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 anywhere
how can noise have a color yeah so i can
just do it here there we go yeah
okay so that's white noise
so that's
the sound of a signal which has
absolutely no periodicity to it it's
entirely an utterly random
why do we call it white noise well we
call it white noise and an allergy 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 and so if it's
varying with a slow frequency it's
changing on slow time scales 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 the difference between a
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 our 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 it
means that certain frequencies are
dominating certain wavelengths 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
are contributing more so if we if we
look at a spectrum for pink noise
did you hear any difference at all was
that low was that supposed to be lower
pitch so well it's not 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 play 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 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 and so what we have is the
lower frequencies contribute more than
the higher frequencies so we hear that
rumble and in fact the one over f noise
if you listen to it again
sounds rather like rainfall
listen to it imagine being sitting
inside and you listen to the rain
outside
you just said one over f
yes did i just say one over 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 one over f
so the white noise is no dependence so
no depends on frequency so it's a
constant so it's flat
so but we can also have blue noise and
you can probably guess what blue noise
is
that's not blue noise that's not blue
noise
yes that's certainly got a periodic tone
hello
with one over 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
one over f so it was 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 one over f is we're weighting it
towards the lower frequencies getting
redder getting pinker what we're doing
now is we're weighting it towards higher
frequencies getting bluer
when i think of white noise i think of
that fuzz on the tv what's that 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 um
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 aerial is working you might
have deviations from white noise but
your white noise means that you have got
everything contributing to the same
extent you've got 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 brady is just record a
lot of white noise and pink noise and
blue noise and send it out there and
charge charge a little bit of money for
it i think we we could set up a business
fairly quickly
phil i want to hear black noise you
always wear black oh that's interesting
there is indeed there is even black
noise there is black noise what's black
so surely that's
exactly that's exactly what it is black
noise is an absence of any noise at all
it's but it's even defined 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
there is that concerto isn't there
that's um that piece of classical music
or meant to be classical which is like a
time 432 or something which is just
silence just pure silence
that's what it is i think it's called
john cage isn't it there's something
ironic that like you know heavy metal
people wear black and yet black noises
silence
no that's good yeah absolutely
and that's because we interact with
ultimately it's because we interact with
our environment and that doesn't require
consciousness it's just you know just
the very fact that these waves these
quantum waves are getting scattered of
objects