bluuebunny/crossref_metadata_2025 huggingface dataset:
Blind estimation method of reverberation time based on concept of modulation transfer function
Authors: Unoki Masashi , Hiramatsu Sota
Published: May 2008

This paper proposes a method for blindly estimating the reverberation time based on the concept of the modulation transfer function (MTF). This method estimates the reverberation time from the reverberant signal without measuring room acoustics. In the MTF-based speech dereverberation method, proposed by the authors, a process for estimating a parameter related to the reverberation time was incorporated. In this paper, we investigate whether the estimation process, previously presented by authors, works as a blind estimation method and point out a problem with their method. We then propose a new method for blindly estimating the reverberation time to resolve the problem. In the proposed method, the reverberation time is correctly estimated by inverse-MTF filtering in the modulation frequency domain. We evaluated the proposed method with their method using both artificial MTF-based signals and speech signals to show how well the proposed method correctly estimates the reverberation time in artificial reverberant environments. Results suggested that the proposed method correctly estimates reverberation times from the observed reverberant signals. [Work supported by a Grant-in-Aid for Science Research from the Japanese Ministry of Education (No. 18680017).]
Realization of a measurement system for physical and acoustic measurements on brick walls
Authors: Barbaresi Luca , Garai Massimo , Guidorzi Paolo , Semprini Giovanni
Published: May 2008

Aim of this study is the development of a system for the measurement of frequency values of some physical variables such as the damping factor, the thickness of a structural element, the structural reverberation time and the longitudinal wave speed propagation in light brick walls. Such variables are required by the UNI EN 12354-1 normative for the analytical estimation of the sound reduction index R of monolithic elements in the laboratory. The results of the calculation, as a function of frequency, will be shown and compared with the measured values of the sound reduction index R.
The relationship between complex vocal signaling and immunocompetence in the brown-headed cowbird (Molothrus ater)
Authors: Levinson Samantha , Merrill Loren
Published: May 2008

Male brown-headed cowbirds (Molothrus ater) use song in mate attraction and in male-male competition to signal their quality to potential mates and competitors. Singing is an energetically expensive activity for birds, so repertoire size, singing rate, and complexity of songs should be honest indicators of a male's overall quality. Resistance to parasites is a major component of male quality, and some aspects of immunity are inherited by his offspring. Females obtain indirect benefits from mating with healthy males by having healthy offspring, so song may signal immune condition to females. Male cowbirds usually sing between four and six different song types when displaying to females. These songs differ in the amount of frequency modulation required during singing, which indicates that the difficulty of production of these songs by the syrinx also varies. In this study, we investigate the correlation between immune function and singing behavior, specifically the size of a bird's repertoire and the complexity of his songs. Understanding the relationship between repertoire size, song complexity, and immune function is important to understanding the role of vocal signaling in mate attraction in songbirds.
Systemic approach to performance prediction and the exploitation of environmental information in naval systems
Authors: Grenard Patrick
Published: May 2008

Interoperability of systems and implementation of network enabled capabilities are at the heart of defense transformation. By providing extensive capabilities for data gathering, processing and presentations, they achieve a greater tactical advantage through superior knowledge of and use of the operational environment. Within the framework of the deployment of the new French Navy information system SIC21, a system of systems is being developed in order to support the implementation of the NATO concept of Recognized Environmental Picture (REP). The metasystem established allows for the assimilation of Rapid Environmental Assessment (REA) data, and for a local or remote production of the REP. In order to support decision making and to guide actions local exploitation of the REP is carried out through embedded tactical decision aids. They rely on advanced performance prediction tools including propagation modelling capabilities called in simulation scenarios. The aims of the implemented models are to predict performances at the appropriate level of granularity, to provide a confidence level on the proposed tactical picture, to define the appropriate level of marine environmental knowledge that should be acquired, to optimise sensor settings, and finally to provide inversion tools for the REA, ensuring consistency with forward modelling used in performance prediction.
On the consideration of motion effects in underwater geoacoustic inversion
Authors: Josso Nicolas , Ioana Cornel , Gervaise Cédric , Mars Jérôme I.
Published: May 2008

The estimation of an impulse response (IR) of a propagation channel is necessary for a large number of underwater acoustic applications: underwater communication, sonar detection and localization, marine mammal monitoring, etc. Basically, it informs us about the distortions of a transmitted signal in one underwater channel. This operation is usually subject to additional distortions due to the motion of the transmitter-channel-receiver configuration. This paper points on the effects of the motion while estimating the IR for shallow water environments in the very low frequencies bandwidth with matching filtering between the transmitted and the received signals. We propose a methodology to compare between the IR estimation in motionless and motion contexts, respectively. Using this methodology an objective criterion for motion effect analysis is proposed in order to measure the distortions due to the motion phenomena. The proposed methodology is applied to real data sets issued from PASSTIME campaign (SHOM, Bay of Biscaie, 2005) proving also its interest for motion effect analysis.
Vertical echosounder versus side-scan sonar mapping of Posidonia Oceanica fields
Authors: Sanchez-Carnero Noela , Espinosa Víctor , Rodilla Miguel , Soliveres Ester , Freire Juan
Published: May 2008

