bluuebunny/crossref_metadata_2025 huggingface dataset:
Phonon dispersion in graphene
Authors: Falkovsky Leonid A.
Published: May 2008

Taking into account constraints imposed by the lattice symmetry, we calculate analytically [1] the phonon dispersion for graphene with interactions between first and second neighbors. We find that the out-of-plane (bending) modes are not coupled with in-plane modes and described only with two force constants, one of which is determined by the corresponding Raman frequency and another by the smallest elastic constant C44. In contrast to calculations by Saito et al, we find the linear dispersion of the bending (out-of-plane) mode around the Γ point with a small but finite sound velocity =1.57 km/s. The sound velocity of this mode is very sensitive to small variations of the force constants. The sound velocities of in-plane modes are = 20.3 km/s and =13.1 km/s. Because of the lack of information for graphene, we compare the present theory with experiments on graphite. The low phonon frequencies in the critical points turn out less than their values in graphite, since the atoms in graphene are more free to move in the out-of-plane direction in comparison with graphite. Accuracy of the comparison can be estimated using the value of the observed splitting of the ZA and ZO' modes in graphite which is around 130 1/cm. [1] L.A. Falkovsky, cond-mat/0702409.
Mechanical (acoustic-like) wave propagation along a vortex array in the superconducting heterostructure
Authors: Maruszewski Bogdan T. , Drzewiecki Andrzej , Starosta Roman
Published: May 2008

Magnetic flux can penetrate the type - II superconductor in the form of Abrikosov vortices (also called flux lines, flux tubes or fluxons) each carrying a quantum of magnetic flux. These tiny vortices of supercurrent tend to arrange themselves in a triangular or quadratic flux-line lattice. Since the vortices are formed by the applied magnetic field, around of each of them the supercurrent flows. Moreover, there also exist some Lorentz force interactions among them. Those interactions form an origin of an additional mechanical (stress) field occurring in the type-II superconductor. The paper deals with an analysis of elastic (acoustic-like) wave propagation solely along vortices in a heterostructure consisted of the superconducting layer put on the superconducting substrate. Dispersion and the amplitude distribution of those waves in the vortex field existing in that structure has been presented.
Experimental confirmation of the theory of acoustic radiation pressure applying on transparent interfaces
Authors: Issenmann Bruno , Nicolas Alice , Wunenburger Regis , Manneville Sébastien , Delville Jean-Pierre
Published: May 2008

Since Rayleigh and Brilloin, the acoustic radiation pressure has been the subject of several theoretical works, but of few quantitative tests. Whereas the radiation pressure acting on perfectly reflecting or perfectly absorbing solid targets is commonly used for the calibration of high intensity focused ultrasonic beams, it has never been quantitatively studied on acoustically transparent interfaces. Using an acoustically transparent liquid-liquid interface deformed by the radiation pressure of a focused, continuous wave beam, we have tested the theory of the acoustic radiation pressure acting on transparent interfaces for the first time. At large intensity, depending on the direction of propagation of the beam, we observe surprising interface shapes such as drop emitting jets and "nipple-like" deformations.
Frequency selectivity in diotic and dichotic masking conditions for normal-hearing and hearing-impaired listeners
Authors: Nitschmann Marc , Verhey Jesko , Kollmeier Birger
Published: May 2008

Previous studies argued that, for broadband maskers, the operational binaural critical bandwidth is similar to the monaural critical bandwidth. The aim of the present study was to test this hypothesis using the notched noise paradigm. Thresholds were measured for a diotic masker and a signal that was either in phase or had an interaural phase difference of 180 degrees. For comparison, thresholds were also measured for a broadband masker (without a notch) at various masker levels to account for possible level effects of the binaural masking level difference (BMLD). Normal-hearing and hard-of-hearing listeners with various degrees of sensorineural hearing impairment participated in the experiment. For all subjects, the thresholds decreased faster for the diotic than the dichotic signal as the notch width increased. The comparison with the data for the broadband masker indicated that this decrease of the BMLD is not due to the decrease of masker level within the auditory filter centered at the signal frequency. The thresholds can be predicted by an equalization-cancellation model assuming a slightly broader auditory filter in the dichotic masking condition. A possible realization of this different binaural auditory filter shape is adding to the on-frequency filter fractions of the adjacent filters.
Assessment of hearing damage when listening to music through a personal digital audio player
Authors: Farina Adriano
Published: May 2008

