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Research Papers

Inverse Patch Transfer Functions Method as a Tool for Source Field Identification

[+] Author and Article Information
Dorian Vigoureux, Jonathan Lagneaux, Jean-Louis Guyader

Laboratoire Vibrations Acoustique,
INSA-Lyon,
25 bis, av. Jean Capelle,
Villeurbanne Cedex F-69621, France

Nicolas Totaro

Laboratoire Vibrations Acoustique,
INSA-Lyon,
25 bis, av. Jean Capelle,
Villeurbanne Cedex F-69621, France
e-mail: nicolas.totaro@insa-lyon.fr

1Corresponding author.

Contributed by the Noise Control and Acoustics Division of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received June 18, 2013; final manuscript received August 7, 2014; published online December 11, 2014. Assoc. Editor: Liang-Wu Cai.

J. Vib. Acoust 137(2), 021006 (Apr 01, 2015) (12 pages) Paper No: VIB-13-1209; doi: 10.1115/1.4029000 History: Received June 18, 2013; Revised August 07, 2014; Online December 11, 2014

Many methods to detect, quantify, or reconstruct acoustic sources exist in the literature and are widely used in industry (near-field acoustic holography, inverse boundary element method, etc.). However, the source identification in a reverberant or nonanechoic environment on an irregularly shaped structure is still an open issue. In this context, the inverse patch transfer functions (iPTF) method first introduced by Aucejo et al. (2010, “Identification of Source Velocities on 3D Structures in Non-Anechoic Environments: Theoretical Background and Experimental Validation of the Inverse Patch Transfer Functions Method,” J. Sound Vib., 329(18), pp. 3691–3708) can be a suitable method. Indeed, the iPTF method has been developed to identify source velocity on complex geometries and in a nonanechoic environment. However, to obtain good results, the application of the method must follow rigorous criteria that were not fully investigated yet. In addition, as it was first defined, the iPTF method only provides source velocity while wall pressure or intensity should also give useful information to engineers. In the present article, a procedure to identify wall pressure and intensity of the source without any additional measurement is proposed. This procedure only needs simple numerical postprocessing. Using this new intensity identification, the influence of background noise, evanescent waves, and mesh discretization are illustrated on numerical examples. Finally, an experiment on a vibrating plate is shown to illustrate the iPTF procedure.

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References

Figures

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Fig. 1

Example of system under study. A vibrating surface Σ radiates in an acoustic volume with a rigid surface Λ and an opening Σ'.

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Fig. 2

System under study: a plate excited by a point force radiating into a semi-infinite acoustic medium

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Fig. 3

Definition of the virtual surface Σ' surrounding the rectangular plate. Top view: Height = 0.045 m.

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Fig. 4

Intensity fields at 1900 Hz. (a) Reference field and (b) identified field.

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Fig. 5

Space averaged intensity on the surface of the plate as a function of frequency. (a) Comparison of reference and identified intensity and (b) identification error in dB.

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Fig. 6

Influence of the evanescent waves. (a) Penetration depth of evanescent waves of an infinite plate as a function of ω/ωc and (b) reduction factor at the distance zs from the plate as a function of ω/ωc.

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Fig. 7

Velocity field (a) computed on the surface of the plate (reference), (b) identified by iPTF and radiated velocity fields computed using (c) reference or (d) the identified field at 4 and 20 cm from the plate at 710 Hz

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Fig. 8

Identification and measurement meshes used in the study on influence of the identification mesh. (a) Identification mesh—λb/2; (b) identification mesh—λb/4; (c) identification mesh—λb/6; and (d) measurement mesh—λa/4.

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Fig. 9

Velocity fields identified at 3900 Hz with the different identification meshes shown in Fig. 8. (a) Reference field; (b) identified field obtained with λb/2 mesh; (c) identified field obtained with λb/4 mesh; and (d) identified field obtained with λb/6 mesh (963 eigen-modes).

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Fig. 10

Identification and measurement meshes used in the study on influence of the measurement mesh. (a) Measurement mesh—λa/2; (b) measurement mesh—λa/4; (c) measurement mesh—λa/6; and (d) identification mesh—λb/4.

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Fig. 11

Velocity fields identified at 3900 Hz with the different measurement meshes. (a) Reference field; (b) identified field obtained with λa/2 mesh; (c) identified field obtained with λa/4 mesh; and (d) identified field obtained with λa/6 mesh.

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Fig. 14

Experimental comparison between reference, identified, and radiated fields as function of frequency. (a) Sound pressure and (b) mean square velocity.

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Fig. 16

FDAC between reference and identified velocity fields as a function of frequency. The dashed line indicates the threshold of good correlation (0.75).

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Fig. 15

Experimental comparison between reference and identified fields at 205 Hz on the plate surface. (a) real part of the reference pressure field; (b) real part of the reference velocity field; (c) reference active intensity field; (d) real part of the identified pressure field; (e) real part of the identified velocity field; and (f) identified active intensity field.

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Fig. 13

System under study: an aluminum plate glued to a wood frame and excited by a shaker. (a) Photography of the system and (b) measurement mesh surrounding the plate.

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Fig. 12

Identification of the velocity when Gaussian noise is added on (a) measured velocity or (b) measured pressure

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