Broadband acoustic invisibility and illusions

TL;DR

This paper demonstrates active acoustic cloaking and holography for broadband sources without prior wavefield knowledge, enabling objects to remain invisible and illusions to persist even with moving broadband sources, advancing practical acoustic stealth and architectural applications.

Contribution

It introduces a real-time adaptive active acoustic cloaking and holography method that works for broadband moving sources without prior wavefield information.

Findings

Successful experimental broadband acoustic cloaking

Effective acoustic illusions for moving sources

Potential applications in stealth and architecture

Abstract

Rendering objects invisible to impinging acoustic waves (cloaking) and creating acoustic illusions (holography) has been attempted using active and passive approaches. While passive methods are applicable only to narrow frequency bands, active approaches attempt to respond dynamically, interfering with broadband incident or scattered wavefields by emitting secondary waves. Without prior knowledge of the primary wavefield, the signals for the secondary sources need to be estimated and adapted in real-time. This has thus far impeded active cloaking and holography for broadband wavefields. We present experimental results of active acoustic cloaking and holography without prior knowledge of the wavefield so that objects remain invisible and illusions intact even for broadband moving sources. This opens novel research directions and facilitates practical applications including architectural acoustics, and stealth.