The active minimization of harmonic enclosed sound fields, part I: Theory

Nelson, P.A.; Curtis, A. R.; Elliott, Stephen J.; Bullmore, A.J.

doi:10.1016/0022-460x(87)90432-9

Cited by 136 publications

(66 citation statements)

References 7 publications

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“…The idea behind Active Noise Control is to use acoustic sources to cancel out incoming acoustic disturbances. This technique, based on the concept of destructive interference, is highly dependent upon the placement of these acoustic sources as well as their number [4,5]. Because the technique relies heavily on the phase of the noise and the canceling acoustic wave, its effectiveness is limited to situations where the noise is limited to a narrow acoustic band or is tonal in nature.…”

Section: Active Noise Control (Anc)mentioning

confidence: 99%

Implementation of multi-layer active structural-acoustic transmission control

Wong

2001

7th AIAA/CEAS Aeroacoustics Conference and Exhibit

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Structural-acoustic vibration is one of the major sources of payload failure during launch. Past research on the topic of structural-acoustic vibration control has focused on actuating a single structural layer to minimize the amount of energy flowing across the boundary. This thesis investigates the use of a dual layer approach to address the structural-acoustic problem and compares the results to a single layer approach.Four different controller configurations were used to experimentally determine which configuration is best suited for multi-layer transmission control. The four controller configurations were the Multi-Input Multi-Output (MIMO) Controller, the Successive Loop Closure (SLC) Controller, the Interference Controller and the Power Diode Controller. The MIMO Controller used a single state-space controller to actively control the two active plates, while the other three configurations used a single controller to actively control each plate. The SLC Controller and the Interference Controller are different because the design order of the two plate controllers for the Interference Controller is reversed compared to the SLC Controller. The Power Diode Controller implements a power diode on one of the two structural plates. The power diode is designed to attenuate acoustic transmission across the plate in one direction only as compared to typical controllers that attenuate acoustic transmission across the plate in both directions.Although the four controller configurations were different, they shared a common goal-to minimize the system's response over the 40-1000 Hz broadband frequency region. The SLC Controller performed the best by posting a 2.08 dB reduction across the broadband region, compared to a 1.06 dB reduction posted by the worst performing controller. These reductions only refer to the differences in open and closed loop performances of the dual layer configuration. Compared to a passive single layer system with the same thickness as the two separate layers combined, the SLC Controller posted a 3.02 dB reduction for the broadband metric.

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Section: Active Noise Control (Anc)mentioning

confidence: 99%

Implementation of multi-layer active structural-acoustic transmission control

Wong

2001

7th AIAA/CEAS Aeroacoustics Conference and Exhibit

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“…Unlike mid-and highfrequency noise, LFN is less attenuated by walls and other soundproofing structures due to the long wavelength involved, it masks higher frequencies more than it is masked by them, and ear protection devices are less effective against it. For low modal densities in the enclosure, a significant reduction in acoustic potential * The archived file is not the final published version of the article energy at the natural frequencies of the room can be achieved using remote secondary sources thanks to strong coupling with the primary field [1]. When the coupling between the sources is weak such as in a free space or for high modal densities, global control can hardly be achieved if the secondary sources are distant by more than half a wavelength from the primary source [2].…”

Section: Introductionmentioning

confidence: 99%

“…Design of remote quiet zones using spot-type sound reducers * Romain Boulandet 1) , Thomas Laurence 1) , Hervé Lissek…”

mentioning

confidence: 99%

Design of Remote Quiet Zones Using Spot-Type Sound Reducers

Boulandet¹,

Laurence²,

Lissek³

2017

Acta Acustica united with Acustica

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SummaryThis paper presents a local control approach to generate remote quiet zones. To deal with situations where global control can hardly be achieved, it is proposed to use an arrangement of spot-type sound reducers as originally suggested by Olson and May. Assuming that cross-coupling between control units is weak, each can be controlled independently and a decentralised feedback controller is implemented without the need for direct monitoring of the primary source. Active noise attenuation in the remote target region is achieved using a linear quadratic optimization based on prior knowledge of the transfer path of the system. The performance of a particular configuration comprising three control units is examined by numerical simulation and experimentally evaluated for a tonal noise source in a free-field environment. An average noise reduction of about 6 dB was measured in a target region of volume 0.25 × 0.25 × 0.25 m 3 for a 160 Hz tonal primary source distant more than one wavelength from the secondary sources. The performance of the control system in relation to changes in the primary field is also considered with a view to extending the concept to more realistic enclosed sound field conditions in future work.

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“…Early research into global noise reduction in a free space involved the use of secondary loudspeakers placed close to the primary sources (Conover [1], Nelson et al [2,3], Ross [4], Hesselman [5], Berge et al [6]). In an enclosed space, a global noise reduction is achieved only for frequencies close to resonance and the secondary source can be located everywhere in enclosures except at nodal points (Nelson et al [2]). Elliott et al [7][8][9] demonstrated the feasibility of a system that attenuates the noise in a local sense.…”

Section: Introductionmentioning

confidence: 99%

A BEM sensitivity formulation for three‐dimensional active noise control

Brancati

Aliabadi

Mallardo

2012

Numerical Meth Engineering

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Abstract. In this paper a novel Boundary Element (BE) formulation for sensitivity analysis of local active noise control in a three-dimensional field is presented. The formulation is based on the Helmholtz differential equation and it is valid for internal as well as for scattering wave propagation problems. The primary noise is attenuated within an enclosure, called control volume, by adding a control source modelled as an object with a vibrating surface. Both the optimum position of the control volume and the optimum location/orientation of the secondary source are determined by minimisation of a suitable cost function. The sensitivities are determined by implicit differentiation. A hierarchical adaptive cross approximation approach in conjunction with the GMRES solver is implemented to accelerate the convergence. Four numerical examples are presented to demonstrate accuracy and efficiency of the proposed formulations.

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The active minimization of harmonic enclosed sound fields, part I: Theory

Cited by 136 publications

References 7 publications

Implementation of multi-layer active structural-acoustic transmission control

Implementation of multi-layer active structural-acoustic transmission control

Design of Remote Quiet Zones Using Spot-Type Sound Reducers

A BEM sensitivity formulation for three‐dimensional active noise control

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