bluuebunny/crossref_metadata_2025 huggingface dataset:
Control parameters of a generalized vibrato model with modulations of harmonics and residual
Authors: Verfaille Vincent , Guastavino Catherine , Depalle Philippe
Published: May 2008

Our previous research focused on vibrato modeling of the harmonics of musical sounds. We demonstrated the need to account for fundamental frequency modulation, global amplitude modulation, but also spectral envelope modulation linked to brightness modulations. This may result from nonlinearities between the excitation signal and the resonating body, and/or from variable spectral sampling of the impedance function as F0 varies. For instance on flute, vibrato results from air pressure modulations. We also observed in sounds with vibrato of wind instruments that the residual also exhibits amplitude modulation, somehow due to air pressure modulations that are responsible vibrato. In a pilot listening test on shakuhashi sounds (for which the residual is obviously modulated), we asked participants to discriminate between the original modulated harmonics plus the amplitude modulated residual, and the original modulated harmonics plus a non-modulated residual, in a AB comparison task (same/different test). Preliminary results show that participants can hear the difference, suggesting that the amplitude modulation on the residual is audible. Subsequently, we developed a generalized vibrato model incorporating modulations on harmonics and residual. This model is presented here with an emphasis on its control parameters.
Subjective evaluations of the performance proficiency for fluctuating musical sounds using fluctuation strength or roughness
Authors: Yasui Nozomiko , Kinou Masafumi , Miura Masanobu
Published: May 2008

The “Fluctuation Strength (FS)” and the “Roughness” were suggested as evaluation indices of hearing sensation concerning fluctuated sounds of low or high frequencies. Past studies have been investigated FS and roughness of modulated pure tones and broadband noise. However, few studies have been reported concerning FS and roughness of attenuating sounds produced by musical instruments and performance proficiency for them. Therefore, the tremolo played on the mandolin and the closed roll played on the snare-drum are employed here as fluctuating musical sounds of low or high frequencies. Introduced here is the FS and roughness as indices for the evaluation of the performance proficiency for tremolo and roll. Specifically, experts of mandolin or snare-drum are asked to play tremolo of various plucking rate (number of plucking per second) and closed roll of various stroking rate (number of stroking per second). An evaluation experiment using the 2AFC method is conducted to evaluate performance proficiency for tremolo and roll. Aesthetic performances of tremolo and roll are described as “smooth, or not fluctuated” by trained players. The amount of physical FS for tremolo and physical roughness for roll are calculated by an original procedure to investigate relations between physical indices and evaluation results.
Musical perception within a highly reverberant room
Authors: Valverde Nelia , Fernandez Marcos D. , Ariza Javier , Ballesteros Jose A. , Ruiz Juan P.
Published: May 2008

The listening of a musical composition generates a unique and different perception in every listener, but, at the same time, the specific acoustic conditions of the room chosen for its performance have a decisive influence in that perception, which can fit in, almost completely, with the acoustic qualification of the room. The aim of this work is to find out how the high reverberance of a room can have a strong influence on the perception of a musical composition. For that aim, the St. Peter's church (in Cuenca, Spain) with a circular plan, a reduced volume and a high reverberance time has been chosen for the performance. A musical composition for voice and electroacoustics has been created specifically for this church. This has been recorded within the church using a HATS in the listener position and a set of music experts have been asked a survey about their impressions on perception after listening the recording using headphones. The results of the psychoacoustic analysis reveal that the high reverberance of this church leads to an extremely low intelligibility and an unclear sound of the recording. This, together with an unbereable background noise, gives a general acoustic perception not very attractive.
Broadband directive sources modeling for acoustic discrete-time domain methods
Authors: Escolano José , Lopez José J.
Published: May 2008

The use of sources with complex directivities in discrete-time domain methods, such as the finite-difference time-domain method or the digital waveguide mesh, is a recently open topic. However, so far, the provided solutions work for discrete frequencies or frequency-independent sources. Both solutions are useful for very particular cases and in most cases, far from real sources. This paper provides an extension in the use of a monopole source combination for broadband directive sources in discrete-time domain simulations. This method results very effective for frequency-independent and dependent sources, even in cases where the directivity diagrams have considerable lobules. Finally, this method will be tested through several examples.
Automatic morphological description of sounds
Authors: Peeters Geoffroy G. , Deruty Emmanuel
Published: May 2008

Morphological description has been proposed by Pierre Schaeffer. It consists in describing sounds by identifying the temporal evolution of their acoustical properties to a set of profiles. This kind of description is especially useful for indexing sounds with unknown cause such as SoundFX. The present work deals with the automatic estimation of this morphological description from audio signal analysis. In this work, three morphological descriptions are considered: - dynamic profiles (ascending, descending, ascending/descending, stable, impulsive), - melodic profiles (asc., desc. fixed, up/down, down/up) - repetition profiles. For each case we present the most appropriate audio features (loudness, pitch, pitch salience, temporal increase/decrease, lag-matrix-periodicity, ...) and mapping algorithm (slope computed from spline approximations of temporal profiles, ...) used to automatically estimate the profiles. We demonstrate the use of these descriptions for automatic indexing (using decision trees) and search-by-similarity of SoundFX.
Instrument sound description and modelisation in the context of computer aided orchestration
Authors: Tardieu Damien , Carpentier Grégoire , Peeters Geoffroy G.
Published: May 2008

