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[Music start]

From Defacto Sound, you're listening to Twenty Thousand Hertz... The stories behind the world's most recognizable and interesting sounds. I'm Dallas Taylor. This is the story of what sound is like under water.

[clip: The Bloop sound]

The sound you just heard is one of the most mysterious underwater sounds we know of. It’s called “The Bloop”. It was recorded in 1997… and it’s unbelievably loud. The sound was roughly triangulated to be coming from a remote region of the southern Pacific Ocean, just west of the tip of South America. The microphones that captured this sound were over 3,000 miles away.

[Bloop sound again]

Could it be a massive, undiscovered monster from the deep? Researchers are still discovering new aquatic life every year. But this sound was several times greater than even the loudest animal in the world, the blue whale. NOAA, the National Oceanic and Atmospheric Administration now believes it was an icequake, or an iceberg scraping the ocean floor. Or was it?

The world’s oceans cover 71% of the Earth’s surface. And while there are a few areas of land that have yet to be explored by mankind, that’s nothing. Almost 95% of the oceans have never been seen by human eyes. It’s like an alien planet, but it’s Earth.

“The Bloop” is only one of the many mysterious, possibly unexplainable, underwater sounds.

Another, is the Western Pacific Biotwang heard in the Mariana Trench.

[Western Pacific Biotwang clip]

Experts think that it’s a new type of dwarf mean ki whale call we’ve never heard before.

[dwarf mean ki whale call]

There’s also a weird beeping sound coming from the ocean floor off the coast of Northern Canada. [beeping clip] It’s so bad that Inuits can hear it on land and it’s driving away animals. The Canadian military even investigated it and can’t figure it out.

There are other unexplained sounds with interesting names like “The Upsweep”… [clip] “The Slow Down”… [clip] and“Julia”… [clip]. As we uncover more of the ocean’s sonic mysteries, maybe one day we’ll learn the truth.

Underwater sound has always been interesting to me. As a kid, I loved to stick my head underwater with a friend and try to talk… [underwater talking SFX] then we would try to see if we could understand what the other was saying. [talking underwater, mildly understandable] It was a fun game, but I always wondered why I’m able to hear anything underwater. There’s no air, so how could sound travel?

Al: There are physical properties of the water that make sound behave in very different ways.

That’s Al Jones, he’s an underwater acoustician, and a former Navy sonar technician. He’s spent years listening to and analyzing water as a medium for sound.

Al: For starters, sound travels about 11… 1200 feet per second in air. Multiply that times four and that's the speed of sound that you get in the water. It's faster in water because of the properties of the medium itself. For instance, sound travels in pure steel, about 14 times fast as it does in the air, so the denser the medium becomes, the more molecules that the sound wave gets to interact with, and it proceeds down its path inherently faster that way.

As a sonar technician on a submarine Al’s role was vital to the safety of the vessel. How important is sound to the operation of a sub?

Al: Sound is crucial, just in the same way that your eyes are, you're navigating around in a thing that does not have windows, does not have outside cameras, you're just driving, essentially by sound.

After a while it becomes very intuitive for you to be able to listen in one direction, notice, that there is something that way. Hearing those things drives us to either analyze what that thing is, or to think, "Danger, danger, we need to drive away from that, because we might hit something.”

Since I don’t have a submarine or sonar equipment, what might it sound like if I tried to listen to the underwater sounds of the ocean?

Al: The first thing that you'll recognize when you're trying to listen underwater is all of the competing activity that you're trying to listen through, in order to find something interesting. Some of the organic things that you hear when you are recording underwater, the motion of the water is very loud, and it's ever-present as you're listening.

Hearing the motors of other ships, like a cruise liner, or even a trawler motor.

The way sound behaves underwater is pretty fascinating. How does sound affect marine life? To answer that question, I spoke with John Hildebrand, who is a professor at the Scripps Institution of Oceanography. He’s an expert in the field of underwater sound.

John: It turns out that the light does not propagate very far into the ocean. If you're at the surface of the ocean, there's light and then maybe the first 100 meters or so in the upper part of the ocean, it's not a very good media to sense your surroundings. We are very visual animals, the sight is our primary way of sensing things and we use sound as a secondary sense but in the ocean, it's exactly flipped because light doesn't propagate very well but sound propagates very efficiently.

I wondered, how were we even able to record these sounds.

John: It's basically underwater microphones, they’re called hydrophones. Once we started to have this technology, then we became aware of this whole universe of sounds that are underwater both from natural phenomena, the sound of bubbles that are created near the surface [bubbles SFX] or the wind blowing across the surface [wind SFX] and waves breaking [waves breaking SFX], but there’s also this entire universe of sound that's made by marine organisms even small creatures that make quite intense sounds.

