A few months ago, I picked up a copy of The Computer Music Tutorial, by Curtis Rhodes. It got me thinking more deeply about sound than I ever have, and got me really curious about just how the hell sound works anyway, what the stuff is. One big concept in the book is the idea that anything that processes a signal is a filter, and there is no fine line between different kinds of filters. I admint, I don’t get this 100%, but to me it seems like another way to think of it is that you can make a huge amount of effects (any effect?) by imagining a room with certain properties. Most people know that reverb and delay are meant to give the illusion of being inside a space. They are models of what would happen to sound in a real space. So, if you, say, play a note on an instrument, what you actually hear is what happens after the sound leaves your instrument, and bounces around the room for a while.

Things start to get really interesting for me when I think about the fact that the room might give you back tones that weren’t in your original sound. In the examples below, I first play a high-pitched bleeph noise, and then send it through a reverb effect I built in SuperCollider. The reverb is just a bank of delays with random lengths, approximating what happens when sound bounces around a room. At first, it sounds like normal reverb. But then, as I adjust the lenghts of the delays, making them closer together, so instead of a scattering of sound, we get a quick, regular repetition, tones begin to emerge that weren’t there to begin with. The reverb is actually generating a tone that’s lower than the sound that’s being fed into the reverb. This begins to feel to me like the virtual room I’ve built is a very simple musical instrument. If we could change the position of the walls quickly (which you can hear me simulate in my computer representation) then we’d have a real instruement, capable of generating a range of pitches.

Here’s the dry signal:

And the wet signal, where the simple beep noise gets transformed, using nothing more than delays into a fairly nasty bass sound.

So, therefore, I proclaim that sound effects and sound sources are not such different things as they appear to be.