Emitting and controlling ultra-low frequency underwater acoustic waves using a marine vibration system with time...

The control and manipulation of waves in optical and/or acoustic science and engineering are widespread. Recently, despite reported studies on high frequency acoustic waves via time modulated media, none of these approaches has demonstrated success with broadband frequency exceeding that of the mechanical system, and all of them were not able to emit ultralow frequency waves. There are both fundamental and practical issues. Achieving ultra-low frequency underwater acoustic wave control via time interfaces remains a major challenge for integrated underwater acoustic devices. Here, we explore the design of a marine vibrator source system based on hydraulic-acoustic energy conversion. The system consists of a hydraulic servo system kept aboard a boat on one side while the other side comprises an underwater vibrator transducer. The transfer of wave energy is a fundamental mechanism for emitting acoustic waves, yet the rules of conventional reaction-mass force intrinsically limit the vibrator force based on the displacement and the acceleration of the reaction mass. We show that this intrinsic limit can be broken for acoustic waves, where the acoustics become controllable by the arrangement of the vibrator system. The marine vibrator acoustic waves open new frontiers in acoustic control and enables diverse focusing and imaging.