FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Ambient Sounds
Just as the main view gives the player visual feedback about where she is, ambient sounds give her aural feedback. Traffic sounds tell her that she's in an urban street; cries of monkeys and exotic birds suggest a jungle. Anything that ordinarily makes distinctive sounds in the real world, such as a fountain or a jackhammer, should make the same sound in your game.
A first - or third-person game should definitely use positional audio if the platform's audio devices support it. Positional audio refers to a system in which different speakers present sounds at different volume levels, allowing you to position the point sources of sound in the three-dimensional space of the world. Some personal computers support as many as seven speakers, but even two-speaker stereo can help
a player detect where a sound is coming from. Correctly positioning sound sources in the 3D space helps the player orient himself and find things that he may be searching for, such as a river, an animal, or another member of the party.
Don't overuse ambient sounds, especially in games that mostly feature mental challenges. A cacophonous environment isn't conducive to thought. Your ambient sounds must also work with the music you choose, which the next section addresses. You may also be limited by the capabilities of your audio hardware, because some machines support only a small number of channels for simultaneous playback; when playing all the sound effects, you may not have channels left to use for ambient sounds.
Music helps to set the tone and establish the pace of your game. Think about what kind of music will harmonize with the world and the gameplay that you're planning. Music sends strong cultural messages, and those must also fit thematically with the rest of the game. A pentatonic scale composition for the shamisen (a traditional Japanese lute) might work well in a medieval Japanese adventure game, but it would certainly sound out of place in a futuristic high-tech game. You will probably collaborate with an audio director to choose or compose music for the game. Many larger commercial games now use licensed music from famous bands.
The music doesn't have to support the game world at every moment; you can choose music to create a contrasting effect at times. The introductory movie for StarCraft uses classical opera as its theme, set against scenes in which admirals calmly discuss the war situation as they prepare to abandon the men on the planet below to their fate. The choice of music accentuates the contrast between the opulence and calm of the admiral's bridge and the hell of war on the surface. In a simpler example, the tempo of the music in certain levels of Sonic the Hedgehog is out of sync with the pace of the level, which, in a subtle way, makes the game harder to play. Don't overuse these techniques, however; the rarer they are, the more effective they are.
In the real world, few pieces of music last as long as an hour, but players may hear the same music for several hours at a stretch in a game. Whatever you choose, be sure it can tolerate repetition. Avoid background music with a wide dynamic range; the louder parts will become intrusive and remind the player that the music repeats itself.
For some years, the game industry has experimented with the difficult problem of writing music that changes dynamically in response to current game situations, a technique called adaptive music. Adaptive music must follow and even anticipate unpredictable situations. Creating adaptive music remains an experimental technique for the moment. On the other hand, game musicians have become extraordinarily skilled at layering—writing separate but harmonizing pieces of music that the audio engine delivers simultaneously by mixing them together at different levels of
volume. The engine determines which piece should be most clearly heard depending on what happens in the game.
