjam , Simons Dick G. , Hermand Jean-Pierre , Meyer Matthias , Le Gac Jean-Claude
Published: May 2008

For shallow-water naval operations, obtaining rapidly an accurate picture of the environmental circumstances often is of high importance. Hereto a multi-sensor approach is required. In this context, the MREA/BP'07 experiment has been carried out south of Elba (Mediterranean Sea), where several techniques of environmental characterization covering the fields of underwater acoustics, physical oceanography and geophysics have been combined [Le Gac&Hermand, 2007]. The required information typically concerns water-column properties, sea surface roughness, and sediment geo-acoustic properties. Estimating these geo-acoustic parameters from inversion of acoustic data received on drifting sparse arrays has proved to be a promising approach. Part of MREA/BP'07 was therefore dedicated to this type of measurement. For validating the resulting geo-acoustic estimates sediment samples were collected. Additionally, measurements were carried out using a multibeam-echosounder. This system provides depth information, but also allows for seafloor classification. The classification approach taken is model-based employing the backscatter data. It discriminates between sediments in the most optimal way by applying the Bayes decision rule for multiple hypotheses, implicitly accounting for backscatter-strength ping-to-ping variability. Here, results of seafloor classification using the multibeam data and a preliminary comparison with the sediment sample analysis and the geo-acoustic parameter estimates as obtained from the drifting arrays are presented.
The application of rapid environmental assessment to sonar performance
Authors: Hines Paul C. , Pecknold Sean , Osler John C.
Published: May 2008

Naval sonar operations and planning in littoral environments requires information from historical databases, in situ sampling of environmental parameters, and models capable of estimating sonar performance and the uncertainty in the estimate. Defence R&D Canada's approach to enable rapid environmental assessment (REA) for sonar incorporates three components: (1) a GIS-enabled database to manage historical environmental data, (2) measurement tools that operate while underway to provide in situ sampling of water column and seabed properties, and (3) a sensitivity model that examines the relative importance of different environmental parameters in order to quantify the impact of incomplete or degraded environmental information, and to specify the appropriate spatial and temporal scales for sampling. In this presentation, the integration of these aspects of REA will be demonstrated using transmission loss data collected in shallow water. Predictions made using REA data provide a substantially better fit to the measurements than those using historical databases.
Low-frequency acoustic signature of hurricane Ernesto
Authors: Traer James , Gerstoft Peter , Brooks Laura , Hodgkiss William , Knobles David
Published: May 2008

The ambient noise level variations produced by Hurricane Ernesto were observed by the SWAMI32, SWAMI52 and SHARK arrays as the storm passed over the SW06 shallow water site. Microseism signals were detected in the water column near 0.1 Hz and were tracked with a beamformer over a period of several days observing variations that were very closely linked to measured surface waves. 5-75 Hz beamforming showed a sound-field dominated by local surface-noise punctuated by brief surges of noise from distant sources. Beamforming and time-domain cross-correlations showed that changes in acoustic environment on the time-scale of hours occurred at all three arrays with good correlation in time and directionality suggesting the storm induced noise-field is homogeneous over many kilometers.
The sea and ocean 3D acoustic waveguide: rays dynamics and chaos phenomena
Authors: Glushkov Alexander V. , Svinarenko Andrey A. , Khetselius Olga Y. , Serbov Nikoly S.
Published: May 2008

It has been carried out modeling of the sea and ocean 3D acoustic waveguide. On the basis of Hamiltonian equations of rays it is studied a dynamics of rays. It has been shown that for acoustic waveguide in a shallow sea with non-level bottom under the rays propagation in a waveguide dependence of the of temporal frequency upon the output angle represents a fractal measure in accordance with Abdullaev-Zaslavsky result. For the ocean 3D acoustic waveguide on the basis of solving the eiconal equations in the Hamiltonian form it has been studied the fractal dynamics, including the chaotic one. There are presented the data of numerical solution of equations for the typical acoustic channel in the North-Atlantic region. The conditions for the Arnold diffusion effect realization are discussed.
Fuzzy Clustering of Oceanographic Sound Speed Profiles for Acoustic Characterization
Authors: Dubberley John , Zingerelli Robert
Published: May 2008

