Phys.org reports how a tsunami that struck Hawaii in 2011–caused by the same earthquake that hit Japan and created the tsunami that triggered the Fukushima nuclear disaster–caused a temporary halt to boat traffic that allowed scientists “a rare glimpse into what the bays might sound like without human activities.” By luck, the tsunami hit while “a Duke University-lead team was recording underwater sound in four bays” on Hawaii’s Kona coat.
It turns out that oceans are pretty loud. On the day of the tsunami, the loudest part of the day reached 98.8 decibels. Why are oceans so loud? “Because sound waves travel and are amplified differently in water than in air.” But 98.8 decibels was quiet compared to a reading on a typical day, as noise from boat traffic can reach up to 125 decibels, and the sound from nearby sonar exercises tops 143 decibels.
So what did the Duke study conclude? It showed that humans created the loudest disruptions and boat traffic and sonar were “significant causes of noise in all four bays.” Human-made noise has long been a concern of conservationists who fear that “interactions caused by dolphin-encounter boat tours and other human activities” are disrupting dolphins’ sleeping behaviors and potentially interfering with their hunt for food, since dolphins rest in the bays during the day to ready themselves for the hunt at night.