Posidonia fields in the "Cabo de Gata" marine natural park, located in the south-east mediterranean spanish coast, have been mapped by means of two different acoustical tools: a vertical single-beam scientific echosounder and a side-scan sonar. The measured transects have been dived and recorded with a video camera in order to validate the predictions from the extracted acoustical data. We compare both the results obtained from the application of commercial software for bottom classification, and the processing with alternative algorithms in the case of the vertical echosounder, with those derived from the analysis of the side-scan sonar data.
Comparison of multi-beam and single-beam seabed backscatter and sampling resolution near normal incidence
Authors: Kloser Rudy
Published: May 2008

The seabed backscatter difference near normal incidence (<30°) is compared between two multibeams (EM300 and EM1002) and two on-axis calibrated single beam EK60 (38 and 120 kHz) echo sounders and found to differ by 7 to 10 dB. A seabed backscatter model supported the calibration of the single beam backscatter near normal incidence. Potential errors due to incorrectly applied equivalent area compensation were found to contribute to this difference but not significantly. Estimating the equivalent area of sampling from multibeam and single beam echosounders highlights the complexities of sampling resolutions as a function of incidence angle and pulse length. These variable sample sizes influence the measured backscatter due to the patchy nature of seabed substrate and fauna. The current backscattering processing method for a national upper slope mapping program relies on producing metrics at the highest spatial resolution. Calibration errors on these metrics for seabed classification for a national mapping program are discussed.
Analysis of Backscatter and Seafloor Acoustical Properties for Geosciences and Biodiversity Mapping Studies in Cook Strait, New Zealand
Authors: Lurton Xavier , Lamarche Geoffroy , Verdier Anne-Laure , Augustin Jean-Marie , Wright Ian , Rowden Ashley , Orpin Alan , Dunkin Miles
Published: May 2008

A quantitative analysis was conducted over sonar backscatter data collected on the Cook Strait region, central New Zealand, featuring multibeam (̃ 30 kHz) bathymetry and backscatter data, groundtruthed by an extensive geological database (photographs, seabed samples, high-resolution seismics). A first processing step removes the effects of the sounder, seafloor topography, and water column. A second step includes sonar image mosaicing, signal calibration and compensation, speckle noise filtering, image segmentation and textural analysis. Backscatter angular dependence is then extracted from the raw data accounting for the co-registered multibeam bathymetry; it is linked to the various facies of this geologically very active region, forming a catalogue usable for future investigation. Some local features are analysed in details, referring to the geological local context. Also the backscatter data from the Haungaroa volcano were used for a proof-of-concept biodiversity mapping exercise. Ecological theory was utilised to predict biodiversity from the seabed substrate heterogeneity, derived from the segmentation of the backscatter data properly pre-processed. The backscatter analysis resulted in the identification of local features with geological, sedimentological, topographic, and possibly biological significance, otherwise not recognised with conventional surveying. This emphasises the potential of backscatter data in submarine seismic hazard studies and large-scale biodiversity mapping.
Seabed biotope mapping using multi-beam backscatter based on reference sites
Authors: Kloser Rudy
Published: May 2008

A multibeam sonar (MBS) was used to discriminate ecological relevant seabed characteristics based on 62 reference sites spanning depths 50 m to 400 m sampled with georeferenced video, sediment grab and rock dredge. The simple ecologically derived terrain characteristics of soft, hard, smooth and rough were found to have the most predictive power for discrimination of the biota using data from video and physical sampling. The acoustic data were corrected for range and incidence angle effects and analysed based on phenomenological characteristics and inversion of a seabed scattering model. Near normal incidence (<16°) the seabed backscatter showed poor correlation to seabed characteristics (cross validation error 32%) and was sensitive to the estimation of the correct seabed incidence angle. Using the trend in backscatter near normal incidence (<30°) greatly improved (cross validation error 4%) the classification but also increased the spatial scale of classification. The length of biotope scales were derived from the video transects with 50% of patches less than 18 m. Referencing the seabed backscatter to a consistent incidence angle (40°) gave the highest spatial resolution derived metric and minimised range, incident angle and beam compensation errors. Using this simple metric, high probabilities of prediction of fauna functional groups were recorded.
Analysis of passive seabed imaging techniques
Authors: Siderius Thomas M.
Published: May 2008