Historic oceanographic sound speed profiles have traditionally been grouped by area and time period, usually one degree square area and monthly time. After grading the profiles, mean profiles and standard deviations are calculated from the accepted profiles and in the acoustics community they are then used to predict the expected acoustic response of the region. Here the historic profiles in NOAA's World Ocean Database 2005 (WOD2005) will be divided into the same area and time periods, but in subsets with a sufficient number of profiles, fuzzy clustering will be employed on acoustically relevant oceanographic parameters (mixed layer depth, surface temperature, sound speed gradient, etc) to divide the population into multiple clusters. A parabolic equation acoustic transmission model is then applied on the WOD2005 statistical profiles and on the fuzzy cluster populations. Conclusions will be drawn about the suitability of this clustering to capture the variability of acoustic response at a given time and place.
Hierarchical spline technique application for real time 3D displaying of seafloor using multibeam sonar data
Authors: Demkowicz Jerzy
Published: May 2008

Multibeam sonar records have a high resolution raster character. Unfortunately, interpolating and approximating and eventually displaying scattered 3D raster data of high volume leads to some difficulties related to a computer processing power. Usually the problem solution leads to multiresolution wavelet approach. The paper presents some advantages of using hierarchical splines as applied to real data from multibeam EM 3002 sonar acquired during acoustic survey on Southern Baltic. The proposed approach is two folded: firstly, all acquired multibeam sonar raw data are interpolated with high density uniform spline interpolation. The knots and control points of interpolated network are saved for defined resolution level. In the next stage, preprocessed high resolution data are combined with low resolution data sets after knot decimation process. Such approach allow real time 3D displaying of multibeam sonar data for different zoom levels
High frequency scattering measurements for mussel bed characterisation
Authors: Snellen M. , Simons Dick G. , Riethmueller Rolf
Published: May 2008

Several approaches exist towards seafloor classification using high-frequency backscattering measurements. The classification approach taken in this paper is a model-based classification employing backscatter data measured by a multibeam-echosounder (MBES) system. The method discriminates between sediments in the most optimal way by applying the Bayes decision rule for multiple hypotheses, implicitly accounting for the backscatter strength ping-to-ping variability. The method's applicability for seafloor classification has been demonstrated by using 300 kHz MBES data collected in the Cleaver-Bank area (North Sea). The area is well-known from a geological point of view due to extensive sampling campaigns and is characterized by a wide variety of seafloor types. Here we apply the classification method to MBES data acquired in the Oosterschelde estuary (the Netherlands) which is known to contain mussel culture spots. Also recordings using a video camera towed close to the seafloor and core measurements have been taken. From the video recordings estimates of mussel coverage as a function of position were derived. Analysis of the MBES results shows that they clearly reveal the presence of the mussel beds, indicating the usefulness of acoustic classification for habitat mapping. A comparison between MBES analysis results, video recordings and sample analysis will be presented.
Ultrasonic guided waves in bone
Authors: Moilanen Petro
Published: May 2008

Recent progress in quantitative ultrasound (QUS) has shown increasing interest towards measuring long bones by ultrasonic guided waves. This technology is widely used in the field of non-destructive testing and evaluation of different waveguide structures. Cortical bone provides such an elastic waveguide and its ability to sustain loading and resist fractures is known to relate to its mechanical properties at different length scales. As guided waves could yield diverse characterization of bone's mechanical properties at the macroscopic level, the method of guided waves has a strong potential over the standardized bone densitometry as a tool for bone assessment. Despite this, development of guided wave methods is challenging, e.g., due to interferences and multiparametric inversion problem. This paper discusses the promises and challenges related to bones characterization by ultrasonic guided waves.
Dual frequency ultrasound measurement of bone - a technique for elimination of soft tissue effects on pulse-echo measurements
Authors: Riekkinen Ossi , Hakulinen Mikko , Töyräs Juha , Jurvelin Jukka
Published: May 2008

