bluuebunny/crossref_metadata_2025 huggingface dataset:
Stable patterns of articulatory movements across inter-subject variability
Authors: Bonaventura Patrizia , Taylor Paul
Published: May 2008

The goal of the present study was to test whether models of portions of curves, representing movements of the crucial articulator for production of place in syllables containing labiodental and alveolar consonants ('iceberg' portions of demisyllables), that had previously been found to be stable across different prosodic conditions (Bonaventura, 2003,2005, 2006; Bonaventura and Fujimura, 2007), a) remained stable across different subjects pronunciations, for each consonantal class b) were significantly different for the two different consonantal movements. Curves were previously extracted from microbeam articulatory data. Curve fitting models were obtained, by using a best fit fourth order polynomial, from 592 curves representing lower lip displacement for production of [f] in 'five' (3 subjects) and from 299 curves representing tongue tip displacement for production of [n] in 'nine' (3 subjects). Coefficients were statistically compared; results showed a) significant difference for all coefficients between subjects pronouncing same consonant, except for the 3rd coefficient, both in initial and final demisyllable, representing stability of slope around a position threshold. These results might indicate stable patterns across inter-subject variability; b) coefficients were significantly different for [f] vs [n] models across speakers, within initial vs. final demisyllable, possibly indicating properties of an identifiable articulatory gesture.
Instrument for Soundscape Recognition, Identification and Evaluation (ISRIE): Signal Classification
Authors: Stammers Jon , Chesmore David
Published: May 2008

ISRIE is a collaborative project between the universities of York and Newcastle and ISVR in Southampton. The work being undertaken at York is in its second year and focuses on signal separation and classification. Developing novel methods for classifying urban and other sounds into distinct categories (such as transportation, industrial, human, animal, etc.) is the focus of this project. The classification system will consist of two main parts: a feature extractor and a classifier. Both time and time-frequency domain techniques have been considered for feature extraction and it is anticipated that a combination of domains will be required for this complex task. To date only simple classifiers have been implemented and development is now focussed on syntactic pattern recognition. The project background and an overview of the techniques involved will be presented along with preliminary results for the classification of urban and other sounds using syntactic methods.
Structural noise characterization and flaw detection in austenitic stainless steels using ultrasonic signals, wavelet analysis and significance testing
Authors: Khelil Mohamed , Thomas Jean-Hugh , El Guerjouma Rachid , Simon Laurent , Boudraa Malika
Published: May 2008

The aim of this study is to characterize the structural noise in order to better detect flaws in several heterogeneous materials (steels, welding, composites œ) using ultrasonic waves. For this purpose, a continuous wavelet transform is applied to ultrasonic Ascan signals acquired using an ultrasonic Non Destructive Testing (NDT) device. The time-scale representation provided, which highlights the temporal evolution of the spectral content of the Ascan signals, is relevant but can lead to misinterpretation. The problem is to identify if each pattern from the wavelet representation is due to the structural noise or a flaw. To solve it, a detection technique based on statistical significance testing in the time-scale plane is used. Typical structural noise signals are then described using an autoregressive model which seems relevant according to the spectral content of the signals. The approach is tested on experimental signals, obtained by ultrasonic NDT of metallic materials (austenitic stainless steel) then of a welding in this steel and indeed enables to separate various components from the signal that is two kinds of structural noises and flaw echoes.
Multipath reflection from surface waves
Authors: Tindle Chris T. , Deane Grant , Preisig James
Published: May 2008

A tank experiment was conducted at Scripps Institution of Oceanography to measure reflection of underwater sound from surface waves. Short pulses at a nominal 200 kHz were transmitted beneath surface waves of wavelength 0.7 m to a receiver at 1.2 m range. The surface wave crests act as curved mirrors for underwater sound and lead to focussing and caustics in the surface reflected pulses. The locations of the foci and caustics move steadily as the wave progresses and lead to rapid variation of amplitude, phase and arrival time of the received pulses. Wavefront modeling has been used to calculate theoretical waveforms for the measured surface wave shape. The theory shows there are typically three distinct reflected eigenrays beneath a wave crest and they interfere to give rapid variation of the received signal. The theory gives good agreement with the details of the time dependent interference of the surface reflected pulses. [Work supported by ONR.]
Renovation of the concert hall The Doelen: A case study on the impact of a stage canopy on stage and room acoustics
Authors: Lautenbach Margriet R. , Vercammen Martijn , Lorenz-Kierakiewitz Klaus-Hendrik
Published: May 2008

