bluuebunny/crossref_metadata_2025 huggingface dataset:
Fin whale (Balaenoptera physalus) movements along the Spanish mediterranean coast
Authors: Castellote Manuel , Esteban José-Antonio , Clark Christopher W.
Published: May 2008

The Ligurian-Corsican-Provençal Basin is a fin whale summer feeding ground, but little is known about the seasonal movement patterns of this population. We acoustically monitored two regions off Spain (eastern and southern) during summer-fall-winter 2006 using seafloor autonomous recording units. Long patterned sequences of 20 Hz pulses and back-beats from Mediterranean fin whales were identified in both study regions using acoustic features as indicators of population identity. Eastern area: fin whale sounds were detected at very high rates (122 pulses/hour) and between 40-80% of time/day. The detection pattern can be explained by whales moving gradually through the acoustic recorder's detection area, suggesting that the area is probably used as a passage between summer and winter grounds. Southern area: detections from the same population were less abundant (21 pulses/hour) and between 10-35 % of time/day. The detection pattern shows a highly variable distribution with no clear trend, suggesting that Mediterranean fin whales continuously remained in and moved out of the detection area of the recorder from November to January. These results show that this southern area is potentially used as a winter ground. This work documents a new dispersion path towards the Alboran sea, a new potential winter ground.
Enhancement of bead-based immunoassays by the use of acoustic radiation force
Authors: Wiklund Martin
Published: May 2008

Radiation forces generated by ultrasonic standing waves have long been used for increasing the speed and sensitivity of bead-based immuno-agglutination tests. More recently, detection methods based on confocal laser-scanning fluorometry and single-step homogeneous bead-based immunoassays show promise for fast, easy and sensitive bioanalytics. If such methods are combined with ultrasonic enhancement, very high sensitivity can be obtained. Here, we analyze and compare the characteristics, performance and limitations of ultrasonic enhancement used in agglutination-based and fluorescence-based immunoassays. Both radiation force aspects, as well as reaction kinetics aspects, are discussed. Finally, we report on novel results where ultrasonic enhancement is performed in microtiter plates, using a fluorescence-based assay. Here, the ultrasound enriches the sample a factor 106-107, and a detection limit of 60 femtomolar is obtained for a thyroid stimulating hormone (TSH) assay. Our results are compared with the results from a high-performance commercial instrument (Luminex xMAP technology).
On sinusoidal modeling of nonstationary signals
Authors: Roebel Axel
Published: May 2008

In this presentation we are going to give an overview over a number of techniques that have been developed in our group to improve the modeling of musical (nonstationary) signals using sinusoidal models. One of the basic problems with sinusoidal models is the fact that the underlying theory is derived assuming stationary sinusoids, while in the real world all sinusoidal components are non stationary. The two topics that will be covered main are, first a technique that allows to distinguish between nonstationary sinusoidal components, noise and transients, and second a new technique for parameter estimation of nonstationary sinusoids using frequency domain demodulation.
Adaptive subspace methods for high resolution analysis of music signals
Authors: Badeau Roland , David Bertrand
Published: May 2008

In the field of music signals analysis, the tonal part of a broad variety of sounds is often represented as a sum of slowly varying sinusoids. The Fourier transform remains a prominent tool for estimating the parameters of this model, due to its robustness and to the existence of fast algorithms. Its main drawback relies in its spectral resolution, bounded by the length of the analysis window. Subspace-based high resolution (HR) methods are conversely not constrained by this limit, since they rely on the particular geometrical structure of the signal model. Nevertheless, they have been seldom used in audio signal processing, mainly due to their high computational cost. Based on recent advances in the field of subspace tracking, enhanced adaptive algorithms for HR analysis have thus been developed, leading to a high resolution time-frequency representation of the signal, called HR-ogram. The application of these algorithms to music signals, made difficult by the high dynamics and the presence of colored noise, has required the tuning of well-adapted preprocessing techniques. The whole tool is now mature, and allows a high quality separation of the tonal part of various musical sounds. This research is supported by the French ANR under contract ANR-06-JCJC-0027-01 (DESAM).
Damped sinusoids and subspace based approach for lossy audio coding
Authors: Derrien Olivier , Richard Gaël , Badeau Roland
Published: May 2008

The new subspace-based techniques recently introduced appear to be well adapted for the parameters estimation of a damped sinusoids + noise signal model. These high-resolution (HR) methods have a better frequency resolution than the Fourier analysis, but they are rarely used in audio coding. Although HR methods would be suitable for parametric coding at low bitrates, we show that they are also efficient for high-bitrate coding where state-of the art codecs are usually transform-based. Our coding scheme first includes a 8-band PQMF filter-bank decomposition. Then, each subband signal is segmented in onsets and a maximum-order HR analysis is performed on each segment with the ESPRIT algorithm. For each component of the model, frequency, damping, amplitude and phase are quantized. The residual signal is not coded. This codec is compared to a MDCT framework, where transform and quantization are the same as in a MPEG-AAC but without inclusion of perceptual modelling and entropy coding. Preliminary objective and subjective tests show the potential of this approach which requires, on mostly tonal signals, significantly less bits than the traditionnal MDCT method for a given quality.
A frequency shifting model of pitch
Authors: Smaragdis Paris
Published: May 2008

