Hypnotic sounds disprove our assumptions about the deepest part of the ocean

The deepest part of the ocean lies in the Mariana Trench near Micronesia. It is dark, mysterious abyss that few of us will ever see. But now we can hear what it sounds like, thanks to a new study from researchers at the National Oceanic and Atmospheric Administration (NOAA), Oregon State University and the U.S. Coast Guard. 

The researchers used a titanium-encased hydrophone to record ambient noise for three straight weeks in July 2015, and what they heard was nothing like what one might expect from a region long thought to be inhospitable to most large marine mammals. 

One might also think that, seven miles underneath the surface, the influence of humans would be too distant to be heard, but that also turned out to be wrong.

“You would think that the deepest part of the ocean would be one of the quietest places on Earth,” said Robert Dziak, a NOAA research oceanographer and chief project scientist, in a press release. 

“Yet there is almost constant noise. The ambient sound field is dominated by the sound of earthquakes, both near and far, as well as distinct moans of baleen whales, and the clamor of a category 4 typhoon that just happened to pass overhead.”

For example, here is the sounds of what is most likely a baleen whale vocalizing just before and after a magnitude 5 earthquake near Guam.

The hydrophone also picked up sound from ship propellers, likely from cargo ships headed to and from Guam, China and the Philippines. 

The Atlantic's City Lab posted several of the other sound files to Soundcloud, and they are each worth listening to.

This whale call, for example, sounds like someone realizing in slow motion that they are coming down with food poisoning:

And this is what a ship propellor sounds like from at least seven miles underwater.

The project's goal was to "establish a baseline for ambient noise in the deepest part of the Pacific Ocean," according to the press release.  

Marine scientists have become increasingly concerned that the seas are getting too noisy for some iconic species -- such as whales, dolphins and fish -- to hunt, reproduce and navigate effectively, given the proliferation of offshore oil and gas drilling, submarine fleets and many other noise sources.

The water pressure at a depth of 7 miles is so great that the researchers had to drop the hydrophone through the water column at just 5 meters per second or less to avoid having the ceramic instrument be crushed by the pressure change.

Atmospheric pressure in the average home or office is 14.7 pounds per square inch (PSI), NOAA said, but it is more than 16,000 PSI at the bottom of the Mariana Trench.