This article originally appeared in Dev.Mag Issue 26, released in October 2008

Interested in making your own sound effects for videogames? This month we'll be looking at Audacity and a few of the common effects that can be used to turn your humble blink-blonks into fantastic kaphwooms.

1_male, eh, Nandrew?

This article deals with a mildly technical side of sound production in Audacity, so it'll assume that you already have a wave file loaded up and ready for priming. In terms of format, you may want to look for a file that's based on the standard PCM WAV structure (it's the most common WAV file format, so you're probably using it already) with a 16-bit 44100Hz quality (these details will be shown in the info box to the left of the file when you load it up in Audacity). You can also opt for a stereo sound format, but mono means a smaller file size and will usually do the job just fine unless you specifically need two channels.

So, to clarify, you'll prefer these in an input file:

• PCM WAV format
  
• 16 bit
  
• 44100Hz (or similar)
  
• Mono

Higher quality is optional, but isn't always necessary.

If you really can't find an input file to meet these requirements, no biggie – you can still try to convert them to the desired format by clicking on the filename in the left info box and selecting the necessary properties in the pop-up menu. Also check the Edit -> Preferences -> File Format menu to make sure that your uncompressed export format is set to the 16-bit PCM.

Maybe some of you remember that funky little sound idea thing back in Issue 24. If you haven't checked it out yet, don't panic – you'll be able to understand this article just the same. But try have a gander at it anyway. Also be sure to grab your own copy of Audacity from here.

Right, now that we've got all the details out of the way, let's look at the interesting stuff.

The Audacity effects

Select all or part of the file that you've loaded up in Audacity (this can be done by clicking and dragging the mouse over the desired file component). This is going to be the section of the file that you apply your effects and filters to.

Now select Effects from the top menu. You'll see a whole list of neat things that can be done to the innocent sound file which is now under your control.

We won't be looking at every effect that's on display, but a few of the simpler ones will be covered. What follows is a description of several effects, giving you their job, their potential for game development and a few useful pointers to get you going in the right direction. Let's go!

Change Pitch

• Technical description: This effect alters, well, the pitch of the sound. How high or low the notes are, so to speak. You can plug in a spoken sentence and decrease the pitch for a deep, manly-man voice or conversely increase the pitch to make it sound like a chipmunk. Wheee!
  
• Game use: This is one of the most commonly used effects to tweak sounds. You may want to change the pitch of an in-game explosion. Perhaps you have a piano somewhere in your game and you want to get several pitch variations of the same sound clip. Or you have a nice cartoony game where you want to take a standard set of sound effects and make them all cutesy by swinging the pitch up.
  
• Hints: This filter is great if you want to speak in your game but need to mask your voice or simply make it sound cooler. Lowering or heightening the pitch just ever-so-slightly will greatly improve the sound in your own ears, and you could potentially voice several in-game characters simply by altering the way you speak each time and applying a pitch effect.

Change Tempo

• Technical description: This is the counterpart of changing pitch. Do you want the same sound to play much faster or a little bit slower than the one you currently have? Tempo can make a bwooooooooooom into a bwumph, and vice versa.
  
• Game use: Maybe you want a quick and tiny explosion noise but only have the Manhattan Project on your hands. Or maybe your character is using a weapon with a high rate of fire and you've only got sound effects which last for at least two seconds. No problemo! Increase the tempo until you're able to justifiably go powpowpow for as long as your character needs.
  
• Hint: By doing some extreme compression or extension of sound effects with the tempo changer, you'll actually start hearing some very, very weird things. This can be rather neat if you're looking for some exotic and/or sci-fi sound effects, so give it a shot.