We present a model useful for tracking of melodies of sounds that can have arbitrary harmonic structure (including inharmonic instruments and noise sources). This model is based on a spectral shift assumption which is capable of tracking melodic movements of an instrument regardless of the irregularity of its spectrum. This technique can be used to simultaneously estimate the spectral character of the instrument to be analyzed in addition to its melody. It is capable of dealing with multiple instances of the same instrument, thereby recognizing chords as well as notes, and can also extract multiple melodies in audio signals composed out of many instruments.
Modeling vocal sounds in polyphonic musical audio signals
Authors: Goto Masataka , Fujihara Hiromasa
Published: May 2008

This paper describes our research aimed at modeling vocal sounds (singing voices) in available music recordings and its applications to singer identification, singer similarity, and lyrics synchronization. Our predominant-F0 estimation method, PreFEst, can obtain the melody line by modeling the input sound mixture as a weighted mixture of harmonic-structure tone models (probability density functions) of all possible F0s and estimating their weights and the tone models by MAP estimation. Since the PreFEst was designed for general melodies, we extended it to specialize in vocal melodies by using vocal timbre models --- vocal and nonvocal GMMs. Those GMMs are trained beforehand and used to evaluate the vocal probability. The GMMs are also used to identify vocal regions, but its strategy should depend on applications. For singer identification and singer-similarity calculation, since the purpose is to model singer's identity by training each singer's vocal GMM, certainly reliable vocal regions should be identified even if most true regions were missed. On the other hand, for lyrics synchronization, since the purpose is to align each phoneme to the estimated vocal melody, vocal regions should be identified without missing any true regions. We achieved this by biasing log likelihoods provided by vocal and non-vocal GMMs.
Timbre transposition based on time-varying spectral analysis of continuous monophonic audio and precomputed spectral libraries
Authors: Beauchamp James W. , Bay Mert
Published: May 2008

A sinusoidal model for solo musical sounds consisting of time-varying harmonic amplitudes and frequencies allows for convenient temporal and spectral modifications. With a harmonic model, analysis frames can be grouped by fundamental frequency (F0) and then clustered in terms of their harmonic spectra. The resulting cluster centroid spectra are used as spectral libraries. When continuous audio monophonic passages are analyzed in the form of harmonic components, F0 vs. time data are used to guide the extraction of parameters from the sound in order to find appropriate library spectra for resynthesis. Two methods for finding appropriate spectra are: (1) best rms match with the incoming spectra and (2) best spectral centroid match. These give similar results, but centroid matching yields smoother spectra over time. Timbre transposition is performed by using a library that belongs to another instrument. We have found that when the target instrument has a unique timbral quality based on its spectrum, the synthesis sounds mostly like that instrument. However, if the target instrument's spectral characteristic is not sufficiently differentiated from the source, the source timbral quality may dominate, probably due to its temporal behavior being transmitted. Results will be demonstrated by audio examples.
Analysis and evaluation of traffic sounds
Authors: Guettes Jens
Published: May 2008

This work focuses on a residential area in Friedrichshain, a district close to the centre of Berlin. A soundscape analysis was made in this area, where the neighbours spent most of their free time, especially their leisure time. Basically, our measurements pointed out that immissions into the flats are mainly due to the low-frequency range under 200 Hz, in particular in the case of closed windows. In addition, this low-frequency range initiates standing waves and vibrations within the flats, causing annoying secondary sounds. Furthermore, effects arose, caused by an impulsive signal structure and a discontinuity in the time structure of the source signals, depending on the street pavement and on the traffic situation. With regard to that point, different physical and perceptive measurement and analysis methods were compared and interviews within the neighbourhood were conducted. Moreover, we tried to correlate the results of the survey with those of our measurements in order to see advantages and disadvantages of the applied methods. The scope of A-weighted measurements was then critically considered. Different ways will be discussed about how the complex evaluation of traffic sounds in the future could be based more on neighbours' perception and needs.
Subjective evaluation of community noise in Canada's National Capital Region and its relation to waking levels of salivary biomarkers
Authors: Michaud David S. , Keith Stephen E. , Tsang Jason , Konkle Anne
Published: May 2008