This study evaluates the sound pressure at the ears of users of personal digital audio players, equipped with in-ear earbuds. More than 50 devices were measured, provided by students aged 15/18. EN standard 50332 specifies the techniques for measuring the sound pressure level at the ears employing an head and torso simulator equipped with binaural microphones, when the gain control of the device is set to maximum. In this study, however, two measurmenets were performed on each device, one at maximum level, and another at the level at which the device had been left by the user after last listening. This way, on a statistical basis, it is possible to relate the effective exposure in daily usage with the maximum loudness of which the device is capable. Furthermore the study did also analyze the spectrum of the test signal: whilst the EN standard mandates for the IEC programme simulation noise, the analysis of thousands songs taken from the players under test revealed a slightly different spectrum, characterized by more boost at low frequencies and larger crest factor. The results of the study did show a relevant hearing risk for users of these personal digital audio players, which exceed noise exposure limits even when used for just one hour per day.
Final consonant voicing and vowel height contrasts in whispered speech
Authors: Gilichinskaya Yana D , Strange Winifred
Published: May 2008

Whispered speech is a naturally distorted speech signal. Whereas it preserves some characteristics of fully phonated speech, some important acoustic cues are removed, diminished or altered. The prominence of acoustic cues in whispered speech may change due to the physical properties of the whispered speech signal, i.e., decreased intensity, the absence of periodic vibration of the vocal folds, damping of F1, shift of the formants and flattening of the amplitude envelope. Such changes affect the acoustic cues both for vowels (e.g. vowel height) and consonants (e.g. voicing contrasts). The objective of the present project was to explore the acoustic cues for post-stressed syllable-final consonant voicing contrasts and the vowels preceding them in continuous whispered speech of American English speakers and to compare the results with those in fully phonated speech. The stimuli were recorded in the carrier sentence "I'll utter /habVC/ off the list". The consonant pairs included voiced/voiceless bilabial stops /b-p/ and labiodental fricatives /f-v/, each combined with 11 AE vowels /i, I, "epsilon", e, æ, a, "turned-v", o, "open-o", u, "horseshoe"/. Preliminary results showed that vowels had longer duration in whispered speech than in fully phonated speech. Spectral dispersion, temporal contrastivness of vowels; F1, and vowel duration cues will be reported in the presentation.
Acoustic properties of the interdental approximant in Kagayanen
Authors: Olson Kenneth S. , Mielke Jeff
Published: May 2008

This paper describes the acoustic properties of the interdental approximant, a rare speech sound reported to date only in a dozen languages in the Philippines. The measurements analyzed here are based on recordings of one female speaker of Kagayanen. The interdental approximant exhibits acoustic characteristics typical of semi-vowels: the formant pattern is similar to that of vowels, and the formant transitions with adjoining vowels have a long duration, usually 35 ms or more. The values of F2 and F3 are analogous to those of the Kagayanen [l], a prototypical voiced alveolar lateral; the only significant formant value difference between the two sounds involves F1: the interdental approximant has a mean of 508 Hz (n=9), whereas the mean for [l] is 368 Hz (n=9). On the other hand, while these two segments sound impressionistically similar, the interdental approximant differs acoustically from [l] in several other respects as well: there is no abrupt change in the formant pattern at the junctures with adjoining vowels, the higher formants (F6 and above) are not reduced in intensity, and F3 is not enhanced in intensity compared to semi-vowels.
Signal-based ray tracing modeling in complex tectonics
Authors: Cristini Paul , De Bazelaire Eric , Revaux Charles
Published: May 2008

The objective of this talk is to present a novel method which can perform the fast computation of the times of arrival of seismic waves which propagate between a source and an array of receivers in a stratified medium. This method combines signal processing concepts for the approximation of interfaces and wavefronts, and ray theory for the propagation of wavefronts. The main idea is to put in adequation the computations with the the precision and the resolution of the source signal in order to avoid unnecessary computational effort. This new approach leads to the redefinition and simplification of the model through which waves propagate. The modifications are governed by the spectral characteristics of the source signal. All rays are computed without any omission at a much lower cost in computing time than classical methods. In addition, we will show how to include surface waves such as head waves within the proposed method.
Binaural Hearing and Systems for Sound Reproduction
Authors: Nelson Philip A. , Park M. , Takeuchi Takashi
Published: May 2008

Recent developments in models of binaural hearing can be usefully adapted and extedned to provide design tools for engineers engaged in the design of systems for sound reproduction. The particular focus of the work described is upon the development of models that give good statistical predictions of human sound localisation, based upon knowledge of the fluctuating acoustic pressures at the ears. Such models can be applied successfully to the prediction of stereophonic image localisation and reveal a number of important features of localisation relevant to audio system design. Developments will also be described in loudspeaker based systems for binaural reproduction that are finding their way into practical use. Binaural hearing models can be used to provide a preliminary evaluation of the performance of alternative designs. Finally, a brief review will be presented of multi-channel loudspeaker-based systems aimed at “full field” sound reproduction. Again, models of localisation provide some useful guidance for the designers of such systems.
The use of moored inverted echosounders for monitoring near-surface processes
Authors: Trevorrow Mark
Published: May 2008