We present a work related to the description of instrumental sound in the context of computer aided orchestration. We define the orchestration problem as the search of instrument sound combinations that sound close to a given target. In the presented approach, instrument sounds are described by a set of acoustic features that are extracted from large sound sample databases. The features are then modeled by a probabilistic distribution. Finally the models are combined to approximate the description of a combination of instrument sounds. We discuss the requirement induced by the orchestration problem on the choice of the acoustic features and detail the chosen set of features. In a second part we describe the method used to learn the probabilistic model of different instruments and playing techniques and show that it allows to learn the models from few samples and to deduce the models of some playing techniques, pitches or dynamics that are not available in the training set. Finally we evaluate the proposed method on classification tasks and describe its integration in a computer assisted orchestration program.
Modeling of piano sounds using FEM simulation of soundboard vibration
Authors: Ortiz-Berenguer Luis I. , Casajus-Quiros Francisco J. , Ibanez-Cuenca David
Published: May 2008

Pattern-matching methods for polyphonic transcription of piano sounds require a set of patterns that can be obtained by modeling the piano-sound spectra. The modeling should take into account not only the string stiffness but also the effect of the soundboard impedance on the string vibration. Studies on that effect corresponding to a wide range of impedance values have previously been carried out by the authors. However, actual impedance values for real pianos must be used in the model. Although the impedance value of a few grand-pianos have been measured by the authors, these results are not significative enough to create a model. Thus, a FEM simulation of soundboard vibration is proposed to obtain nearly-actual impedance values. The simulation considers several cases of vibrating plates from the simplest rectangular one and increasing the similarity to real piano soundboards. The quality of the simulation is verified comparing the obtained results with either recognized theoretical results for the simplest cases or measured values for the more complex ones. The complexity of the simulated soundboard is limited to the case that produces only slight variations in the modeled spectrum. [This work has been supported by Spanish National Project TEC2006-13067-C03-01/TCM.]
Soundscapes: from noise annoyance to the music of urban life
Authors: Guastavino Catherine , Dubois Danièle S.
Published: May 2008

Through an overview of empirical research over the past ten years, we present an interpretation of the evolution of the concept of soundscape. From a strictly acoustic definition in terms of physical descriptors, it evolved into a more complex notion integrating the effects of noise on citizens. Soundscape research therefore requires the contribution of human sciences (psychology of perception, cognitive psychology, sociology, anthropology of senses). There is converging evidence that people judgments of noise is related to the meaning given to the activities producing the noise. Consequently, physical descriptions in acoustics have to face the diversity of human reactions to noise correlated with the diversity of activities, the diversity of source producing noises within a diversity of physical environments (natural, architectural). This paper focuses on major emerging issues in soundscapes research, namely - the integration of such a diversity of pieces of knowledge within a general knowledge - the translation of these diverse conceptualizations into physical descriptions - the elaboration of convincing physical measurements for decision makers. We will draw consequences for further developments in the cooperative and pluridisciplinary research and for producing guidelines for new orientations in community policies.
The soundscape of church bells - sound community or culture clash
Authors: Kiser Brenda H. , Lubman David
Published: May 2008

Church bells have long communicated important information to the surrounding community, creating a sound neighborhood. The community relied on the sound neighborhood to learn of events such as weddings, births and deaths, impending danger, church services, and the curfew. The bells thus provided communal identity. This paper reviews the sound neighborhood created by the bells of the church of St. Mary-le-Bow in the City of London, popularly known as “Bow Bells.” The ringing of these bells has for centuries defined London's Cockneys and has featured in London's folklore and history since the 14th century. The current status of the soundscape is presented. Sound examples are given. This paper also discusses the future of the soundscape of church bells in light of current societal changes.
The application of the soundscape approach in the evaluation of the urban public spaces
Authors: Rychtarikova Monika , Vermeir Gerrit , Domecka Markieta
Published: May 2008

An important issues in the development of European cities is the design and renovation of the urban public areas. Typically, broad variety of approaches (sociological, ecological, environmental, physical, etc.) is needed. Earlier studies show the necessity of the transversal multidisciplinary approach in this issue. In order to study the acoustical dimension, the concept of soundscape needs to be proposed and elaborated. Soundscape approach differs from the classical statistical noise analysis in the evaluation of a context-related noise and in the extrapolation of environmental sounds in its complexity. Nowadays, even by using recently developed sophisticated acoustical and psycho-acoustical measurable and quantifiable parameters, it still remains difficult to grasp the complete meaning of a soundscape in words only or by numbers only. Our hypothesis is that the description of the city soundscape might be successfully done by combination of acoustical numbers and words. This article will propose a method for acoustical characterization of urban areas in the framework of the Belgian federal project: SD/TA/05A Design and renovation of urban public spaces towards sustainable cities (DRUPSSuC).
Ergonomics of intern environments: privacy and reactions to noise pollution
Authors: Mattia G. Mario , Bruel Per V.
Published: May 2008

