Active noise cloaking of 2D cylindrical shells

Eggler, Daniel; Chung, Henry; Montiel, Fabien; Kessissoglou, Nicole

doi:10.1016/j.wavemoti.2018.08.006

Cited by 24 publications

(21 citation statements)

References 30 publications

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“…The same number of control sources and error sensors for excitation from an incident plane wave or a primary monopole source is attributed to the same excitation frequency used for both primary excitation cases, whereby the number of control sources and error sensors is only dependent on the acoustic wavelength as discussed previously. 31 Figure 4(a) shows the controlled field arising from application of active cloaking using the optimal control source strengths derived in the absence of flow, clearly highlighting that cloaking is not achieved when convection effects are neglected. Further, constructive interference between the primary and secondary acoustic fields increases the total acoustic response in regions around and particularly downstream of the cylinder.…”

Section: Resultsmentioning

confidence: 99%

“…The residual field, resulting from destructive interference between the primary and secondary fields, resembles the incident field. Interior cloaking has been applied to both acoustic [27][28][29][30][31][32][33][34][35] and elastic [38][39][40] domains. Bobrovnitskii 27,28 proposed a novel method where cloaking was achieved by covering the body with a smart skin containing structural actuators, structural sensors, and pressure sensors capable of inducing surface impedances such that the body becomes non-scattering.…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, conventional ANC techniques have also been implemented to acoustically cloak rigid and elastic cylindrical shells. 31 Active structural acoustic cloaking was introduced, whereby control forces directly applied to the shell were driven to modify the structural responses such that the resultant structure-borne sound field generated the cloaked field. Friot et al 32,33 devised a method using two layers of error sensors to mitigate the requirement of a priori knowledge in order to experimentally demonstrate cloaking of one-dimensional 32 and three-dimensional 33 objects with conventional ANC techniques.…”

Section: Introductionmentioning

confidence: 99%

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Active acoustic cloaking in a convected flow field

Eggler

Karimi

Kessissoglou

2019

The Journal of the Acoustical Society of America

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Acoustic cloaking has mostly been considered within a stationary fluid. The authors herein show that accounting for the effects of convection in the presence of fluid flow is critical for cloaking in the acoustic domain. This work presents active acoustic cloaking in a convected flow field for two different incident fields, corresponding to a plane wave and a single monopole source, impinging on a rigid body. Monopole control sources circumferentially arranged around the rigid body are used to generate a secondary acoustic field to destructively interfere with the primary scattered field arising from the incident excitation cases. The authors show that for sound waves in a moving fluid, active cloaking can only be achieved using a convected cloak, which is dependent on Mach number. V

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Active acoustic cloaking in a convected flow field

Eggler

Karimi

Kessissoglou

2019

The Journal of the Acoustical Society of America

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“…The analytical simulations of the active illusions presented in this paper were conducted within MATLAB. The incident and scattered acoustic fields of the rigid cylinder were approximated using truncated multipole expansions given in 45 . Analytical results for the incident and scattered acoustic fields for both plane wave and monopole source excitation were numerically validated using COMSOL Multiphysics 5.4.…”

Section: Methodsmentioning

confidence: 99%

Active acoustic illusions for stealth and subterfuge

Eggler

Kessissoglou

2019

Sci Rep

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Acoustic illusion devices present a novel approach for defeating detection systems such as sonar by misrepresenting information about the target. These devices are currently designed for a predetermined illusion using metamaterials. We present the first active acoustic illusion utilizing monopole control sources and error sensors arranged circumferentially around a rigid object to generate the desired illusion in the global acoustic field. We also utilize control sources and error sensors in a line array to generate an illusion in the forward-scatter region of the object. Multiple types of illusions are achieved for a given control configuration.

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“…The active control of acoustic scattering with secondary sources that are not on the surface of the sphere has been considered by a number of authors , such as Vasquez et al 5 , Norris et al 6 , Eggler et al 11 and Liu et al 10 , although Cheer 9 found that, for a hard sphere, this was less effective than when they were positioned on the surface of the sphere.…”

Section: Active Control With Secondary Sources Away From the Surfamentioning

confidence: 99%

Active control of the sound power scattered by a locally-reacting sphere

Elliott

Orita

Cheer

2020

The Journal of the Acoustical Society of America

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Active control of the sound power scattered by a sphere is theoretically investigated using spherical harmonic expansions of the primary and secondary fields. The sphere has a surface impedance that is uniform, real, and locally reacting while being subjected to an incident monochromatic plane wave. The scattered power is controlled with a number of monopole sources, initially on the surface of the sphere, and is expressed as the sum of squared amplitudes of the spherical harmonics due to both the scattered and control fields. This quadratic function is minimized to identify the optimal strengths for different numbers of control sources. At low frequencies, the scattered field is dominated by the first few spherical harmonic terms, and its power can be significantly reduced with a single controlling monopole for a soft or absorbent sphere and with two monopoles for a hard sphere. The number of secondary sources required to significantly attenuate the scattered field at higher frequencies is found to be proportional to the square of the frequency, and the attenuation also falls off rapidly if the secondary sources are moved away from the surface of the sphere, no matter what its surface impedance.

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Active noise cloaking of 2D cylindrical shells

Cited by 24 publications

References 30 publications

Active acoustic cloaking in a convected flow field

Active acoustic cloaking in a convected flow field

Active acoustic illusions for stealth and subterfuge

Active control of the sound power scattered by a locally-reacting sphere

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