Recently, a passive technique has been developed to image seabed layering. The method exploits naturally occurring acoustic noise generated on the sea-surface, primarily from breaking waves. The processing exploits the noise coherence through cross-correlations between sensors to recover travel times to significant seabed reflectors. To make this a practical tool, beamforming is used with a vertical array of hydrophones and this greatly reduces the required averaging times. Several data sets using moored arrays have shown stable returns from the seabed. Imaging seabed layering over extended areas requires the array to move which has been accomplished by allowing the array to drift. This, however, introduces a number of complications. If the array moves too rapidly, there is potential for the ensonified seabed (in the beam) to change within the averaging time. Another potential problem could be caused by vertical motion of the array (e.g. by surface coupling). In this case, Doppler shifts may cause degradation in the cross-correlation peaks. In some cases, these degrading factors may be reduced through signal processing. In this presentation potential mechanisms that degrade passive seabed imaging will be described with possible mitigating signal processing. Numerical modeling and measured data sets will be analyzed.
Comparing time domain Green's functions with simulated noise and ambient noise data cross-correlation for a horizontal array
Authors: Fried Stephanie , Sabra Karim G. , Roux Philippe , Kuperman William A.
Published: May 2008

Previous work has shown that an approximation of the Green's function can be extracted from ambient noise data through cross-correlating the received signals along an array. The resulting Green's function approximation gives accurate time-of-arrivals for the multipaths between hydrophones but can only approximate the magnitude of the arrivals in the time domain Green's function. Nevertheless, some useful information can be obtained from the relative amplitudes of the correlated returns assembled. Further, a Monte Carlo noise model simulation for a similar environment for which noise data was collected reproduces the same cross-correlation arrival structure for the processed ambient noise data and the theoretical time domain Green's function arrival structure. [Research supported by ONR].
Characterization of Ultrasound Propagation Through Ex-vivo Human Temporal Bone
Authors: Ammi Azzdine Y. , Mast Douglas T. , Huang I-Hua , Abruzzo Todd A. , Coussios Constantin C. , Shaw George J. , Holland Christy K.
Published: May 2008

Knowledge of cranial and intracranial ultrasonic properties is essential for optimal results in brain vasculature imaging and therapy. The aims of this study were to perform measurements of the intracranial acoustic pressure field, to identify ultrasound parameters that maximize penetration and minimize beam aberration, and to estimate the speed of sound and the attenuation per unit length in the temporal bone (TB). In vitro experiments were conducted on five human skulls. In a water-filled tank, two unfocused (0.12 and 1.03 MHz) and one focused (2.00 MHz) transducers were consecutively placed near the TB of each skull. The acoustic pressure field was measured in a volume estimated to encompass the middle cerebral artery (MCA). For each measurement, the intracranial distance from the position of maximum acoustic pressure to the estimated MCA origin was quantified. The pressure reductions at these locations relative to the free field were also estimated. The intracranial -3 dB depth of field and beam width were investigated as a function frequency. The speed of sound in TB at 1.03 MHz was 1752.1 to 3285.3 m/s. This work provides quantitative information on the cranial and intracranial ultrasound properties, which are needed for optimal insonation of the brain vasculature.
Estimation of in vivo cancellous bone elasticity
Authors: Otani Takahiko , Mano Isao , Tsujimoto Toshiyuki
Published: May 2008

Effect of decreasing bone density (a symptom of osteoporosis) is greater for cancellous bone than for dense cortical bone, because cancellous bone is metabolically more active. Therefore, bone density or bone mineral density at cancellous bone is generally used to estimate the onset of osteoporosis. Elasticity or elastic constant is one of fundamental mechanical parameters and directly related to the mechanical strength of bone. Accordingly, elasticity is a preferable parameter to assess the fracture risk. A novel ultrasonic bone densitometer LD-100 has been developed to obtain mass density and elasticity of cancellous bone with a spatial resolution comparable to that of the peripheral quantitative computed tomography system. Bone mass density and bone elasticity are evaluated using ultrasonic parameters based on fast and slow waves in cancellous bone using a modeling of ultrasonic wave propagation path. Elasticity is deduced from measured bone mass density and propagation speed of fast wave. Thus, elasticity of cancellous bone is approximately expressed by a cubic equation of bone mass density.
Fracture and bone defect assessment using quantitative ultrasound wave propagation
Authors: Szczupak Mikey , Xia Yi , Cheng Jiqi , Qin Yi-Xian
Published: May 2008

Nondestructive evaluation of early fracture and monitoring its healing, particularly in non-typical fracture, is critical yet challenge. Quantitative ultrasound test along the long bone is largely dependant on bone density, gap size, the level of maturity of the callus, and mineralized status. We propose that the ultrasonic velocity (UV) is dependent on fracture gap size and the degree of porosity. The objective of the study was to develop an analytical and a multiple ultrasound sensing system for non-invasive fracture assessment. An analytical model was generated as a function between UV and the gap size in long bone. The ultrasound measurements were performed in the intact pig femur with controlled fracture sizes, e.g., 1mm, 3mm and 5mm. A serial ultrasound transducers were aligned 3 cm above bone with an angle approximately equal to the critical angle. The results indicated that the UV decreased with increase of fracture size in a linear manner (r=0.96), in which UV decreased 6.7%, 16.3% and 26.8% for 1, 3 and 5 mm gaps, respectively. The simulation result significantly matched the experiment measurement (r=0.98). The results demonstrated that quantitative ultrasound has potential to the diagnosis of fracture, monitoring fracture healing, and other bone disorders.
Array transducer applied to low-frequency guided wave ultrasonography: An in vivo study on human radius and tibia
Authors: Kilappa Vantte , Moilanen Petro , Chen Tianhui , Ma Hongqiang , Timonen Jussi , Cheng Sulin
Published: May 2008

