Any activity that occurs under the sea has the potential to generate noise pollution that disrupts marine animals. The most significant sources of damaging noise are seismic surveys, blasting, construction and sonar devices. Animals that are the most sensitive to underwater noise are those that use echolocation or sonar for feeding and navigation. Dolphins appear to be particularly sensitive to high-pitched noises, such as those caused by pile-driving or drilling, and can be affected from distances of up to 1-2 km. Whales tend to be affected by deeper sounds. Their behaviour has been shown to be influenced by noises from airgun operations up to 7 km away, and to be adversely affected by such noises occurring within 3 km. Noise pollution in Darwin Harbour is a concern for Australian Snubfins, Indo-Pacific Humpback Dolphins and Indo-Pacific Bottle-nosed Dolphins.