The near-surface ocean is a difficult place to conduct measurements of physical and biological processes. High-frequency inverted echo-sounders (IES), moored a short distance below the surface, provide a simple means for sustained, high-resolution monitoring. In particular, long duration deployments are useful in capturing transient events, such as storms or solitary wave trains, and placing their occurrence within the context of longer term trends. Lessons learned from use of these moored IES systems can be applied to modern ocean observatories. A number of long duration deployments of a self-contained 200kHz IES were made in the late 1990's. Three specific examples will be discussed. Firstly, an investigation of calibrated volume scattering from near-surface bubbles in the NE Pacific Ocean showed the frequent occurrence of vertical, plume-like structures drawn downwards up to 25 m. Within the plumes, the backscatter cross-section exhibited an exponential decay with depth, with e-folding scale in the range 0.5 to 2.5 m. Secondly, imaging of near-surface internal solitary waves was performed from a mooring near the Oregon coast, supplementing measurements made with nearby temperature sensors. These measurements showed some suggestion of scattering by turbulence. Thirdly, through the use of both backscatter intensity and echo statistics, a moored IES demonstrated quantitative monitoring of migratory zooplankton and fish populations.
The vibration sound absorption theory of soft materials
Authors: Zhang Xin An
Published: May 2008

During the past 2 years, a new theory has been established for soft materials that the vibration of materials brings the sound absorption, regardless whether they have pores in them or not. This theory is totally different from Classical theory, such as the Rayleigh model and the Zwikker and Kosten theory. Firstly, an empirical sound absorption coefficients formula of fibrous materials was found. Secondly, the theory sound absorption formula of thin fiber layers was obtained by the vibration sound absorption analysis and the applying of conservation law of energy. This formula agrees well with the empirical sound absorption formula of fibrous materials (mentioned above). Based on this achievment and applying classical laws of conservation of momentum and conservation of energy, the sound absorption theory formula of membrane (diaphragm) was also obtained, which have been well justified and also agree with the practice. This paper will review and discuss the main point about the vibration sound absorption theory and its establishment.
The influence of geometrical features of rooms on their acoustic response - insight based on measurements in physical models
Authors: Mijic Miomir , Sumarac Pavlovic Dragana
Published: May 2008

In a previous paper by the same authors, an analysis of the influence of geometrical features of rooms on their acoustic response was presented (Acta Acustica, Vol 93, 2007, 1012-1026). The analysis was based on ray tracing simulation. The results have shown that geometrical characteristics of rooms do influence reverberation time, and this influence is realised by the structure of sound energy paths through the room. It was concluded that room geometry influences reverberation time both at macro and micro levels, and this influence cannot be separated. To validate these conclusions in a real sound field, additional measurements have been conducted in specially prepared physical models of rooms. In several models of different shapes selected from previous results, scaled 1:10, the changes of scattering were introduced by appropriate modifications of interior surfaces. The results have confirmed the previous study conclusions.
Numerical study of sound transmission loss using an indirect boundary element method
Authors: Cassidy Matthew , Cooper Richard K. , Gault Richard , Wang Jian
Published: May 2008

The purpose of this study was to simulate transmission loss tests at the acoustic facilities of FG Wilson, Larne, UK. A hemi-anechoic chamber adjoins a reverberation room via a transmission plug where canopy panel sections are mounted for testing. Boundary element methods in LMS Virtual.Lab are used in conjunction with a baffle model to simulate the test facilities for transmission loss. On one side of this wall the reverberation room is modelled as a diffuse field using a series of defined plane waves, and on the other the hemi-anechoic chamber is represented as a free field. Experiments were carried out on a steel plate and lead sheet following the ISO 15186 standard for measurement of sound insulation using sound intensity. Source room sound pressure levels were recorded with a microphone, and an intensity probe was used to map the sound intensity field on the receiving side. Transmission loss for a frequency range was calculated as stated in the standard and compared with the results for the computational analysis. Comparison of the computational simulation with the experimental yielded a sufficient agreement.
Prediction of the Sound Transmission Loss of Multi-layered Small Sized Elements
Authors: Schoenwald Stefan , Gerretsen Eddy , Martin Heiko J.
Published: May 2008

In this paper an improved method for the prediction of the sound transmission loss of multilayered finite structures, like glazing will be presented. The sound transmission loss of an infinite structure is predicted with a common transfer matrix as a function of the angle of the incident sound wave. Then Villiot's spatial windowing method is applied to take into account the finiteness of the element. Usually an ideal diffuse distribution of the incident sound power is assumed and the prediction results are integrated over all angles of incidence. The obtained prediction results tend to underestimate sound transmission loss due to the dominance of the small values for gracing incidence. Often simple ad-hoc corrections are used for improvement, like Beranek's field incidence, that fail for multilayered structures. Kang suggests that the incident sound power on a surface of a room generally is Gaussian distributed on the angle of incidence and introduces a weighting function for the integration of the prediction results over the angles of incidence. New in this paper is that spatial windowing as well as a Gaussian distributed sound power is considered for the prediction of the transmission loss. The results of the prediction are validated by experiment.
New method for measuring sound absorption coefficients in an industrial hall
Authors: Ducourneau Joël , Planeau Vincent , Chatillon Jacques , Nejade Armand
Published: May 2008

