Delivering Sound Energy along an Arbitrary Convex Trajectory

Abstract

Accelerating beams have attracted considerable research interest due to their peculiar properties and various applications. Although there have been numerous research on the generation and application of accelerating light beams, few results have been published on the generation of accelerating acoustic beams. Here we report on the experimental observation of accelerating acoustic beams along arbitrary convex trajectories. The desired trajectory is projected to the spatial phase profile on the boundary which is discretized and sampled spatially. The sound field distribution is formulated with the Green function and the integral equation method. Both the paraxial and the non-paraxial regimes are examined and observed in the experiments. The effect of obstacle scattering in the sound field is also investigated and the results demonstrate that the approach is robust against obstacle scattering. The realization of accelerating acoustic beams will have an impact on various applications where acoustic information and energy are required to be delivered along an arbitrary convex trajectory.

A linear sensor array with self-bending sensitivity

“…Finite-energy approximations were then observed with light in [2]. In [4,5], the concept was translated to acoustics and a method for creating a sound field that seemingly bends along a convex trajectory in free space without any external force was presented. Obviously, the wave itself is not accelerated.…”

“…Rather, the amplitude envelope of the sound field appears to be bent. The concept of [4,5] is illustrated in Fig. 1: A caustic is pre-defined along which the wave front folds.…”

“…This envelope is then referred to as caustic. The same concept was applied to acoustic fields by [4,5] using an array of acoustic transducers that controlled the phase profile of the evolving sound field.…”

Acoustic contrast control in an arc-shaped area using a linear loudspeaker array

“…17,18 However, the feasibility of applying the scheme to a personal audio system has not been investigated. Inspired by the aforementioned work, in this letter, the performance of a generated sound field in an arc-shaped area using a linear loudspeaker array is investigated.…”

“…1(c). According to the caustic theory, [16][17][18] the curving boundary can be treated as the envelope of the curve's tangent lines, which are produced by manipulating the spatial phase profile on the boundary y ¼ 0, where the sound sources are placed.…”