Velocity (VFAS) of a first arriving signal for f < 0.5 MHz is expected to have an enhanced sensitivity to endosteal osteoporotic changes as compared to using higher frequencies. In this study a group of males and females (aged 10-87 years) was measured by using a new array probe (fc = 0.4 MHz) on the radius and tibia. In addition, peripheral quantitative computed tomography was used to assess the bone mineral density (BMD) and cortical thickness (CTh) at the same bone locations. Initial results (n=57) showed that the repeatability error of the VFAS data (CVrms) was 0.5%. When VFAS data for the radius was plotted by age it characterized well, yet better than BMD or CTh, the typical growth and loss curve of bone. VFAS for the radius was strongly correlated with total BMD (r = 0.84, p < 0.001), cortical BMD (r = 0.77, p < 0.001), subcortical BMD (r = 0.66, p < 0.001) and CTh (r = 0.59, p < 0.001). Corresponding results for the tibia were similar but clearly weaker than those for the radius. In conclusion, the low-frequency VFAS had good accuracy and it predicted well both the geometry and material properties throughout the cortex.
Cross-sectional ultrasonic tomography of the medullary cavity of child bones - Limits of resolution
Authors: Lasaygues Philippe , Guillermin Régine , Debieu Eric , Lefebvre Jean-Pierre , Petit Philippe
Published: May 2008

In children with bone diseases, ultrasonography has proved to be a highly effective tool for assessing congenital disorders. However, with standard devices, this method of examination is limited and not suitable for diagnostic large purposes as tumors or sub-periostal infectious. Authors dealt with the imaging of more adult bones than children, and the main aim has usually been to assess the thickness of the diaphysis and/or to estimate the wave velocity crossing the structure. Our group has been focusing on the cross-sectional radial imaging process, using ultrasonic computed tomography, of child bones. Although this method is known to provide a potentially valuable means of imaging objects with similar acoustical impedance, problems arise when it is proposed to obtain quantitative tomograms of more highly contrasted media. Finding solutions involves either using non-linear schemes. In this paper, we recall the advantages and limitations of ultrasonic computed tomography methods when dealing with highly contrasted scatterers. The results obtained are promising and suggest that the geometrical and acoustical characteristics of children's bones can be efficiently determined using this ultrasonic computed tomography method.
Model study on assessment of bone by ultrasonic guided waves through a varying layer of soft tissue
Authors: Tatarinov Alexey , Sarvazyan Armen
Published: May 2008

Propagation parameters of ultrasonic guided waves in long bones are sensitive to changes of the cortical thickness, which is one of bone parameters affected by osteoporosis. Meanwhile, the guided waves in bone can be masked by the longitudinal waves in the overlying soft tissues, especially in obese patients. The goal of this study was to explore a possibility to minimize the effect of soft tissue on quantitative assessment of propagation parameters of axial guided waves in long bones. Phantoms and animal bone fragments modeling the axial gradients of the cortical thickness in the human proximal tibia were used. The specimens were covered by a layer of soft tissue of varied thickness. Ultrasonic signals were acquired in the pulse mode at 0.1 MHz by the surface transmission. The specimens were scanned lengthwise and the acquired signals were plotted versus the scanned distance. Analysis of the obtained waveform profiles along the tested specimens allowed quantitative evaluation of the variations of the cortical thickness despite the presence of a 5-6 mm soft tissue layer. The ratio of the acoustic wavelength to the soft tissue layer thickness defines the level of the soft tissue effect.
Variability of velocities provided by axial transmission due to irregular geometry of cortical bones
Authors: Pham Thiên-Ly , Talmant Maryline , Laugier Pascal
Published: May 2008

Early predictions of the velocities of axially transmitted waves on cortical bones were based on waveguides such as plate and tube of regular geometry and uniform thickness. We investigate the role of the actual irregular geometry by means of numerical simulations comparing monodirectional and bidirectional multielement modalities. Propagation was simulated using a finite difference method in a set of human radii previously examined by a bidirectional device. Individual geometry of the samples was reconstructed from X Ray tomography (pixel=100mm). The material constituting the bone models was considered to be a transverse isotropic medium with chosen fixed elastic properties taken from literature. In addition simulations were performed on plate of either constant or variable thickness. Preliminary results perfomed on 9 samples show that bidirectional technique reduces the variability of the velocities of axially transmitted waves compared to monodirectional array when irregular geometries are involved. Whereas bidirectional velocity is significantly correlated to the velocity obtained in plates whose thickness is equal to the mean thickness of the specimen (r2 =0.77, p=0.0018, RMSE=29m/s), no significant correlation is found for monodirectional velocity. The effect is mainly attributed to the irregular external surface of real samples.
Excess ultrasonic attenuation due to inhomogeneities in porous media
Authors: Naas Mouna , Sebaa Naima , Fellah Zine , Fellah Mohamed , Lauriks Walter , Depollier Claude
Published: May 2008