Predicting the sound pressure level at a workplace requires in-situ characterization of the facings. This work describes a new method for the measurement of the sound absorption coefficient of flat panels present in industrial halls. In such room, it is necessary to separate the echo coming from the studied panel from the others due to the entire reverberation. This separation has been achieved in space by an acoustic array and in time by an impulse sound source. The array processing uses a multipolar weighting to achieve a directivity constant with frequency and with attenuated side lobes. This weighting requires a limited number of microphones. The impulse source has been designed using the inverse impulse response from the emission system (equalizer, amplifier, loudspeaker). This inverse filtering technique allows equalizing the response of the emission system in order to radiate very short pulses. Sound absorption coefficient of several flat facings have been evaluated by mean of this new device in a semi-anechoic chamber and in an industrial hall designed for testing. The results show a good agreement with others techniques except at low frequencies for which the array length is too small and the absorption coefficients too low.
Handling of uncertainties for CE marking concerning Sound Transmission Loss of glazings
Authors: Rehfeld Marc
Published: May 2008

A joint working group between CEN TC 126 (building acoustics) and CEN TC 129 (glass in building) has been created to handle the redaction of a test code, (give rules for CE marking) and particularly handle uncertainty problems. A round robin has been organised, at which 23 European labs have participated, and two configuration of double glazings have been tested: one with two monolithic glass components, the other with one monolithic and one highly damped laminate component. The paper will present the specifications and main results of this round robin, the questions that occurred concerning the possible ways to decrease uncertainty values, as well as the conclusions and decisions of the working group.
Analysis of uncertainty in building acoustic predictions using Monte-Carlo methods
Authors: Muehleisen Ralph T.
Published: May 2008

One of the most common tasks in architectural acoustics is the prediction of the acoustic performance of some aspect of a building, such as the background sound level of a room, the reverberation time of an enclosure, or the sound transmission of a wall construction. The accuracy of a prediction is not only dependent upon the computation model, but also upon the accuracy of the data of the model. Because of the complicated, non-linear interaction of various inputs, assessing the accuracy of a prediction can be difficult. One way to provide more accurate predictors and estimate the error in the prediction of complicated, multiple input systems is to utilize the Monte-Carlo method. In this talk, the application of Monte-Carlo methods to building acoustic predictions is presented.
Diffuseness and sound field distribution at room boundaries
Authors: Chazot Jean-Daniel , Guyader Jean-Louis
Published: May 2008

In the present work, a classical modal analysis is used up to medium frequencies to study the sound field distribution, and its diffuseness, particularly at boundaries. Due to intensification zones at boundaries, the diffuse field distribution at room boundaries can not be assimilated to the distribution inside the room. Moreover, diffuseness at room boundaries, that is of interest for sound insulation measurement, is usually only related to an incidence angle while inside the room volume several descriptors such as a correlation function and the spatial uniformity are necessary to characterize a diffuse field. In this paper, we present a new descriptor adapted to characterize the sound field diffusivity at boundaries. This descriptor is called Boundary Diffuse Field Index. Its averaged value over a specific surface can be related to a limit incidence angle, and its standard deviation can be related to the spatial distribution over the surface. Finally, thanks to this descriptor, Sabine's assumptions of diffuse sound field are also evaluated in this study.
Evoked-potential study of hearing directivity and sound-receiving apertures in dolphins
Authors: Popov Vladimir V. , Supin Alexander Y.
Published: May 2008

Positions of sound-receiving apertures were searched-for in bottlenose dolphins using the ABR technique. The receiving-area position was computed basing on ABR delays at various sound-source positions. Two acoustic apertures were revealed in such a way: for frequencies of 32 kHz and higher, the receiving area was located near a proximal part of the lower jaw (the mandibular acoustic window); for lower frequencies, the receiving area was located near the tympanic bulla. In another experimental series, AEP thresholds to near-field stimuli were measured with transducer positioning next to various points of the dolphin's head. Again, at stimulus frequencies of 32 kHz and higher, the lowest threshold area was next to the mandibilar acoustic window; at lower frequencies, the lowest threshold area was next to the bulla. The conclusion is that dolphins have at least two acoustic apertures differing in their frequency sensitivity. Directional sensitivity of these two apertures was investigated by measuring ABR thresholds at different frequencies and different sound source positions. At higher frequencies, the best-sensitivity direction estimated by ABR thresholds was near the head midline, at lower frequencies the best-sensitivity direction deviated laterally. These data were interpreted as indicating different axis directions of the two receiving apertures.
Tuning curves derived from auditory brainstem responses point to a defect in outer hair cells of hypothyroid mice
Authors: Walsh Edward , Korte Megan , McGee Joann
Published: May 2008