When opened in 1966, the main concert hall in De Doelen, Rotterdam, the Netherlands, was provided with six canopies above the stage platform. Their function was twofold: to provide a large part of the audience with early reflections; to create good ensemble conditions for the musicians on stage. Despite good reviews after the opening, a few years later the canopies were removed to get rid of unwanted reflections at the recording microphones positions just below the canopy. Since then, a significant percentage of the orchestra is unhappy about the acoustic conditions on stage. During the design process of the renovation, possibilities to re-introduce a stage canopy are investigated. Objective acoustic parameters obtained by carrying out measurements in the hall as well as in a 1:10 scale model and by calculations with a ray-tracing computer model are examined. Parallel, three questionnaire rounds gave an impression about the musicians' subjective judgement about the stage acoustics. In this paper the acoustic differences of three situations (without canopy, with original canopies and with new canopy design) and the search for an optimal balance between improving the stage acoustics without altering room acoustical conditions in the audience are discussed.
Region of control for low frequency modal equalisation in small listening rooms
Authors: Mäkivirta Aki
Published: May 2008

Small-size listening rooms are characterized by sparse modal density with pronounced spectral colouration when the decay times at low frequencies are large. Various active approaches for reducing the modal decay time have been suggested in the literature. A review of the salient principles of these approaches is given. Active control of the modal decay time at the primary listening position by using the primary radiator for control is demonstrated and evaluated for performance. The locality and size of the region of control, and the amount of control achieved, are studied in light of the experiment. Effect of the modal equalizer filter to the perceived response flatness, audibility of low frequency resonances, and the required amount of modal equalization are discussed in light of the experiment.
The future of UK hospital design
Authors: Popplewell Adrian
Published: May 2008

The importance of acoustic conditions within hospitals is highlighted by recent research indicating that patient recovery times are significantly influenced by the noise levels within wards. Added to this are concerns about speech privacy and confidentiality, patient and staff comfort, communication between patient and doctor, and the effects of vibration on sensitive medical equipment, all of which makes the acoustic design a key parameter in any hospital development. This paper will discuss the practical issues associated with the implementation of the current national guidance on hospital acoustics (Health Technical Memorandum 2045) and the new, currently unpublished replacement, Health Technical Memorandum 08-01. The experiences of the author with several large Private Finance Initiative projects, designed to the current standard, have illustrated the practical difficulties of fully complying with all its requirements and the design solutions which can be adopted. Speech privacy and confidentiality has been a critical issue in developing the new design standard. With Arup Acoustics as key contributors to this document, and acoustic designers of one of the first major projects in the UK to comply with this standard, the author is in a prime position to be able to assess the practical and technical implications of the future guidance.
Development of 'sound and vibration design guidelines for health care facilities'
Authors: Rockstroh Kurt
Published: May 2008

"The Guidelines for Design & Construction of Healthcare Facilities" is utilized by the majority of the United States and its federal agencies involved in funding health care projects. As part of the development of the 2010 Edition of "The Guidelines" a joint sub-committee of ASA, INCE, NCAC and the Health Guidelines Revision Committee was formed to develop sound and vibration guidelines. This presentation will explain the collaborative process used to develop, publicize, review and formally vote acceptance of the sound and vibration guidelines. The presentation will also outline the major components of the new guidelines.
Considerations about the acoustical properties of Teatro Nuovo in Spoleto after the restauration works
Authors: Cocchi Alessandro , Cesare Consumi Marco , Shimokura Ryota
Published: May 2008

In 2003 the municipality of Spoleto decided to stop the performances within the Teatro Nuovo, among the others also of "Two World Annual Festival", as it was necessary to modify some material, repair the floor, refurbish pictures and so on: the first author was charged with all the acoustical aspects and he decided to perform extensive acoustical measurements. During this measurement campaign, a flutter echo was detected in the stalls, so it became necessary to detect the origin of this problem, then to find some modification able to remove this problem: we have already presented our studies on this subject, from which a new design of the orchestra pit was derived. For fire safety reasons it was necessary also to remove some elastic panels from the boxes, and an acoustically equivalent technical solution was adopted. Even the stalls floor was removed and a new solution was adopted incorporating the heating plant and an acoustical solution. In this paper we will present the results of measurements performed after the opening of the theatre (a typical Italia Opera House of the end of the Eighteen Century) and some consideration about the acoustical results so obtained.
Radial distance sampling with passive acoustics: The prospect of estimating absolute densities of cetaceans from static acoustic datalogger data
Authors: Tougaard Jakob
Published: May 2008

Recording animal vocalisations with a static acoustic datalogger can be viewed as a form of point transect sampling and results analysed within the framework of distance sampling theory. The key element is the radial detection function, which specifies the probability of detecting a vocalisation as a function of distance from the datalogger. This function can be modelled theoretically or preferably determined experimentally and from it the efficient radial detection distance can be determined. Radial detection functions were determined for two different harbour porpoise dataloggers (T-PODs, version 1 and version 3) by means of concurrent visual tracking of porpoises. 52% and 82% of the porpoises within 100 m from the T-PODs were detected by the V1 and V3 T-POD, respectively and 11% and 30%, respectively were detected between 100 and 200 m from the T-PODs. Effective detection radius (EDR) was 97 m and 150 m for the two T-PODs, respectively. Porpoises echolocate almost continuously. If it is assumed that silent periods rarely exceeds 1 minute in duration an average detection rate on the version 3 T-POD for the study site of 2.7 detection positive minutes per hour can be converted into a density estimate of 0.69 porpoises/km2.
Computer-aided detection of non-stereotyped bowhead whale calls in the presence of seismic airgun signals
Authors: Thode Aaron , Mathias Delphine , McLennan Miles , Greene Charles R.
Published: May 2008