Some research has suggested an association between long-term exposure to traffic noise and relative risk of cardiovascular disease (Babisch et al., 2005; Willich et al., 2006). It has been assumed that noise may act as a nonspecific stressor. Acute exposure to noise can evoke physiological and behavioural changes reminiscent of a stress response in rodents (Michaud et al., 2003), but it is equivocal that this occurs in humans chronically exposed to traffic noise. This pilot project examined annoyance to community noise and salivary biomarkers known to be influenced by stressor exposure. A face-to-face interview subjectively assessed community noise for 60 residents (30 males, 30 females; mean age 41.3, SD = 14.98). Traffic sound levels will be determined and respondents categorized into high (>65 dBA, Leq24) and low (<50 dBA) noise areas. Participants also provided saliva samples upon awakening, 30-min after awakening, and prior to bedtime. Concentrations of salivary biomarkers of alpha-amylase and cortisol were spectrophotometrically determined using commercial enzyme-linked immunosorbant assays. Two-way (high-noise versus low-noise) mixed-model analyses of variance will examine differences in questionnaire and salivary responses. Sex differences will be evaluated with independent t-tests, and polynomial regression analyses will relate salivary biomarker levels to high- or low-noise areas.
The association between residential quality of life and aircraft noise annoyance around Frankfurt Airport
Authors: Schreckenberg Dirk
Published: May 2008

A large field study on aircraft noise annoyance with 2312 residents from 66 areas within a radius of 40 km around Frankfurt Airport was performed between the announcement and implementation of the airport extension (4th runway). For the address of each participant aircraft noise levels were calculated. This presentation concentrates on results with regard to the relationship between perceived - not noise-related - environmental situation and social quality of life in the residential area (i.e. infrastructure, economic development, neighbours, attractiveness of the area) and aircraft noise annoyance. Furthermore the impact of actual perceived residential situation and the expected future situation after airport extension on noise annoyance before the change in aircraft noise exposure occurs is compared. Results of the analyses will be presented and discussed.
Noise annoyance indicators for various industrial noise sources: Results and comparisons
Authors: Alayrac Marion , Viollon Stéphanie , Marquis-Favre Catherine
Published: May 2008

Characterizing the environmental impact of an industrial plant goes through a better understanding of the noise annoyance caused by industrial noise sources, which are numerous and various. A first step was to construct a perceptive typology of various industrial noise sources from a categorization test and based on perceived similarities. Now, laboratory tests are carried out, for each perceptive category separately, through the same experimental procedure, by testing the influence of the sound pressure level and of the noise spectral characteristics (low frequency noise, tonal noiseœ) on noise annoyance. The effect of spectral modifications due to the noise propagation on noise annoyance is also assessed. Subjects have also to judge the annoyance induced by an ambient noise exposure, built with a background noise and an industrial noise for which the emergence level is controlled. Different types of background noises are studied. Through a statistical analysis, indicators are developed for each perceptive category, based on classical indicators such as sound pressure level or loudness (for instance), or on indicators improved to suit spectral characteristics noticed. In this paper, the results of those listening tests are detailed and compared.
Social survey on the road traffic noise effect on the quality of life in Moroccan cities
Authors: Kharbaoui Weam , Garoum Mohammed , Bahoussa Abdelaziz , Rhachi Mohammed
Published: May 2008

Because of the fast growth of the urbanisation, the noise road traffic causes annoyance, and a wide range of negative effects on the health in many Moroccan urban areas. This problem becomes so serious that it is necessary to develop an adequate global noise policies, regulations, and laws. Unfortunately there is a lack of sufficiently technical, scientific, and social data allowing a precise evaluation of this pollution. The objective of this work is to complete our preliminary social survey and make a further step in the evaluation of the Moroccan urban community response to road traffic noise. The questionnaire used contains 55 closed and open questions and was performed using the ISO-15666 recommendations. The sample was composed of 1200 adults chosen randomly in Rabat, Salé and Tetouen cities. The targeted population consisted on persons of both sexes of 18 and more years old. According to the road traffic condition in Moroccan cities, results were analysed and compared with those obtained in several European cities.
Realistic floor vibration criteria for MRI operation: A compilation of case studies
Authors: Jurdy Basel , Yantis Michael
Published: May 2008

Vibration criteria published by various magnetic resonance imaging (MRI) manufacturers have been found to be too conservative with respect to allowable floor vibration resulting from MRI operation. The floor vibration produced by the MRI operation is greater than the published criteria. Previous experience by the authors has shown that there is an allowable threshold for MRI operation induced vibration, above which the MRI will not operate properly. This paper reports results of a survey of structural floor systems for 1.5T and 3.0T MRIs that are working satisfactorily. The most common floor systems have been analyzed structurally using finite element analysis to determine the forced response to a standardized input. Measurement results for some of the floors during MRI operation is also included.
Study case of a centre for biomedical analyses: the importance of an acoustic analysis of the current situation and definition of the targets to be achieved
Authors: Krajcarz Fabien
Published: May 2008