Quantitative ultrasound (US) measurements have been suggested for screening of osteoporosis. However, soft tissues overlying bones affect reliability of the measurements. In this in vitro study, a novel dual frequency ultrasound (DFUS) technique is introduced for elimination of the errors induced by soft tissues on bone pulse-echo US measurements. In DFUS, US reflection from soft tissue-bone interface is measured with two different US frequencies. By knowing the frequency specific US attenuation and speed in adipose and lean tissues, the effect of soft tissue can be determined. DFUS, conducted at frequencies of 2.25 MHz and 5.0 MHz, was validated using human trabecular bone samples (n = 25) covered with heterogeneous soft tissues. DFUS, reduced (p < 0.01) the mean error induced by soft tissues from 58.6% to -4.9% and from 127.4% to 23.8% in broadband ultrasound backscattering and integrated reflection coefficients (at 5.0 MHz), respectively. Our results suggest that DFUS is a technique capable to minimize the errors induced by the soft tissue overlying the bone. As no reflection information within soft tissue (adipose-lean tissue interface) is needed in pulse-echo measurements DFUS may enhance the accuracy of ultrasound measurements. Thereby, DFUS shows a significant clinical potential.
Improved standardization methods for clinical measurements of BUA and SOS
Authors: Wear Keith A.
Published: May 2008

BACKGROUND: Although calcaneal broadband ultrasound attenuation (BUA) and speed of sound (SOS) are good predictors of osteoporotic fracture risk, BUA and SOS measurements exhibit substantial inter-system variability. PURPOSE: 1) Compare phase insensitive (PI) detection, which suppresses phase cancellation, and conventional phase sensitive (PS) detection for measurement of BUA. 2) Test a new compensation formula for reducing variability in SOS measurements. METHODS: Data from 73 women were acquired using a GE Lunar Achilles Insight bone sonometer. Radio frequency data were processed off-line using both PI and PS algorithms. RESULTS: BUA measurements (mean ± sd) were 81.4 ± 21.4 dB/MHz (PS) and 67.2 ± 9.7 dB/MHz (PI). Compensation of SOS measurements reduced 1) average transit-time-marker-related SOS variability by 75% in 73 women and 2) bandwidth-related SOS variability by 80% in a bone-mimicking phantom. CONCLUSION: These new methods will enable a substantial improvement in consistency in bone sonometry. The mention of commercial products, their sources, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products by the Department of Health and Human Services.
Monitoring of trabecular bone induced microdamage using a nonlinear wave-coupling technique
Authors: Renaud Guillaume , Callé Samuel , Remenieras Jean-Pierre , Mitton David , Blanchi Julie , Defontaine Marielle
Published: May 2008

Bone tissue contains microcracks which may affect its mechanical properties as well as the whole trabecular structure. The relationship between crack density and bone strength is nevertheless poorly understood. Efficient nonlinear (NL) ultrasound methods have been widely developed for nondestructive testing and geophysical applications to detect microdamage. Moreover it has been reported that elastic nonlinearities increase with induced damage. We propose to monitor trabecular bone microdamage using a NL wave coupling technique. Ultrasonic short bursts times of flight (TOF) are modulated as result of NL interaction with a low-frequency (LF) wave in the medium. TOF modulation (TOFM), or propagation velocity variations, are directly related to NL elasticity variations. This technique allows measuring the instantaneous TOFM as a function of the LF pressure. It is thus possible to analyze separately elasticity variations in tension and in compression, and to distinguish the tension to compression phase from the compression to tension phase (hysteresis). In several trabecular bone samples, different TOFM amplitudes in tension and in compression are observed, probably due to microdamage. For increasing damage levels progressively induced by quasi-static compression testing, linear and nonlinear ultrasound parameters are compared to biomechanical parameters.
Simulation of ultrasound wave propagation through trabecular bone samples with and without bone marrow
Authors: Goossens Liesbet , Vanderoost Jef , Jaecques Siegfried , Boonen Steven , D'Hooge Jan , Lauriks Walter , Van Der Perre Georges
Published: May 2008

