ABSTRACT
The Under Water Speaker (UWS) has been installed on the hydrofoils (HF) for avoiding the collisions with large cetaceans. However, its utility is still uncertain whether the sound produced by the UWS corresponds to the audible range of major large cetaceans. This is a major reason why we conduct the present study which explores the way to improve the UWS from biological aspects. Under the present research project, we examined three sub-projects:
1.1 Characteristics of the HF underwater noise One of the reasons of the collision is considered that the HF underwater noise is possibly hard for cetaceans to recognize approaching vessel. It is probably because the noise level is too low and hardly transmits to a long distance. Therefore we analyze the characteristics of the HF underwater noise.
