Acoustic streaming measurements in annular thermoacoustic engines

Experiments with an annular thermoacoustic engine employing quasiadiabatic interaction between traveling acoustic waves and an inhomogeneously heated porous material indicate the presence of a closed-loop mass flux. A qualitative modeling of the enthalpy flux in the thermoacoustic core provides an opportunity to estimate the thermal convection associated with this mass flux, by using temperature measurement at different positions in the system. The estimated acoustically induced mass flux is in accordance with recent theoretical results

On the use of acoustic streaming for heat transfer applications

Abstract: This study aims at investigating a possibility to use surface acoustic waves (SAWs) in order to drive acoustic streaming and other nonlinear effects leading to heat transport through a microchannel. As a beginning in this exploratory study, a solid-fluid interface submitted to a temperature gradient is considered, and three distinct mechanisms of heat transfer are estimated analytically. The type of SAW that could be used for an efficient transfer of heat is also discussed

Systèmes thermo-acoustiques de transfert de chaleur : répartition interne de température en régime transitoire

L'objet des travaux présentés ici porte sur l'étude théorique et expérimentale de l'évolution en régime transitoire de la distribution de température au cœur d'un réfrigérateur thermoacoustique. Un modèle analytique de ce comportement est présenté, dans le cadre d'une théorie linéaire. Il prend en compte les effets des différents flux de chaleur présents dans l'empilement. Ce modèle analytique permet d'interpréter de façon quantitative, après ajustement réaliste de paramètres inconnus, le comportement transitoire d'un prototype expérimental de réfrigérateur thermoacoustique

Comportement Non Linéaire des Suspensions d'un Haut-parleur: Mesure Dynamique à l'Aide d'une Méthode de Contrôle Actif

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Dynamic measurement of loudspeaker suspension parameters using an active harmonic control technique

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A simple predistortion technique for suppression of nonlinear effects in periodic signals generated by nonlinear transducers

International audienceMechanical transducers, such as shakers, loudspeakers and compression drivers that are used as excitation devices to excite acoustical or mechanical nonlinear systems under test are imperfect. Due to their nonlinear behaviour, unwanted contributions appear at their output besides the wanted part of the signal. Since these devices are used to study nonlinear systems, it should be required to measure properly the systems under test by overcoming the influence of the nonlinear excitation device. In this paper, a simple method that corrects distorted output signal of the excitation device by means of predistortion of its input signal is presented. A periodic signal is applied to the input of the excitation device and, from analysing the output signal of the device, the input signal is modified in such a way that the undesirable spectral components in the output of the excitation device are cancelled out after few iterations of real-time processing. The experimental results provided on an electrodynamic shaker show that the spectral purity of the generated acceleration output approaches 100 dB after few iterations (one second). This output signal, applied to the system under test, is thus cleaned from the undesirable components produced by the excitation device; this is an important condition to ensure a correct measurement of the nonlinear system under test

Nonlinear Force Factor Measurement of an Electrodynamic Loudspeaker

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Dynamic measurement of loudspeaker suspension parameters using an active harmonic control technique

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Analysis, Synthesis, and Classification of Nonlinear Systems Using Synchronized Swept-Sine Method for Audio Effects

A new method of identification, based on an input synchronized exponential swept-sine signal, is used to analyze and synthesize nonlinear audio systems like overdrive pedals for guitar. Two different pedals are studied; the first one exhibiting a strong influence of the input signal level on its input/output law and the second one exhibiting a weak influence of this input signal level. The Synchronized Swept Sine method leads to a Generalized Polynomial Hammerstein model equivalent to the pedals under test. The behaviors of both pedals are illustrated through model-based resynthesized signals. Moreover, it is also shown that this method leads to a criterion allowing the classification of the nonlinear systems under test, according to the influence of the input signal levels on their input/output law

Nonlinear Force Factor Measurement of an Electrodynamic Loudspeaker

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