人間の耳には聞こえない2種類の超音波を出し、音波を曲げて交差させ、交差地点だけに「聞こえる音」を届ける技術が開発されました。Audible enclaves crafted by nonlinear self-bending ultrasonic beams | PNAShttps://www.pnas.org/doi/abs/10.1073/pnas.2408975122Researchers created sound that can bend itself through space, reaching only your ear in a crowdhttps://theconversation.com/researchers-created-sound-th