Sounds of Deepest Part of the Ocean Surface for First Time

Image NOAA resurfacing specially designed hydrophone from the busy Challenger Deep Mariana Trench. 

Just listening closely to the Ocean is an invaluable treasure. In the ocean, through the water medium sound waves and acoustic data carry incipient information. We are literally immersed in a sea of sounds and ocean acoustic has rapidly settled as a new frontline of ocean science. 

The study of ocean sounds can be used to create better enhanced dimensional ocean maps with acoustic layers, used for the creation of more effective conservation and management plans for Marine Protected Areas MPAs, used to increase our understanding of the ocean and the marine organisms that inhabit it, used for the understanding of global issues such as global currents and global climate change and serve the natural disaster sectors for example by enhancing tsunami and earthquake warning systems. 

Sounds of the ocean range from whale to dolphin communications, to earthquakes and marine traffic to ocean crust activity and scientists have been listening into the ocean for some time now but until today no one knew what sounds echoed in depths of the ocean.  

On March 2 the Oregon State University reported “For what may be the first time (in history), scientists have eavesdropped on the deepest part of the world’s oceans”...”instead of finding a sea of silence, they discovered a cacophony of sounds both natural and caused by humans”.

NOAA Teamed up with researchers and scientists of the University and with the support of the US Coast Guard and its logistics managed to make history in the remote Pacific Ocean waters of Micronesia, the deepest part of the World, the Mariana Trench. 

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

The news of the release of the deep ocean sounds went viral on the web over the hours and attracted the attention of most of the high profile massive news media. 

Daily Mail reported; "One of the most hostile places on Earth, known as the Mariana Trench in the Pacific Ocean, has turned out to be surprisingly noisy”.

For the past several months Dziak and his colleagues have been analysing the sounds and trying to differentiate natural sounds from ships and other human activities.

The team actually  deployed the hydrophone in the Challenger Deep in the Mariana Trench in 2015 but they could not recover the equipment until late 2015 when they began then the meticulous work of analysing the data extracted from the depths of the ocean. 

NOAA explained that the hydrophone was deployed from the Guam-based US Coast Guard Cutter Sequoia in July 2015. “The device recorded sound continuously over 23 days, completely filling the flash drive. However, scientists had to wait until November to retrieve the hydrophone due to ships’ schedules and persistent typhoons. The device remained anchored to the seafloor until scientists returned,” NOAA went public recently. 

The hydrophone was uniquely designed for the scientific mission and had some gear which allowed it to perform interesting behaviours such as the ability to resurface from its anchored seafloor position after receiving an acoustic signal from the “mother” ship above. 

“It is (like) sending a deep-space probe to the outer solar system,” Dziak told the press. “We're sending out a deep-ocean probe to the unknown reaches of inner space At that depth the pressure is immense,” Dziak added. 

“We know more about the surface of the Moon and Mars than we do about the ocean’s seafloor,” the US Coast Guard news release affirmed. And just as in Space the Challenger Deep’s is an inhospitable environment. 

The ceramic hydrophone used in the mission was house in a cylindrical titanium pressure case capable of withstanding the 16.1 thousand pounds of pressure per square inch of the Challenger Deep. Inside the housing a ceramic pressure sensor specifically designed for deep-ocean work skeletonned the electronics, disk storage, pre-amplifier and battery case.

“Getting these first recordings wasn’t easy in an underwater trough deep enough to hold Mount Everest,” Haru Matsumoto Oregon State Ocean Engineer who worked with NOAA Engineer Chris Meinig to adapt the hydrophone added. 

“We had to drop the hydrophone mooring down through the water column at no more than five meters per second to be sure the hydrophone, which is made of ceramic, would survive the rapid pressure change,” Matsumoto explained.   

