Introduction to sound
Sound plays a vital role in the lives of dolphins and porpoises. They use echolocation to navigate and to find objects, such as prey and group members. In addition, bottlenose dolphins use signature whistles, which are individually unique signals, used to keep contact with group members, especially important for mother-calf pairs.
Sound pollution is an extensive problem in marine habitats. Coastal species, such as bottlenose dolphins and harbour porpoises, are especially affected because they live in habitats where an increasing amount of pleasure crafts operate. Unfortunately, these small fast boats usually make sounds in the same frequency band as the ones dolphins and porpoise use. This can have potential effects such as loss of contact with group members and reduced feeding success.
Spectrograms and sound librarys
Send on the left is a visualisation of a spectrogram. Spectrograms are visual illustrations of sounds, depicting the frequency at the y-axis and the time at the x-axis.
Seen top and middle are the whistles of two different bottlenose dolphins. Below is the whistle of a third dolphin recorded in the vicinity of a boat. This figure illustrates how sound pollution can mask the sounds used by the animals.
The creation of a sound library to store such information
would consist of three phases:
A. The recording of sounds
B. Analysing and selecting required sounds
C. The building of the database
A sound library consists of sound files, spectrograms and relevant data, such as recording time and the place and possible origin of the sounds.