2pSP6 – Directive and focused acoustic wave radiation by tessellated transducers with folded curvatures

Ryan L. Harne*: harne.3@osu.edu
Danielle T. Lynd: lynd.47@osu.edu
Chengzhe Zou: zou.258@osu.edu
Joseph Crump: crump.1@themetroschool.org
201 W 19th Ave., N350 Scott Lab, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA
* Corresponding author

Popular version of paper 2pSP6 presented Mon afternoon, 26 June 2017
173rd ASA Meeting, Boston, Massachusetts, USA

Directed or focused acoustic wave energies are central to many applications, broadly ranging from ultrasound imaging to underwater ecosystem monitoring and to voice and music projection. The interference patterns necessary to realizing such directed or focused waves, guiding the radiated acoustic energy from transducer arrays to locations in space, requires close control over contributions of sound provided from each transducer source. Recent research has revealed advantages of mechanically reconfiguring acoustic transducer constituents along the folding patterns of an origami-inspired tessellation, as opposed to digitally processing signals sent to each element in a fixed configuration [1] [2] [3].

Video: Origami-inspired acoustic solutions. Credit: Harne/Lynd/Zou/Crump

One such proof-of-concept for a foldable, tessellated array of acoustic transducers is shown in Figure 1. We cut a folding pattern into piezoelectric PVDF (type of plastic) film, which is then bonded to a polypropylene plastic substrate scored with the same folding pattern. Rather than control each constituent of the array, as in digital signal processing methods, the singular driving of the whole array and the mechanical reconfiguration of the array by the folding pattern leads to comparable means to guide the acoustic wave energies.

Figure 1. Folding pattern for the array, where blue are mountain folds and red are valley folds. The laser cut PVDF is bonded to polypropylene to result in the final proof-of-concept tessellated array prototype shown at right. The baffle fixture is needed to maintain the curvature and fixed-edge boundary conditions during experiments. Credit: Harne/Lynd/Zou/Crump

To date, this concept of foldable, tessellated arrays has exemplified that the transmission of sound in angularly narrow beams, referred to technically as the directionality far field wave radiation, can be adapted by orders of magnitude when the array constituents are driven by the same signal. These arrays can be adapted up to a point dictated by the foldings of a Miura-ori style of tessellated array.

Our research investigates a new form of adaptive acoustic energy delivery from foldable arrays by studying tessellated transducers that adopt folded curvatures, thus introducing opportunity for near field energy focusing alongside the far field directionality.

For instance, Fig. 1 reveals the curvature of the proof-of-concept array of star-shaped transducer components for the partially folded state. This suggests that the array will focus sound energy to a location near the radius of curvature. The outcomes of these computational and experimental efforts find that foldable, tessellated transducers that curve upon folding offer straightforward means for the fine, real-time control needed to beam and focus sound to specific points in space.

Due to the numerous applications of acoustic wave guiding, these concepts could enhance the versatility and multifunctionality of acoustic arrays by a more straightforward mechanical reconfiguration approach that controls the radiated or received wave field. Alternatively, by strategically integrating with digital signal processing methods, future studies might uncover new synergies of performance capabilities by using actively controlled, origami-inspired acoustic arrays.

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