of sound in seawater. For example, blue and fin whales produce intense infrasonic (very low frequency) songs that can be heard over an entire ocean, while humpback songs can be heard over many hundreds of miles. At least, that was the way it used to be. With the advent of modern shipping, ocean noise in the low-frequency range (10-300 Hz) has been doubling approximately every decade, drastically reducing these ranges within only a single lifespan for some of the large whale alive today. Although the long-term impacts on marine mammals from this rising level of noise are not yet known with certainty, increased noise in overlapping frequencies is known to obscures or eliminates an animal's ability to hear. Because we know how vital sound communication to these amazing animals, such interference can certainly have serious implications for reproduction and survival. Consider that you are at a restaurant with your small child. Now imagine that you are blind and can only find them by hearing where they are. The restaurant is initially fairly quiet so your child can roam around just about anywhere and you can still find
them from the sound of their movement and voice. Next imagine the restaurant getting louder and louder and think about how much closer you would need to be to still be able to effectively find your child. Also think about how you might feel if you were unable to find them in the escalating background din. Commercial shipping is not the only form of human sound introduced into what are, in many ways, naturally relatively noisy places. Increases seen in ocean noise arising from human sources aren't ubiquitous and there is a certain amount of local variability. However, there is sufficient information to suggest that shipping is a major component of this global problem, and one that is only expected to get worse. The amount of underwater noise is related to not only the amount of commercial shipping, but also the size and speed of vessels on the water. Each of these is continually increasing. Of additional and particular concern is that commercial vessel traffic is also expected to expand into some of the few remaining relatively pristine environments, such the Arctic as it opens to passage. Many of these areas are
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Marine Technology Reporter 23
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