Acoustic lens that diffuses plane waves composing of multiple spherical obstacles

Recently, a non-electrical smartphone loudspeaker based on acoustic horn has been created and marketed. An acoustic horn is directional and has the advantage of propagating strong sound pressure in the direction the horn is facing. However, it has the disadvantage that sound pressure cannot be expected in any direction other than the direction in which the form facing. This study proposed an acoustic lens in the form of a cylinder composed of multiple spherical obstacles. The density of the sphere was calculated using the phase difference equation and the equation proposed by Kock et al. The density of the sphere at the center of the lens is lower than at the circumferential direction. This change in density slows down the apparent sound speed passing through the further from the center. In this work, FDTD simulations were performed to evaluate the sound directivity for the acoustic lens. This work also test manufactured the acoustic lens and performed an experiment in an anechoic chamber to evaluate the characteristics of the lens.