Imagine you're diving in the ocean - I don't know what you're doing there to be honest
but your engulfed in the big blue.
Then out of nowhere, maybe infront of you, maybe behind you, maybe above or below you,
a large shadow appears - hundreds of times bigger than you.
It's a submarine.
Holy god, that's terrifying.
Even scarier is the thought that at any time they could turn on the active sonar.
Something that probably wouldn't even cross your mind, but that would be very bad for
you.
So what actually happens if you get hit by sonar?
Sonar is a navigation technique that uses sound to detect one's surroundings and measure
distances.
It's used by some animals like dolphins and whales, and its first recorded use by humans
dates back to 1490 and is credited to Leonardo da Vinci - that fella is always up to something.
There are two types of sonar.
Passive sonar and active sonar.
Passive sonar is basically just the act of listening for sound so you can detect things
like fish or other vessels.
Active sonar is what we're interested in, and involves emitting a sound from a transmitter
and using a receiver to pick up the sound's reflections off objects.
Sonar is used by both surface vessels and submersibles, by both civilians and military.
You might think sonar is a little "ping" sound like in the movies although a sonar technician
is more likely to refer to it as a "pulse" than a "ping", or you might even think it's
at a frequency undetectable by humans.
The truth is, sonar comes in a wide range of frequencies and can vary in its intensity
depending on what equipment is being used and for what purpose, but it can be incredibly
loud and travel great distances.
You can find videos on YouTube of divers apparently being pinged by sonar.
Now these are just videos on YouTube so we'll have to take them with a grain of salt but
the people posting these videos all seem to say the same thing, the sonar's sudden arrival
in the otherwise peaceful ocean is very frightening, and it's also very loud - you can feel it
in your body.
It's important to note that no submarine or any other vessel can be spotted in these videos;
and there's a couple of reasons for that.
One, this type of active sonar can travel great distances, and remember, sound travels
much faster and further through water than air.
Two, sonar operators are generally very careful in where they use high-intensity sonar, due
to its effects on marine life and divers nearby.
They usually only do it miles away from the coast, and because this kind of sonar gives
away their position, which is kind of the opposite of what you want to be doing in a
submarine - if you can hear it, they're probably just testing the equipment or training operators.
Here's a few examples of what different types of sonar sound like:
So how loud can sonar get?
Well, it's actually up there with the loudest sounds in the world.
The US Navy for example, has sonar emmitters that can generate up to 235-decibel pressure
waves.
These sound waves can travel for hundreds of miles underwater.
Even 300 miles away from the source they could be as loud as 140 decibels, depending on the
conditions of the water.
So if you can see the vessel when it's using that kind of active sonar, you're in a lot
of trouble.
100 decibels is around when your hearing can start being damaged, and 120 is around when
the sound starts to become painful.
At such high sound levels, the intensity of the sound can create significant pressure
changes in the water, creating something that's more akin to a shockwave than a normal soundwave,
almost like a bomb blast.
At 200 decibels, the vibrations from these pressure waves can rupture your lungs, and
that's no good.
Decibels are not measured on a linear scale, but a logarthmic one, so an increase of 10
decibels corresponds to approximately double the perceived loudness.
At 210, decibels, the vibrations would be enough to hemorrhage your brain tissue, and
that's definitely not good at all.
So if you're too close to a boat using high-intensity active sonar, the pressure waves could rupture
your organs and it's a pretty terrible way to die.
Thankfully, it's extremely unlikely to occur, and there are no records of anyone ever being
killed in this manner.
But even hundreds of miles away it could still be enough to cause painful hearing loss and
induce nausea and dizziness.
Thankfully, submarines and other vessels have various methods of deploying sonar, including
ultrasonic which would be undetectable to humans - their use of high-intensity sonar
is fairly limited for the reasons mentioned earlier; it gives away their position in a
big way and they're aware of how damaging it could be for nearby life.
In fact, in scenarios where a vessel is in port and may be threatened by underwater divers
with explosive charges, high-intensity active sonar is considered a possible means of defence.
So, even though it's possible, it's pretty much implausible that you would ever be hurt
by active sonar - they're just very careful using this stuff.
And your chances of coming across a military submarine are very slim; they typical operate
in remote areas at depths beyond the reach of recreational divers.
Although, I think even just hearing sonar would be terrifying, even when it's so far
away it doesn't do any damage.
The underwater soundscape is probably pretty calm 99.999% of the time; the most you're
gonna hear is bubbles and water moving.
Then out of nowhere, a loud piercing "ping" sound.
I'd never want to go back into the water if that happened to me.
Marine life seems to agree, as animals like whales will swim hundreds of miles to get
away from the sound of active sonar.
Some cause themselves injury or death by beaching themselves or rapidly changing depths and
suffering severe decompression sickness as a result.
Put yourself in the whales' shoes, or flippers or whatever.
Imagine one day we're all just chillin on Earth like we always are and then suddenly
we get hit by a terrible sound or blinding light by some alien species that are technologically
advanced to the point of basically being gods to us.
And the reason they did it was part of some experiment or operation beyond our comprehension.
They didn't even mean to cause us harm nor do they even really care, it's just a by-product
of something else they were doing.
If aliens exist and have the same level of consideration for Earth as we do, we're in
a lot of trouble.
And you're in a lot of trouble right now, if you haven't subscribed that is.
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Until then, stay safe.