In 2007 thirty-five autonomous recording packages were deployed over a 150 mile swath in the Beaufort Sea to monitor the annual migration of the bowhead whale (Balaena mysticetus) population during seismic exploration activities. Over 1350 days worth of acoustic data were gathered, generating a need for computer-aided assistance in detecting calls. Bowhead whales produce over ten types of frequency modulated calls, and the frequency range, duration, and fine structure of individual calls vary considerably even within each call type, creating difficulties when using simple matched-filtering or spectrogram correlation. Numerous airgun signals also display frequency-modulated structure, complicating the challenge. In this presentation a three-stage process is presented for detecting arbitrary bowhead whale calls in the presence of seismic airgun signals, implemented in JAVA and MATLAB, with components extracted from the industry-supported PAMGUARD software package. The first stage runs several "energy-based" detectors simultaneously across multiple frequency bands to capture events, and a second stage analyzes the timing of these detections to remove regular periodic sequences, such as those expected from airguns. The final stage attempts to trace contours on spectrograms. Both genetic algorithms and direct optimization are used to optimize the program's 21 input parameters. [Work supported by Shell Exploration and Production Company].
Experience with VoxNet: a rapidly-deployable acoustic monitoring system for bio-acoustic studies
Authors: Girod Lewis , Allen Michael , Collier Travis , Blumstein Daniel T. , Estrin Deborah , Taylor Charles
Published: May 2008

Terrestrial bioacoustic census is a difficult problem because of propagation characteristics, obstructions, the diversity of bioacoustic sources, and the impact of noise. To address this problem we have developed VoxNet, a complete hardware and software platform for distributed acoustic monitoring applications. Each VoxNet node is a portable, self-contained processor with a small four-channel acoustic array. Using a distributed set of VoxNet nodes, a forested habitat can be monitored and the behavior of animals can be recorded and analyzed acoustically. In this work we present our experiences applying VoxNet to bioacoustic census. This work is based on data collected using the system during a deployment in Chiapas, Mexico at the Chajul Biological Field Station. The Chajul station is located in a region of dense rain forest and is home to Mexico's most diverse ecosystem. Using VoxNet in this harsh environment, we obtained census estimates based on observation of bird calls.
Characterization of seabed geo-acoustic structure for a shallow water environment
Authors: Knobles David
Published: May 2008

Full-field inversion methods over large frequency bands and spatial scales attempt to exploit the sensitivity of the frequency and spatial dependence of the acoustic field of the properties to the seabed. A comprehensive set of broadband impulsive and narrowband tonal acoustic recordings in the 5-3000 Hz band from two L-arrays separated by 20 km were made in a shallow water area on the New Jersey continental shelf during the Shallow Water 2006 (SW06) experiment. In addition, surface ship of opportunity passages on both arrays were recorded along with noise during the passage of tropical storm Ernesto. Reverberation and transmission loss data in the 25-9200 Hz band from explosive sources were also collected at a nearby site prior to the SW06 experiment. Numerous full-field geo-acoustic inversion methods and analyses of all these acoustic data with supporting range and azimuth-dependent geo-physical measurements are employed to characterize the seabed properties. For example, the analyses of these data permit inferences about the frequency-dependence of the seabed sound speed and attenuation to be made. The overlapping data types act to reduce the intrinsic ambiguities associated with inversion, quantify the spatial variability, and serve as independent validation.
Short range geoacoustic inversion with a vertical line array
Authors: Jiang Yong-Min , Chapman Ross , Gerstoft Peter
Published: May 2008

During the SW06 (Shallow Water 06) experiments, short range geoacoustic inversion experiments were carried out at a source-receiver range of 230 m to determine the sea bed properties at fine spatial scales. Acoustic signals were collected at 16 hydrophones on a vertical line array from source depths of 15-65 m in 10 m intervals. For this experimental geometry, the angular coverage for reflectivity versus grazing angle is 7-25°. This paper combines the information extracted from low-frequency (100-900 Hz) and mid-frequency (1500-4500 Hz) LFM signals transmitted from the same source position to estimate multi-layered geoacoustic models. The model parameterization was based on the number of resolved sub-bottom reflections in the data. An inversion approach using adaptive simplex differential evolution was applied to the data to invert for the sub-bottom sound speeds and layer thicknesses. The temporal variation of the water column sound speed profile was included in the inversion. The estimated sound speeds are consistent with the range-averaged profile that was estimated previously from longer range data for the same radial path from the array. (Work supported by Office of Naval Research).
Three dimensional geoacoustic inversion on the New Jersey shelf
Authors: Ballard Megan S. , Becker K.m.
Published: May 2008

