Challenger Deep is an extreme environment.

It's the deepest ocean abyss we're aware of at this time.

I view the work we're doing at Challenge Deep similar to what astronomers and astrophysicists do in deep space where they send a probe out to investigate the deepest regions of our solar system.

We are putting a deep ocean probe into the far reaches of deep innerspace to getting a new view of how our planet works.

Well, we're hoping to accomplish two major things. First was to achieve the technical challenge of getting a hydrophone and mooring system to survive going to that deepest part of the ocean.

HASHIMOTO>> The challenge is, actually is, you know, make the system to withstand this pressure--enormous pressure--which is about 16,000 psi. The Challenge Deep hydrophone by far, the deepest hydrophone we have ever designed.

DZIAK>> Secondly, we wanted to make the first sound recording ever made at Challenge Deep.

HASHIMOTO>> It's away from all the sound sources, including ships, waves, and whales.

It should be quiet.

HAXEL>> We weren't expecting to hear very much. And we were a little bit shocked because we did see a lot of other sounds. We saw ships. We saw marine mammals that were typically very near the surface. So the sound was getting down into the deepest parts of the canyon--propagating down in there. Our analysis packages, you know, transform the data into a visual display. We call it a spectrogram. Basically what the spectrogram is is a time-frequency breakdown.

DZIAK>> It makes it fairly easy to see what the different sources of sound are on the record.

So when an earthquake goes by, it'll show up as a big yellow blip.

Baleen whales are much higher frequency, giving anything from fifty to a hundred hertz or higher.

When a typhoon rolled through, like we had at the end of the record, it makes so much noise in the whole water column, from the wind and the wave noise coming up the sea surface, that that whole bandwidth of sound is all bright yellow. So that stands out.

It's been known since the 1960s that sound is increasing in the ocean. And this is thought to be due to increasing global shipping because of increases in global commerce worldwide.

What we don't know is how this increase in sound is affecting marine ecosystems and marine animals that use sound to navigate or even to find food.


HASHIMOTO>> That is the motivation why we are studying this trend of ocean noise. What we're collecting now would help us compare the data 10 years from now.

HAXEL>> In the true vein of ocean exploration, it's allowing us to look at the earth in a new way.

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