For the clinical assessment of osteoporosis, ultrasound has been proposed as an alternative or supplement to the Dual-Energy X-ray Absorptiometry technique. However the interaction of ultrasound waves with (trabecular) bone remains relatively poorly understood. The aim of the present study was to improve the understanding of this interaction by simulating ultrasound wave propagation in fifteen trabecular bone samples from the human lumbar spine, using μCT based Finite Elements Modelling. The model included only the solid bone, without the bone marrow. Two structural parameters were calculated: the bone volume fraction (BV/TV) and the structural (apparent) elastic modulus (Es), and the ultrasound parameter Speed Of Sound (SOS). At 1 MHz, correlations between SOS and the parameters BV/TV and Es were rather weak but the results can be explained from the specific features of the trabecular structure and the intrinsic material elastic modulus Ei. The correlation found between the simulated SOS values and those calculated from the simple bar equation was poor when the three directions are considered separately. However at lower frequencies (50-300 kHz), this correlation significantly improved. Currently we investigate the correlations between SOS and the structural parameters when the bone marrow is included in the FE model.
Dual frequency ultrasound technique enables determination of soft tissue composition and improves reliability of
in vivo
ultrasound bone densitometry
Authors: Karjalainen Janne P. , Töyräs Juha , Rikkonen Toni , Jurvelin Jukka , Riekkinen Ossi
Published: May 2008

Soft tissues diminish reliability of the bone ultrasound backscatter measurements. In this study, the ability of a single broadband transducer dual frequency ultrasound (DFUS) technique to monitor the changes in soft tissue was investigated in a body builder during a 21 week training and dieting period, inducing a weight loss of 16.5 kg (18%). Then, DFUS was applied to correct the errors induced by soft tissues on the measurements of integrated reflection coefficient (IRC) in human distal femur. In DFUS, US reflection from soft tissue-bone interface is determined with two different US frequencies and, by knowing the frequency specific US attenuation and speed in adipose and lean tissues, their content can be determined. The dual energy X-ray absorptiometry (DXA) indicated that significant changes in quantity and composition of soft tissue, but not in bone density, took place during the diet. As compared with DXA, the single transducer DFUS could determine local soft tissue composition (r2 = 0.88, n=8, p < 0.01). The change in uncorrected IRC associated significantly with the change in body composition (r2 = 0.56, n=8, p < 0.05). The IRC values, corrected by DFUS, showed only minor variation (SD = ± 1.26 dB) during the diet.
Bulk waves velocities are dependent on frequency in cortical bone
Authors: Baron Cécile , Grimal Quentin , Talmant Maryline , Laugier Pascal
Published: May 2008

Any model of ultrasound propagation in cortical bone requires the knowledge of the effective elastic properties of bone at, let's say, the mm scale. It is well known that the porous network of cortical bone interacts with ultrasonic waves and plays a major role in the mechanical behaviour. The purpose of the present work is to emphasize that, in cortical bone, there is some variation of the effective bulk wave velocities, and consequently of the elastic properties, with frequency in the MHz range due to the effect of the porous network. A Finite Difference Time Domain (FDTD) code is used to simulate the ultrasonic propagation of compression and shear waves, transverse to, and along the bone axis, in cortical bone volumes reconstructed from micro-computed tomography (microCT). The resolution of the microCT data allowed to model the 3D networks of resorption cavities and Haversian pores. It is found that, for porosities typically above 5-6 %, the effective phase velocity is dependent on the frequency. Preliminary results indicate that the influence of the frequency is more important in the range 1-5 MHz.