Journal of Materials

Perelomova A.

The nonlinear phenomena in the field of high intensity sound propagating in a gas with a chemical reaction, are considered. A chemical reaction of A → B type is followed by dispersion and attenuation of sound which may be atypical during irreversible thermodynamic processes under some conditions. The first and second order derivatives of heat produced in the chemical reaction evaluated at the equilibrium temperature, density and mass fraction of reagent A, are taken into account. The instantaneous equations are derived which govern dynamics of perturbations in non-acoustic modes, and conclusions of the efficiency of their nonlinear excitation by sound are drawn. The advantage of this study is accurate description of dispersion. Acoustic perturbations of any characteristic duration as compared to the duration of chemical reaction are considered, along with periodic, aperiodic perturbations and impulses. The conclusions concern also acoustically active gases.

Colinot T., Guillot L., Vergez C., Guillemain P., Doc J., Cochelin B.

This paper presents how the bifurcation diagram of a saxophone model is affected by the contact force limiting the displacement of the reed when it strikes the mouthpiece lay. The reed impact is modeled by a nonlinear stiffness and damping activated by contact with the lay. The impact model is compared with the "ghost reed" simplification, where the reed moves through the lay unimpeded. Bifurcation diagrams in both cases are compared, in terms of amplitude of the oscillations and location of the bifurcations, on the solution branches corresponding to the first and second register. The ghost reed simplification has limited influence at low values of the blowing pressure parameter: the diagrams are similar. This is true even for "beating reed" regimes, in which the reed coincides with the lay. The most noticeable discrepancies occur near the extinction of the oscillations, at high blowing pressure.

Grothe T., Amengual Garí S.V.

A method is proposed here to synthesize the acoustic response of a room to a musical reed wind instrument with tone holes played by a musician. The procedure uses convolution of a) two measured pulse responses and b) the mouthpiece pressure during playing. The novelty of the approach is to include the sound radiation directivity of the source in the impulse response measurement of the room by using the wind instrument's air column as an exciter. At the reed input end of the air column pressure pulses at typical peak pressures of several kilopascals are generated using a compressor and a solenoid valve, which provides a high SNR even at distant measurement positions. For auralization purpose, the source signal measurement is done very close to the sound generation locus, i.e. inside the mouthpiece. Because this measurement is largely insensitive to room acoustics, the proposed method can be considered a very convenient alternative to music recordings in anechoic conditions. As a proof of concept we report here experimental results for the case of a bassoon. The method can be extended to auralizations of reed and lip-reed musical instruments in virtual acoustic scenes, and sheds light on the importance of the reflective and radiative properties of the air column for the sound coloration.

Luan Y., Sgard F., Benacchio S., Nélisse H., Doutres O.

The IEC 60318-4 ear simulator is used to measure the insertion loss (IL) of earplugs in the ear canal of an acoustical test fixture (ATF) and is designed to represent an average acoustic impedance (in a reference plane) of the human ear. The ear simulator is usually modeled using a lumped parameter model (LPM) which has frequency limitations and inadequately accounts for the thermo-viscous effects in the simulator. The simulator numerical models that can better deal with the thermo-viscous phenomena often lack essential geometric details. Most related studies also suffer from the lack of experimental validation of the models. Therefore, a transfer matrix (TM) model of the IEC 60318-4 simulator is proposed based on a direct assessment of its geometric dimensions. Such a model is of particular interest for designing artificial ear simulators. The variability in the simulator impedance due to the geometric uncertainties is quantified using the Monte Carlo method. The TM model is validated using i) a finite element (FE) model of the simulator and ii) impedance measurements with a sound intensity probe. It is found to better describe the simulator impedance above 3 kHz compared to the LPM. The TM model is then coupled to a FE model of an occluded ATF ear canal to simulate the IL of an earplug in the frequency range [100 Hz, 10 kHz]. In the model, the simulator is considered as a cylindrical cavity terminated by an equivalent tympanic impedance which is determined from the TM model to simulate the sound pressure measured at the real microphone position (not at the reference plane) in the ATF ear canal. The simulated IL is validated against i) that obtained with a complete FE model of the corresponding system and ii) measurements using an ATF. The TM model is shown to better agree with the simulator FE model than the LPM above 6 kHz regarding the earplug IL simulated using this method.

