Many marine organisms rely on their ability to hear for their survival. Sound is a highly efficient means of communication underwater and is the primary way that many marine species gather and understand information about their environment. Many aquatic animals use sound to find prey locate mates and offspring avoid predators guide their navigation and locate habitat as well as to listen and communicate with each other. Oceans are full of sound. Waves, earthquakes and icebergs - all contribute to the underwater soundscape. But so do human activities and this can be a problem for marine life as it can seriously affect their physiology behaviour, reproduction and even survival. Being able to produce and detect sound in an environment where light penetrates only a few hundred metres is crucial for animals to communicate, feed, avoid predators and navigate vast underwater habitats. Large whales generate low frequency communication calls that can travel thousands of kilometres. While the snapping shrimp, native to the western Atlantic, can produce a loud snapping sound capable of stunning and killing its prey. The noise generated by humans changes the natural acoustic environment of our oceans and our capacity to produce it is increasing. Noise is often the unintentional by product of transport infrastructure development and industry. Yet noise can also be produced deliberately. Many navies use sonar system to detect ships and submarines while geologists survey the seabed for oil and gas using seismic airguns. The noise produced by an airgun can exceed 200 decibels louder than a gunshot at a range of one metre. Sound travels further and four times faster in water than in air at a speed of almost 1500 metres per second. The noise produced by humans can therefore spread considerable distances underwater. These sounds can be relatively constant such as the noise produced by the engine of a ship and propeller or sudden and acute in the case of naval sonar and seismic airguns.