Based on an analysis of ABR derived tuning curves, recent reports suggest that the mechanics of passive transduction in hypothyroid mice, although delayed developmentally, eventually become indistinguishable from normal animals, whereas the mechanics of active transduction remain grossly abnormal throughout life, raising the possibility that the outer hair cell system is at least partially responsible for abnormalities observed in mutant animals. Moreover, results of in vitro studies have shown that although OHCs are electromotile, they appear unable to withstand extensive voltage excursions in the whole cell voltage clamp environment; i.e., they appear fragile. These data led us to question the structural integrity of the OHC lateral wall in hypothyroid mice. Preliminary studies suggest that the cortical cytoskeleton is abnormal in at least some regions of the OHC lateral wall and preliminary confocal immunofluorescence images of the constituent proteins, f-actin and α-II spectrin, suggest that spectrin is either absent or expressed in very low levels in the cytoskeleton of OHCs harvested from the hypothyroid progeny of Tshr mutant dams. We suggest that a cytoskeletal defect involving the f-actin cross-linking protein, spectrin, might compromise the efficient transfer of force along the long axis of OHCs, effectively diminishing the power of active amplification.
Acoustic communication in Panthera tigris: A study of tiger vocalization and auditory receptivity revisited
Authors: Walsh Edward , Armstrong Douglas L. , Napier Julie , Simmons Lee G. , Korte Megan , McGee Joann
Published: May 2008

Preliminary findings reported at the 145th meeting of the Society suggested that confrontational tiger roars contain energy in the infrasonic portion of the electromagnetic spectrum. This discovery generally supported the proposition that free ranging individuals may take advantage of this capability to communicate with widely dispersed conspecifics inhabiting large territories in the wild. Preliminary ABR findings indirectly supported this view suggesting that although tigers are most sensitive to acoustic events containing energy in the 0.3 to 0.5 kHz band, they are most likely able to detect acoustic events in the near-infrasonic and infrasonic range based on the assumption that felid audiograms exhibit uniform shapes. In this study, the spectral content of territorial and confrontational roars was analyzed and relevant features of ABR based threshold-frequency curves were considered in relation to the acoustical properties of both roar types. Unlike the confrontational roar, infrasonic energy was not detected in the territorial roar; however, like the confrontational roar, peak acoustic power was detected in a frequency band centered on ̃ 0.3 kHz. In addition, ABR recordings acquired in a double walled sound attenuating chamber recently installed at the Henry Doorly Zoo suggest that acoustic sensitivity is significantly underestimated under "field" conditions.
Evoked potential audiometry in sea lions
Authors: Mulsow Jason , Reichmuth Colleen
Published: May 2008

Auditory sensitivity in the otariid pinnipeds (sea lions and fur seals) has traditionally been studied using a relatively small number of trained subjects and psychophysical techniques. Recent refinement of auditory evoked potential techniques with odontocete cetaceans has elevated interest in adapting these methods for sea lion subjects, with the goal of increasing sample size and efficiency in audiometric studies. To date, several basic electrophysiological characteristics of the California sea lion (Zalophus californianus) auditory system have been described, and these findings have allowed for the development of more advanced techniques in investigations of sea lion hearing. Most notable is the recording of the envelope following response (EFR) evoked by narrow-band, sinusoidally amplitude-modulated tones. This method can provide significant advantages in the detection of low-amplitude electrophysiological signals in noise using Fourier analysis and objective statistical detection of responses. Currently, EFR audiometry in the California sea lion and Steller sea lion (Eumetopias jubatus) is proving to be a promising method for rapidly assessing the variation of hearing capabilities among individuals, including the detection of hearing loss.
Preliminary Results of a Behavioral Audiometric Study of the Polar Bear
Authors: Bowles Ann E. , Owen Megan A. , Denes Samuel L. , Graves Stefanie K. , Keating Jennifer L.
Published: May 2008

The hearing of polar bears is of great interest because little is known about hearing of large terrestrial carnivores, they are amphibious, their predatory habits differ from most bears, and there is an increasing need for data to manage anthropogenic noise in maternal denning habitat. Behavioral auditory thresholds were collected from two female polar bears at the San Diego Zoo (ZSSD) in 2006-2007, and are now underway with two females and a male at SeaWorld San Diego (SWSD). Thresholds were measured at 19 frequencies between 125 Hz and 31.5 kHz using shaped 500 ms tones, a 'go/no-go' response protocol, and staircase presentation order with catch trials. Holding areas in both facilities were sound-isolated to the extent practicable. Threshold measurements were limited by background noise below 5 kHz, but sensitivity could be measured to below 0 dB at higher frequencies. To date, the bears have detected sounds down to the noise floor from 125 Hz to about 14 kHz. Their sensitivity declines rapidly above 20 kHz. The results suggest that their auditory threshold functions are narrower or shifted to lower frequencies than those of small carnivores. [Supported by Polar Bears International, ZSSD, SWSD and the author's organizations]
Probabilistic PCA and Ocean Acoustic Tomography Inversion with an Adjoint Method
Authors: Berrada Mohamed , Badran Fouad , Thiria Sylvie
Published: May 2008

