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Sea Mammal Research Unit
SMRU > Research > Acoustics

Acoustics

Acoustics in marine mammal research has many aspects. Marine mammals rely heavily on the acoustic modality to communicate, navigate and explore their environment. We study how marine mammals use sound, but also take advantage of the animals’ acoustic activity to detect and track them. Thus, acoustics can be used to study the abundance and distribution of marine mammals.

Human activities in the oceans introduce additional noise into the environment that can affect marine mammals in a variety of ways. Effects range from masking of animal signals to habitat exclusion and even to permanent physical damage and mortality. We study the mechanisms underlying these effects in order to mitigate the effects of human noise pollution

Approaches

We use a variety of recording techniques to study marine mammal sounds. Amongst the most informative is passive acoustic localization in which an array of hydrophones is used to localize a sound source. This is used to study the vocal behaviour and interactions of individual animals in larger groups, but also to track individuals during acoustic surveys for abundance estimates.

Passive acoustic monitoring is conducted by placing static hydrophone buoys in areas of interest to monitor acoustic activity. Combined with automatic detection software these buoys can log the presence of different marine mammal species and are an important tool in studying cetacean distribution and abundance. 

Playback techniques employ powerful underwater speakers. They are used to study functional aspects of marine mammal sounds but also reactions to anthropogenic noise. Often several of these techniques need to be combined to study marine mammal acoustics.

Recording tags attached to the animals are increasingly used on deep-diving species to monitor the individual acoustic behaviour at depth. These devices are usually attached with suction cups and need to be retrieved to recover the data. 

Examples

Passive acoustic monitoring and passive acoustic localization are used extensively to monitor cetacean abundance and distribution. Functions of marine mammal sounds are studied primarily in bottlenose dolphins, killer whales, sperm whales and grey seals. Controlled exposure experiments are used to assess the potential impact of anthropogenic noise on beaked whales and active acoustic devices are being developed to decrease cetacean by-catch and predation on fish farms. All of these projects create a large amount of information on marine mammal sounds which helps to understand the biological mechanism and functions of marine mammal sound production.

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Recording vocalisations
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Human activities increase ocean noise that can affect marine mammals

 

 


 
 
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