Hearing is incredible.
Think about it: a tiny little bit of tissue in your ear, a tenth of a millimetre thick,
moves in response to changes in air pressure,
and converts them into tiny vibrations in fluid,
and then those get converted into electrochemical impulses that go the brain,
where they are somehow decoded into what you experience as sound.
And if all of that is working properly,
then you're able to pick out one source of sound from another, in 3D space,
and your brain is optimised to pick out words and language
even through huge amounts of noise.
It'll even filter out constant, steady noise like a fan or the wind whistling through trees.
To give an idea of just how difficult a task that is:
this is the waveform of the sound that's on this video.
Same information, just presented differently,
but it's not something that you can make sense of with your eyes.
And it's not like your eardrum only resonates at a few frequencies.
Human hearing in a healthy, young person runs from
somewhere up around 20,000 cycles a second, all the way down to 20.
Which means the eardrum can pick up air movements with wavelengths
that range from a couple of centimetres for high frequencies,
to 10 or 20 metres for really low bass.
The sort of low, rumbling bass that you would get from, say, a jet engine.
Just over there is Amsterdam Schiphol airport.
In terms of aircraft flying in and out, it's the busiest airport in Europe.
Six runways. Two control towers,
one just for the new runway that's over there that opened in 2003.
That runway is five kilometres away from the terminal.
If you look at aerial photos,
you can see plane after plane after plane lined up on a fifteen-minute taxi,
including going on a bridge across a road and a canal.
It was raining when my plane landed, but I just about got that shot out the window.
But there was one residential area, just back there, where there was
nothing but flat ground between those houses and the back end of jet engines.
I mean, of course it was flat ground, it's the Netherlands,
but there was one spot just back there where it got significantly louder
for the people who lived there.
And those local residents were not happy.
Of course, the one day I'm here,
they're actually landing on that runway, not taking off
so the engines are pointed the other way, but the point still stands.
The local residents were not happy.
This is the solution.
Well, not a solution, at least something to help.
This is a park that serves two purposes: one, to be land art,
the sort of high-concept big sculpture that's created
by moving enormous amounts of earth and rock.
This was designed by an artist.
I mean, I'd send up a drone to show you, but, you know, airport.
But the second purpose is sound dampening.
These ridges are metres apart, roughly, very roughly,
around the same wavelength as the low rumble you get from a jet engine.
Not exact, of course, but in the same order of magnitude,
close enough to be disruptive.
So rather than the sound waves just rolling over the land,
instead they're scattered in all directions, up and away, not onwards.
Not perfectly, not even close, but enough to bring the noise level at those houses
back down within acceptable limits.
The architects claim that one of the inspirations for this
was people noticing that the engine noise sounded quieter when the fields were ploughed.
Because, yes, your brain can filter out constant, steady noise.
It can even, over time, get used to filtering out intermittent, loud noise,
like living next to an airport.
But that filtering job is a lot easier if the noise would just be a little less loud.