While Biot's theory seems well adapted to model the acoustical waves propagation in cancellous bone, some of its predictions do not agree with the experimental results. The excess of attenuation of the fast wave is one of these discrepancies. In this paper we propose a modified Biot's model which takes into account the fluctuations of the physical parameters and their correlations. As a result of this model, we show that this excess of attenuation is due to several processes: i) classical Biot's attenuation, ii) scattering leading to the extension of the wave path, iii) mode conversion. Some comparison between experimental results and numerical simulations are proposed.
Integrated transducers for marine animal tags using thick film PZT
Authors: Lou-Mo/ller Rasmus , Ringgaard Erling , Zawada Tomasz , Gudbjoernsson Sigmar , Hilmarsson Haraldur
Published: May 2008

The technology of printing PZT ceramic layers onto curved substrates using pad printing is demonstrated by the application of a transmitter/receiver system printed on alumina cylinders. The cylinder is used as housing for a Data Storage Tag (DST) for marine animals. DST's are used for monitoring behaviour and lifecycle of animals, providing valuable knowledge for marine biologists and researchers. Electrodes and PZT ceramic is printed directly onto the alumina housing using the pad printing technique, which eliminates the need for complex assembly procedures and other post processing steps. Since the PZT is situated on the external surface of the housing, direct contact between the acoustic elements and the marine animal is ensured and the elements do not take up valuable space inside the tag. The manufacturing of the active elements and the technology of pad printing PZT thick film is presented. The piezoelectric properties of the film and the acoustic properties have been tested under laboratory conditions. According to the obtained results one can conclude that the transmitter/receiver system was able to assure sufficient sensitivity in the required distance keeping the power consumption on an extremely low level. Second generation devices will be ready for commercialisation in the near future.
Personal sound system design for mobile phone, monitor, and television set: cylindrical shape approach
Authors: Chang Ji-Ho , Park Jin-Young , Kim Yang-Hann
Published: May 2008

Personal sound system that focuses sound on the user and reduces in the other zone has great interest in these days because it has significant needs to be applied in personal devices such as mobile phone, monitor, and television set. We have shown the feasibility of the personal sound system using a line array of loudspeaker units [C.-H. Lee et. al., J. Acoust. Soc. Am., 122, 3053 (2007)] based on acoustic contrast control [J.-W. Choi, Y.-H. Kim, J. Acoust. Soc. Am. 111, 1695(2002)], with the successful result of about 20dB difference between the front and the side region for 800-5kHz range. Continuing this research, we try to apply acoustic contrast control in cylindrical shape instead of two-dimensional planar shape that was used before in order to reduce the level of side lobes more. That is, acoustically bright zone and dark zone are determined as cylindrical shape surrounding the array of loudspeakers. Computer simulation and experimental result will be addressed and evaluated by comparing to the previous result. (This work was supported by the Korea Science and Engineering Foundation(KOSEF) through the National Research Lab. Program funded by the Ministry of Science and Technology(M10500000112-05J0000-11210).)
Efficient Directivity Pattern Control for Spherical Loudspeaker Arrays
Authors: Zotter Franz , Pomberger Hannes , Schmeder Andrew
Published: May 2008

With an appropriate control system, directivity pattern synthesis can be accomplished with spherical loudspeaker arrays, e.g. in the shape of Platonic solids or spheres. The application of such devices for the reproduction of natural or artificial directivity patterns poses a relatively young field of research in computer music and acoustic measurements. Using directivity measurements with microphones, the directivity patterns of the individual speakers on the array can be determined. Usually, the directivity of the whole array may be regarded as a linear combination of these patterns. In order to gain control, the measurement data of the linear system need to be inverted. Given L loudspeakers and M microphones, this inversion yields the desired control system, an expensive LxM multiple-input-multiple-output (MIMO) filter. We introduce discrete spherical harmonics transform and decoder matrices to reduce the number of channels required for this control system, thus reducing the computational effort. However, this step often leads to a sparse MIMO-system, in which many off-diagonal transfer functions vanish. If applicable, the computation of the non-zero transfer functions only can be done at even much lower cost. A case study for an icosahedral loudspeaker array is given, showing the properties of the sparse MIMO-system.
Relative calibration and characterization of 1/4" condenser microphones under different environmental conditions
Authors: Guianvarc'H Cécile , Giuliano Albo Paolo Alberto , Gavioso Roberto , Benedetto Giuliana , Pitre Laurent , Guillou Arnaud , Bruneau Michel , Bruneau Anne-Marie
Published: May 2008

