Researchers from the University of California Berkeley have produced a “bottle” beam of acoustic energy in open air that can precisely redirect sound waves. The concept of the bottle beam is a tool to be able to bend these waves along set trajectories without the need for waveguides or other mechanical assistance. The bottle beam is also able to flow around objects in its path while maintaining its shape. Sound waves travel through the high pressure wall of a curved shell to flow around a zero pressure center, which holds together the sound waves so they are able to travel over some distance. The acoustic bottle beam is uninfluenced by solid objects that are placed in its path, with the shape and characteristics of the sound waves reforming after flowing around the object. The high pressure exterior of the acoustic bottle also applies a dragging force to the surrounding air, so no sound waves can pass through the zero pressure interior of the bottle, which makes it suitable for acoustic trapping.
Source: Berkeley Lab