The acoustical ergonomic is an important target for any room acoustics, intelligibility and community noise. The authors explain the experience on metrological and neuropsychological approach to the human reaction to noise. Environmental sound quality, room acoustics and interference of perceived sound (interference with the privacy) can start subjective effects and strong reaction by humans. The author explains experience and research of human reactions on noise interference, privacy, stress, ... annoying sounds (also with very low levels), rooms with stationary waves, long reverberation time, low acoustical building insulation, are the first cause of complain from the community. We suggest noise limits, international standards, neuropsychological interpretation of the acoustical annoyance.
A study on the adaptation of soundscape to covered spaces: Part 2
Authors: Ozcevik Asli , Yuksel Can Zerhan
Published: May 2008

This study is the second part of a research on the Adaptation of soundscape to covered spaces. A modern and a historical shopping center were compared and evaluated by means of subjective and objective evaluations. The consistency of the objective (time histories) and subjective (listening tests) findings showed that covered commercial areas may have a specific sound environment. The formation of streets is generally the basic spatial design concept that connects open and closed shopping areas. Therefore one of the studies that authors proposed at the previous paper was the comparison of open and closed shopping areas. In this study the soundscapes of a modern and a traditional street having shopping as a basic function will be determined by soundwalks and listening tests, and the findings will be compared with those of the previous studies.
Use of a versatile acoustic room for audiology applications
Authors: Laroche Chantal , Giguère Christian , Vaillancourt Véronique
Published: May 2008

For several decades, hearing tests have been carried out in audiometric test rooms which must meet acoustical requirements set forth in standards on ambient noise levels (i.e., ANSI S3.1-1999 (R2003)). It is however generally accepted that acoustical environments in which individuals with hearing loss function daily seldom correspond to environments found in audiometric rooms. Constraints regarding the sound attenuation by room walls (i.e., costs) can thus be minimized with a more rigorous control over certain acoustical characteristics within the sound room (i.e., reverberation time), thereby allowing to recreate more realistic environments of daily living. During the planning stage of the Research Unit on Noise and Communication at the University of Ottawa, the researchers opted for a versatile acoustic room with reversible panels that not only offers adequate sound attenuation by walls but also some control over reverberation time, thereby allowing to recreate more typical acoustic environments. The characteristics of this versatile acoustic room, as well as examples describing applications of use (effect of repetition on speech recognition, attenuation by headphones used with portable audio systems, effect of hearing protection on speech recognition within military noise environments) will be presented.
Application examples of beamforming method
Authors: Cerniglia Andrea
Published: May 2008

Acoustical beamfoming technique is a powerful method for noise source investigation, suitable for many different applications. Thanks to this technology is possible to identify where the noise is coming from, in a very clear and understandable form, both in static or dynamic situations. In addition on standard features, some advanced functions can helps to make correlation between subjective and objective parameters, for better understanding of acoustical phenomena. The paper describes some real applications of a very innovative beamforming system, based on a spherical antenna. The described measurements coming from several fields as automotive, enviromental noise, occupational noise, architectural acoustic, noise barriers investigation.
The influence of shallow atmospheric structure on tropospheric ducted infrasound from the Buncefield oil depot explosion
Authors: Green David N. , Hort Matthew , Bowers David
Published: May 2008

The vapour cloud explosion which destroyed the Buncefield oil depot, UK, on 11th December 2005, has proven to be a benchmark ground truth event for infrasonic studies. The regional infrasonic returns, those that propagated in the stratosphere and thermosphere, have been analysed in detail elsewhere. Here, we present the results of a study into infrasound ducted in the troposphere, recorded within 250 km of the source as air-to-ground coupled waves by a dense seismometer network. These tropospheric arrivals exhibit large waveform differences across the UK, both in amplitude and waveform shape. We numerically model these infrasound arrivals using a wave number integration method, incorporating a velocity profile derived from the UK Met Office numerical weather prediction model. Although some of the waveform variability is due to ground conditions at the recording site, we show that consistent changes in waveform shape across a 200 km swath of stations are correlated with a change in the wind vector in the lowermost 2 km of the atmosphere. Also, small amplitude, high-frequency precursors to the dominant acoustic signal, which might be misinterpreted as evidence of a small initial explosion, are shown to be consistent with the dispersion expected from a thin, shallow wind jet.
Regional and telesonic propagation of volcano-acoustic signals
Authors: Garces Milton , Fee David
Published: May 2008

