Game Audio Guide
Welcome to the GameBurp game audio guide. This guide was created to give you some basic information on how to edit and use sound effects files. The ideas and methods can be applied to any audio files you have. You can download a free game sound effects pack here - www.gameburp.com/free-game-sound-fx
There's also a collection of 2000 sound effects specially designed for use in games and apps you can get on this website, more details here - www.gameburp.com
The examples in this guide use Audacity free audio editor. Audacity is completely free to use and open source which is why I include it in examples in this guide. You can apply these principles to any other audio editor as well.Audacity can be downloaded free from here - https://www.audacityteam.org Further information on how to use Audacity the manual is here - https://www.audacityteam.org/help/documentation/
I'll be updating this guide over time with more examples and details so check back. Use the navigation below to quickly jump to any section.
1 - Basic Game Audio Editing Tasks
Converting to Other Audio File Formats
Convert from Stereo to Mono
Convert Sample and Bit Rate
Changing Sound Volume/Gain
2 - Audio Problems to Avoid
Avoiding Audio Clipping
Avoiding Pops and Clicks
3 - Creating New Game Sound Effects
Adding Audio Effects
Layering Sounds Files Together
Using a Section of a Sound
Pitch Shifting & Time Stretching Audio
4 - 2000 Game Sound FX Collection - Usage Tips
Audio Mix & Volumes
Sound Files & Implementation
Sound File Management
5 - Useful Links for Game Audio
This section will go through some basic audio editing tasks using Audacity free audio editor. Please note: If you're using a game engine most allow you to import the uncompressed WAV files as they are and the engine will deal with the final audio output format for you. These audio editing guides are just if you need to edit the audio files yourself.
Converting to Other Audio File Formats
In general terms the most common audio files are the uncompress WAV and AIFF formats, and the compressed formats MP3, AAC, and OGG. The audio files in the '2000 Game SFX Collection' are in two formats. WAV stereo 44.1kHz 16bit, and compressed OGG (saved at 20% or 2/10).
When you're ready to export your audio files, go to top menu bar, 'File > Export Audio'. The 'Save as type' drop down lets you select the audio format to save to along with an 'Options' button to further refine the export settings.
If you're using audacity and need to export to either MP3 or AAC(.m4a) audio formats you need to download the LAME encoder to export MP3 and the FFmpeg library to export to AAC audio format. Go to top menu bar, 'Edit>Preferences > Libraries', click download and follow the instructions. Other audio software will generally have these export formats built in already.
Convert from Stereo to Mono
When converting stereo to mono files there's two method you can use. You can combine the left and right channels into one singular mono channel, or you can split the stereo into separate left and right channels then use either as a single mono channel on its own. You should try to keep the audio in stereo where possible as the audio in mono will flatten the stereo field. You would only do this if you have to use WAV of AIFF formats and you need to save disk space. The OGG files are in stereo but are compressed already and should not be converted to mono.
Method 1 in Audacity, convert both channels to one single mono channel - First select the stereo audio clip. In the Top Menu Bar go to 'Tracks > Stereo Track to Mono'. You now have a single mono channel.
Method 2 in Audacity, split stereo into left and right channels - Within the audio channel controls to the left of the audio waveform (beside the audio track name), click down drop down menu arrow > Split to Stereo to mono). You now have 2 separate mono channel, delete one and use the other.
Convert Sample and Bit Rate
If you are using WAV of AIFF format and need to save disk space you can reduce the kilohertz rate. In Audacity in the lower left corner, under the words 'Project Rate (Hz):' you can select the drop down menu and change the Hz rating from 44.1 to 32, 22 ect. The lower the Hz number the smaller the files size but the more the audio will reduce in quality so its a balance between file size and audio quality.
Changing Sound Volume/Gain
In Audacity you can increase/decrease the gain level of an audio clip with the audio channel Gain Slider. The gain slider is to the left of the waveform with a minus and plus sign. The slider beneath it is your pan control left and right.
When you move the gain slider you will see the number of dB increase or decrease. You can also double click to input a number. The waveform doesn't update automatically (Just a quirk of Audacity), to update the waveform visual graphic go to top menu bar, 'Tracks>mix and render', the waveform visual graphic will then update. Make sure you don't clip the audio level into the red by increasing the gain.
