In November 2015, they dropped a hydrophone to the Challenger Deep in of the deepest points in the ocean. This location is so deep that if Mount Everest was dropped at this point, the top would not reach the surface water.
The scientist could hear sounds of many marine animals and specifically whales. Whales are one of the loudest creatures, but scientists were still surpassed to hear them at this depth. They also hear ships passing over and also typhoons passing by.
"Yet there really is almost constant noise from both natural and man-made sources, said Robert Dziak from Oregon State University. "The sound of earthquakes dominates the ambient sound field at Challenger Deep, both near and far was well as the audible moans of baleen whales and the overwhelming clamor of a category 4-typhoon that just happened to pass overhead."
The noise has led to problems in some animals such as the sperm whale. They rely heavily on sounds to communicate, and the noise has led to them not being able to hear each other. Scientists are now predicting a drop in the whale population as this will result in increased difficulty in both hunting and mating.