The French regulations concerning the limits on noise levels in medical establishments include the acoustic performances of existing buildings used to accommodate defined medical activities and in which the regulations are normally observed. Nevertheless, there are cases which are either outside the list of the buildings covered, or merit special treatment. One example is described here: a centre for biomedical analyses in a large regional teaching hospital covering a technical area of several hundreds square meters. This concentration of human activities and technical equipment without any acoustic attenuation measures was the spark for a considerable labour movement. In this article we describe the challenges of these situations, the pitfalls to be avoided and any post-project and design stage measures to be implemented.
Acoustic design criteria for naturally ventilated buildings
Authors: Field Chris D.
Published: May 2008

This paper proposes satisfactory indoor noise level criteria for office buildings which are compatible with achieving minimum natural ventilation standards set out in green building rating systems for sustainable building design. Indoor air quality standards related to the use of natural ventilation in buildings conflict with the control of ingress of external noise through ventilation openings to meet internationally recognized background noise limits for building use. These standards generally assume, however, that buildings are sealed and air conditioned to meet the stated recommended indoor noise levels. It is not feasible, however, that these noise standards can be expected or are appropriate to be achieved in naturally ventilated buildings. Therefore, to account for the thermal comfort benefit of natural ventilation and the ability to locally control natural ventilation and noise levels by closing of windows, an allowable exceedance of the recommended indoor noise levels is explored. The allowable deviation from existing background noise level guidelines is determined, which is considered to be an acceptable compromise for increased thermal comfort.
The effect of additional thermal lining on the acoustic performance of a wall
Authors: Nurzynski Jacek
Published: May 2008

External thermal insulation systems (ETICS) are commonly used in Poland mainly for thermorenovation of multifamily residential buildings constructed in seventies using industrialized methods. Additional layer improves thermal performance of a wall but also causes decrease of sound insulation in certain frequency range. Usually the acoustic effect of thermorenovation is unnoticed by inhabitants, but in the case of noisy locations it is sometimes perceived as an appearance of a new tonal outside noise source. The paper presents results of investigation on the influence of additional lining on the acoustic performance of massive wall based on laboratory tests. Resonance frequency, its location and influence on single number quantities is discussed. The problem of sound reduction index improvement prediction acc. to EN 12354-1, separate acoustical characteristics of lining and testing acc. to ISO 140-16 is also considered.
The Nordic voice ergonomic group: legislation and vocal health
Authors: Jonsdottir Valdis Inigbjörg
Published: May 2008

Research has revealed a number of factors which have a negative impact on voice function (e.g., activity noise, background sound, poor acoustics, long duration of voice usage, speaking distance). In these circumstances vocal loading increases, potentially giving rise to voice disorders. Currently, practical measures within society for the improvement of speakers' working conditions and the prevention of voice loading are not satisfactory. Voice experts from the five Nordic countries met in Reykjavik in May 2006 to inaugurate the Nordic Voice Ergonomic Group, with the aim of investigating the current situation within voice ergonomics, with a particular focus on sound-related problems. The group found that occupational safety and health legislation relating to speech communication in educational working environment differs between Nordic countries. Moreover, this legislation does not specifically deal with speech communication or the risk of voice disorders. This presentation will report on the details of the current legislation and the Group's suggestions for legislative change which might prevent disturbance in speech communication and decrease the risk of vocal disorder as an occupational hazard.
Reflection of sound from a forest: Effective tree spacing for a scattering model with a single line of cylinders
Authors: Wunderli Jean Marc , Salomons Erik
Published: May 2008

A scattering model for the reflection of sound at forest rims is presented by the authors in another contribution to this conference. The forest is thereby modeled by a single row of cylinders with the effective spacing as single free parameter. In the present article an engineering scheme for this effective tree spacing is presented. The scheme is based on results of numerical calculations with the Euler model for sound propagation in a model forest consisting of cylinders. The numerical results show that forests are widely transparent for incoming as well as reflected sound waves. Multiple reflections can be neglected. Reflections from trees deep inside the forest experience additional propagation attenuation and are therefore weakened relative to contributions from trees in the first row. Apart from geometrical spreading foliage attenuation is the most prominent effect. The penetration depth of the forest reflection is proportional to the wavelength. The frequency dependent penetration depth is derived by means of a statistical analysis for numerous situations. Assuming the effective tree spacing to be inversely proportional to the penetration depth, the engineering scheme for the effective tree spacing is derived. Comparisons of the frequency response with measurements show good agreement.
Buzz-saw noise : propagation of shock waves in aero-engine inlet ducts
Authors: Fernando Rasika , Marchiano Régis , Coulouvrat François , Druon Yann
Published: May 2008

