whale does. Hearing that subtle click is harder if there’s a lot of noise around you.” The researchers used underwater microphones to measure the noise created by about 1,600 individual ships as they passed through Haro Strait, in Washington State. The two-year study captured the sounds made by 12 different types of vessel, including cruise ships, container ships and military vehicles, that passed through the strait about 20 times a day. Some ships are quieter than others but the average intensity of noise next to all the ships was 173 underwater decibels, equivalent to 111 decibels through the air – about the sound of a loud rock concert. Whales are not usually located right next to ships and so would be subjected to noise of about 60 to 90 decibels – around the level of a lawnmower or a vacuum cleaner. Veirs said scientists have already identified the impact of underwater noise upon baleen whales – a class of fauna containing the largest animals on Earth. But, the new research underlines the threat posed to smaller whales, dolphins and porpoises. “Ships have been thought of as low- frequency sources of noise, like the rumbling of lorries or trains,” he said. “Most noise is at that low frequency but the background noise of the ocean is raised even in the high frequencies. This could be causing a significant problem that we need to look into more.” There