Al: You'll hear invertebrates more than just about anything else, and they make a lot of noise. Shrimp [Shrimp SFX], crabs [crabs SFX], jellyfish [jellyfish SFX], even starfish make sound [starfish SFX]. When you have a lot of shrimp together, that tends to sound like bacon grease frying in a pan [shrimp SFX]. The snapping of their claws is a manner of communicating or a manner of drawing prey toward one another. If you have a lot of shrimp you’re going to hear a lot of activity.

John: People described some of the sounds of whales as a song [whale song]. It's song because it's repetitive, it's melodic in some way.

Al: If you've been out on a whale watching cruise, you can sometimes hear them so loud, you can hear them out in the air, because they are so loud underwater.

[whale song out of water]

When you're listening underwater, to whales, that can be incredibly cathartic. It's such a pure sound, the way that those sounds manifest themselves underwater [whale song]. Hearing them underwater, in person, is quite an experience.

John: Baleen whales, the large whales are a little different. They do have songs where the males will just broadcast the same thing [Baleem whale song]. Songs have meaning and from even hearing a very small piece of the song, you can relate the whole meaning.

You know there's this game that's called name that tune. If you just hear a few notes, then I can name the rest of the tune. I can do this with you if I say, "Jingle." right?

You know the rest and you're thinking about Santa right and the presents under the tree. There's a whole complex of things that go along with that. A song is a very efficient way if there's a standardized message you want to get across. It's a very efficient way of doing that because from tiny pieces of it, you get the whole message [whale song]. "I am the one that you would like to breed with. I am the most fit male that you will encounter. Come on over."

So basically, whales have their own version of a love song.

John: The blue whales or large whales are specialized for broadcasting these sounds a long way so that if your girl is 20 miles away, she'll still hear you. The Baleen whales when they sing, the big ones that are singing very intensely. Those are very intense sounds. If you position your body near a Baleen whale where they're making these sounds, your whole body would be vibrating. Now, how far does it go? At low frequency, there's essentially no absorption of sound at all. Water is like a window for sound. So that's why these intense songs of the large whales like a blue whale, you could have a whale off of California and you could probably hear it in Hawaii.

The vocalizations of whales are some of the most beautiful sounds in nature. But unfortunately we’re in danger of losing them. Or at least, driving them away. Underwater noise pollution is on the rise. It’s a big problem that we’re just now discovering. We’ll talk about that, and how we can fix this problem, in a moment.

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MIDROLL

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The underwater world of the ocean is sound rich, just as much as it is here on land. Our ears are the perfect tool for our atmosphere, but not so much for underwater. However, on the flip side, the hearing instruments of marine life are perfect for their environment.

Unfortunately, marine life doesn’t have the ability to protect their own hearing, so we have to do it for them. Underwater noise pollution is a big problem, and we’re just now barely scratching the surface of it’s affects the underwater ecosystem. I wanted to know more about this phenomenon so I reached out to Christophe Haubursin at Vox.com. He’s done some great field research on underwater noise pollution so I'm going to have Christophe take over for a bit...

Christophe: I recently went scuba diving for the first time ever. And I went in expecting muffled peace and quiet, but as soon as I got down a few yards, I couldn't help but notice that there was sound all around me [motor boat SFX]. And it was coming from boats. As far as I can tell, the Earth's water is not silent.

So I did a little digging and according to the Scripps whale acoustic lab, man made or anthropogenic noise in oceans has doubled every decade for the last 50 years. And that is a really big problem for animals that use sound as their primary sense of communication. Just listen to this audio of how noise from a passing boat totally drowns out dolphin communication. [dolphin clip]

But arguably, the worst culprit of underwater sound is a process that sounds like this [underwater explosion SFX]. That is seismic surveying. It's a process that allows companies to essentially locate spots on the ocean floor where they can drill for fossil fuels. So you'll have boats with about 30 or 40 air guns that'll all go off at once [seismic surveying clip], and those will move back and forth over large parts of the ocean. And bubbles from the horns expand and contract about every ten seconds, typically, and that creates a huge amount of acoustic energy, and that helps them map geological structures very deep into the ocean floor. And that process is about as loud as a jet at takeoff. And this can go on for weeks at a time.

A study of seismic survey noise between 1999 and 2009 found that air gun sounds were recorded almost 2,500 miles away from the survey ship itself. And at some locations, they were recorded on 80% of days for over a year. And that changes how animals behave. For animals like whales who rely on complex sound communication systems to socialize and find food and mate, that poses a huge problem.