It's best to control your audio volume levels from within your game engine with code or control sliders, that way you can fine tune it quickly and easily in a 'non-destructive' way.
When editing or manipulating audio files there are two big problems to avoid which can cause your audio to distort and for pop and clicks to appear. It's important to avoid these happening as it can badly spoil your audio.
Avoiding Audio Clipping
First is the issue of dealing with your final output levels. You should never allow your audio to exceed the maximum volume level. When the audio does 'clip' you'll see a red mark on your output levels to indict clipping has occurred. When this 'clipping' happens it will distort the audio causing a very nasty harsh sound.
You generally manage this by always keeping an eye on the final output level meter and making sure your audio level always stays below the maximum level. If problems occur you can reduce the gain/volume level of any sounds that are causing the levels to clip.
Avoiding Pops and Clicks
After cutting, trimming or cropping an audio file on play back a click sound can occur at either or both the start and end cut points. It's caused by the audio starting or ending with the level not on the zero amplitude line. This is something we'll want to remove when it occurs.
When clicks are heard at the start or end points we can use a very short fade in at the start cut point and a longer fade out at the end cut point of the audio file. You select the region of audio first, then go to top menu bar 'Effects>Fade In or Fade Out'.
Generally you'll want an extremely short fade in time. Zoom right into the area to select the region to fade in, otherwise the attack time on the sound could be too slow. This will cause a delay feeling when the sound is trigger in your game. You may however want this type of slow building attack time, e.g. in the swell of a magic spell type sound.
When doing the fade out you can make this much longer. The length you select to fade out with is a matter of taste and stylistic choice, a cause of, try it, listen, then re-adjust till it sounds good to the ear. Note that if you make the fade too long it will increase the files size, so you may want to balance between saving on file size and audio aesthetics.
Just to note: other types of pops and clicks can also appear throughout a sound file due to things like slight digital errors ect. These can be removed with declicker effects in audio editing software. In audacity there is an effect called 'click removal' which will deal with those types of problems.
This section will go through a number of methods you can use to create new sounds effects and variations from existing sound effects files.
Adding Audio Effects
Adding an effect to a sound is a easy way of getting a new sound. In Audacity you can select from a large range from the top menu bar under 'Effects'.
When adding effects you may need to add additional length to the end of the file to allow room for effect otherwise it can sound cut off. This is particularly the case when adding reverb or delay effects.
In Audacity to extend the length of audio (before adding an effect), make sure the cursor is placed at the end of the audio clip (press 'K' key, or press the 'skip to end' transport button). Go to top menu bar, 'Generate > Silence' (input in 2 seconds). We now have an extra section at the end of the audio.
Now apply the effects under the top menu bar 'Effects', select the particular effect you want. After the effect is applied you can then delete the end section that isn't needed. Select the section to remove then press the delete key. You can add a slight fade out to the very end section to prevent any click, select section you want to fade, go to top menu bar 'Effects>Fade Out'. Then join the 2 sections, select them both, top menu bar 'Edit>Clip Boundaries>Join'. You'll now have a clean audio clip with your effect added.
Layering Sounds Files Together
Nearly all the sounds in the '2000 Game SFX Collection' have been made by layering multiple sounds together in a variety of ways. This technique is very powerful and gives a huge amount of possibilities to create new and interesting sounds and variations.
Instead of just placing in multiple audio files all with the same start time. By offsetting and staggering these start times we can get interesting rich textures and combinations of sounds. Drag and drop in the audio clips, select the 'Time Shit Tool' from the toolbar. Now click and drag any audio clips to offset them. Hit the space bar after each adjustment to hear the sound played back. To see the audio clips on the whole screen use the top menu bar 'View>Fit in Window + Fit Vertically' or use the other view settings that will position the audio clips where you can see them clearly.
When layering multiple sounds together be very careful to watch your overall audio output level so it does not clip and create a distorted sound (as mentioned in the 'problems to avoid' section above). This will easily happen when multiple sounds are playing back all together. Your output level should always stay below the maximum level and out of the red clipping point. Use the gain slider to reduce the levels of any problem audio clips. (See the 'Changing Sound Volume/Gain' section above).