Perturbative inversion, based on a linearized relationship between sound speed in the sediment and modal eigenvalues, is applied to data from the Shallow Water Experiment 2006. Data were collected by towing a low-frequency sound source out and back along radials, spanning a 90 degree angular sector, from a common receiver location. Range-dependent estimates of horizontal wave numbers are obtained along each of the radials using high-resolution signal processing techniques capable of detecting and localizing changes in sub-bottom properties, and that are particularly sensitive to changes in layer structure. Wave number estimates at each range are used in a linearized inversion algorithm to estimate local sediment properties. Locations of the R-reflector and other layering information are used as a priori information in the inversion algorithm. The additional information both constrains the solution of an otherwise ill-posed problem and emphasizes the layered structure of the sediment. These methods have been shown to yield accurate estimates of the sound speed profile deep into the sediment using very few perturbations to the forward model. Combining the local inversion results, a three-dimensional map of sediment sound speed structure is obtained for a 25 km2 region of the seafloor. [Supported by NDSEG and ONR]
Modal inversion using the acoustic field emitted by a moving source and measured on a vertical line array of hydrophones
Authors: Becker K.m. , Ballard Megan S.
Published: May 2008

As part of the Shallow Water Experiment 2006 (SW06), a low-frequency continuous wave acoustic source was towed out and back along radials from a fixed vertical line array of hydrophones. The resulting modal pressure field, measured on synthetic range apertures created by the relative source motion, is used to derive input data to inversion algorithms for estimating bottom properties. The inversion algorithms considered are based on well established relationship between modal eigenvalues and geoacoustic properties of the sediment. In this talk, linear inversion methods based on modal input data will be reviewed for their application to the SW06 data. The first step in these methods is the accurate estimation of modal eigenvalues from the pressure field data. For a moving source, theory predicts a Doppler shift along with frequency spreading proportional to both the transmitted frequency and tow speed. Propagating modes and their corresponding modal eigenvalues are predicted to correspond with the Doppler shifted frequencies. An emphasis of this work is on Doppler shift as an observable in the data and properly accounting for it in inversion. Sediment sound speeds estimated from data are consistent with sandy sediments found in the experimental area. [Work supported by ONR and NDSEG]
Combined optical and acoustical characterization of single ultrasound contrast agent microbubbles
Authors: Sijl Jeroen , Rozendal Timo , Vos Hendrik J. , Dollet Benjamin , De Jong Nico , Lohse Detlef , Versluis Michel
Published: May 2008

Contrast enhancement in medical ultrasound imaging is provided by the non-linear characteristics of coated microbubbles used as Ultrasound Contrast Agents (UCA). Optical time-resolved observations of the UCA microbubble dynamics have revealed new non-linear bubble behavior such as "compression only" and "thresholding" behavior. Up to now, the contributions of such behavior to the non-linear acoustic response of UCA microbubbles is not known. Theoretically, the sound emission of an oscillating microbubble is derived from the unsteady Bernoulli equation and mass conservation assuming incompressible and irrotational flow. An experimental validation of this relation between the radial dynamics and the sound emission of a microbubble is not straightforward. We present a combined optical and acoustical setup to characterize individual BR-14 (Bracco Research S.A., Geneva, Switzerland) UCA microbubbles. The bubbles were isolated in a capillary fiber by an active flow control. During insonation the radial response of the single microbubble was recorded with the Brandaris ultra high-speed camera while the resulting acoustic response was measured with an accurately calibrated sensitive transducer. The sound emission calculated from the measured radius-time curves gives excellent quantitative agreement with the directly measured sound emission for both the linearly oscillating microbubbles and bubbles displaying "compression-only" and "thresholding" behavior, which indeed resulted in a strong non-linear sound emission.
Dynamics of microbubbles targeted to surfaces: numerical and experimental modelling
Authors: Manasseh Richard , Payne Edward , Ooi Andrew
Published: May 2008

Numerical calculations and illustrative experiments are presented on the volumetric oscillations of microbubbles on and near surfaces. There is a considerable theoretical and experimental literature on the acoustic interactions of bubbles. In the present study, the surface was represented by a mirror-image bubble and the nonlinear frequency response calculated by integrating acoustically coupled sets of Rayleigh-Plesset-like equations. A significant shift was found in the peak nonlinear response frequency of a bubble targeted onto a surface. This effect is increased when other bubbles are nearby on the surface. Owing to the asymmetric influence of the surface, experimental images were dominated by shape-mode instabilities, making optical determination of the peak nonlinear response frequency difficult. Moreover, it was found that even if bubbles are separated by only a small fraction of the sound wavelength, time delays owing to the finite speed of sound have a surprisingly significant influence. Calculations on the symmetric mode of mutual oscillation showed that the introduction of time delays significantly modified harmonics of the spectrum.
Ultrasound contrast imaging of angiogenisis in a murine tumor model
Authors: Lucidarme Olivier , Taillade Laurent , Guibal Aymeric , Mule Sebastien , Comperat Eva , Badachi Yasmina , Jouannot Erwan , Rixe Olivier , Bridal Lori
Published: May 2008