When high bypass ratio aircraft engines run at takeoff operating conditions, blade relative flow velocities can exceed sonic speed, thus generating forward propagating shock waves that spiral inside the intake before being radiated. “Buzz-saw” or “multiple pure tone” noise then occurs, and measured acoustic spectra close to the fan display tones at the blade passing frequency and its harmonics, along with those of the engine shaft rotation frequency. This work first attempts to reformulate McAlpine and Fisher's frequency domain model for the propagation of a sawtooth waveform spiralling inside a hard-walled and lined cylindrical duct with uniform flow. The nondissipative Burgers equation is solved, and modal attenuation and dispersion are added using a split-step computational method. In practice, shocks do not only occur at blade tips, but on a significant portion of the blade span. The plane wave hypothesis being no longer valid, a new three-dimensional model is presented for a no-flow case. This model is based on the computation of the axial variations of the mode amplitudes under the influence of the nonlinear modal interactions. The formalism of this new model, along with the preliminary results are also presented.
Origin of the sound prduced by volcanic eruptions
Authors: Vergniolle Sylvie
Published: May 2008

Volcanic eruptions present different regimes, which can be understood and classified in the framework of a two-phase flow, either an annular flow such as in hawaiian fire fountains or a slug flow in strombolian explosions. The gas, exsolved at depth, carries physical information about the dynamics of strombolian activity, which in turn may lead to a better understanding of volcanic systems. The sound produced by volcanic eruptions is mostly infrasonic, although the landing of magma fragments on the ground is in the audible range. The first cause for sound generation is related to the gas overpressure when the sound waves are produced by a slug breaking at the surface. Gas overpressure induces oscillations of the gas volume and pushes passively the liquid film above the slug, and has been modeled accordingly. Sometimes the overpressure is small and the bubble vibration prior to breaking does not exist. In that case, the sound is produced by the gas escaping through a small hole on the bubble nose and is modeled as an Helmholtz resonator. The second class of sound source is related to the expulsion of a gas-ejecta mixture at a large velocity. Examples of volcanic sound waves will be presented.
Infrasound monitoring and global atmospheric dynamics
Authors: Blanc Elisabeth , Le Pichon Alexis , Ceranna Lars
Published: May 2008

The development of the Infrasound International Monitoring System, used for the verification of the Comprehensive Test Ban Treaty, offers a powerful way to measure, atmospheric waves permanently and at a global scale. Infrasonic waves propagate in the channel formed by the temperature and wind gradients of the atmosphere. Long term observations provide information about the evolution of the propagation conditions and then of atmospheric parameters. The monitoring of continuous sources, as ocean swell, gives the characteristics of the stratospheric wave duct submitted to stratospheric warming effects. Large scale gravity waves, which are also observed by the network, produce a forcing of the stratosphere at low and middle latitudes and long-lived changes in the stratospheric circulation towards high latitudes, leading to fluctuations in the strength of the polar vortex. These fluctuations move down to the lower stratosphere with possible effects on the tropospheric temperature. Gravity wave monitoring in Antarctica reveals a gravity wave system correlated with the wind and the temperature gradients in the stratosphere. Gravity waves associated with magnetic storms are generally not observed. However, wave systems coming from North could reveal other processes related with the global dynamics of the stratosphere.
Time reversal of acoustic waves in the nonlinear regime: basic physics and application to ultrasound contrast imaging
Authors: Tanter Mickael , Couture Olivier , Fink Mathias
Published: May 2008

Time reversal invariance of acoustic waves propagation remains valid even in the nonlinear regime in nondissipative media. This very interesting property that was extensively used in linear acoustics can also find potential applications in the nonlinear regime. Harmonic imaging coupled to the use of contrast agents is a topic of wide interest in ultrasonic medical imaging. Images are built at twice the excitation frequency that corresponds to the resonance frequency of the bubbles embedded in the medium. Consequently, the contrast becomes important between areas of low and high concentration of bubbles. However, at a high mechanical index, the harmonic components of backscattered echoes depends on the intrinsic nonlinear properties of tissues as well as the bubble's resonance. The focused beam is generating harmonics during its nonlinear propagation. It results in a degradation of the harmonic image contrast. Time reversal is an elegant way to find the emission codes allowing us to cancel the harmonic components due to nonlinear propagation of the ultrasonic beam. In the absence of bubbles, if the backscattered echoes are time-reversed and reemitted by the array, the harmonic components of the resulting wavefront are transferred back to the fundamental frequency during propagation. Experiments conducted with 1D-linear arrays illustrate these cancellation techniques.
Computational time reversal acoustics imaging of embedded defects in solid media
Authors: Griffa Michele , Anderson Brian E. , Ulrich Tj , Le Bas Pierre-Yves , Johnson Paul A. , Huang Lianjie
Published: May 2008

