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PINK NOISE VS WHITE NOISE
Hi everybody I'm Dennis Foley from Acoustic Fields and today I want to talk about the
difference between pink noise and white noise because it's driving me crazy! No, not really
but I get a lot of inquiries, almost weekly, about these two terms and people are really
getting them confused and twisting around what they actually mean and more importantly
what we, as engineers, use them for. So let's talk a little bit about it.
Pink vs White noise. Pink Noise is the noise that you use to EQ your equipment. We've all
heard, well you run pink noise through your equipment and you do your measurements and
stuff like that especially with EQ. Pink noise is very, very, very important. That's the
noise that we use for our equipment. So, some people get that right, some people think white
noise is the way to go and I think here is where the confusion lies and if we get some
definitions and a little bit of science behind it I think that it will be a lot clearer for
all of us.
Pink noise is the energy in every octave. Okay? Let me repeat that, pink noise is the
energy in every octave. White noise is the energy in every frequency. That's the major
difference between the two noises if you will.
We perceive sound in octaves, so we perceive sound in pink noise and people will say well
pink noise is tailor to the frequency response to our ears. Well not really true. Pink noise
is the energy in every octave, we perceive sound in octave bands and the physical structure
of our ear, if you look at it closely, is designed to work with octaves.
The octave is how we hear sound. Our ears are constructed in such a way that it's octave
friendly so we hear sound in terms of octaves. Inside that octave is pitch. You hear singers
say "Oh he has good pitch" or "She has good pitch" well that pitch is found inside the
octave range of our hearing.
If a high note jumps off an octave and a low note jumps off an octave, it's the same number
of keys on a piano or the same number of frets on a guitar. The notes are the same. Sound
producing activity or the notes, to our ears are a few bands. Maybe 5 or 6 different bands
of frequencies but the number of frequencies is many.
Okay let's illustrate this point through example and I think we're getting to the real core
of the issue here and through this illustration we will really get a hang of the difference
between pink noise and white noise.
From 400 cycles to 500 cycles that's a 100 Hz difference, that's 1 octave. From 5k or
5,000 cycles to 10,000 cycles, that's 5,000 Hz but it's still 1 octave. This is the key,
right here. Look at this ratio. Each one of these frequencies is exponentially more in
mathematical number than those, so we have more frequencies. The relationship is the
same, the octave relationship is the same but look at the huge mathematical difference.
So white noise has more energy from 5K to 10K than 400 to 500. So there's more energy
because there's more frequencies.
So for further clarification, we know that pink noise distributes energy the way we hear
in octave bands. Pink noise, the energy is the same from 400 to 500 as it is from 5K
to 10K. Pink noise is the equal energy per octave. Where pink noise is all about pressure
and energy in each octave, white noise is all about the individual frequencies in each
octave. So you can see hopefully the difference here. I am really hopeful that this will clarify
some of the things that I've been hearing and some of the questions I've been getting.
Thank you!