Gontier F., Lavandier C., Aumond P., Lagrange M., Petiot J.

The impact of urban sound on human beings has often been studied from a negative point of view (noise pollution). In the two last decades, the interest of studying its positive impact has been revealed with the soundscape approach (resourcing spaces). The literature shows that the recognition of sources plays a great role in the way humans are affected by sound environments. There is thus a need for characterizing urban acoustic environments not only with sound pressure measurements but also with source-specific attributes such as their perceived time of presence, dominance or volume. This paper demonstrates, on a controlled dataset, that machine learning techniques based on state of the art neural architectures can predict the perceived time of presence of several sound sources at a sufficient accuracy. To validate this assertion, a corpus of simulated sound scenes is first designed. Perceptual attributes corresponding to those stimuli are gathered through a listening experiment. From the contributions of the individual sound sources available for the simulated corpus, a physical indicator approximating the perceived time of presence of sources is computed and used to train and evaluate a multi-label source detection model. This model predicts the presence of simultaneously active sources from fast third octave spectra, allowing the estimation of perceptual attributes such as pleasantness in urban sound environments at a sufficient degree of precision.

Cailly W., Walaszek H., Brzuchacz S., Zhang F., Lasaygues P.

Guided Wave Tomography is a nondestructive imaging technique that consists in inverting guided wave propagation data to localize defects. In particular, this technique should provide quantitative information about the corrosion state of metallic plates by reconstructing a thickness map from diffraction or time-of-flight measurements. In this paper we first present an analytical framework for corrosion profile reconstruction considering the 1D case. Due to the fact that, in practice, the low frequency ultrasound range (typically 50 to 100 kHz) is used for long range inspections, the first-order shear deformation approximation is relevant for plate thicknesses encountered in metallic structures. This leads to an analytical description of guided wave phenomena: diffraction, refraction and mode conversion, for 5 modes: A0, S0, SH0, A1 and SH1. The validity of an analytical approach to modeling thickness loss defects, in particular the validity of the first Born approximation, is discussed by comparing with elastodynamic numerical results. The comparison results show that the nonlinear behavior with depth increase, or width increase, of the defects (distortion) can be fully described using a multimodal high order Born series. Consequently, a consistent iterative inversion Born series based algorithm can be used to deal with the reconstruction of strong thickness losses.

Marquis-Favre C.

Noise annoyance models using only mean energy-based indices provide weak prediction. Actually various factors influence noise annoyance. different studies from the literature are carried out in laboratory conditions to understand some factors with the long-term aim of enhancing noise annoyance models. Laboratory experiments of assessing noise annoyance are based on imaginary or simulated context. The method with imaginary context is often questioned as participants listen to noise sequences. The current study aims at comparing the two methods in terms of total annoyance model testing. It revealed that annoyance models, respectively built within imaginary and simulated contexts, provided similar prediction when they were tested using in-field annoyance responses. Thus, the laboratory method with imaginary context seems to be as suitable as the method with simulated context to assess annoyance in laboratory conditions.

Maeder M., Peplow A., Meindl M., Marburg S.

Over many years, scientists and engineers have developed a broad variety of mathematical formulations to investigate the propagation and interactions with flow of flow-induced noise in early-stage of product design and development. Beside established theories such as the linearized Euler equations (LEE), the linearized Navier–Stokes equations (LNSE) and the acoustic perturbation equations (APE) which are described in an Eulerian framework, Galbrun utilized a mixed Lagrange–Eulerian framework to reduce the number of unknowns by representing perturbations by means of particle displacement only. Despite the advantages of fewer degrees of freedom and the reduced effort to solve the system equations, a computational approach using standard continuous finite element methods (FEM) suff ers from instabilities called spurious modes that pollute the solution. In this work, the authors employ a discontinuous Galerkin approach to overcome the difficulties related to spurious modes while solving Galbrun's equation in a mixed and pure displacement based formulation. The results achieved with the proposed approach are compared with results from previous attempts to solve Galbrun's equation. The numerical determination of acoustic modes and the identification of vortical modes is discussed. Furthermore, case studies for a lined-duct and an annulus supporting a rotating shear-flow are investigated.