Time reversal acoustics (TRA) techniques can exploit the nonlinear processes emerging from the interaction between the incident waves and nonlinear scatterers in solid media in order to localize and characterize the scatterers themselves. When nonlinear scatterers are embedded, their localization can be obtained through a mixed experimental/numerical TRA procedure: the forward propagation is performed experimentally, while the time reversal (TR) backward propagation is simulated using computational codes and a reference model of the solid. The synergetic use of dedicated processing of the forward propagation signals collected at the time reversal mirror (TRM), for example with nonlinear elastic wave spectroscopy (NEWS) techniques, and the calculation of the backpropagated wave fields at each point within the specimen leads to imaging of the nonlinear scatterers. We show examples of nonlinear scatterer (macroscopic cracks, distributed microcracks) imaging by such a procedure, exploiting high performance (parallel) computational codes. We address issues in the imaging method related to the discrepancy between the reference model of the specimen and the real specimen itself. Finally, we address the implementation of the technique for non-destructive Evaluation (NDE) real-world applications using multi-threaded computational codes to be run on common multicore desktop computers.
Evaluation of local nonlinearity using time reversal acoustic focusing
Authors: Dos Santos Serge , Sutin Alexander , Sarvazyan Armen , Goursolle Thomas
Published: May 2008

Time reversal acoustic focusing can be used for local assessment of nonlinear properties of media [Sarvazyan A., Sutin A. , JASA, 115 (5): 2595 (2004)]. Time Reversal focusing provides high acoustic pressure leading to a nonlinear response localized in space and time. Interaction area of two overlapping focused beams acts as a virtual localized source generating ultrasonic waves with combination frequencies. Measurements of the intensity of this signal allow estimation of the nonlinear parameter in the focal region. The first experiment was conducted in water with spatially varying acoustical nonlinearity produced by a microbubble column or contrast agent Optison. We used two synchronized TRA aluminium reverberators to focus ultrasonic waves with frequencies 660 kHz and 776 kHz. Various parameters such as amplitude and frequency of the primary field, the position and number of emitters, choice of initial excitation (tone burst, binary, shirp-coded) were optimized for the nonlinear signature extraction. The second experiment was conducted in steel samples where surface vibration were measured by laser vibrometer. Excitation frequencies were between 490 kHz and 860 kHz . These experiments show again that amplitude dependence of nonlinear generated components was slightly less than the product of primary component that is predicted by classical nonlinear theory.
Effects of materials conductivity on the viscosity measurement using a QCM
Authors: Serfaty Stéphane , Caplain Emmanuel , Griesmar Pascal , Le Huerou Jean-Yves , Gindre Marcel
Published: May 2008

Quartz crystal microbalance (QCM) is commonly used to characterize the viscosity of soft materials. For biomedical applications the modified BVD model of QCM is unsuitable due to the conductivity of the biomaterial. In order to take into account the electrical effects, a new model including a static lossy capacitor is proposed. A theoretical study of the shear wave propagation in the quartz shows that these effects modify the static and the motional branches of the BVD circuit. The conductivity effects of the material at the surface of the QCM can be modeled by same parallel elements added in both branches. In the motional branch the electromechanical coupling factor is applied to these elements. To validate the new lumped element model measurements for KCl mixtures are achieved. The results show that an accurate extraction of viscosity (<5%) can be obtained for a middle of conductivity less than 0.3 S/m. In addition for water/glycerol mixtures the resonant frequency shift and damping follow an accurate linear shape (<5%) according to the square root of the liquid viscosity and density product. These results increase (up to 200 times) the validity domain of viscosity compared to the classical modified BVD model.
Experimental study on the effects of N-wave sonic-boom signatures on window vibration
Authors: Naka Yusuke , Makino Yoshikazu , Ito Takeshi
Published: May 2008

For fulfillment of overland supersonic flight, it is important to understand the effects of sonic booms on buildings, since these effects, including vibration of walls and rattling noise from windows, are believed to be the main causes of annoyance in indoor spaces. In this study, the vibration of windows impacted by sonic booms is investigated through in-laboratory experiments by using a device developed at Japan Aerospace Exploration Agency (JAXA). Rattle is captured as high-frequency components of the acceleration of the windows. The effects of sonic booms having N-shape signatures with various values of peak overpressure, rise time, and duration are investigated. Results show general tendency of increase of rattle with increasing peak overpressure and decreasing rise time, as expected. However, the results also indicate a possibility that these parameters, as well as duration, affect the time-frequency structure of the acceleration (and hence rattle) of windows in a somewhat complicated manner.
Transmission gaps and Fano resonances in a simple acoustic waveguide: Analytical model
Authors: El Boudouti El Houssaine , Mrabti Tarik , Al-Wahsh Hosni , Djafari-Rouhani Bahram , Akjouj Abdellatif , Dobrzynski Leonard
Published: May 2008

