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Research Papers

Two Step Optimization of Transducer Locations in Single Input Single Output Tonal Global Active Noise Control in Enclosures

[+] Author and Article Information
J. Ignacio Palacios

 SENER Ingeniería y Sistemas, 392 Provença Street, 08025 Barcelona, Spainjignacio.palacios@sener.es

Jordi Romeu

Department of Mechanical Engineering, Acoustic and Mechanical Engineering Laboratory, Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Spainjordi.romeu@upc.edu

Andreu Balastegui

Department of Mechanical Engineering, Acoustic and Mechanical Engineering Laboratory, Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Spainandreu.balastegui@upc.edu

J. Vib. Acoust 132(6), 061011 (Oct 08, 2010) (8 pages) doi:10.1115/1.4002122 History: Received October 13, 2009; Revised May 28, 2010; Published October 08, 2010; Online October 08, 2010

Global active control of sound can be achieved inside enclosures under low modal acoustic fields. However, the performance of the system depends largely on the localization of the elements of the control system. For a purely acoustic active control system in which secondary acoustic sources (loudspeakers) and pressure transducers (microphones) as error sensors are used, several optimization strategies have been proposed. These strategies usually rely on partial approximation to the problem, focusing on the study of number and localization of secondary sources without considering error transducers, or selecting the best positions of secondary sources and error transducers of an initial set of candidate locations for these elements. The strategy presented here for tonal global active noise control of steady states comprises two steps; the first is rather common for this sort of problem and its goal is to find the best locations for secondary sources and their strengths by minimizing the potential energy of the enclosure. The second step is the localization of the error transducer, which ensures the results of the first step. It is analytically demonstrated that for a single input single output system, the optimum location of error transducers is at a null pressure point of the optimally attenuated acoustic field. It is also shown that in a real case, the optimum position is that of a minimum of the optimally attenuated acoustic field. Finally, a numerical validation of this principle is carried out in a parallelipedic enclosure.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Representation of the enclosure with the primary source (circle) and the available positions for the secondary source (wall)

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Figure 2

Left: acoustic potential energy as a function of the secondary source position in the plane x=1.35 m at 150 Hz. Right: inverse of the acoustic potential energy as a function of the secondary source position in the plane x=1.35 m at 150 Hz.

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Figure 3

Initial acoustic field (left) and final acoustic field (right) after the application of the ANC

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Figure 4

Modal participation factors before and after the application of the ideal ANC

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Figure 5

Value of the cos θ parameter as a function of the secondary source position in the plane x=1.35 m at 150 Hz

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Figure 6

Left: acoustic field at the walls of the enclosure after the application of the ideal ANC at 150 Hz. Right: acoustic potential energy in the enclosure for every location of the error microphone.

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Figure 7

Acoustic field at the walls of the enclosure after the application of a real ANC at 150 Hz

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Figure 8

Left: modal participation factors before and after the application of the real ANC. Right: modal participation factors after an ideal minimization of the acoustic potential energy and with one error microphone in a real case at 150 Hz.

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Figure 9

Left: acoustic field at the walls of the enclosure after the application of the ideal ANC at 177 Hz. Right: acoustic potential energy in the enclosure for every location of the error microphone.

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Figure 10

Left: acoustic field at the walls of the enclosure after the application of the ideal ANC at 266 Hz. Right: acoustic potential energy in the enclosure for every location of the error microphone.

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