Adaptive acoustic energy delivery to near and far fields using foldable, tessellated star transducers

Abstract

Methods of guiding acoustic energy arbitrarily through space have long relied on digital controls to meet performance needs. Yet, more recent attention to adaptive structures with unique spatial configurations has motivated mechanical signal processing (MSP) concepts that may not be subjected to the same functional and performance limitations as digital acoustic beamforming counterparts. The periodicity of repeatable structural reconfiguration enabled by origami-inspired tessellated architectures turns attention to foldable platforms as frameworks for MSP development. This research harnesses principles of MSP to study a tessellated, star-shaped acoustic transducer constituent that provides on-demand control of acoustic energy guiding via folding-induced shape reconfiguration. An analytical framework is established to probe the roles of mechanical and acoustic geometry on the far field directivity and near field focusing of sound energy. Following validation by experiments and verification by simulations, parametric studies are undertaken to uncover relations between constituent topology and acoustic energy delivery to arbitrary points in the free field. The adaptations enabled by folding of the star-shaped transducer reveal capability for restricting sound energy to angular regions in the far field while also introducing means to modulate sound energy by three orders-of-magnitude to locations near to the transducer surface. In addition, the modeling philosophy devised here provides a valuable approach to solve general sound radiation problems for foldable, tessellated acoustic transducer constituents of arbitrary geometry.

Active manipulation of Helmholtz scalar fields: near-field synthesis with directional far-field control

“…In [31] far-field time reversal was used to overcome those challenges. Another approach is the smart design of transducers with adaptive structures such as classical rectangular panels in an infinite baffle [42], foldable tessellated star transducers [53], Helmholtz resonators with computerized controls [30] and modern metamaterials [49].…”

Acoustic wave focusing by doubly curved origami-inspired arrays

“…Where rms is the root mean square value of p ( x , y , z , t ) and the reference pressure in air is p ref = 20 μ Pa and in water is p ref = 1 μ Pa . These modeling approaches for shaped acoustic transducers are widely used and verified for their efficacy in model prediction (Ebbini and Cain, 1991; Jensen and Svendsen, 1992; Ross et al, 2005; Wan et al, 1996; Zou and Harne, 2017).…”

“…For instance, tessellated water-bomb and star-based arrays of acoustic transducers studied by Lynd et al (2017) and Zou et al (2018) have wave guiding properties in the near and far field in addition to the ability to fold into compact shapes for transport. Moreover, the reconfiguration of such origami-inspired acoustic arrays empowers means to control interference phenomena and thus modulate the wave guiding properties (Lynd and Harne, 2017; Zou et al, 2018; Zou and Harne, 2017, 2018).…”

Deployable linear and spiral array structures based on a Kresling-inspired mechanism with integrated scissor arms

“…Yet, these arrays have portability challenges due to their size and construction, nor are they reconfigurable to optimize transducer placement for varying frequencies. Recently, Zou and Harne (2017) have shown that tessellated star origami functions as a reconfigurable and portable wave guiding array where the tessellated star facets are assumed to be vibrating baffled pistons that radiate acoustic pressure.…”