Volcanic explosions are reliable sources for studying infrasonic propagation. Large amplitude acoustic explosions with known locations and onset times provide useful constraints for the signal changes induced by atmospheric variability. As part of the Acoustic Surveillance of Hazardous Eruptions (ASHE) project, two four-element infrasound arrays with collocated seismometers have been deployed 37 and 251 km from Tungurahua Volcano, Ecuador since February 2006. During this period Tungurahua has been in near-constant eruption, with energetic tremor signals and a multitude of energetic explosions. A combination of array processing and energy threshold detectors have been used to identify over 12 000 explosions at the nearby array (RIOE, 37 km), with the peak pressure of the largest explosion around 24 Pa. Many of the larger explosions are recorded at the more distant LITE (251 km) array as well. To further supplement the dataset, select data from infrasonic sensors at distances of 3-5 km from the crater will be used. State-of-the-art wave propagation and atmospheric models will be used to assess the influence of long-range propagation on the volcanic signals. By selecting a data subset with high signal to noise ratios, it should be possible to infer statistically significant atmospheric propagation effects.
Nonlinear propagation modeling of infrasound
Authors: Norris David , Bongiovanni Kevin , Masi James
Published: May 2008

The significance of nonlinear propagation effects on infrasound is studied using the Nonlinear Progressive Wave Equation (NPE) [B. E. McDonald and W. A. Kupperman, J. Acoust. Soc. Am., 81, 1406--1417 (1987)]. The NPE model accounts for nonlinear effects associated with a weak shock front, including shock-driven energy loss and self refraction. Numerical implementation is accomplished using a pseudospectral approach, which provides excellent computational efficiency while still maintaining acceptably small numerical errors. The nonlinear effects are isolated by generating NPE predictions with the nonlinear terms turned on and off. With the nonlinear terms off, the NPE reduces to a standard linear PE formulation. Waveform predictions through a realistic atmosphere are compared to ground truth observations to evaluate the NPE model performance and assess the influence of the nonlinear effects along the propagation path.
Wide band time reversal acoustic nonlinear diagnostics
Authors: Ulrich Tj , Sutin Alexandr , Tencate Jim A.
Published: May 2008

Time reversal acoustics (TRA) techniques provide a means to focus energy at a localized time and space, or at an unknown location (i.e., source or scatterer not known a priori) without the need to calculate time delays, as is necessary for phased arrays. The experiments demonstrate that time reversal focusing provides localized surface vibration with amplitude sufficient to induce measurable nonlinear effects and does so over a wide frequency band. Because the amplitude is spatially focused, time reversal enables local probing of this nonlinearity that can be used for nonlinear imaging. The nonlinear effects for wide band frequency signals were measured by phase-inversion method combining two signals of opposite sign in order to cancel the linear response and preserve quadratic nonlinearities. The method works effectively for nonlinear NDE of thin plates where laser Doppler Vibrometer can be used for measurements of the surface vibration and TRA focusing of acoustic waves. Presented results include crack and delamination diagnostic is epoxy graphite composites, diffusion bonded metallic disks and impact surface damage in glass. Scanning electron microscopy and optical images are also shown to demonstrate the types of damage features detected using this method.
Second order dispersive effect on zero-group velocity Lamb modes
Authors: Royer Daniel , Clorennec Dominique , Prada Claire
Published: May 2008

After a local and transient loading of a plate, the acoustic energy decay in the source area can be explained by three mechanisms: the energy transport phenomenon at the Lamb wave group velocity, the material damping and the second-order dispersive effect. Generally, the first mechanism dominates the other two. However, some dispersion curves of Lamb modes present a minimum frequency for a nonzero wave number. Since at these points the group velocity vanishes, no energy transport occurs, and the slower other two phenomena can be observed. Using laser-based ultrasonic techniques, we show that the mechanical response of various thin metallic plates to a laser pulse impact is dominated by the resonance of the zero group velocity S1-Lamb mode. In the first microseconds, we observed a t-1/2 decay of the local vibration amplitude, which cannot be explained by the material damping. We demonstrated that this effect is ascribed to the second-order term in the dispersion relation. After this power law decay, the mechanical displacement undergoes an exponential decay corresponding to the wave damping. Then, we show that the local attenuation of the plate material can be measured without any mechanical contact.
Refracting characteristics of backward propagating Lamb modes
Authors: Germano Massimo , Alippi Adriano , Bettucci Andrea , D'Orazio Annunziata
Published: May 2008

Lamb waves are acoustic modes propagating along thin plates or shells and result from the coupling of longitudinal waves and shear vertical waves (polarized along the thickness direction), taking place at the surface boundaries for satisfying the boundary conditions of the waveguide. Their nature being a composition of two differently polarized components, it permits that, for some combination of frequency and wavenumber, a Lamb mode is propagating which has its group velocity contradirected with respect to the phase velocity. These are the so-called “backward” Lamb modes, and one of them takes place at the starting region (low wave number) of the S1 mode dispersion curve in aluminum. Peculiar features of a wave packet of a symmetric Lamb mode S1, backward propagating in an aluminum waveguide, are observed and anomalous behavior in refraction, diffraction and interference of this peculiar mode is experimentally put in evidence. Particularly, contradirected refraction is put in evidence, as it takes place at the boundary where a forward propagating mode is coupled to a backward propagating one, and change from forward to backward mode is obtained in case of a wedge shaped laminar plate, which goes through a zero point of the group velocity.
An ultrasonic technique using shear waves interactions to characterize new hybrid gels
Authors: Banet Philippe , Griesmar Pascal , Vidal Frederic , Le Huerou Jean-Yves , Chevrot Claude , Teyssie Dominique , Serfaty Stéphane
Published: May 2008