A simple acoustic device consisting of two dangling side resonators grafted at two sites on a slender tube is designed to obtain possibly transmission stop bands where the propagation of longitudinal acoustic waves is forbidden. Contrary to all known systems of this kind, a spectral transmission gap of nonzero width occurs here even with this simple structure. This is obtained by combining appropriately the zeros of transmission of the side resonators. Sharp resonant states inside the gaps can be achieved without introducing any defects in the structure. This results from an internal resonance of the structure when such a resonance is situated in the vicinity of a zero of transmission or placed between two zeros of transmission, the so-called Fano resonances. A general analytical expression for the transmission coefficient is given for these systems within the framework of the Green's function method. The amplitude and the phase time of the transmission are discussed as a function of frequency and it is shown that the width of the stop bands is very sensitive to the number of the side resonators. These results should have important consequences for the suppression of low-frequency noise and for designing filters.
Measurements on quarterwavelength tubes and Helmholtz resonators
Authors: Soto-Nicolas Alberto
Published: May 2008

The aim of this work is to determine what are factors limiting the prediction of the resonance frequency in unflanged quarter wavelength tubes and cylindrical Helmholtz resonators. When Helmholtz resonators are cylindrical, the frequency resonance may be predicted by solving a frequency 4th order polynomial equation. This formula may be used in quarter wavelength tubes too by just eliminating the value of the internal end correction. Some measurements were carried out showing that the accuracy in the prediction of the frequency resonance is limited by three factors: The uncertainty of values of end corrections, the visco-thermal effects not considered by the formula and the error in the estimation of the sound speed.
Focused borehole radiator
Authors: Kas'Yanov Dmitry
Published: May 2008

A promising type of borehole acoustic radiators intended for both stimulating borehole geotechnological processes and investigating the borehole environment is considered. The basic difference of the radiators under consideration from the existing ones is the possibility of focusing the acoustic field into a preset region of borehole environment. Elastic fields produced by focusing borehole radiators in rock are studied. Limiting abilities of focusing borehole systems are investigated. Optimal type of focusing borehole radiator is shown for well stimulation. It is demonstrated that borehole radiators with a variable focal distance can be designed, which provides a real opportunity to control the distribution of elastic fields in the borehole environment. This property may be very important in developing the acoustic technologies for stimulating productive reservoirs of geotechnological boreholes.
The acoustical research of shear viscoelastic properties of nanoparticles suspensions
Authors: Damdinov Bair , Dembelova Tuyana , Badma Badmaev
Published: May 2008

The acoustical research of some physical properties of nanoparticles suspensions has been carried out in this work. Mechanical properties of the SiO2 and YAG particles suspensions have been investigated. Resonance method is used for measurement of viscoelastic properties (shear modulus and shear viscosity) of the suspensions. It was shown that the viscosity and elasticity depend on size and concentration of particles. Colloid suspension of nanoparticles of silica dioxide (SiO2) and yttrium alumina garnet doped by neodymium (Nd:YAG ) are synthesized. The shear viscoelastic properties of the colloid suspensions have been measured by acoustical method. The researching of colloid suspension of SiO2 nanoparticles of different concentration by the acoustical resonance method is shown that viscosity and shear modulus decrease with nanoparticle concentration increasing. The nonlinear behavior of viscosity and elasticity in depending on shear influence amplitude has been shown. Investigation of viscosity of suspensions of Nd:YAG nanoparticles in ethanol in depending on concentration has been carried out. The decreasing of shear modulus of the suspensions with concentration decrease has been shown. The work was supported by RFBR 05-02-16584a and 07-02-90103-Mong-a.
New approach to the problem on long-wave sound scattering by a Rankine vortex
Authors: Belyaev Ivan , Kopiev Victor
Published: May 2008

The well-known problem of sound scattering by a Rankine vortex at small Mach number M is considered. Despite the long history of the problem (Pitaevskii 1958, O'Shea 1975 etc.), solutions obtained by different authors still are not free from essential objections. The main difficulty is that the slow decay of the mean velocity field at infinity hinders a correct formulation of the problem. Most authors use a plane wave as the incident field in the leading approximation in M (Sakov 1993, Ford and Smith 1999, Howe 1999), however to obtain a physically reasonable solution the second approximation in the incident field is to be chosen beforehand. It is shown that instead of the plane wave condition, the condition of a point source far from the vortex should be posed. In the new formulation the correct solution of the problem of nonresonant sound scattering by the Rankine vortex is determined from the matching procedure in M. This solution is compared with the previous results, and areas where these results hold are revealed. Existing solutions for resonant scattering (Kopiev and Leontiev1987, Sozou 1990) are analyzed too and a result unifying the previous ones is found.
Construction of symmetrical and asymmetrical notches from elementary steps in isotropic plates
Authors: Benmeddour Farouk , Grondel Sébastien , Assaad Jamal , Moulin Emmanuel , Dupont Lucie
Published: May 2008

