Cross-spectral method of measuring acoustic intensity by correcting phase and gain mismatch errors by microphone calibration

Krishnappa, G.

doi:10.1121/1.385314

Cited by 37 publications

(22 citation statements)

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“…24 This relative calibration (and the subsequent corrections of the measurements) is realized by exposing them to the same sound field in a small cavity, and by measuring their cross-spectra in the frequency range of interest. 29 As an example, Fig. 2 presents the four coefficients T pp , T pu , T up and T uu (amplitude and phase) of the transfer matrix from 50 to 200 Hz and for three different values of heat power Q.…”

Section: Measurement Of the Transfer Matrix Of The Thermoacousticmentioning

confidence: 99%

Theoretical prediction of the onset of thermoacoustic instability from the experimental transfer matrix of a thermoacoustic core

Guédra

Pénelet

Lotton

et al. 2011

The Journal of the Acoustical Society of America

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The aim of this paper is to propose a method to predict the onset conditions of the thermoacoustic instability for various thermoacoustic engines. As an accurate modeling of the heat exchangers and the stack submitted to a temperature gradient is a difficult task, an experimental approach for the characterization of the amplifying properties of the thermoacoustic core is proposed. An experimental apparatus is presented which allows to measure the transfer matrix of a thermoacoustic core under various heating conditions by means of a four-microphone method. An analytical model for the prediction of the onset conditions from this measured transfer matrix is developed. The experimental data are introduced in the model and theoretical predictions of the onset conditions are compared with those actually observed in standing-wave and traveling-wave engines. The results show good agreement between predictions from the model and experiments.

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Section: Measurement Of the Transfer Matrix Of The Thermoacousticmentioning

confidence: 99%

Theoretical prediction of the onset of thermoacoustic instability from the experimental transfer matrix of a thermoacoustic core

Guédra

Pénelet

Lotton

et al. 2011

The Journal of the Acoustical Society of America

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“…4) Measurement Bandwidth: Microphones, even with manufacturer guaranteed tolerances are known to have substantial phase response mismatches [27]. It is assumed that most of these mismatches can be digitally equalized, albeit with small remaining discrepancies [28]. Even then, the phase mismatches of the individual array components are an important source of error [29], [30].…”

Section: ) Magnitude Errormentioning

confidence: 99%

“…After obtaining the particle velocity vector, the time-averaged acoustic intensity can be calculated using (28). b) G.R.A.S.…”

Section: ) Comparison With Conventional Arraysmentioning

confidence: 99%

Theoretical Analysis of Open Spherical Microphone Arrays for Acoustic Intensity Measurements

Hacıhabiboğlu

2014

IEEE/ACM Trans. Audio Speech Lang. Process.

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Acoustic intensity is a vectorial measure of acoustic energy flow through a given region of interest. Three-dimensional measurement of acoustic intensity requires special microphone array configurations. This paper provides a theoretical analysis of open spherical microphone arrays for the 3-D measurement of acoustic intensity. The calculations of the pressure and the particle velocity components of the sound field inside a closed volume are expressed using the Kirchhoff-Helmholtz integral equation. The conditions which simplify the calculation are identified. This calculation is then constrained to a finite set of microphones positioned at prescribed points on an open sphere. Several open spherical array topologies are proposed. Their magnitude and directional errors and measurement bandwidths are investigated via numerical simulations. A comparison with conventional open-sphere 3-D intensity probes is presented.

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“…25,27 In particular, a relative calibration of the six microphones has been made preliminarily by exposing them to the same sound field 28 in the frequency range of interest ͑f ͓150 Hz, 200 Hz͔͒, in order to prevent from large errors due to phase shifts between the sensors ͑inherent to the sensors themselves͒. 25,27 In particular, a relative calibration of the six microphones has been made preliminarily by exposing them to the same sound field 28 in the frequency range of interest ͑f ͓150 Hz, 200 Hz͔͒, in order to prevent from large errors due to phase shifts between the sensors ͑inherent to the sensors themselves͒.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Active control of thermoacoustic amplification in an annular engine

Desjouy

Pénelet

Lotton

2010

Journal of Applied Physics

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A new thermoacoustic engine with its resonant frequency freely controlled by metallic-bellow unit AIP Conf.In this paper, a new method is proposed to control the thermoacoustic amplification in thermoacoustic engines. This method, based on the active control of the spatial distribution of the acoustic field by means of auxiliary acoustic sources, is applied here to an annular thermoacoustic engine. Two auxiliary acoustic sources are used to tune the spatial distribution of the sound field in the engine in such a way that the thermal-to-acoustic energy conversion occurring into the thermoacoustic core is maximized. An experimental study of this device is proposed, which should be considered as a proof-of-concept study, aiming at demonstrating that the addition of auxiliary acoustic sources can be used advantageously to improve the efficiency of thermoacoustic engines. The overall device is characterized below and above the onset of thermoacoustic instability. It is demonstrated that below the onset of thermoacoustic instability, there exists an optimum phase shift between the auxiliary sources which maximizes the acoustic power available in the annular waveguide. When the device is operated above the onset of thermoacoustic instability, it is demonstrated that the appropriate tuning of the two auxiliary sources enables to improve significantly the acoustic work produced into the engine ͑compared to the case without active control͒, that the additional output acoustic power is significantly larger than the input electric power supplied to the acoustic sources, and that the overall efficiency of the engine is thus significantly increased. A discussion about the applicability of this new method for the improvement of actual, high power thermoacoustic engines is also provided.

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Cross-spectral method of measuring acoustic intensity by correcting phase and gain mismatch errors by microphone calibration

Cited by 37 publications

References 0 publications

Theoretical prediction of the onset of thermoacoustic instability from the experimental transfer matrix of a thermoacoustic core

Theoretical prediction of the onset of thermoacoustic instability from the experimental transfer matrix of a thermoacoustic core

Theoretical Analysis of Open Spherical Microphone Arrays for Acoustic Intensity Measurements

Active control of thermoacoustic amplification in an annular engine

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