So you’ve heard a white noise.
Did you know there was pink and blue noise?
And indeed perhaps green noise, and red noise, and a whole range of other noises.
Where do all those different colors come from?
And what is white noise anyway?
How can noise have a color?
Yeeh,so I can just do it here. There we go, yeah
Okay, that’s white noise.
So that’s the sound of a signal,
which has absolutely no periodicity to it.
It’s entirely and utterly random.
Why we called it white noise
Well, we call it white noise in an analogy with spectrum,
with spectrum of light from a rainbow, for example, or any type of spectrum.
So all frequencies contribute equally.
So just as you have with white light
all colors contribute equally, in this case, all frequencies.
What does that mean?
Well, you can think of a wave
and a wave varies in time.
So if it’s varying with a slow frequency,
it’s changing on slow timescales.
And it’s not, you know, very rapid.
But then you can also have high frequency waves,
which oscillate back and forth very very quickly.
So you get a difference between a tu tu tu tu and tu tu tu….
That’s what I’m talking about.
You mix those all together all those different frequencies
from the very very slow to the very very high,
and you mix them all together equally.
And what you get is white noise.
So what you were hearing was a sample of white noise,
which has been generated very simply on a computer,
which covers frequencies from very very low close to zero Hertz
all the way up to about 20 kilohertz, something like that.
And it’s an equal mixture of all those frequencies.
And that’s what this is showing us.
It’s showing us the power associated with each frequency.
And so you mix it all up so all the powers contribute equally,
and what you get is white noise.
So that’s a spectrum for white noise.
So just as we have, you know,
if you have a pink color or a red color or a blue color in terms of light,
如果你看到过粉色 红色 蓝色的灯光
It means that certain frequencies are dominating,
certain waves and certain frequencies are dominating.
If you’ve got pink noise,
then what you have is the lower frequencies,
which are moving towards the red end of the spectrum
or contributing more.
So for you, if we look at aspect for a pink noise.
You hear any difference at all?
Was that lower…was that supposed to be a lower pitch?
So, well, it’s no, it’s… that’s meant to be pink noise.
So it’s meant to be different from white noise.
Can you hear any difference?
We’ll replay the two back to back and see if you can hear any difference.
Can you hear that lower frequency rumble?
-Yeah, it’s deeper. -It is. It’s deeper.
-是 声音更沉 -对 更沉
And that’s what we’d expect,
because in this case when we look at the frequency spectrum,
then what we find is instead of it being flat, it tails off.
So what we have is the lower frequencies contribute more than the higher frequencies.
So we hear that rumble
and in fact the 1/f noise if you listen to it again.
Sounds rather like rainfall.
Listen, those’ve must been sitting inside the unison of the rain outside.
– Okay. – Did you just said 1/f?
Yes, did I just say 1/f?
Okay, yeah, so that’s how the frequency spectrum goes.
So the the power in this case goes inversely with the frequency.
So as we’re going up in frequency,
the power is dropping down,
so it goes as 1/f.
So the white noise has no dependence.
So no depends on frequency, so it’s a constant, so it’s flat.
So, but we can alter of blue noise.
And you can probably guess what’s blue noise is.
-That’s not blue noise. -That’s not blue noise.
Yes, that’s certainly got a periodic tone.
With 1/f, so it falls off with frequency.
So it’s inversely dependent on frequency.
If we have blue noise,
then you probably can guess what it’s going to do.
But, let’s have a listen to blue noise first of all.
The power last time was proportional to 1/f, so it’s falling off with frequency.
Now it’s proportional to F, so it’s growing with frequency.
And it’s exactly the same, so what we’re doing with 1/f?
It’s what waiting it towards the lower frequencies getting redder or getting pinker.
What we’re doing now is we’re waiting it towards higher frequencies getting bluer.
When I think of white noise,
I think of that fuzz on the TV.
That’s exactly, that’s a visual representation of what we’re hearing here,
in terms of exactly the same idea,
where we get a great deal of frequencies all contributing together.
Once we have all those frequencies contributing,
so we don’t have a spectrum with a ramp like it on this,
where it’s a flat spectrum.
We call that white noise,
in some cases, depending on the equipment you have;
and depending on the type of setup you have;
and depending on how your area is working.
You might have deviations from white noise.
But your white noise means that you have got up everything contributing to the same extent.
You’ll get a lot of websites saying that
what you should do is fall asleep with pink noise,
because it gives you a more sort of harmonious brain rhythm.
There seem to be some papers that make suggestions along those lines.
I’m not entirely convinced
I’ve got to admit, I must admit that
part of me thinks that what we should do pretty
is just record a lot of white noise and pink noise and blue noise,
白噪音 粉噪音 蓝噪音并将它们
and send it out there in charge.
Charge a little bit of money for it so I think we could set up a business fairly quickly.
I wanna hear black noise, you always wear black.
Oh, that’s interesting, there is indeed, there is even black noise.
噢 那真有趣 真的有黑噪音吗
There is black noise.
-So. -What’s black that show there is no noise.
Yeah, exactly, that’s exactly what it is.
Black noise is an absence of any noise at all.
It’s, but, it’s even to find you can find a wiki entry on black noise,
which I didn’t even realize until very recently.
-That’s what we should do, so black noise. -Yes. [laugh]
-我们应该制作黑噪音 -是的 ［笑］
There is that concerto, isn’t that? That’s um…
不是有一曲协奏曲嘛 是那个 嗯
that piece of classical music, meant to be classical,
just like a time of 4′ 32″ or something,
which was just silence, just pure silence.
That’s what it is.
It’s called John Cage, isn’t it?
There’s something ironic that like, you know, heavy metal people wear black,
有些讽刺 你知道 玩重金属的喜欢穿黑色
and yet black noise is silence.[laugh]
No, that’s good, yeah absolutely.
And that’s because we interact with it ultimately,
because we interact with our environment.
And that doesn’t require consciousness,
It’s just, you know, there’s just the very fact that these waves,
these quantum waves are getting scattered off of objects.
So you’ve heard a white noise.