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Acoustic cloaking and holography in the laboratory
In this thesis project we aim at demonstrating and optimizing acoustic invisibility and acoustic illusions in laboratory experiments. We achieve this with a large number of secondary microphones and loudspeakers that record and emit secondary soundfields that create the desired effect.
Rendering objects transparent to acoustic, elastic, or electromagnetic waves (cloaking) or making objects appear where there are none (holography) has fascinated mankind for centuries. No longer just the domain of science-fiction movies, recent advances in transformation optics have brought such technologies much closer to reality. However, most existing studies are geared towards electromagnetic waves, for instance to achieve invisibility to radar waves. More recently, similar ideas have started to emerge in the acoustic community, where passive materials or active secondary sources are used to manipulate incident fields to hide objects or to virtually create them. Recently, we have shown that the machinery developed in our laboratory for immersive wave experimentation (CIWE [1]) can also be used to cloak objects, or to make objects appear holographically (van Manen et al., 2015 [2]) . These ideas have already been validated in 1D physical experiments (Börsing et al., 2019 [3]) . Currently, 2D acoustic cloaking and holography experiments are underway in CIWE, which leverage a recently constructed 2D immersive experiment with hundreds of microphones and loudspeakers (Becker et al., 2020 [4]). In these experiments, the acoustic wavefield recorded on a dense surface of receivers is extrapolated to a dense surface of secondary sources in real-time. The secondary sources then emit the extrapolated wavefield to effect the desired response – for instance hiding a circular rigid object from the incident acoustic wavefield. A significant advantage compared to other methods is that our approach is completely broadband in space and in time.
[1]https://eeg.ethz.ch/research/centre-immersive.html
[2]Broadband cloaking and holography with exact boundary conditions. van Manen et. al., J. Acoust. Soc. Am., 137, EL415-EL421 (2015), http://dx.doi.org/10.1121/1.4921340.
[3] Cloaking and Holography Experiments Using Immersive Boundary Conditions. Börsing et. al, Phys. Rev. Appl., 12(2), 024011 (2019), https://doi.org/10.1103/PhysRevApplied.12.024011.
[4] Real-time immersion of physical experiments in virtual wave-physics domains. Becker et al., Phys. Rev. Appl., 13(6), 064061 (2020), https://doi.org/10.1103/PhysRevApplied.13.064061.
Rendering objects transparent to acoustic, elastic, or electromagnetic waves (cloaking) or making objects appear where there are none (holography) has fascinated mankind for centuries. No longer just the domain of science-fiction movies, recent advances in transformation optics have brought such technologies much closer to reality. However, most existing studies are geared towards electromagnetic waves, for instance to achieve invisibility to radar waves. More recently, similar ideas have started to emerge in the acoustic community, where passive materials or active secondary sources are used to manipulate incident fields to hide objects or to virtually create them. Recently, we have shown that the machinery developed in our laboratory for immersive wave experimentation (CIWE [1]) can also be used to cloak objects, or to make objects appear holographically (van Manen et al., 2015 [2]) . These ideas have already been validated in 1D physical experiments (Börsing et al., 2019 [3]) . Currently, 2D acoustic cloaking and holography experiments are underway in CIWE, which leverage a recently constructed 2D immersive experiment with hundreds of microphones and loudspeakers (Becker et al., 2020 [4]). In these experiments, the acoustic wavefield recorded on a dense surface of receivers is extrapolated to a dense surface of secondary sources in real-time. The secondary sources then emit the extrapolated wavefield to effect the desired response – for instance hiding a circular rigid object from the incident acoustic wavefield. A significant advantage compared to other methods is that our approach is completely broadband in space and in time.
[1]https://eeg.ethz.ch/research/centre-immersive.html [2]Broadband cloaking and holography with exact boundary conditions. van Manen et. al., J. Acoust. Soc. Am., 137, EL415-EL421 (2015), http://dx.doi.org/10.1121/1.4921340. [3] Cloaking and Holography Experiments Using Immersive Boundary Conditions. Börsing et. al, Phys. Rev. Appl., 12(2), 024011 (2019), https://doi.org/10.1103/PhysRevApplied.12.024011. [4] Real-time immersion of physical experiments in virtual wave-physics domains. Becker et al., Phys. Rev. Appl., 13(6), 064061 (2020), https://doi.org/10.1103/PhysRevApplied.13.064061.
The aims of this thesis are twofold:
1) perform further acoustic cloaking and holography experiments to hide and create objects of various shapes, and
2) carry out experimental and numerical sensitivity studies to improve our understanding of the underlying sensitivities to parameters such as source and receiver spacing.
The project entails significant experimental and theoretical work using our laboratory facilities as well as numerical simulations to validate the experimental results. A publication is likely!
The aims of this thesis are twofold: 1) perform further acoustic cloaking and holography experiments to hide and create objects of various shapes, and 2) carry out experimental and numerical sensitivity studies to improve our understanding of the underlying sensitivities to parameters such as source and receiver spacing. The project entails significant experimental and theoretical work using our laboratory facilities as well as numerical simulations to validate the experimental results. A publication is likely!
If you are interested in this opportunity, please get in touch with us: Theodor Becker (theodor.becker@erdw.ethz.ch) Dirk-Jan van Manen (dirkjan.vanmanen@erdw.ethz.ch)
If you are interested in this opportunity, please get in touch with us: Theodor Becker (theodor.becker@erdw.ethz.ch) Dirk-Jan van Manen (dirkjan.vanmanen@erdw.ethz.ch)