Measurement condenser microphones are commonly used in air at ambient temperature and pressure. However, several applications require to use such microphones in environments which are significantly different. In particular, for the determination of the Boltzmann constant by an acoustic method, measurements take place in a cavity filled with pure argon or helium over a wide pressure range at the temperature of the triple point of water. For this application, it is important to determine the microphone frequency response and acoustic input impedance with a low uncertainty in these gas conditions. A few previous works have examined the influence of static pressure, temperature and gas composition on microphone sensitivity. In one case, these results were supported by a theoretical investigation using a lumped-element model. The aim of the present work is to compare theoretical results from different lumped-element models with experimental relative calibration results obtained using an electrostatic actuator technique. Measurements are performed on 1/4" condenser microphones maintained in argon and helium environments, at 273.16 K, in the pressure range between 50 kPa and 700 kPa. The results are used to test the existing theoretical models and to compare the microphone properties with the manufacturer's data.
Green's theorem as the foundation of interferometry
Authors: Ramírez Adriana Citlali , Weglein Arthur B.
Published: May 2008

A prerequisite for applying full wavefield theory to marine exploration is the completeness and proper sampling of recorded data, which can be satisfied with data extrapolation/interpolation techniques. Green's theorem can be applied to acoustic measurements of the Earth's subsurface to obtain exact equations that incorporate boundary conditions for the retrieval of the Earth's Green's function in positions where it was not measured. Recently, a number of papers on seismic interferometry have shown methods to reconstruct the Green's function between a pair of receivers by using data cross correlations. Current interferometry methods require dual measurements (pressure field and its normal derivative) which are not always available. The lack of dual measurements has encouraged the arrival of algorithms using high frequency and one-way wave approximations to the normal field derivative. The approximations are compromises to the exact theory and, hence, produce artifacts. We present a unifying framework for a broad class of interferometry techniques using Green's theorem. This framework and foundation allows errors and artifacts to be anticipated and fully explained as a consequence of approximations made within Green's theorem. We also develop a set of more effective interferometry methods, where fewer (or none) approximations are made and the result is improved.
Precision positioning for deep-water archaeology
Authors: Bingham Brian
Published: May 2008

Underwater archaeology makes use a variety of tools for deep-water exploration, but the defining characteristic of archaeology, what distinguishes the endeavor as scientific in purpose, is the quantifiable techniques employed for precision navigation. Precise positioning enables the collocation of archaeological results into a common reference frame, creating a persistent data products with the spatial context to enable interpretation. With this common context, data products such as site-maps, micro-bathymetric maps and photomosaics afford the capability to perform measurements with known accuracy and resolution, a key differentiator of the science of archaeology. Acoustic ranging is the meter stick of marine archeology. Archaeology has leveraged standard navigation techniques: long baseline (LBL) positioning, ultra-short baseline (USBL) tracking, Doppler velocity log (DVL) dead-reckoning, etc. However, the extreme precision required for archaeology has driven the development of new precise ranging instruments. This paper presents the capabilities and limitations of today's precision ranging instruments which use discrete sequence spread spectrum (DSSS) signal processing to provide the requisite performance. In addition to a technical discussion, the paper presents the results of recent field work in the Aegean, the Mediterranean and the East Coast of the Unites States.
High Overtone Bulk Acoustic Resonators Based on Thinned Single-crystal Piezoelectric Layers: Filters and Frequency Sources Applications
Authors: Gachon Dorian , Masson Jeremy , Courjon Emilie , Ballandras Sylvain
Published: May 2008

The thin film bulk acoustic wave resonators exploiting the thickness-extensional vibration mode of piezoelectric thin films is a key technology as alternative solutions to standard SAW resonators. Lakin have emphasized the capability of High Overtone Bulk Acoustic Resonators to present high quality factors at frequencies in the GHz range. HBAR spring from the conjugation of the strong coupling coefficient of deposited piezoelectric thin films and of the high intrinsic quality of used substrates. The piezoelectric film and the two electrodes on its both sides are used as transducer whereas the acoustic energy is mainly trapped in the substrate. The resonant frequency corresponds to a half wavelength in the entire thickness of the device and, in opposition to FBAR, we can utilized both odd and even harmonics. The fundamental, generally in the vicinity of 10 MHz, has no specific interest but Q.f products around 1.1×1014 have already been obtained for high overtones using aluminum nitride thin films deposited onto sapphire. In view of improving the Q factor of thin films, it is desirable to use a single-crystal piezoelectric material such as lithium niobate. We show and compare the fabrication in both approaches. Different measurement results are exposed for both approaches for the fabrication of oscillator and filters are shown and discussed.
Influence of the shape of the membrane of computed cMUT using FEA/BEM analysis
Authors: Clatot Stanislas , Sadoulet Emeline , Arbey Olivia , Daniau William , Garcia Julien , Lardies Joseph , Ballandras Sylvain , Berthillier Marc
Published: May 2008