We present an Ocean Acoustic Tomography (OAT) inversion in a shallow water environment. The idea is to determine the celerity c(z), z is depth, knowing the acoustic pressures caused by a multiple frequencies source and collected by a sparse receiver array. The variational approach minimizes a cost function which measures the adequacy between the measurements and their forward model equivalent. This method introduces also a regularisation term in the form (c(z)-cb)tB-1(c(z)-cb), which supposes that c(z) follows an a priori normal law. To circumvent the problem of estimating B-1, we propose to model the celerity vectors by a probabilistic PCA. In contrast to the methods which use PCA as a regularization method and filter the useful information, we take a sufficient number of axes which allow the modelization of useful information and filter only the noise. The probabilistic PCA introduces a reduced number of non correlated latent variables η which act as new control parameters introduced in the cost function. This new regularization term, expressed as η tη, reduces the optimization computation time. In the following we apply the probabilistic PCA to an OAT problem, and present the results obtained when performing twin experiments.
Effects of elastic properties on the wave propagation in cancellous bones - a simulation study -
Authors: Nagatani Yoshiki , Saeki Takashi , Matsukawa Mami , Sakaguchi Takefumi , Hosoi Hiroshi
Published: May 2008

For diagnosing osteoporosis, ultrasonic systems are considered a powerful tool, because ultrasonic waves strongly depend on the elasticity and structure of cancellous bones. We have reported the separation of longitudinal waves into fast and slow waves, a phenomenon that is strongly connected to the alignment of bone trabeculae.In order to understand this complicated wave propagation, we have simulated the wave propagations with the finite-difference time-domain (FDTD) method using three-dimensional X-ray CT images of actual cancellous bones. In this simulation, the effects of elastic properties in the solid portions are important. One idea is to adopt the experimentally observed ultrasonic properties of cortical bone. However, we should remind the possible problems like the elasticity difference between cancellous and cortical bones, individual differences, and anisotropy. In this study, then, we have investigated the influences of elastic properties, Poisson's ratio, and densities of solid portion (trabeculae). As a result, we confirmed that the small changes give strong influences on not only the wave speed but also the amplitudes of fast and slow waves. The influence on the amplitudes seems to come from the changes of acoustic impedance of trabeculae. The results show the importance of elastic properties in the simulation.
Wave propagation in cancellous bone in terms of Biot's theory
Authors: Pakula Michal , Padilla Frederic , Kaczmarek Mariusz , Laugier Pascal
Published: May 2008

The paper is focused on modelling of wave propagation in cancellous bones using Biot's theory. Almost all required input mechanical and structural parameters for 31 pure femoral trabecular bone specimens were measured individually. Then frequency dependent wave parameters predicted by the model were compared with the results of ultrasonic tests performed on the same specimens. To compare the predictions to measurements, additional interactions of the plane harmonic wave with the slab of cancellous was considered. The most important finding is the significant contribution of the fluid/bone and bone/fluid boundaries on the global attenuation loss. The corrected values of attenuation coefficient are of the same order of magnitude compared to measured values. The theoretical results exhibit higher attenuation of fast wave compared to that of the slow wave in good agreement with experimental observations. Moreover the amplitude ratio of simulated time domain signals of both longitudinal waves (accordingly to the Biot's model with boundary corrections), are of the same order of magnitude compared to the amplitude ratio of experimental time records. However, an analysis in the frequency domain shows that the frequency content of the simulated pulses of the fast and slow wave differs from that observed in the experiments.
Multi-modal acoustic propagation in pipes with arbitrary defects: theory and experiments
Authors: Kirby Raymond , Horoshenkov Kirill V. , Bin Ali Tareq
Published: May 2008

Underground sewer systems are prone to flooding incidents caused by obstructions such as sediment deposits and wall deterioration. An efficient method for identifying and characterising these obstructions involves measuring the amplitudes of the reflected and transmitted acoustic normal modes excited by a point source in the sewer pipe. However, the behaviour of higher order modes in relatively large pipe work is often difficult to predict and interpret. In order to provide a greater physical insight into the measured data and to guide future experimental work, theoretical predictions have been developed and validated. The presented theoretical work is based on a finite element method and a mode matching technique. In this paper the predicted and measured sound fields are analysed for up to four acoustic modes reflected from two different obstacles (axisymmetric and non-axisymmetric) deposited in a 150 mm diameter uPVC pipe.
Benchmarking for acoustic simulation software
Authors: Molares Alfonso R. , Sobreira-Seoane Manuel A.
Published: May 2008