Microvascularization modifications should precede tumor size-changes during anti-angiogenic therapy. We applied contrast functional ultrasound imaging (fUSI) to detect changes in Wilms tumors with anti-angiogenic treatment (Bevacizumab). Human Wilms tumor cells was grafted in left kidney of 32 mice. Once tumors had >5mm diameter, mice received : placebo, N=14; Bevacizumab for 21days, N=11; and Bevacizumab for 10days followed by placebo for 11days, N = 7. On days -1, +1, +9, +14 and +21 with respect to treatment start, fUSI was performed (CPS mode, SonoVue). Linear time intensity curves were obtained from regions in kidney cortex and matched-depth of tumor for first bolus passage and 50s following acoustic destruction of contrast. Excised tumor weight decreased with increased treatment duration: 3.7+/-1.8 g (placebo), 2.3+/-1.9 g (Bevacizumab-10days, placebo-11days), 1.4+/-0.7 g (Bevacizumab-21 days) [p<0.05]. Area under the bolus-passage curve (AUC) and the plateau intensity of the destruction-reperfusion were greater from D+9 to D+21 [p<0. 04] in the placebo than Bevacizumab-21day. For the group treated during the first 10 days, fUSI values were comparable to those of the treated group until D+14, then increased to become slightly superior to those of the placebo group by D+21. Noninvasive fUSI demonstrated revascularization after suspension of anti-VEGF therapy.
Numerical acoustic modeling code applied to sonar transducers and arrays: review and perspectives
Authors: Vanderborck Gerard
Published: May 2008

In this paper a review based on several examples of Thales Underwater Systems (TUS) design and modeling of transducers will be presented: several examples like wide band free flooded ring flextensional and bender transducers, high frequency transducers with thermal analysis modeling included, will be discussed. An approach of the problem of the mutual impedance computation appearing in array modeling will be also presented. Tus used since several decades FEM - BEM codes to design acoustic transducers and arrays. The perspectives in transducer and array modeling will be indicated like the possibility to take into account the non-linearities in the material, the time dependent problem and the use of new kind of piezoelectric material will be also discussed. Specific aspect of single crystal transducers modeling will be presented. The increase of the computing power will also permit to take into account the complex problem of the interaction between transducers in an array (mutual impedances). We will conclude on complex ultra wide band antenna (based on strong transducers interactions) optimization and the associated modeling architecture issues.
Underwater tensor sensors based on optical fiber bragg gratings
Authors: Guillot Francois M. , Trivett David H. , Rogers Peter H.
Published: May 2008

This paper deals with the development a new type of low-noise underwater tensor sensor aimed at improving the performance and the design of directional arrays. The transducer can be configured either as a particle velocity sensor (dipole) or as fluid shear sensor (quadrupole). The sensing principle of the device relies on the interference signal from two Bragg gratings written on the same fiber, and illuminated by a tunable, narrowband light source. The gratings are a few centimeters apart, and they each reflect a portion of the incident light. The fiber is epoxied to two spacers separated by a small gap situated between the gratings. This assembly is then adhered to two plates connected by a hinge, which is located below the gap. One plate is held rigidly and the tip of the other (free) plate experiences transverse vibrations, when ensonified. These vibrations produce periodic gap length changes, which modulate the interference signal from the two gratings. The modulation is related to the amplitude of the sound wave and is monitored with a photodetector. A noise analysis will be presented and the performance of prototype sensors will be discussed.
Beampattern optimization for a conformal projecting array of transducers with baffle effect and mutual coupling among elements
Authors: Ma Yuanliang , He Zhengyao
Published: May 2008

Beampattern optimization for projecting arrays is much more challenging in comparison with receiving arrays, particularly for conformal projecting arrays. It is because the array elements have to work in resonance state for efficient projecting and the variation of radiation impedance has strong effect on the array performance. The radiation impedance for each element is determined by a lot of factors, i.e, the element position, baffle property, mutual coupling and velocity weighting vector of the array. Thus beampattern optimization for a projecting conformal array must take into account all these factors. One thing makes the topic more difficult that the mutual impedance for each element is changeable along with the weighting vector change. In this paper a global solution approach is formulated and a boundary element model combined with transducer equivalent circuits is developed. The driving voltage weighting vector is deduced through an optimization algorithm. Computer simulation together with experiments are conducted for a 14-element conformal array. The results agree well. The multiple beampatterns formed within a wide observation sector exhibit uniform beamwidth and low sidelobes. The source level for each beam is maximized in constraint of the maximum driving voltage of array elements being constant.
Design of a phase array ultrasonic sensor using vibration decoupled concept
Authors: Lin Chia-Yu , Cheng Chih-Chiang , Wu Wen-Jong , Chen Chuin-Shan , Shieh Jay , Lee Chih-Kung
Published: May 2008

