Marine Mammals and Low-Frequency Sound: Progress Since 1994 - National Research Council, Commission on Geosciences, Environment and Resources, Ocean Studies Board, Committee to Review Results of ATOC's Marine Mammal Research Program - Google Books

http://books.google.de/books?id=yrg5NdcQeGEC&lpg=PP1&hl=de&pg=PA94#v=onepage&f=true

Sound has become a major tool for studying the ocean. Although the ocean is relatively opaque to light, it is relatively transparent to sound. Sound having frequencies below 1,000 Hertz (Hz) is often defined as low-frequency sound. The speed of sound is…