Alotaibi Y.A., Selouani S., Yakoub M.S., Seddiq Y.M., Meftah A.

The robustness of speech classification and recognition systems can be improved by the adoption of language distinctive phonetic feature (DPF) elements that can increase the effective characterization of a speech signal. This paper presents the results of applying Hidden Markov Models (HMMs) that perform Arabic phoneme recognition in conjunction with the inclusion and classification of their DPF element classes. The research focuses on classifying Modern Standard Arabic (MSA) phonemes within isolated words without a language context. HMM-based phoneme recognition is tested using 8, 16, and 32 HMM Gaussian mixture models. The monophone configuration is designed with consideration of 2-gram language model to evaluate the inherent performance of the system. The overall correct rates for classifying DPF element classes for the three versions of HMM systems are 83.29% 88.96%, and 92.70% for 8, 16, and 32 HMM Gaussian mixture model systems, respectively.

Forssén J., Mauriz L.E., Torehammar C., Jean P., Axelsson Ö.

Field measurements and numerical modelling were used to study the acoustic performance of a low screen in an urban road setting. The results show the usefulness of low screens as well as suggests improvements in screen design. For the measurements, an acoustic screen built up from concrete modules was temporarily installed beside a small park on the reservation between a two-lane road and a track for walking and cycling. A larger traffic system, of which the two-lane road is a part, determines the daytime equivalent noise level within the urban area. The screen height was about 1.4 m as measured from the level of the road surface and the width of the screen top was 0.3 m. Measurements were carried out both at 20 m distance from the road (within the park) and at 5 m distance from the road (at the cycle track). Insertion loss in maximum level, using controlled lightvehicle pass-by at 50 km/h, was measured to 10 dB at 5 m distance and to 6 dB at 20 m distance, at 1.5 m height. Insertion loss in equivalent level was measured within the park to 4 dB at 1.5 m height. A listening experiment confirmed a perceived improvement from installing the screen. The measured results were also compared with predicted results using a boundary element method (BEM) and a noise mapping software, the latter showing good agreement, overestimating the equivalent level insertion loss by 1 dB in the park. The BEM comparison showed reasonable agreement in maximum level insertion loss considering that facade reflections were excluded, with an overestimation of 5 dB at the cycle track, and good agreement in the park, overestimating by up to 1 dB the equivalent and maximum level insertion losses. BEM predictions were used to also investigate other screen designs, showing a positive effect of an acoustically soft screen top, significant for a screen width of 0.2 m and increasing for wider screens.

Carcagno S., Di Battista A., Plack C.J.

Regulations on safe ultrasound exposure limits are based on a very limited number of studies, which have only considered audiometric threshold shifts as indicators of hearing deficits. The purpose of the current study was to assess the effects of exposure to high-intensity ultrasound on a range of measures of hearing function, which included audiometric thresholds, as well as subclinical measures of hearing deficits: speech-in-noise understanding, supra-threshold auditory brainstem response wave I amplitude and latency, and frequency following response levels to amplitude modulated (AM) tones. Changes in these measures were assessed before and after exposure of the left ear to high-intensity ultrasound in a group of nine young listeners. These changes were compared to those observed in a control group of nine young listeners. Exposure consisted in the presentation of a 40-kHz AM tone at levels of 105, 110, 115, and 120 dB SPL for 10 minutes at each level, plus an exposure to a 40-kHz unmodulated tone during an ultrasound detection task, for a total duration of 50 seconds. None of the measures of hearing function was found to change significantly more for the left compared to the right ear, for participants of the exposure group compared to control participants. Electroencephalographic recordings obtained during exposure to the AM tone did not show significant phase-locked activity at the modulation frequency or at low-frequency subharmonics of the ultrasound tone. One out of nine participants was able to perform the ultrasound detection task above chance level, although due to limitations of the experimental setup the mechanism by which she could detect the presentation of the tone remains unclear.