Phase array ultrasonic sensors have been used widely to generate higher directional radiating patterns in which piezoelectric units are distributed sparsely in space. In this study, we present a novel design of a phase array ultrasonic sensor based on the concept of vibration decoupling. Decoupling is achieved by careful design of source aperture, and such design allows piezoelectric units tightly located in the same structure. The phase array sensor is designed herein as a cylinder with a dumbbell shape groove to decouple vibration, and finite element analysis is used to optimize the design. Two piezoelectric discs are adhered on the bottom plate of the sensor whereby desirable wave generation and detection are controlled adaptively. By electrical steering, the sensor thus operates as a dipole mode. Finally, prototypes of the sensor are made and experiments are conducted to verify simulation results.
Characterization of laminated glasses by means of an inversion method using Finite Elements
Authors: Frances Monllor Jorge , Ramis Soriano Jaime , Alba Fernandez Jesús , Segovia Eulogio Enrique E. , Vera Guarinos Jenaro
Published: May 2008

The experimental determination of elastic modules and loss factor in laminated glass components is of great interest in building acoustics since at present there are a lot of building systems using these types of devices. This makes it necessary to predict the transmission losses in a partition. Even though described in regulation, the process is not exempt from serious difficulties. In this work we present a method in order to obtain the parameters mentioned above for a laminated glass composed of a sequence of isotropic layers by solving the model-based inverse problem for frequency admittance experimentally obtained. The parameter that best describes the mechanical constants of material of the layers is obtained by minimizing the discrepancy between the real numerically and numerically predicted waveform. This is done using an iterative optimization. A sensitivity study of the parameters uncertainty is performed in order to establish the feasibility of this technique.
Ultrasonic Airflow Meter in Greenhouse Using Acoustic Reflection against Wall
Authors: Saito Ikumi , Wakatsuki Naoto , Mizutani Koichi , Okushima Limi
Published: May 2008

In this paper, we described an ultrasonic airflow meter in a greenhouse using an acoustic reflection against a wall. The ultrasonic airflow meter is available for measuring the spatial mean wind velocity and direction, which consists of two sound probes and the wall of the greenhouse. Use of sound probes has advantage that the airflow accumulated along sound paths from a loudspeaker to a microphone is obtained in contrast to point measurements. The wind velocity and direction are calculated from time of flights (TOFs) of direct and reflected signals. The wind velocity and direction were measured in a greenhouse of 7.2 m × 29.0 m under factitious winds generated from two large electric fans located at the one side of the greenhouse. In addition, we detected air convection generated from two pairs of fans. These were measured every 20 seconds for 120 minutes. Regarding the measurement; by the proposed airflow meter and a reference; by a conventional one, their mean wind velocities were 0.12 and 0.15 (m/s), respectively. The presented airflow meter using the acoustic reflection against the wall is convenient to measure the wind velocity and direction in large-size facilities such as the greenhouse.
An experimental study of Sound Transmission Loss (STL) measurement techniques using an impedance tube
Authors: Yousefzadeh Behrooz , Mahjoob Mohammad , Mohammadi Nader , Shahsavari Ali
Published: May 2008

A comparison between the two sound transmission loss (STL) measurement techniques using an impedance tube (i.e. two-load method and anechoic termination method) is presented. A modified B&K type 4206 impedance tube has been designed and built. STL tests have been carried out for three homogeneous and isotropic materials with disk-type test samples of identical diameters and different thicknesses. In addition, the results have been compared with those of the classical and more reliable method of two-room. For both methods, the effect of downstream (tube termination) boundary conditions have been completely studied. The two-load method yields results which matches with two-room measurements, especially when the two boundary conditions are considerably different. The anechoic termination method, on the other hand, is significantly dependant on the termination boundary conditions.
Two dimensional finger-string interaction in the concert harp
Authors: Le Carrou Jean-Loic , Wahlen Elio , Brasseur Emmanuel , Gilbert Joël
Published: May 2008

The sound of the concert harp partly depends on the way the string is plucked. The vibrating string is brought into a state of initial conditions by the finger-string interaction and then oscillates according to two transverse planes. In order to understand the plucking action of the concert harp, a one-dimensional model of this interaction has been developed in a previous paper [Le Carrou et al, Proc. ISMA (2007)]. The parameters of this model were deduced from measurements of the string's and finger's trajectories. The aim of the present paper is to extend this model to a more realistic one, including a two-transverse trajectory for each one of the interaction's elements. To do so, a special experiment with a high-speed camera, which films the interaction, is set up. Specific image processing, based on edges detection, helps to automatically track both objects' positions. The results show that the finger-string interaction takes place in two planes and permits us to obtain the parameters of the two-dimensional model for the finger-string interaction.
Evaluating Vocal-Tract Influence in the Production of Saxophone Multiphonics
Authors: Scavone Gary , Lefebvre Antoine , Da Silva Andrey R.
Published: May 2008