The interactions of the fundamental Lamb modes with discontinuities in an isotropic structure will be presented and analyzed in a simple and a fast way. The key point is to decompose the symmetrical or asymmetrical notch into two elementary steps. The fundamental antisymmetrical and symmetrical Lamb modes contributions are separated by means of the simple arithmetic operations of addition and subtraction. The power reflection and transmission coefficients are then computed with the well-known average power flow equation described in a previous work [NDT&E international, Vol. 41, p.1-9 (2008)]. Using these coefficients, the symmetrical notch can be constructed from one elementary symmetrical step while the asymmetrical notch is constructed from the superposition of asymmetrical down- and up-steps. Mode conversions phenomena are observed and analyzed for the asymmetrical steps and notches case. Finally, an experimental device is realized to test aluminum plates with different notch depths. Good agreement is found between experimental and numerical results.
Analysis of wavefronts for the piston source acoustic fields
Authors: Perov Dmitry V. , Rinkevich Anatoly B.
Published: May 2008

The development of modern acoustic methods is based to a great extent on a thorough investigation of the structure of acoustic fields and on the refinement of methods of their analysis and calculation. The study of the local features of acoustic field and its space-time structure is an urgent problem of physical acoustics. This work is dedicated to analytical investigation of space-time structure of wavefronts corresponding to the acoustic fields which are radiated by the piston source into elastic media. It is assumed that the spatial distributions. Various spatial distributions of acoustic field over the surface of the transducer are taken into consideration.
Study of acoustoelasticity behavior of concrete material under uniaxial compression
Authors: Chaix Jean-François , Lillamand Ivan , Ploix Marie-Aude , Garnier Vincent , Corneloup Gilles
Published: May 2008

The general subject concerns the non destructive testing of prestressed structures in civil engineering. In this topic we are interested in the feasibility of stress evaluation in concrete by ultrasonic methods. To do that, we use the acoustoelasticity theory which exploits the nonlinear behaviour of media to establish the link between stress and ultrasonic velocity. This theory has been validated in homogeneous media and used in steel (to evaluated stresses in steel bolt for example). Concrete is a heterogeneous medium where the ultrasonic velocity measurement is more difficult than in steel. The scattered waves induce uncertainty in the measured values but the nonlinear behaviour of concrete is more important than the one of steel. We show an application in high performance concrete submitted to uniaxial compression. We measure velocities of longitudinal and transversal transmitted ultrasonic waves in the direction and perpendicularly to the stress at different level of the stress test. The sensibility of the different velocities is observed and the potential to evaluate stress in concrete is shown. Prospects particularly concern extension of tested formulations and in situ measurements. This study is supported by ANR-ACTENA, a French research program.
Linking static and dynamic NDT through fractional derivatives
Authors: Salmi Ari , Hintikka Tuomas , Saranpaa Pekka , Karppinen Timo , Hæggström Edward , Serimaa Ritva
Published: May 2008

Static testing of mechanical properties of materials is widely used and well documented. Several extensively employed NDT techniques relying on induced mechanic wave motion (dynamic strain) exist. Comparing results obtained with dynamic NDT techniques to each other and to certified static tests is problematic especially for polymer materials whose absolute mechanical moduli depend on loading frequency. We present a study performed on 102 block-shaped dry samples of Norwegian spruce wood (Picea Abies [L.] Karst., a complex natural polymer) using ultrasound propagated in the longitudinal wood direction with frequencies ranging from 50 kHz to 8 MHz. The samples were also tested using a standardized three-point bending test providing longitudinal elasticity estimates at near-zero frequency (static MOE). We validate experimentally the Pritz[1] five-parameter fractional derivative model and we link together the static test and the ultrasonic NDT technique. Our results allow predicting the static MOE from the dynamic MOE obtained with ultrasonic test equipment, and permit comparison of data obtained with ultrasonic methods applying different frequencies. [1] T. Pritz, Five-parameter fractional derivative model for polymeric damping materials, Journal of Sound and Vibration, 265(5), 935-952 (2003)
Species differences in low-level otoacoustic emissions may be explained by “hot regions” in the cochlea
Authors: Siegel Jon
Published: May 2008

Otoacoustic emissions evoked by low-level transients (TEOAE) and single tones (SFOAE) appear to excite the same emission mechanism, a concept originally formulated by Kemp and others and confirmed quantitatively by Kalluri and Shera (JASA 121, 2097–2110 (2007)). We have studied emissions evoked by single tones (SFOAE) measured using the suppression method. In humans, 50-70 dB SPL tones most readily suppress SFOAE evoked by lower-level tones when the suppressor is near the frequency of the evoking tone, suggesting that most of the emission originates near the peak of mechanical activity induced by the evoking tone. However, in chinchillas, Mongolian gerbils and mice, emission components originating basal to the peak appear to be relatively larger than in humans. The range of frequencies evoking the largest SFOAE correspond to those where spontaneous emissions are detected, from roughly 0.5 - 6 kHz in humans, 4-12 kHz in chinchillas, 15-30 kHz in mice and still higher in bats. Stimulus tones below this “hot” frequency range appear to generate the largest SFOAE components basal to the peak. The existence of “hot regions” in the cochlea may explain the apparent species differences in emission behavior between humans and small mammals. (Supported by NIH grant DC-00419 and Northwestern University.)