Name: The Deep Ocean Noises We Still Can’t Identify
Uploaded: 2025-04-01T04:53:17.000Z
Duration: 15 min 50 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Permeating the ocean in every direction is a mystery that has haunted scientists for decades.

A mystery that began as tensions between the U.S. and the Soviet Union were coming to a boiling point.

During the Cold War, different branches of the American military set up stations around the world to monitor Soviet activity, including in the deep ocean.

SOSIS, a classified network of passive very specific goal in mind, to detect Soviet submarines.

But when the Cold War fizzled out in 1990, the Navy decided to change gears.

It offered scientists at NOAA the opportunity to use their sonar arrays in the Pacific to monitor environmental conditions.

It would give researchers the ability to monitor volcanic activity in the Pacific Northwest and study hydrothermal systems.

By 1991, NOAA was fully integrated into the system and began recording data.

But as soon as they started listening, they started hearing a strange sound.

The repeating pulses sound almost like an underwater car alarm, or some strange geologic process that we don't understand.

The noise is so loud that it can be recorded throughout the Pacific.

And more than 30 years later, it still hasn't stopped.

It was named upsweep, but maybe sound from hell would have been more fitting.

And as spooky as this was, it was only the start of the strange sounds the scientists recorded.

And the loudest sound of all came to be known as the bloop.

This sound was picked up by placed more than 3,000 kilometers apart.

Were the scientists picking up clandestine military exercises?

It turns out the ocean is much, much noisier than we'd ever guessed.

As more research stations have placed hydrophones across the oceans, we've gotten better at identifying certain things.

But there is still so much we still can't identify.

Why does the ocean have so many strange sounds?

And why have scientists managed to guess at the origins of certain sounds while others remain an utter mystery?

At its most basic level, sound is compressed energy, a vibrating wave.

It requires a substance to travel through, whether that's solid, liquid, or gas.

Like the iconic tagline for the movie Alien says, in space no one can hear you scream.

That's because space is a vacuum with an extremely low density of particles available for sound to vibrate through.

Given the importance of particles in carrying sound, it's probably no surprise that noise travels differently above water and below.

Water molecules are much more tightly packed than gases, making the ocean about 800 times denser than air.

So when a sound wave vibrates a molecule of water, the vibration gets passed on much faster to the next molecule than when sound moves through air.

In fact, sound travels almost five times faster in water than in air.

But the distance that sound travels in water relies on more than just speed.

The physical and chemical properties of the ocean all contribute to how sound waves move.

Temperature, salinity, and pressure all play a role.

Near the ocean surface is the lowest pressure, but the highest temperature.

And the high temperature causes sound to move faster.

In the deepest parts of the ocean is the coldest temperature, but the highest pressure.

And in that case, the high pressure is what causes sound to move faster.

But between a few hundred and a thousand meters is a zone of low temperature and relatively low pressure, where the speed of sound is minimal.

A sound wave in this channel will naturally radiate in all directions.

But when it travels into shallower or deeper water outside of the channel, it encounters an area with faster sound transmission.

And when the sound waves encounter this, the waves tend to be refracted or bent back towards the of lower speed without losing much energy.

This means that sounds tend to stay in this channel, traveling slowly over great distances.

This zone is known as the so far channel, or the deep sound channel.

It preserves sound so well that in an experiment from 1960, the sound of explosives detonated in the waters off the coast of Australia were heard all the way in Bermuda, nearly 20,000 kilometers away.

Thanks to the so far channel, scientists can monitor everything from underwater volcanoes to earthquakes.

And as scientists have learned about the way sound moves in the ocean, they've been able to listen in more and more.

They've placed hydrophones and other passive recording systems all around the world.

And it turns out the ocean is a very noisy place.

As of the most recent surveys, there are 126 marine mammal species, around 35,000 known fish species, and nearly 250,000 marine invertebrates.

And a lot of these creatures are soniferous, or sound producing.

We didn't even always know that whales could sing.

But today we know that all marine mammal species make sounds, either echolocation for hunting or sounds for communication.

In fact, certain baleen whales communicate at frequencies that are specifically suited to so far, allowing them to stay in touch over long distances while migrating.

But in at least one case, the cetacean communication seemed to go wrong.