The validation of acoustic simulation software is still an obscure and imprecise matter. Validation studies of commercial implementations are rarely provided by vendors which are reluctant to show their product weakness. On the contrary in open academic implementations validation studies are one of the keys to make them used, rather than marketing. However, they demand from users a high level of knowledge and imply, generally, so long calculation times that make them impractical for common industry purposes. The aim of this study is to contribute to clarify this point setting a simple benchmark to measure the accuracy and performance of different software packages for sound field calculations. The benchmark is presented by its application with two widely used commercial implementations of finite element method and with an open-source implementation of boundary element method developed at the Southern Denmark University. The validation is performed against analytical formulae and also against experimental results. In order to study the balance between accuracy and computational cost the results are finally presented in terms of relative error versus calculation time.
Spatialized additive synthesis
Authors: Verron Charles , Aramaki Mitsuko , Kronland-Martinet Richard , Pallone Grégory
Published: May 2008

In virtual auditory environments, a spatialized sound source is typically simulated in two stages: first a "dry" monophonic signal is recorded or synthesized, and then spatial attributes (directivity, width and position) are applied by specific signal processing algorithms. In this paper, a unified analysis/spatialization/synthesis system is presented. It is based on the spectral modeling framework that analyses/synthesizes sounds as a combination of time-varying sinusoidal, noisy and transient contributions. The proposed system takes advantage of this representation to allow intrinsic parametric sound transformations, such as spatial distribution of sinusoids or diffusion of the noisy contribution around the listener. It integrates timbre and spatial parameters at the same level of sound generation, so as to enhance control capability and computational performance.
Loudspeakers simulation of sound environments for the car industry
Authors: Gauduin Benoı̂t , Hourcade Sylvain , Le Hir Nathalie , Guyader Gaël
Published: May 2008

Car manufacturers are strongly interested in sound quality: they need to understand the expectations of their customers in terms of engine sound signature, door closure noise, etc. ... In order to allow engineering teams of research departments to perform psychoacoustics tests under controlled and realistic conditions, GENESIS supplies high fidelity listening 3D simulators on loudspeakers. Based on binaural recordings, these simulators, called transaural, are calibrated to obtain the best fidelity in terms of spatial and spectral components. In this presentation, we will discuss the requirements regarding sound system and room installation and present the precision reachable in terms of frequency response. Measurements and results achieved on such systems will be shown, with a particular focus on the two systems built for RENAULT and GENESIS. Finally, in order to perform equivalent psychoacoustics tests on both RENAULT and GENESIS sites, we will develop the procedure of comparison and validation of both transaural systems.
Determination of Condition for Fastest Negative Group Velocities of Lamb-Type Waves under each Density Ratio of Solid and Liquid Layers
Authors: Nishimiya Kojiro , Mizutani Koichi , Wakatsuki Naoto , Yamamoto Ken
Published: May 2008

Lamb-type waves are coupling modes of leaky Lamb waves on a layer structure. The Lamb-type waves have complicated propagation characteristics more than ordinary Lamb waves on a uniform elastic plate. In the characteristics, we examine the negative group velocities. Generally, the negative group velocities of Lamb waves are slower than positive group velocities under the same condition. If the negative group velocities are applied to fabricating some new application, it is desired that the speeds of negative group velocities are comparable to those of positive group velocities. Consequently, we aim to obtain the faster negative group velocities. Lamb-type waves show more discriminative characteristics in negative group velocities than ordinary Lamb waves. In this research, we consider the Lamb-type waves in a solid/liquid/solid structure. It is described the conditions for obtaining the fastest negative group velocities of Lamb-type waves. The conditions, which are the acoustical impedance ratio, are expressed as the function of the density ratio of solid and liquid layers. These results are verified by numerical calculations.
Teaching Communication Acoustics and Physiology at the girl's day
Authors: Kob Malte
Published: May 2008

The girl's day is an annual event for young female pupils who wish to have their own experiences during a day in a potential future work place. In our department a team of 19 phoniatricians, speech therapists, phoneticians, engineers, audiometrists and assistants works on diagnosis and therapy of disorders of voice, speech, hearing and swallowing. For several years, our department has been visited by a group of 16 to 20 pupils who are guided in small groups through a sequence of stations with hands-on exercises in the field of voice and hearing acoustics. The experiments include the measurement of a voice range profile, recording and visualisation of voice signals, subjective and objective assessment of voice disorders, and listening tests. The experiences with organisation and feedback of the girl's days are reported.
Cymbal Synthesis
Authors: Bilbao Stefan
Published: May 2008