A new approach for the analysis of vocal-tract influence in single-reed woodwind instruments during performance was recently reported (Scavone et. al., 2008). Two types of vocal-tract influence were observed. When the downstream air column provides only weak support of a given note, players can use a strong and narrow-bandwidth upstream resonance to override the reed vibrations, such as when pitch bending or playing extended register notes. Performers can also use a more wide-bandwidth upstream resonance to affect subtle timbre variations when playing notes over the full range of the instrument. The research reported here addresses the performance of multiphonic tones, for which the results of the previously mentioned study were less conclusive. While it is clear that upstream influence is involved in the production of multiphonics, we are interested in determining whether performers must support a specific intermodulation component or a wider bandwidth range of components for proper production. The latest results of this research will be reported.
Lateral directivity of aircraft noise
Authors: Krebs Walter , Thomann Georg
Published: May 2008

A three-dimensional model was developed to characterise the directional sound emission of different aircraft. The model is based on spherical harmonics and defines the directional spectral sound pressure level at a reference distance. The parameters of the model are derived from acoustic measurements on real aircraft traffic. With the help of this model different physical effects on sound propagation and sound impact are analysed. Variations with respect to a rotational symmetric sound emission are outlined and compared to the engine installation corrections proposed in the revised Doc 29 3rd edition. In addition the influence of the ground effect on A-weighted sound levels is analysed for different receiver heights and ground impedances.
Identification of aerodynamic sound sources: the key problem in noise control
Authors: Fedorchenko Alexander
Published: May 2008

Despite the recent advances in the noise control technology, the key mechanisms of aerodynamic sound emission remained poorly studied. The "well-recognized" methods of TCAA did not lead to any breakthrough in this topical problem, and what seems most disappointing, the family of "acoustic analogies" is still used by many for definition of aerodynamic noise sources, though the sufficient set of mathematical proofs has been given by the author that this model is wrong. Experimental approaches aimed at localization of aerodynamic noise sources, including the method of acoustic imaging via using a microphone array, are considered, and their inherent limitations are pointed out. Unfortunately, no current experimental technique enables one to measure instantly all sound sources and sound disturbances inside the zone of generation, and so the latter is often regarded as a kind of "black box". The two-medium nonlinear theory of aerodynamic sound, based on the original decomposition of each flow variable into two components, for unsteady background flow and for acoustic field, has been created, that promotes better comprehension of the noise generation phenomena and opens new ways in flow/noise control. The main properties of this theory are now indicated in comparison with the most detrimental delusions originated from "acoustic analogies".
On the sound generated by boundary-layer vorticity
Authors: Iemma Umberto , Morino Luigi , Camussi Roberto , Caputi Gennaro Giovanni
Published: May 2008

Turbulent boundary layers generate broadband noise as the effect of vortical-disturbances scattering into acoustic waves. The paper presents a formulation for evaluating of acoustic pressure in the field in terms of the transpiration velocity, here defined in terms of vorticity and closely related to Lighthill equivalent source. Specifically, the formulation used allows one to obtain, in the frequency domain, a matrix relationship between the transpiration velocity at a number of points on the body surface (those arising from boundary-element discretization) and the pressure at given points in the irrotational region. From this, the relationship between the corresponding PDF is easily obtained using the Wiener-Khintchine theorem. The paper will include the general formulation, validating numerical results, and comparison with experimental data. The inverse problem, that is, determining the source intensity on the body surface from field noise (in particular, the invertibility of the operator), will be also addressed.
A numerical study on multimode sound propagation in lined ducts and radiation to the far field
Authors: Sugimoto Rie , Astley R Jeremy , McAleer Claire R. , Achunche Iansteel
Published: May 2008

In previous articles, the authors developed a hybrid scheme for analysing bypass duct noise, in which a numerical analysis using finite element method for in-duct propagation and an analytic radiation code with fully represented effects of bypass shear layer are coupled. Such procedure permits detailed study on the interaction between duct configurations, such as geometry and acoustic liner impedances, and modal propagation and attenuation, and also the effects on the radiation pattern, within practical timescale and at modest computational cost. The scheme has been applied to realistic aero-engine bypass ducts and has been integrated with an optimisation programme. The numerical results obtained so far have revealed that for ducts with acoustic liners highly attenuated modes are not necessarily those with high mode angles, which is contrary to general anticipation. The aim of the study in the current paper is to understand the physics behind this phenomenon and its effect on the radiation to the far field. Detailed investigation on modal attenuation is performed by using the hybrid scheme. The effect of modal power distribution at the duct exit on the directivity pattern of the radiated noise to the far field is also discussed.
Numerical strategies for investigation of gust-airfoil interaction
Authors: Margnat Florent , Le Garrec Thomas , Fedala Djaafer , Gloerfelt Xavier , Kouidri Smaine
Published: May 2008

