My Love Affair with Pink Noise

My Love Affair with Pink Noise

I have a music project on my computer called "The Sound Lab". It's basically where I play around with stuff, outside of making songs. A sandpit of sorts.

The stuff I've done in The Sound Lab includes playing around with:

• Comparing results of different guitar effects, amplifier and speaker cabinet simulators
• Merging of different drum samples
• Poly-rhythmic beats

All this stuff sometimes generates ideas which go onto making songs.

WTF is Pink Noise?

Pink noise is static noise - but it's a special kind of static noise. As I understand it, it follows your ear in that it sounds the same volume at the lowest frequencies, as it does the highest frequencies.Wikipedia says:

In pink noise, each octave (halving/doubling in frequency) carries an equal amount of noise energy. ... There is equal energy in all octaves of frequency. ... At high enough frequencies pink noise is never dominant. (White noise has equal energy per frequency interval.)

White noise on the other hand, which is also static noise, is completely random and dominant at higher frequencies as hiss. Anyway, that's how I understood it. Here's a link to a pink noise MP3.

And...?

So why is this even relevant? Well, a few weeks back I discovered that pink noise is used by some people when mixing songs. They basically adjust volume levels of each instrument until it's hidden behind the pink noise, to ensure that nothing is over-powering the frequency range.

So I tried it, and it kinda works. I use it as a measurement for each of my mixing stages. At the moment (and this may change as I learn new stuff), I gain-stage all my raw recordings to about -18dB of pink noise. I do the same at mixing, gain-staging post-FX levels to about -9dB of pink noise. These are just rule of thumbs and as I learn more about mixing, I might change things around a bit.

Full Audio Spectrum Analysis

Below you can see comparisons of some tracks I recorded - rhythm guitars, bass, drums and pink noise. Before any mixing or effects processing has occurred, you can see how each instrument  slightly overlaps into each other's space. This means I need to filter (scoop) gaps into the tracks during mixing, so you'll be able to hear each instrument clearer overall.

Spectrum analysis of rhythm guitars (green), bass (blue), drums (magenta) and pink noise (purple)

But more importantly using pink noise gave me an idea for doing other stuff. I love my science and I love empirical evidence. And as I entered into this new world of digital audio effects, amplifier and speaker cabinet simulators, I needed something to be able to compare against.

After playing heavy metal in a garage the size of a very small car for years, my hearing is going downhill fairly quickly, so that wasn't something good to use to compare anything with. But this pink noise, it was perfect. I could pump pink noise into anything and see what the output looks like.

Below is a graphic of a renowned amplifier simulator called LePou's LeXTAC. LeXTAC has three input channels,

• Ch 1 (Clean/Yellow): gain, bass, middle, treble, contour, power amp gain volume, 3 positions pre eq, gain boost.
• Ch 2 & Ch 3 (Blue & Red): gain, bass, middle, treble, contour, power amp gain, volume, 3 positions pre eq, gain-structure, gain boost and plexi mode.

Comparing LePou's LeXTAC Red (green), Blue (blue) and Yellow (magenta) channels to pink noise (purple)

At the default settings, you can see the Clean/Yellow channel (magenta) is significantly louder than the Red and Blue and maintains the bass frequencies better than the other two. Even if I drop the overall volume of the Yellow channel, I'll still need to consider louder bass and treble response.

To be perfectly clear, this was all relative. I wasn't expecting to take measurements or rely on concrete data. It was a simply a way to say "these amp sim channels drops the bass and follow the pink noise curve, while this one is flatter and has more bass and treble".

Comparing to your Favourite Songs

The other thing you can do is compare it to your favourite songs. One of my all-time favourites is Nine Inch Nails, The Wretched. It goes through a number of themes, but my favourite bit starts at 1:48. It has all these weird effects, vocal effects, the beat. Here is the spectrum analysis of this song part compared to pink noise.

Comparing Nine Inch Nails The Wretched to pink noise

Don't get me wrong, frequency spectrum analysis isn't the only thing that makes a song. Mid / Side separation would play a huge part, as I'm sure a bunch of other factors - but this is a simple way to see how the mix "looks" when comparing it to your own mixes.