Time domain sound synthesis based on a physical model of the cymbal presnts special problems, due to the need for a strongly nonlinear model of shell vibration. When standard numerical methods such as finite difference schemes are employed, various computational issues arise; among these are numerical stability, a proper treatment of numerical boundary conditions, which are nontrivial at the free edge and center of the the cymbal, and the extra concern of working in polar coordinates. Coupling with mallet and bow models, possibilities for increased computational efficiency using spectral methods, and general strengths and weaknesses of difference methods in this context will be discussed.
Applications of passivity theory to the active control of acoustic musical instruments
Authors: Berdahl Edgar , Niemeyer Guenter , Smith Julius O.
Published: May 2008

The dynamic behavior of any acoustic musical instrument can be modified by closing a feedback loop around even a single sensor and actuator. The ultimate goal is to make the acoustics of the instrument programmable by way of a digital feedback controller, while the instrument retains its tangible form. In this talk, we describe a class of controllers that are applicable to passive acoustic musical instruments, and we present sound examples from laboratory experiments on a vibrating string. First, we briefly introduce positive real functions. Next, we design positive real controllers allowing the quality factor and resonant frequency of instrument modes to be individually controlled. Because positive real controllers are passive, they are stable if the instrument is passive. This means that neither a full instrument model nor complete state measurements are required. Finally, we describe a class of simple passive nonlinear controllers that can emulate various kinds of friction, stiffening and softening springs, etc. Passivity of these controllers follows from the local passivity of the controller components. Controller parameters may often be tweaked so that the controllers are no longer passive but still perform useful functions, such as bowing emulation.
Digital algoritm for sound synthesis: Realism and complexity for creativity
Authors: Bensoam Joël
Published: May 2008

Modalys, a sound synthesis software developed at Ircam for research and musical applications, make it possible to build virtual instruments based on physical models in order to obtain the broadest range of expressive variations in the instrument in response to intuitive controls. An instrument, as a complex structure, is described by the mechanical/acoustical interactions of its components (strings, tubes, soundboard, 3D FEM objects...). New research has recently been carried out in two directions: On one hand, a generic digital algorithm able to treat a large class of non linear interaction models (lip-reed, contact and friction, aero-acoustics jets, etc) was built. Based on a Gauss-Siedel strategy, this algorithm is used indifferently regardless of the modeled structure's complexity and guaranties convergence and robustness of the whole sound synthesis. On the other hand, efforts are made to infer from measurements the physical parameters needed for the sound synthesis (geometric or gesture parameters for example). Due to the lack of a complete analytical formulation (digital algorithm), derivative based methods to solve inverse problem (Newton, gradient, etc) are not allowed. Evolution Strategy (ES), especially for multiobjective optimization, are then investigated.
Singing Integrals or wind instruments modeling using Boundary Integral Equations
Authors: Iemma Umberto
Published: May 2008

The paper deals with the modeling of woodwind musical instruments using a Boundary Integral Equation (BIE) formulation. Specifically, the BIE is used to model the acoustic response of the instrument bore, and is numerically solved by means of a Boundary Element Method (BEM). The latter takes advantage of an analytical solution for the calculation of the BEM coefficients, thus allowing for the representation of the problem as an open-domain problem. This peculiarity avoids the use of approximated boundary conditions at the open end of the pipe. The formulation is used to: evaluate the input impedance of the resonating air column; identify the frequency dependent transfer function relating the inflow of the instrument with the signal measured at a specified location (the Reed-To-Microphone transfer function); extend the analysis to a realistic performing environment to obtain the "Reed-To-Listener" transfer function. Standard techniques are used to take into account the interaction of the bore with the nonlinear exciting device. Numerical results are obtained for single-reed instruments in terms of tuning properties, convergence of solution, directivity patterns, and simple synthesized sounds. Issues related to the possibility of real-time simulations are briefly addressed. Specifically, the identification of digital filters from the calculated transfer functions is investigated, and some preliminary numerical result included.
An approach and technique for acoustic modelling of contact
Authors: Rath Matthias
Published: May 2008

Vibration of solid objects can often be modelled by modal description, which exists when certain operators in a differential equation are linear. Discrete-time algorithms can represent the behaviour of "modal objects" without artefacts, exact (with precision of finite computer architecture), if based on analytical solution, not numeric approximation. In particular, the energy associated with the state of the system is then preserved and the algorithm stable. A scenario of two objects interacting only during contact, however, is non-linear: a non-zero linear function cannot be zero in a half-space of the system's state-space. Existing computational models are based on approximate, numeric solution and cannot guaranty stability in situations with longer contact phases, such as rolling or sliding. General principle of our approach is: although any possible term for the interaction force must be non-linear, it may be piecewise-linear, and during each linear phase the whole system (of interacting solids) may be simulated by modal description. The question of "switching" between the different phases is here critical but may be solved in a way that assures control over the system's energy. Our implemented new contact model is stable in any condition and overcomes artefacts found with previous techniques.