Holographic Whisper: Rendering audible sound spots in three-dimensional space by focusing ultrasonic waves
Super directional speaker kit 110990449 SeeedStudio製|電子部品・半導体通販のマルツ
Amazon.com: ELTEM/PROPA-U50 / Directional Loudspeaker, Directional Speaker, Ultrasonic Speaker, Directional Sound System for Museums, Exhibits, Art Gallery and Digital Signage – Black : Everything Else