It went down and under...7 miles deep…

The only way to take informed decisions and to be able to have a grip on the ocean science and its evolution is by acquiring data. Historical data of global ocean temperatures is used today on daily basis by the climate change sector to produce models and take decisions. This is only possible thanks to the long decades of work of acquiring basic data such as temperature and salinity. While there is decades of information on certain data such as temperature of the oceans there is no “official” historical data base of ocean depths sounds. The data which was gathered by the team of NOAA while unique can not be compared with other data. It is the first of its kind. Has the Trench always been this noisy? Is noise increasing? What kind of noise dominate over the years and decades? These types of question and many important others can not be answered yet but NOAA has now set the precedent mark for the database which could one day be used for comparisons. 

“Human-created noise has increased steadily in recent decades and getting these first recordings allows scientists in the future to determine if the noise levels are growing and how this might affect marine animals that use sound to communicate, navigate and feed, such as whales, dolphins and fish,” NOAA recognized. 

“Our plan is to make a baseline record of sound levels at Challenger Deep to investigate the levels of anthropogenic sound at these depths as well as gauge the contribution from natural sources such as submarine earthquakes and volcanoes,” Dr. Robert Dziak -research oceanographer with NOAA and a chief scientist of the project said expanding the importance of the program to another sector, natural disasters.

Tropical cyclones which originate in the Pacific Ocean cause heavy rain and floods, strong winds, large storm surges and tornadoes. The destruction from a tropical cyclone is massive and affects society, economy and environment. The 2013 Pacific Typhoon Season was the most active Pacific Typhoon Season since 2004 as well as the deadliest since 1975. By the time it ended over 6.8 thousand people had lost their lives, millions were affected and over 22.8 billion USD in damages were registered. Global estimations of tropical cyclones fatalities are set on an average of 10 thousand per year although some urge for a revision of these numbers. 

There was a Before-and-After Hurricane Katrina and a Before-and-After the 2004 Asia Tsunami which killed over 280 thousand people -a quarter of a million dead and thousands more missing. While large natural disasters are impossible to ignore smaller scale natural disasters which happen almost every month go unheard and still when added up account for a shocking amount of damage. How much of these can be prevented?

NOAA explained that Joe Haxel -OSU co-investigator of the project will lead a planned return to Challenger Deep in early 2017. There and then researchers will deploy the hydrophone for a longer period of time and attach a deep-ocean camera. 

Perhaps permanent hydrophones will one day be found in all trenches of the world linking us to the acoustic window of the Global Trench System. 

As the news of the “first-ever-to-be-heard-deep-ocean-sounds” broke out the World was surprised once again by a Tsunami Warning which spread through the region of Indonesia. Media reported a 7.8 Magnitude Earthquake hit the coast of Indonesia. From Outer Space NASA´s Terra Satellite and the Joint Typhoon Warning Center tracked and informed on the short but powerful Yalo Cyclone, MIT News reported on a new acoustic theory which could aid the sector of aid tsunami detection and researchers of the University of California San Diego revealed a new mysterious sound in the depths of the ocean which they assure communities of fish, shrimp, jellies and squid use as a feeding bell. 

Yes, the ocean is sure a noisy place but noise is to data what information is to music. 

Analysis of sound and acoustic now becomes the prime value. What sound is important and what sound is just gibberish? Which sounds come before or after earthquakes or slides? Which sounds come before tsunamis and giant waves? What sounds are those which endangered Whales under international protection measures make when in distress? What is the sound of a too busy shipping lane and international oceanic route? What is the sound of the Cyclone that dies off and what is the sound of a Cyclone that grows? These and many questions require immediate response. 

Near Guam in Micronesia out in the deepest part of the Ocean, Pacific Ocean Challenger Deep the sounds flooded the drive of NOAA´s hydrophone. 

....Anchored on the seabed the hydrophone captures the call of a toothed whale or dolphin...7 miles deep under surface water... 

deep below the hydrophone picks up the distant sound from what seems to sound like a Bryde's whale…

...steady, rhythmic noise from a ship propeller miles away comes in loud and strong...

...the sound of a 5.0 magnitude earthquake that breaks open the ocean crust…

...the sound of a dramatic typhoon...