Using a Section of a Sound
With this method we can use smaller sections of an existing sound to create variations from a single sound clip. First open your audio file, now select a section with the 'Selection Tool' from the toolbar. Hit the space bar to listen and reselect till you have a section you like. Now trim the audio, ctrl+T, or top menu bar, 'Edit>Remove Special>Trim Audio'. After trimming the audio use the fade-in and fade-out technique to prevent clicks at the cut points, (as mentioned in the 'problems to avoid - avoiding pops and clicks' section above).
Pitch Shifting & Time Stretching Audio
Pitch shifting and time stretching are two methods we can use to create new sounds by changing pitch and length properties of a sound file.
Time Stretching will lengthen or shorten the sound while keeping the same pitch. Go to top menu bar, 'Effects>Change Tempo'. Extreme lengthening will cause audio artifacts so use with caution.
Pitch Shifting will lengthen or shorten the sound while also changing the pitch. Go to top menu bar, 'Effects>Change Speed'. (Use the 'Change Speed', not the 'Change Pitch' as that's a pitch correction tool).
In Audacity there is another tool to manipulate pitch dynamically. Go to top menu bar, 'Tracks>Add New>Time Track'. This will create a new time track in the editor window above your audio clips. If you select the 'Envelope Tool' from the tool bar you can now draw multiple points directly onto the time track area. The left side number bar will tell you the percentage of pitch that has change. You can increase the possible pitch range limits, go to the drop down arrow on the left side of time track > Set Range (reset lower and upper percentage limits). You can now position points on the time track and play around to get some interesting effects. Hit the space bar to hear your changes each time. You can make adjustments, export a sound, make more adjustments and create a collection of interesting variations.
The following are some general overall usage tips when using sound effects from the '2000 Game SFX Collection'. These tips can also be applied to any other sounds effects or audio you may use.
Audio Mix & Volumes
The sounds in the collection have been maximised in volume level and generally peek at -1dB. They are designed so you can attenuate (reduce) the volume levels to suit the needs within your games or apps. It's best and easiest to adjust the sound effects volume/gain with code or with the game engine audio sliders, as you can readjust in a 'non-destructive' way, quickly hearing the results of the edit without overwriting the original audio file.
What levels you set the sound effects to are a matter of audio aesthetical choice and depends what emphases, importance or suitability you want to give different sounds within your game. It's important to pay attention to the audio mix and how sounds relate to each other. The audio elements should be adjusted and fine tuned just like any other aspect of a game, just as you would continually adjust the graphics or gameplay elements.
Sound Files & Implementation
With any editing of the audio files always start work from the uncompressed high quality WAV files. Don't start editing with the OGG files as these are already compressed and are just to be used as is, (they are included for your convenience if you need that format). The OGG files supplied in the '2000 Game SFX Collection' are compressed at 20% out of 100% and are exported directly from the uncompressed WAV files.
The Sound effects are located within 30 different category topic folders. Each audio files name starts with their main category section name in uppercase to make them easier to find. Don't let file names dictate their exact end use. Use whatever sound effect best suits your games need. You can easily swap in different ones to see what effect they have on different game elements. A pop sound could be an interface button press, a computer beep an item collection sound, a retro jump sound could be a level complete sound. It all depends on the theme, style of the game, and mood you want to create. With all these 2000 sound files you can test a huge amount of different ideas to find the ones that suits best.
End users or game players may very likely hear a particular sound or set of sounds hundreds if not thousands of times over the course of playing your game, so it's worth playing attention to what the player will have to listen to repeatedly. You could apply subtitle changes to the sound like random pitch shift variation when the sound is retriggered to help prevent it becoming overly repetitive. It's worth making sure no audio elements stands out unnecessarily and distracts from the gaming experience. When the audio is implemented correctly it should ideally become almost invisible to the user, unifying with the game experience as a whole.
Sound File Management
After you download the '2000 Game Sound FX Collection' zip file, save it safely and securely so you can always return and unzip a fresh sound effects set if you need to in the future. It may be useful to keep the original sound files in their folders particular folders, copying and pasting sounds out to other project folders when need. That way you can easily reaccess the full sound set at a later stage. Of course use whatever workflow methods work best for you.
Always read the audio documentation of the game engine, framework or software development kit (SDK) you are using and their directions as to how audio and sound effects should be used within their particular systems. Below is a list of audio related documentation for various game development tools you may find useful.