Thickness shear mode transducer techniques using AT-cut quartz crystal can be used to measure viscoelastic parameters of soft materials (gels, colloidal suspensions œ) during their formation. Today the control of hybrid materials synthesis and evolution has a great interest, particularly for biomedical applications such as drug delivery. With those materials, a challenge is to obtain new structures constituted by interpenetrating organic- inorganic polymers networks (IPN) to get novel therapeutic behaviours. In this paper, the monitoring of ultrasonic shear waves propagation in the material at 6 MHz is presented for different thermosensible hybrid (poly-N-isopropylacrylamide (PNIPAM) - silica). We show that at a mesoscopic scale it is possible to analyze mechanical interactions between different networks related to chemical bounds. The network evolution observed with our technique is in good agreement with the Fourier transform infrared analysis of NIPAM polymerization. As shown in previous work for silica gels, a precursor characteristic time of gelation process (in liquid phase) can be determined to describe the polymerization kinetic. By its nondestructive character and its simplicity of measurement, this technique allows an online optimization of new hybrid materials.
Genetic manipulation engineers the elasticity of arabidopsis thaliana
Authors: Salmi Ari , Mustonen Kimmo , Immanen Juha , Helariutta Yrjö , Hæggström Edward
Published: May 2008

Arabidopsis thaliana is a model species widely used in plant science studies. It grows fast and exhibits wood formation in its stem and root resembling softwood produced by angiosperm trees. The Arabidopsis model allows rapid testing of methods for wood composition modification possibly adaptable for tree breeding. We estimated ultrasonically the modulus of elasticity in Arabidopsis stems and roots in both radial and in-plane direction for two commonly used ecotypes (Columbia and Landsberg erecta). Plants were grown in greenhouse conditions and six inflorescence stems per ecotype were measured in vivo applying 4 MHz out-of-plane and 2 MHz in-plane ultrasonic tone bursts. The effects of AtCAD1 gene expression silencing in Col ecotype were tested using the same method. We recorded a (10%, p=0.1) decrease in the elastic modulus of the lignin-decreased Atcad 1 samples (10-20% decrease in lignin content), and a significant (29%, p=0.02) difference between the sound velocities in the two ecotypes. In-plane elasticity results are also presented. The results are the first ultrasonically measured modulus values for this commonly used plant model species, creating a quantitative mechanical measure for the effects of wood composition modification.
The design and modeling of a lateral acoustic particle manipulator exhibiting quarter-wave operation
Authors: Glynne-Jones Peter , Hill Martyn , Harris Nicholas R. , Townsend Rosemary J. , Ravula Surendra K.
Published: May 2008

Prior work [Petersson et al., 2004] has demonstrated the operation of a half-wave acoustic particle manipulator, whose forces act in the plane of a silicon substrate. In a half-wave device particles are directed to the centre of a channel. Devices acting in plane have manufacturing advantages, and lend themselves to many microfluidic applications. We demonstrate, for the first time, such a device with a quarter-wave mode that is able to manipulate particles to the side of a channel in addition to a near half wave mode. The design utilises resonant “islands” to create the necessary pressure release boundary condition. The device is conventionally milled in brass, permitting cheaper and quicker fabrication than in silicon. Finite element modelling is presented to elucidate the operation of both half and quarter-wave devices. In contrast to essentially one-dimensional planar devices, the two-dimensional distribution of the velocity and pressure fields result in particles being constrained to a line within the channel.
A semianalytical finite element method for elastic guided waves propagating in helical structures
Authors: Treyssède Fabien , Frikha Ahmed
Published: May 2008

Steel multiwire cables are widely used in civil engineering as load-carrying members. The basic element of these cables is usually a simple straight strand made of a straight core and one layer of helical wires. Several difficulties arise in the understanding of guided ultrasonic waves in such structures, partly due to the helical geometry and the interwire coupling effects. In the context of nondestructive evaluation, this paper aims at theoretically investigating the propagation of elastic waves in helical waveguides. A numerical method is chosen based on a semianalytical finite element technique that relies on a specific nonorthogonal curvilinear coordinate system. This system is shown to be translationally invariant along the helix centerline so that a spatial Fourier transform can be explicitly performed along the axis and the problem is reduced to two dimensions. A single helical wire is first considered. The convergence and accuracy of the proposed method are assessed by comparing finite element results with reference solutions. The method is then extended to study a seven wire cable with simplified contact conditions. Dispersion curves are presented for wave numbers as well as energy velocities. Significant differences with the infinite straight cylinder are observed.
Numerical simulation of acoustic wave propagation via a liquid with gas bubbles
Authors: Kudryashov Nikolai , Teterev Nikolai
Published: May 2008