In 1989, researchers picked up calls from the North Pacific that sounded like a blue or fin whale.

But instead of being in the normal 15 to 25 Hertz range, this whale was calling at 52 Hertz, a much higher frequency.

Nicknamed 52, the cetacean earned the moniker of the loneliest whale, because scientists believed its wrongly pitched calls might mean it had trouble interacting with its species.

The unusual whale's voice continued to be picked up for decades, leading scientists to speculate that it was a malformation, or maybe that the whale was some kind of hybrid between two species that don't normally mate.

It's a mystery that still hasn't been definitively solved to this day, though some now think there may be more than one whale communicating at this frequency. 52 might not be the loneliest whale after all.

And mysterious whales are only the start when it comes to see creatures making strange sounds.

Forget Cthulhu, there are probably hundreds of species of fish and invertebrates who chatter away without us being able to identify them.

For example, it took years for scientists to figure out that the crackling sound that they heard near coral reefs was made by snapping shrimp, whose claws produce a loud snap when they snap them shut fast enough to create a projectile, lethal bubble they use for hunting.

There are also daily choruses in coral reefs around the world, when the intensity of sound increases by two to three orders of magnitude after sunset and just before sunrise.

Scientists don't know how many species contribute to this sudden cacophony, but in one case they discovered that a major contributor of the noise around New Zealand came from hungry sea urchins.

Their skeleton was acting as an amplifier for the sound of their chomping.

The ocean is chock-full of organisms who are making noises, whether it's because of their hunting or their feeding or just because they want to stay in touch with friends.

And all of that noise means there are a lot of sounds we haven't identified yet.

But on top of the organisms are all of the geological processes happening underwater, and that adds yet another layer of complication.

As we've talked about in previous videos about underwater volcanoes, the seafloor is a hotbed of geologic activity.

Tectonic plates spreading apart or subducting under each other create magma and earthquakes and even violent eruptions.

All these geologic processes produce sounds that can be picked up on hydrophones.

But there are also massive glaciers and icebergs in the North and South Poles, and those huge slow-moving structures also create noise.

In fact, they're now thought to be responsible for multiple noises that were previously unidentified.

Remember the bloop, the loudest ocean sound that's ever been recorded?

Researchers heard it in 1997 on hydrophones scattered across the Pacific.

They were trying to listen to underwater volcanic activity, and this noise was nothing like the sounds they'd been hearing.

Maybe it was a secret military exercise, maybe it was a giant squid, maybe it was a really really loud whale, or it could be an undiscovered deep-sea creature.

Then in 2005, researchers put hydrophones closer to Antarctica and captured the bizarre noise again.

It was an ice quake, the incredibly loud sound of an iceberg cracking and breaking away from the Antarctic glacier.

The more scientists listened to the movement of ice, the more they realized it explained other mysterious sounds too.

The noise Julia is now thought to have been a large iceberg running aground, its bottom slowly scraped away by the seafloor.

But even as researchers have expanded their arrays, certain sounds have remained a mystery.

That's the case for upsweep, the repeated lifting noise that scientists have been hearing around the Pacific for more than 30 years.

Although it's getting quieter, the sound can still be heard.

And even weirder, it fluctuates seasonally, its intensity peaking in the spring and fall.

The origin point of the sound is thought to be in an area of activity, but we still don't know what it is.

It's yet another mystery of the deep ocean, one that we may never solve.

Despite all the things we don't know yet about underwater sounds, there are a few key things we're becoming more and more aware of.

First, a lot of organisms like living in noisy neighborhoods.

When researchers played recordings of healthier reefs around reefs that had been degraded, 50% more fish ended up repopulating the degraded reefs than those without any recordings.

The same preferences are true of coral larvae, who spend an initial life phase away from the reefs before settling back into them to grow into coral structures.

Research like this seems to prove that noise plays a crucial role in these coastal communities.

But the other thing researchers have proved is that humans are increasingly contributing to ocean noises, and we do not make the kind of noise that aquatic species appreciate.

Motorboat noise around reefs has a negative impact on fish reproduction, and shipping traffic definitely causes issues for whales, who hunt and communicate using frequencies that are similar to the noises the ships make.

Subtitles ListPlay Video

The Deep Ocean Noises We Still Can’t Identify

figure

tend

brilliant

identify