The possibility to excite and detect acoustic waves in fluids using capacitive micro-machined ultrasonic transducers (cMUT) built on silicon using clean room techniques offers attractive opportunities for manufacturing high quality low cost imaging probes. CMUTs developed for acoustic imaging exploit the first flexural mode of thin and stiff membranes, leading to bandwidth larger than 100%. These transducers can be accurately designed using mixed finite element analysis/boundary element methods (FEA/BEM). Periodic FEA particularly allows for the simulation of devices exhibiting complicated shape interfaces and involving materials of different nature. BEM also are particularly well-suited to provide an accurate description of any stacked medium assuming flat interfaces for the radiation area and the layer interface for 2 and 3D structures as well. In this work, we have analysed the influence of the shape of the MUT membrane on the spectral response of the transducer. 3D Computations have been conducted considering radiation coniditions in the substrate on the backside (silicon) and in viscous water on the front side. we have particularly focused the computation on solutions allowing for reducing parasitic modes in the actual operation of the transducer. The efficiency of the different configuration are compared in termes of emitted pressure contributions.
Data fusion technique applied to steam wastage estimation and fault detection in an industrial process heating application
Authors: Ramadas Sivaram Nishal
Published: May 2008

Data fusion, the process of combining information obtained together from many heterogeneous sensors to form a single composite picture of the environment, is used widely in many applications. Modern steam heating systems consist of mechanical devices known as 'traps', which are robust and reliable but inevitably over time can wear and fail, with the possibility of leaking steam. To diagnose such faulty steam traps and the level of leakage under operating conditions in a closed system is difficult. This paper presents the preliminary work carried out to integrate together data recorded from commercial sensors (such as piezoelectric acoustic emission devices, pressure transmitters, and thermocouples) to estimate steam wastage and fault detection in a steam system. Experimental data were acquired from a purpose built steam wastage test rig (built similar to the method outlined in the British Standard for determination of steam loss from traps), capable of simulating varying condensate loads by injecting preheated water into a steam test line. The captured composite data is then used to develop a signal processing algorithm to diagnose effective trap operation and quantify the rate of steam loss in the system and the results are discussed.
A stepped plate transducer as ultrasonic range sensor
Authors: Je Yub , Park Jong-Kyu , Yi Dong Hoon , Lee Haksue , Moon Wonkyu
Published: May 2008

A new type of highly directional ultrasonic transducer is designed and tested as an ultrasonic range sensor by using the parametric acoustic arrays. To get intensive primary waves, a modified stepped plate transducer is proposed. Gallego-juarez et al.(1978) first proposed stepped plate transducer for high power radiation at one frequency. The steps with the height of half-wavelength of sound in air compensate discrete phase difference on the vibrating plate. However, two collimated beams are required for the parametric acoustic array. The position and height of the steps are modified to compensate the flexural vibration for two frequencies in this transducer. The transducer diameter is 50mm. The optimal primary frequencies are designed as 80kHz and 120kHz to generate difference frequency of 40kHz efficiently. The proposed transducer has the HPBW of 5° that is much higher directivity than general ultrasonic range sensor(Generally 20° on same size). The maximum SPL is 130dB at primary frequencies and 95dB at difference frequency on 75Vpk input. These experimental results show that the proposed transducer can successfully improve the spatial resolution of ultrasonic sensor. [Research is partly supported by MIC/IITA Intelligent Robot Sensor and partly supported by DAPA and ADD UD070054AD]
Improvement of low frequency signal radiation performance for piezoelectric loudspeakers
Authors: Ohga Juro
Published: May 2008

Piezoelectric loudspeaker is characterized by their very simple constructions, but their radiation performance at low frequency region is poor because their diaphragms are too stiff for large amplitude vibration. This paper proposes two innovative methods for improvement of low frequency radiation performance of piezoelectric direct-radiator loudspeakers. One is a flat-shape loudspeaker unit with a tuck-shaped flexible diaphragm by a sheet of piezoelectric film. The other is a paper cone loudspeaker unit with a large radiator driven by revolution of piezoelectric ultrasonic motors. A loudspeaker system with satisfactorily wide frequency range for music is constructed by combination of these two sorts of loudspeaker units.
Geometrical optimization of vented boxes
Authors: Pellerin Guillaume
Published: May 2008

Today, low frequency reproduction with loudspeakers in vented box is limited by two factors: the volume of the box, and non-linear airflow through the vent. We propose a novel approach that takes into account aerodynamical parameters, leading to original profiles and an improved functioning of the vented box. For example, under certain alignment conditions, there exits a second cut-off frequency below the first one, localized on the lower impedance hump. Using this lower cut-off frequency and an adapted vent profile makes it possible to radiate frequencies under 40 Hz with box volumes smaller than 1 liter and small drivers. A prototype will be demonstrated.
Synthesis of wave front in the sound field recording/reproduction system based on the boundary surface control principle
Authors: Enomoto Seigo , Ikeda Yusuke , Ise Shiro , Nakamura Satoshi
Published: May 2008

Based on the boundary surface control (BSC) principle, a new recording/reproduction system is developed to realize high fidelity three-dimensional sound field reproduction. Theoretically, by using this new system, physically faithful reproduction could be achieved in any acoustic environments. Sound recording/reproduction systems based on the BSC principle require many loudspeakers and many microphones. In this new system, the microphone array system to record 3D sound field consists of 70 microphones, and the loudspeaker system to reproduce the recorded 3D sound field consists of 62 full-range units and 8 sub-woofer units. To evaluate the ability of this system, the wave front which is measured in the soundproofed room is compared with the reconstructed wave front within this system. The experiment shows that the reconstructed secondary wave front is very similar to the primary wave front in lower frequency.
Sound localization in multiple regions: theory and applications
Authors: Kim Yang-Hann , Chang Ji-Ho , Park Jin-Young
Published: May 2008

