Sound and Impact Attenuation Effects of Small Projections Inspired by Dorsal Ridge Tubercles in Finless Porpoises

Abstract

Finless porpoises have numerous small tubercles on their dorsal ridges. The fluid dynamics of these tubercles were investigated in terms of sound and impact attenuation upon water entry. The experiments were conducted using streamlined models with small tubercles attached to the body surface. As a result, streamlined models with tubercles uniformly attached to the front part of the body showed a significant sound and impact attenuation effect, indicating that tubercles play an important role in masking the breathing sounds of finless porpoises to avoid predation by natural enemies, such as killer whales.