Acoustic transducer design for active reflection cancellation in a finite volume wave propagation laboratory

This thesis describes the design, fabrication and experimentally obtained electro-acoustic response of an acoustic transducer suite constructed for use in the Wave Propagation Laboratory (WaveLab) at ETH Zürich. Wave-Lab aims to immerse a physical acoustic experiment within a real-time virtual numerical environment by implementing immersive boundary conditions (IBCs)[1, 2]. When scale-model ultrasonic experimentation is not possible, a system with IBCs allows for low frequency, reflection-free acoustic measurements in a small physical domain. Additionally, the WaveLab IBCs are implemented to simulate interactions with virtual scatterers and media with arbitrary physics of wave propagation. The physical experiment of the WaveLab facility consists of a water tank measuring only 2 m on a side. The IBCs are realized through a massive computational engine coupled with a dense array of sensing and emitting acoustic transducers, which are used to sense and inject intricate wavefields at hundreds of locations inside the physical experiment. Criteria for the transducers are discussed in terms of individual and overall system response. The design parameters and associated models include sensitivity, scattering strength, directivity, frequency response, noise floor, and the dynamic range of the system. The transducer designs and models are presented alongside their physical prototypes and experimental results