John: In many parts of the ocean we've raised the ambient noise level by 30 dBs. Now I'm going to say, "I'm going to move into your office and I'm going to increase that noise level by 30 dBs. A, I believe it would be very annoying but B, I think there's long-term damage. You're needing to wear ear plugs just to go to work.

A study by Susan Parks at Syracuse University compared recordings of North Atlantic right whale calls from the 2000s [2000’s whale calls] to those recorded in the 1950s. [1950’s whale calls] It seemed like the older recordings had been slowed down, [1950’s whale call] until she realized something amazing. The whales were calling in a different pitch. Again, here’s what the whale calls sounded like in the 50’s [1950’s whale call]. And here’s what it sounded like in the 2000’s [2000's whale call] She found that these whales are actually changing their frequency over decades. Why? Because the higher pitched calls can be heard more clearly amongst all of the noise from ships. This is the same concept as when you’re at a noisy party, you raise the pitch of your voice to project over the noise.

John: The Gulf of Mexico where the noise levels are so high. The whales that depend on low frequency sounds like blue whales or humpbacks they're all gone. They're not there.

There's only one Baleen whale that's left in the Gulf of Mexico and it confines itself to a little corner where the sound levels are not quite so bad. It's called the Bryde's whale and surprise there are only a couple dozen of them left.

The most pristine place where we've recorded right now is in the Arctic and it's that way because when the ice comes in, there are no ships and also, the ice keeps the surface of the ocean calm. Those are the lowest levels we've recorded anywhere.

Research suggests that human-made noise can damage marine mammals hearing organs, sometimes causing death. All of this sounds pretty foreboding, but John thinks a solution may not be too far off.

John: The first step is we got to care. We got to realize, "Yes there's a problem" and then we have to care. The quality of the ocean is based on the sound level just as much as it is on things like pollution from plastic and overfishing and all these kind of things.

If you go on a cruise ship, big nice awesome cruise ship, it's quiet and it's quiet because they want the people on that ship to have a good experience. They've done a lot of tricks to insulate all of the cabins and parts of the ship where people are from the noise of the propulsion and generators and all this thing so there are things you can do.

The Navy cares about this deeply because they don't want their ships to be detected. So what they found is you can design more complicated propellers, you can insulate all the machinery. You put the machinery on shock mounts. If you said, "Here's a commercial ship, we're going to have a sound criteria, if you output sound above this level, you cannot come into port," then the industry cares and they design ships that are quiet and then over the span of maybe a decade or two, we could I think get it down maybe 10 dBs or more. It would be a help.

Sight is our primary sense. But for marine life, sound is the way they communicate, breed, feed, and literally find their place in this world. The ocean makes up about 70% of the Earth, and we’ve only explored roughly 5 percent of it. It’s truly an alien environment, one that we still don’t completely understand. And in order to preserve it, we need to be aware of how we affect it. Just like cutting down the rain forests, the sound humans make could have just as devastating of an affect on the planet. But all is not lost.

John: I’m hopefully that there's some future technology that we haven't even thought of that can maybe do the same job without generating so much noise, but this is something that we have to pay attention to first.

In 2015 the Navy agreed to limit sonar testing in critical ocean habitats near Southern California and Hawaii. In 2016 NOAA unveiled a plan to assess the human impact on underwater environments and to use quieter research vessels. And in 2014 the International Maritime Organization adopted guidelines for lowering noise from commercial ships with noise-dampening techniques. Unfortunately these guidelines are not yet mandatory. But some experts believe, if instituted, it could lower ship noise by up to 99 percent. Now that sounds great.

Twenty Thousand Hertz is presented by Defacto Sound. A sound team dedicated to making the world sound better. Find out more, and get it touch at Defacto Sound dot com.

This episode was produced and edited by Kevin Edds… and me, Dallas Taylor… with help from Sam Schneble. It was sound designed and mixed by Colin DeVarney.

Thanks to underwater acoustician, Al Jones, who provided a great first hand experience about life on a submarine and sounds he’s recorded from the ocean. As well as John Hildebrand from the Scripps Institution of Oceanography. His passion for reducing sound pollution in our waters is only rivaled by his knowledge on the subject.

We’re also thankful to have been joined by Christophe Haubursin from “Vox dot com”. We live in a world of too much information and too little context. Vox cuts through the clutter. I’ve been a subscriber for years. Be sure to go over to Youtube and subscribe. You can find their channel at youtube dot com slash V-O-X.

Like the music you hear on this episode of Twenty Thousand Hertz? Each song is provided by our friends at Musicbed. You can listen to all of them on our exclusive playlist. Start listening now at music.20k.org.

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You'll find all of the links I mentioned in the show description.

Thanks for listening.