González-Mohino A., Jiménez A., Rufo M., Paniagua J.M., Nas S.V., Olegario L.S.

This paper describes a non-invasive ultrasound method to analyze and develop the usefulness of ultrasound testing of both raw and cooked samples of pork loins (with different cooking conditions), and in different measurement conditions (frozen and thawed). Besides studying ultrasound pulse velocity (UPV), other ultrasound parameters were included such as FFT (Fast Fourier Transform) and attenuation, neither of which being commonly studied in this kind of work. The experimental study was carried out on pork loin pieces with 3 cm thickness, using a pair of transducers in through-transmission mode (frequency range up to 100 kHz), and another one in pulseecho mode (frequency range up to 1000 kHz). The ultrasound parameters studied showed good discrimination between samples in the different conditions of measurement and cooking. These results consolidate ultrasound testing as a non-destructive method well suited to this kind of meat product, both raw and cooked.

Zhang J., Zhang L., Ge R., Yang L., Xia J.

Functionally gradient materials with special mechanical characteristics are more and more widely used in engineering. The functionally graded beam is one of the commonly used components to bear forces in the structure. Accurate analysis of the dynamic characteristics of the axially functionally graded (AFG) beam plays a vital role in the design and safe operation of the whole structure. Based on the Euler-Bernoulli beam theory (EBT), the characteristic equation of transverse free vibration for the AFG Euler-Bernoulli beam with variable cross-section is obtained in the present work, and the governing equations of the beam are transformed into ordinary differential equations with variable coefficients. Using differential quadrature method (DQM), the solution formulas of characteristic equations under different boundary conditions are derived, and the natural frequencies of the AFG beam are calculated, while the node partition of a non-uniform geometric progression is discussed.

Zhao T., Lin S.

In this paper, the design of large-size rectangular ultrasonic plastic soldering system is studied by using the band gap theory of phononic crystal and coupled vibration theory of large-size rectangular tool. In practical engineering applications, lateral vibration of the large-size rectangular tool will seriously cause the displacement of the tool's radiation surface uneven. So the lateral vibration of the tool should be suppressed. As we all know, phononic crystal materials can suppress the vibration and they are composed of two or more different materials periodically (including matrix material and scattering material). This paper uses periodic slotted structure to suppress the lateral vibration of the large-size rectangular tool. The lateral vibration band gap of the large-size rectangular tool which has periodic slotted structure in this paper is simulated. In addition, the influence of the scatterer's size on the lateral vibration band gap is also obtained. At the same time, the magnitude and uniformity of the tool's radiation surface displacement before and after slotting is compared in experiments. The research shows that by reasonably designing the periodic structure and size of the phononic crystal, the lateral vibration of the large-size rectangular tool can be effectively suppressed, and the displacement of the tool's radiation surface can be more even.

Arackal R.S., Jothi T.J.

The present study experimentally investigates the effect of the growth of inner layer on noise emission characteristics of wall jets. The plate length L considered for the current study vary in the range of L/h = 2.5 to 30, where h is the nozzle height. The jet is issued from a nozzle having the exit dimensions of 20 cm in width and 2 cm in height h. The jet Reynolds number, based on the nozzle height and jet exit velocity Uj, is varied up to 7.0 · 104. Acoustic measurements revealed the distinct variations in the noise levels with different plate lengths. The L/h = 2.5 wall jet has an increase in noise levels by around 10 dB compared to that of a free jet (background noise). Wall jets in the range of L/h = 5 to 20 radiate higher noise levels compared to other plates, while the least noise emissions are observed from fully developed wall jets (L/h > 20). The significant sources identified for noise emissions are the trailing edge and the secondary shear layer in the wall jets. The low frequency noise corresponding to the Strouhal number (based on h) below 0.2 is characterized as the trailing edge noise. The spectra of the wall jets collapse in the Strouhal number range (based on the inner layer thickness of wall jets) of ∼0.2 to 1.0 indicating the secondary shear layer noise of wall jets.