Numerical case study on biomimetic pulse train signal multiplexing for underwater acoustic ranging

Abstract A numerical case study is presented on the multiplexing of biomimetic pulse-train signals for underwater acoustic ranging. The proposed signal mimics the click sequences of bottlenose dolphins during their searching phase, aiming to reduce acoustic detectability while maintaining reliable ranging performance. Numerical simulations were conducted for a coastal region off Tomakomai, Japan, with a water depth of approximately 50 m. Signal propagation was analyzed using a ray-tracing model while considering multipath propagation and ambient noise. The results show that the arrival time can be reliably estimated at ranges up to 500 m under the assumed environmental conditions. A survey scenario using an autonomous underwater vehicle was also examined. Assuming a 10 h survey mission, five seabed transponders were sufficient to maintain communication with at least four units within the survey region, demonstrating the feasibility of acoustic positioning using the proposed signal. Because the signal acoustically resembles natural underwater sounds, it is expected to be less detectable by marine organisms and other observers than conventional artificial signals, thereby reducing acoustic disturbance while supporting covert underwater operations. These results are derived from numerical simulations under the assumed environmental and operational conditions.