[whispering] I'm inside one of the Inchindown oil tanks,
an old oil storage facility in Inverness, in Scotland.
This tank is 237 metres long and it's not meant for humans.
When it was in use by the Royal Navy
all this colossal space would have been filled with fuel oil.
With these oil tanks, the Royal Navy accidentally created
the greatest reverberation chamber in the world.
Flat surfaces enclosed by solid rock,
and a chamber big enough that sound takes a whole second or more
to go off the far wall and bounce back.
But still narrow enough that you get lots of reverberation
from all the close surfaces as well.
- The construction started in 1938
and it carried on right through the beginning of the war
up to around about 1943.
The Admiralty had decided that they required bomb-proof storage for their oil.
So they set about building a number of oil tanks across Britain.
And this, Inchindown, is one of them.
The construction required six tanks to be built.
The entire complex could easily contain 100,000 tonnes of fuel
but one single Royal Navy battleship can drink 5,000 tonnes.
So it could go very, very quickly.
It is a truly amazing chamber of sound,
a cathedral of oil and a cathedral of sound.
- So now I'm going to shut up for a bit.
Preston here is going to fire a starting pistol,
a very, very loud bang.
On the screen is a visual display of that sound.
Different frequencies will reverberate for different amounts of time
so you will see that and hear that.
And as it gets quieter we will turn up the level
on the microphone so it's easier for you to hear.
Right, everyone ready?
Thank you to the Bannerman Group for letting us into the tunnels,
to Allan, Alan and Preston for helping with everything here,
to Matt Gray who is behind the camera
and who's had some musical experiences over on his channel.
Go for it.
Aagh!
That is terrifying.