Wave propagation through a liquid with gas bubbles is numerically investigated, in 1D and 2D cases. The mathematical model is constructed in one-velocity, two-temperature approximation. The liquid is described by the empiric Tait equation. The bubble oscillations are described by Rayleigh-Plesset-type equation. The heat exchange between bubbles and the liquid is taking into account. Comparison of analytical solutions to results of numerical simulation has shown, that the developed model adequately describes dynamics of the wave propagation in a gas-liquid mixture. In the 2D case different regimes of wave propagation through a liquid containing gas bubbles are found. The leading wave with damped wave train is formed in a gas-liquid mixture out of bell-shaped impulse. The pressure splash can appear behind, on and before initial solitary wave in a liquid with a bubble channel and exist for a long time. The heat exchange effect on wave propagation is investigated. It is shown that properties of the wave propagation and it structure depend on the gas volume content, wavelength and on the bubble area width.
Complex edge resonance in elastic waveguides
Authors: Pagneux Vincent
Published: May 2008

The resonance for different configurations of elastic waveguides with a free edge is studied from the point of view of complex resonance. We determine numerically the variations of the real part and of the imaginary part of the complex resonance frequency as a function of the Poisson ratio. For three different configurations, semi-infinite 2D plates, elastic cylinder and circular hole through a plate, the results show similar behaviours which are: a real resonance frequency for a zero Poisson ratio and a real resonance frequency that corresponds to a Lamé mode at one positive value of the Poisson ratio. In all the configurations, these free edges have complex resonances which have very high quality factors. The two Poisson ratio where the complex resonance frequency has a zero imaginary part (infinite quality factors) corresponds to trapped modes for which there is a decoupling between the propagating waves and the evanescent waves. The first decoupling at zero Poisson ratio is due to the special structure of the elasticity equations there and the second decoupling is due to the decoupling between the propagating Lamé mode and the higher order evanescent modes.
Time-domain acoustic pressure fields from axisymmetric impulse sources by Rayleigh's Integral
Authors: Warshaw Stephen I.
Published: May 2008

This paper shows how Rayleigh's Integral is used to efficiently and rapidly calculate time-domain pressure waveforms and wavefronts radiated from a planar baffle due to axisymmetric normal impulse accelerations that converge toward or expand away from a fixed center of symmetry. These accelerations are prescribed with simple functional forms and histories. The Rayleigh Integrals are evaluated by Gaussian integrations that seem peculiarly suited to the integrands. The acoustic fields are presented as “snapshots” of pressure contours of the evolving wavefront structures emerging from the baffle surface, and as functions of time at selected key points. As a bonus, significant insights are provided by graphs of slant range versus time that clearly identify key signal paths from the source points to the field points. The presented methods avoid the complexities inherent in more standard transform and harmonic source treatments. They also provide insights into actual acoustic fields generated by impulsive sources, as, e.g., above the ground surface over a deeply buried explosion. [J. R. Banister and W. V. Hereford, J. Geophys. Res. 96(D3), 5185-5193 (1991)] Simpler examples were reported earlier. [S. I. Warshaw, JASA 77, S60 (1985); JASA 79, S90 (1986); JASA 80, S106 (1986), and 12 ICA Toronto, L3-6 (1986)]
Temperature-dependent diffusing acoustic wave spectroscopy with resonant scatterers
Authors: Leroy Valentin , Derode Arnaud
Published: May 2008

The influence of a slight temperature change on the correlation of multiply scattered acoustic waves is studied, and experimental results are discussed. The technique presented here, similar to diffuse acoustic wave spectroscopy, is based on the sensitivity of a multiple scattering medium to a slight change. Ultrasonic waves around 3 MHz are transmitted through a sample made of steel rods in water and recorded by an array of transducers at different temperatures. The cross-correlations between highly-scattered signals are computed. The main effect of the temperature change is a simple dilation of the times of arrival, due to a change of the sound velocity in water. But the scatterers also play a role in the progressive decorrelation of waveforms. An analysis resolved in both time and frequency shows that at some particular frequencies, the resonant behavior of the scatterers are responsible for a significantly larger decorrelation. Interestingly, the experimental results allow one to detect the presence of a small resonance that was not detected earlier on the same scatterers with classical measurement of the scattering mean freepath. A simple model is proposed to interpret the experimental results.
Ultrasonic wave propagation in heterogeneous solid media
Authors: Rossat Mathieu , Chaix Jean-François , Garnier Vincent
Published: May 2008

