Sometimes in life you just have to stop and smell the roses, or in this example stop and listen to the deepest part of the ocean. Considering that mankind is becoming more prevalent throughout the landmasses as well as his ships becoming more prevalent on the ocean itself NOAA wanted to know what the baseline noise level of the ocean was and to find this out they started putting hydrophones in various places in the ocean to record what the baseline noise level and noises were.
Included in this array of hydrophones was one placed at the bottom of the Marianas Trench at the place known as Challenger Deep. Now challenger deep is a place that has a few challenges to it. To begin with it is 10,898 to 10,916 m (35,755 to 35,814 ft) deep by measurement from submersibles. Considering that Mount Everest is 29,000 feet above sea level one can begin to imagine how deep this is when you consider that you have to add slightly more than another mile to the height of Mount Everest to get how deep Challenger Deep is.
With this much water over your head the pressure is about 111 MPa (16,099 psi). And although most hydrophones are built to work in the water and they are liquid tight, they are not quite that liquid tight. For this one they had to have a special one made encased in titanium, and even this one only lasted 23 days. But it did record some interesting noises in its short lifetime.
Anyone who has ever worked sonar can tell you what this is:
The sound of the engines and screws on a surface ship.
In the next recording you can hear the sounds of a baleen whale(s) (right whales, gray whales, blue and humpback whales etc.) followed by something that is very unique, the sound of an earthquake. This particular earthquake was located about 190 miles away. It was a small magnitude 5 earthquake close to the island of Guam on 2015 July 16.
You can hear the whales at around 03 and 17 seconds into the recording, and the earthquake is just pretty obvious.
And finally we have a combination of the single call of baleen whale and those of an odontocete whale(s) (sperm whales, belugas, narwhals, dolphins, porpoises).
Living here on land we have no gut feeling for what the fish and other aquatic animals experience. Listening to the sounds and realizing that there are aquatic animals Extending from the surface to a little over 6 3/4 miles down in the ocean and realizing that their world is filled with these noises as much as our world is filled with light from the sun it is easy to understand why we humans don’t really know how to interpret what we see in aquatic animal behavior, and how our actions affect these animals.
There are a lot of things we may not have considered such as, do the surface animals tend to shut down at night and reduce the background noise? If they do does that create a rhythm within the majority of the dark ocean which would induce a circadian rhythm into the animals living below the sunlight region? And if it does do our transiting ships with their loud engines and screws disrupt this rhythm of the ocean?
Are there other things within noises that we do not presently know about that may be affecting the aquatic life even within the sunlit region? There is no way to answer these questions until you know what the norm is for the ocean and that is one good reason for the NOAA to record these values. That way in the future as this data is studied and as our world changes we will have a better idea of what effect, if any, our presence creates for the oceans norm.
Please note: the pictures indicate the depth as 10,971 m. This reading is via sonar and is not as accurate as the readings taken when the submersibles actually go down and measure their depth as they go.
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