Sound travels with greater efficiency in water than does light, which is quickly absorbed and scattered. As a consequence, a wide variety of marine taxa use sound for communication, foraging and generally sensing their environment. Since the 1970s there has been increasing concern about the potential impacts of underwater anthropogenic noise on marine animals. Sources range from short-term coastal ones such as pile driving, to those which contribute long-term, sustained increases in ambient noise, such as shipping. Cetaceans (whales, dolphins and porpoises) are a group of marine animals thought to be at particular risk to impacts from anthropogenic noise. One type of study that has been used to determine the short-term impacts of noise on various taxa is the Behavioural Response Study (BRS) where animals are exposed to a noise and their behavioural responses are measured. While BRS are relatively straightforward for captive animals, most species of cetaceans are not kept in captivity and experiments with adequate levels of control are difficult. One such study, however, is the Behavioural Response of Australian Humpback whales to Seismic Surveys (BRAHSS), which commenced in 2010. Migrating humpback whales were exposed to high level, impulsive sounds from arrays of seismic airguns off the Sunshine Coast, north of Brisbane, and off Dongara in Western Australia. The airguns, from a single 20 in3 airgun to an array of 3130 in3 , were towed behind a source vessel while whales were tracked and their behaviours observed from small boats and land stations. The success of the project required the accurate estimation of the received levels of the source vessel noise and airgun noise, as well as careful measurement and interpretation of behavioural data. This large study is an example of the need for careful study design and collaboration between experts in several fields including underwater acoustics and animal behaviour.

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