To check up concrete structures “in situ” engineers often employ ultrasonic waves. The implementation of tests and analysis of results even inversion of the problem need good knowledge about propagation phenomena. These phenomena require understanding interaction between ultrasonic waves and scatters, such as granular, porosity, and cracks. This defect can come from fabrication or mechanical damage. The size and the shape of obstacle have an influence on the spatial scattering of ultrasonic waves. We propose to show you the possible using multiple scattering in homogeneous models of propagation and the last work on a sphere in a hard media. Our objective is to bring obstacle geometries closer to the reality. Consequently, we study spheroidal scatters with various aspect ratios.
Comparisons between multiple scattering methods and time-domain numerical simulations for elastic waves
Authors: Chekroun Mathieu , Le Marrec Loic , Lombard Bruno , Abraham Odile , Piraux Joel
Published: May 2008

Propagation of elastic waves in heterogeneous medium composed of scatterers embedded in a homogeneous matrix is considered. Both matrix and scatterers are isotropic elastic media. The multiple scattering regime is assumed, and the focus is put on the coherent field obtained by averaging several equivalent realizations of disorder. Classical methods, such as Independent Scattering Approximation, Foldy or Waterman-Truell's model, provide expressions of the complex effective wave number of the coherent field, leading to an effective phase velocity and effective damping factor. Two-dimensional time-domain numerical simulations are performed for studying the validity of these analytical or semianalytical methods. To reduce spurious effects, such as numerical diffraction, to a negligible level, a high-order numerical scheme and an immersed interface method are used together. Comparisons between theoretical and numerical values of the effective phase velocity and damping factor are proposed and analyzed in terms of the frequency, the scatterer density, and the propagation length.
Sensitivity of high-frequency inferior colliculus neurons to sinusoidal amplitude-modulation of low-frequency tones
Authors: Carney Laurel H.
Published: May 2008

Responses of neurons in the inferior colliculus of awake rabbit were studied using sinusoidally amplitude-modulated (SAM) tones with a wide range of carrier and modulation frequencies. Neurometric thresholds for detection of modulation were estimated by applying both average rate and temporal metrics to neural responses. For neurons tuned to high frequencies, neurometric thresholds for SAM detection were substantially lower for mid- to high-level carriers at frequencies in the tail of the tuning curves than for carriers near the characteristic frequency (CF). Sensitivity to SAM for low carrier frequencies was often superior to sensitivity for near-CF carriers at low sound levels. These results suggest that psychophysical SAM detection thresholds at sound levels above approximately 60 dB SPL may be supported by “tail” responses of neurons tuned octaves above the carrier frequency. Improvement of psychophysical SAM detection thresholds with sound level is thus consistent with the contribution of a large population of responsive and sensitive “off-CF” neurons as level is increased. The fact that many auditory neurons, in both the peripheral and central nervous system, respond across several octaves at mid-to-high SPLs must be taken into account when considering “across-channel” interactions in tasks that involve both simple and complex sounds.
Cross-spectral synergy and consonant identification
Authors: Christiansen Thomas Ulrich , Greenberg Steven
Published: May 2008

The auditory processing of consonants was investigated using an information-theoretic approach. Listeners identified eleven different Danish consonants spoken in a Consonant + Vowel + [l] environment. Each syllable was processed so that only a portion of the original audio spectrum was present. Three-quarter-octave bands of speech, with center frequencies of 750, 1500 and 3000 Hz, were presented individually and in combination with each other. Confusion matrices were computed, and from these the amount of information transmitted for each of three phonetic-features - voicing, manner and place of articulation - was computed for each condition. From such analyses one can determine whether information associated with any given phonetic feature combines linearly across the acoustic spectrum or not. Our results indicate that information associated with voicing and manner-of-articulation combines in quasilinear fashion across the frequency spectrum. In contrast, place-of-articulation cues are integrated synergistically - information associated with two or three channels combined is far greater than predicted from the amount of information associated with individual spectral bands. Because consonants are essential for understanding speech, and place-of articulation information is crucial for decoding consonants, spoken language perception is likely to reflect highly non-linear processes.
Integration of acoustic cues for consonant identification by cochlear implant users
Authors: Svirsky Mario , Sagi Elad
Published: May 2008

Users of cochlear implants (CIs) obtain substantial benefit from their devices, but their speech perception is (on average) less than perfect and there are significant individual differences among patients. In particular, their consonant identification levels are lower than those of normal hearing listeners, or even most users of hearing aids. We have developed a simple quantitative model (multidimensional Phoneme Identification or MPI model) to predict consonant confusion matrices for individual cochlear implant users based on their discrimination of three consonantal acoustic cues: place of stimulation in the cochlea, silent gap duration, and percentage of energy above 800 Hz. Despite using only three degrees of freedom (i.e., JND for each cue) the model can explain most of the consonant pairs that are confused (or not confused) by individual CI users. However, when a listener's measured JNDs are used as inputs to the model, the predictions that result tend to have a higher percentage of correct responses than shown by the listener. One possible explanation is that CI users' speech perception may be limited not only by their basic psychophysical capabilities but also by their imperfect integration of different acoustic cues. [Work supported by NIDCD (R01-DC03937).]
5 mHz oscillations in OAE intensity following sound exposure
Authors: Kemp David , Brill Oliver J.
Published: May 2008

