Developers tend to oversee audio and leave it for the later stages of production, which is a tremendous mistake because audio greatly contributes to the feel of the game. When there is good sound, it feels right. However, when the sound is bad or there is none at all, the game loses many points straightaway.
It is important to take audio into account from the very beginning. Use it to create a mood and provide constant feedback to the player.
Understandably, you might not have an audio artist or a musician on board throughout the whole project. So, what can you do if you lack sound design or composing skills? Worry no more, procedural effect generators can rescue you!
They are perfect for quick prototyping and game jams. In no time, with a little bit of tweaking, you can have a placeholder sound effect ready to be included in your game logic. The sound designer can replace it later with a more up-to-the-standard version.
In this recipe, we will take a tour around Sfxr, one of the procedural sound effect generators.
Before you start experimenting with Sfxr, you need to download it. Fortunately, the tool is free, open source, and cross-platform. Visit its creator's website at http://www.drpetter.se/project_sfxr.html and choose the download link that suits your purposes best.
If you are interested in taking a peek into the source code, Sfxr's repository is hosted in Google Code available at https://code.google.com/p/sfxr.
Sfxr does not require installation. Once you have downloaded and uncompressed it, you can run it normally. The user interface might seem cluttered because it presents all options on a single screen, but it is actually very easy to use.
Follow these steps to generate cool sound effects lightning fast:
- From the GENERATOR panel, you can choose the kind of sound effect you want: shot, power-up, jump, hit, and so on. Every time you click on an effect, it will generate a new random sound and play it.
- Feel free to keep clicking until you get something similar to what you are after.
- Once you have a base sound, the MANUAL SETTINGS panel will let you customize its properties further. You can change the wave shape as well as the myriad of parameters you can see in the screenshot. Every time you make a change, it is advisable to click on the PLAY SOUND button to check how the setting affects the result.
- If you want to stop working on a sound and continue later, you can hit SAVE SOUND. This will generate a file Sfxr understands. The next time you run the application, you can get it back with LOAD SOUND.
- The sample frequency is customizable, so you can switch between 44 KHz and 22 KHz.
- You can also alternate between 8 bit and 16 bit for the sample size.
- When you are happy with the sound you have, click on the EXPORT .WAV button to generate a sound file that is playable in Libgdx.
Great, now you have a sound effect you can use in your game straightaway. Easy!
There is no need for any explanation here, as there is no need to explain the Sfxr internals.
Sfxr is not the only procedural sound generation tool out there, although it is extremely popular and widely used for prototyping and game jams such as Ludum Dare. Here is a list of derived and alternative tools:
- Bfxr: This is very similar to Sfxr but with a wider range of settings, available at http://www.bfxr.net
- AS3fxr: An Action Script 3 version of Sfxr; this can be used from browsers and is available at http://www.superflashbros.net/as3sfxr/
- Sfxr for Android: This is a free mobile version of Sfxr, available at https://play.google.com/store/apps/details?id=be.minimal.sfxr
- Abundant music: This is a free browser-based procedural music generation tool, available at http://abundant-music.com
Additionally, it is worth mentioning SunVox, a free, cross-platform, graph-based tool for music composing. It does not do procedural music generation, but it is a simple enough tool to use for a non-expert to achieve decent results. It is available at http://www.warmplace.ru/soft/sunvox.