It is often required to have several listening zones, which allows us to have different sounds that we select. For example, in a room, someone wants to listen sound from TV set, and other wants to listen music. In a car, a driver might wants to hear the information coming from his/her navigator system, and the passenger at the back side wants have a quiet zone so that he/she can sleep. To accomplish this kind of acoustic zones, we need to generate multiple sound zones by using multiple speakers. The performance has to be evaluated in accordance with how well one can listen the sound that is expected to have. We proposed to maximize the acoustic contrast between the zones that are defined. The basic concept associated with this approach was proposed by Choi and Kim [J. Acoust. Soc. Am., Vol.111(4), 1695-1700, Apr. 2002.], but this paper extend this fundamental idea to multiple zone cases. Theoretical formulation which shows what we have proposed is well addressed and several practical cases, including car audio system will be demonstrated. [This work was supported by the Korea Science and Engineering Foundation (KOSEF) through the National Research Lab. Program funded by the Ministry of Science and Technology (M10500000112-05J0000-11210)]
Sound focused personal audio system design: Performance improvement in acoustic contrast control by spatial weighting for obtaining spatially averaged acoustic potential energy
Authors: Park Jin-Young , Chang Ji-Ho , Lee Chan-Hui , Kim Yang-Hann
Published: May 2008

In acoustic contrast control [J.-W. Choi and Y.-H. Kim, J. Acoust. Soc. Am. 111. 1695 (2002)], spatially averaged acoustic potential energy is used as a representative spatial parameter because acoustic contrast control aims to maximize spatially averaged acoustic potential energy ratio between acoustically bright and dark zone. Therefore, spatial averaging process should be concerned carefully because control performance is sensitive to how to determine bright and dark zone. We have already got successful result in feasibility study for personal audio system with over 20dB difference between bright (frontal) and dark (side) zone [C.-H. Lee et al., J. Acoust. Soc. Am. 111, 3053 (2007)], without any spatial weighting in spatial averaging of acoustic potential energy. Recently, we're trying to improve the control performance by giving spatial weighting in spatial averaging process because how to give spatial weighting has to do with the improvement of control performance to satisfy the original purpose of personal audio system more closely. In this paper, it will be covered the investigation for how to give spatial weighting in averaging process and shown experimental evaluations for a sound focused personal audio system. [Supported by the Korea Science and Engineering Foundation (KOSEF) through the National Research Lab. Program funded by the Ministry of Science and Technology (M10500000112-05J0000-11210)]
3D sound field rendering under non-idealized loudspeaker arrangements
Authors: Sontacchi Alois , Zotter Franz , Höldrich Robert
Published: May 2008

The approach to realise periphonic sound field reproduction based on spherical harmonics (multi-pole theory) has already been well-known as Ambisonics and Higher Order Ambisonics, respectively. By the aid of an N-dimensional orthogonal set of vectors any arbitrary source free sound field can be described. Reproduction is realized by projection of the encoded sound field on a regular loudspeaker distribution over a spherical surface. The used set of vectors exhibits a defined hierarchic with interesting symmetries. In the original scheme sound sources represented by plane waves (sources in far distance) can be encoded independent of the decoding process on the regular loudspeaker layout. Usually, in practice - in contrast to theory, 3D loudspeaker layouts are requested for the upper hemisphere. This restriction is caused by the physical configuration. First of all that demand bounds the reproduction of sound sources to the upper area. Furthermore caused by these facts idealized regular layouts considering the 3 dimensions are impossible. Within this contribution we will show how the symmetries of the spherical harmonics can be used to obtain optimized decoding rules and to overcome insufficient irregular loudspeaker arrangements.
Between the frog and the tip - bowing gestures and bow-string interaction in violin playing
Authors: Askenfelt Anders
Published: May 2008

The motion of the bow gives a natural visualization of a string performance. Watching the player's bowing may augment the communicative power of the music, but all relevant bow control parameters are not easy to capture by a spectator. The string player controls volume of sound and tone quality continuously by coordination of three basic bowing parameters (bow velocity, bow-bridge distance, and bow force), which set the main conditions for the bow-string interaction. At a more detailed level of description, the tilting of the bow, which among other things controls the effective width of the bow hair, enters into the model. On a longer time scale, pre-planned coordination schemes ('bowing gestures'), including the basic bowing parameters and the angles between the path of the bow and the strings, builds the performance. Systems for recording bowing parameters will be reviewed and results from old and current studies on bowing gestures presented. The player's choice and coordination of bowing parameters are constrained both in attacks and 'steady-state' according to bow-string interaction models. Recent verifications of these control spaces will be examined. Strategies for starting notes and examples of how players do in practice will be presented and compared with listeners' preferences.