Otoacoustic emission (OAE) intensity is highly stable in healthy ears but can be temporarily reduced following noise exposure. This reduction in OAE intensity is well correlated with temporary noise induced hearing threshold elevation and is presumed to be due to metabolic fatigue in the outer hair cells. These cells are responsible for the generation of OAEs and are essential for the maintenance of normal hearing threshold. The severity and recovery of post exposure OAE reduction in an individual is therefore of interest for hearing protection purposes. This paper concerns the regulation of outer hair cell status and the effect of overstimulation on that regulation. We measured OAE level fluctuations following mild over stimulation (e.g., 100 dBSPL for 2 ms) in order to observe the dynamics of OAE regulation. We propose this parallels outer hair cell physiological regulation. Under-damped oscillations in OAE level occur typically at a frequency of 5 milliHertz after sound exposure. We find oscillations are excited by both the onset and offset of overstimulation and a linear model explains our observations. The oscillation is clearly not itself a fatigue process but fatigue is revealed by the need for a small depression of the baseline of the OAE oscillations.
Does overexposure modify the fine structure of distortion product otoacoustic emissions
Authors: Reuter Karen , Hammersho/i Dorte
Published: May 2008

It is investigated, whether the pattern of distortion product otoacoustic emission (DPOAE) fine structure (quasiperiodic variations across frequency) is altered by an acoustical overexposure. DPOAE fine structures are determined in 16 normal-hearing humans using a high frequency-resolution and primary levels of L1/L2=65/45 dB. DPOAEs are measured both before and after the subjects are monaurally exposed to a 1 kHz tone lasting for 3 min at an equivalent threshold sound pressure level of 105.5 dB. After the exposure the DPOAE levels are shifted to lower values and recover to the initial levels within 20 min. The DPOAE fine structure pattern is analyzed by an automatic classification algorithm, which determines ripple center frequency, ripple spacing, ripple height, and ripple prevalence. For some individuals, an alteration of some of the parameters could be observed after the exposure, i.e., either a more pronounced or a less pronounced fine structure could be observed after the exposure. Across subjects, no shift of the fine structure pattern in frequency could be observed, also none of the calculated parameters changed consistently after the exposure. The results do not support the idea that the DPOAE fine structure might contain more information about the state of hearing than the DPOAE level.
Changes in distortion product otoacoustic emission (DPOAE) fine structure due to contralateral acoustic stimulation
Authors: Mauermann Manfred , Kollmeier Birger
Published: May 2008

Contralateral acoustic stimulation (CAS) can cause changes in the amplitude of the 2f1-f2 DPOAE in humans - most probably mediated by the medial olivocochlear reflex. DPOAE amplitude changes due to CAS show large interindividual variability and large changes from suppression to enhancement for small changes of the primary levels. The underlying mechanisms of these effects are still not fully understood. We hypothesize that the two interacting DPOAE sources might be differently affected by the CAS. If so, CAS will cause specific changes in DPOAE fine structure. Therefore, DPOAE fine structures were measured using frequency-modulated primaries (f2: 1500-3000 Hz, f2/f1: 1.2; L2: 60 dB SPL; L1: 58, 63, 68 dB SPL) without and with a broadband CAS (50 dB SPL). The fine structure changes and shifts according to CAS were analyzed in detail - including latency windowing to separate the contributions from the two interacting DPOAE sources. The results indicate, e.g., that there is no “true” enhancement in terms of enhanced cochlear activity during broadband CAS. Rather there are slight frequency shifts in DPOAE fine structure due to changes in the relative contribution of the two DPOAE sources. This shift can lead to observations of “pseudo” enhancement of up to 20 dB for isolated frequencies.
Otoacoustic emission latency and cochlear mechanics
Authors: Moleti Arturo , Sisto Renata
Published: May 2008

Otoacoustic emission (OAE) latency data provide important information about several aspects of cochlear mechanics. Time-frequency analysis techniques, euther based on the wavelet transform or on Matching Pursuit algorithms, permit to get accurate estimates of the latency of transient evoked OAEs (TEOAEs). Wavelet estimates of the TEOAE latency of 14 young subjects, recorded at different stimulus levels from 60 to 90 dB pSPL, are used here to test several predictions of transmission line cochlear models. The experimental relation between latency, frequency, and stimulus level, is used to get estimates of cochlear tuning at different stimulus levels, which can be compared with behavioral and other OAE-based estimates.These estimates can be used to get information about the functional form of the cochlear amplifier nonlinearity. The comparison between the TEOAE latency and the auditory brainstem response (ABR) latency may help discriminating between different models for the OAE backward propagation. Wavelet latency and phase-gradient delay may be estimated on the same TEOAE waveforms. The comparison between these two characteristic times permits, in principle, to identify the place-fixed or wave-fixed nature of the TEOAE generation mechanisms.