High-Speed Vessel Noises in West Hong Kong Waters and Their Contributions Relative to Indo-Pacific Humpback Dolphins (Sousa chinensis)
Figure 3
1/3 octave band sound pressure levels for a small tour boat (referred to as “Wala wala”) in West Lantau (a), Beaufort sea state of 1. The orange line indicates the ambient sounds of Southwest Lantau number 2, located between the Soko Islands with very little boat traffic and no vessels present during recording. The red line indicates South Lantau Vessel Fairway, a busy traffic area, especially for ferries. South Lantau Vessel Fairway was recorded with several ferries and a shrimp trawler present. Selected sound spectra for the small tour boat and humpback sounds are displayed below (b). (c) shows the distribution of sound pressure levels for the Jetfoil high-speed ferry at varying distances, with a Beaufort sea state of 4 at West Lantau Station number 3. The ambient sound levels are the same as those for the small tour boat. (d) shows selected sound spectra for the Jetfoil compared to those of humpback dolphin communication sounds at a distance ≤100 m.