The noise generated by the interaction between a gust and an airfoil in a uniform flow is investigated. This problematic is of major industrial interest, regarding fans, turbomachinery, or wind turbine applications. A two-dimensional symmetric Joukowski-type airfoil is immersed without incidence in a flow at Mach number 0.5, disturbed by a harmonic gust at 45° of incidence (4th CAA Workshop on Benchmark Problems, 2004). Our methodology is first to perform a high-order direct resolution of Euler's equations of the disturbed flow over the airfoil and the associated acoustic emission, which is taken as a reference simulation. Second, the near aerodynamic field is simulated with Fluent 6.3 solver based on finite volume method with second-order schemes. The aerodynamic data thus obtained are used for far field acoustic prediction, based on Ffowcs Williams and Hawkings analogy. Finally, following another hybrid approach, the noise is predicted by using integral formulations with source field from the DNS. The aim of the study is to provide insight into the efficiency and validity of these numerical strategies commonly used. Comparisons with results of the CAA workshop are given, covering various wavenumbers values.
A stochastic source model for turbulent noise prediction including sweeping time dynamics
Authors: Siefert Malte , Ewert Roland
Published: May 2008

We extend a low-cost computational aeroacoustic approach by taking into account temporal effects of the modeled turbulent flow. As the noise production is determined by the turbulent frequency spectrum rather than the wavenumber spectrum, temporal properties of the turbulent flow play a role in many cases. We focus on the most dominant temporal effect, on sweeping, i. e. the advection of inertial range structures by the energy containing large scales. By introducing a feedback-mechanism of the turbulent field onto itself, we are able to incorporate this effect in the fast random particle method, which was successfully applied to different cases such as slat noise, jet noise and others. It is shown that sweeping reproduces important properties of spatio-temporal correlations of the turbulent flow, which are not grasp by most turbulence-models. The influence on the sound generation will be discussed for aeroacoustic simulations of jet and trailing edge noise.
Sound amplification in a lined duct with flow: PIV measurements
Authors: Marx David , Aurégan Yves , Bailliet Helène , Valière Jean-Christophe
Published: May 2008

An experimental investigation of the acoustic behavior of a liner in a rectangular channel with grazing flow has been conducted. The liner is a locally reacting structure. When increasing the velocity of the grazing flow the transmission coefficient increases at resonance frequency. The transmission coefficient can even become larger than 1 meaning that acoustical energy is produced by the liner. This amplification of the sound wave is accompanied by an increase in the stationary pressure drop induced by the liner (up to 300%). This effect is attributed to a modification of the flow induced by the acoustic wave. Thus, the flow is measured using Particle Image Velocimetry (PIV) imaging technique and a comparison of velocity maps with and without sound amplification is performed. Some differences occur and will be presented.
Where do we stand on standards for noise
Authors: Lang William
Published: May 2008

Almost 40 years ago, Henning von Gierke organized and chaired a symposium at the ASA Cleveland meeting with the above title. The chairs of nine writing groups of the ANSI-predecessor working on methods for the measurement and rating of noise presented summaries of their tasks and their progress in 1968. If a symposium on the same theme were to be held today, there would be reports from fifty-four working groups of ANSI Accredited Standards Committees on Acoustics (S1), Bioacoustics (S3), and Noise (S12). These committees are cornerstones of the ASA standards program. As the first ASA Standards Director, Henning revitalized the Society's standards program to become the productive organization it is today. The progress in standardization in America during the past four decades is a tribute to his foresight and participation. He also contributed to international standardization as the leader of the U.S. delegation to ISO TC/43 (Acoustics) and its subcommittee on noise (SC1), and for three decades he chaired ISO TC/108/SC4 on human exposure to mechanical shock and vibration. Trained as an engineer, Henning was a leader of national and international standardization efforts to relate the mechanical energy in sound waves to the responses of the human organism.
Henning von Gierke's continuing contribution: Underwater whole-body vibration
Authors: Gourlie Sarah , Hamilton Mark F.
Published: May 2008

Henning von Gierke was a leader in the characterization of human response to sound and vibration and in the development of international standards in this area. One focus of his research was using a multidisciplinary approach to create biodynamic models for whole-body vibration with the aim of predicting and preventing injury in vehicles. The focus of this presentation is whole-body vibration underwater with the aim of predicting discomfort or possibly injury to divers from low-frequency sonar. The frequency range of interest is 40-80 Hz, which encompasses the resonance of human lung. For this purpose, a biodynamic model developed by von Gierke to simulate thoracic, abdominal, and spinal responses to different vibrational excitations in air [H. E. von Gierke, J. Acoust. Soc. Am. 50, 1397 (1971)] is adapted for underwater conditions. It is assumed that the diver is neutrally buoyant and will therefore experience whole-body acceleration equal to the particle acceleration produced by the sound field in the absence of the diver. Emphasis is placed on determining the appropriate source distribution on the body as well as adjusting von Gierke's model to accommodate the decrease in lung compressibility with diver depth and mass loading on the chest. [Work supported by ONR.]