Enhancing Virtual Environments with Sound
By Andrea L. Ames
Find a quiet room, go in and close the door, close your eyes, and listen. Do you hear anything? Probably not. It's a quiet room, after all. Would you say it's silent? Possibly.
Now, listen harder. What do you hear? The whoosh of warm or cool air rushing from air vents? People's footsteps falling in the hall outside the door? Birds chirping outside the window? A clock ticking faintly? Perhaps even the hum of computer equipment. When you create realistic virtual worlds, you need to consider more than triggered sounds, like the creak made when a door opens and the slam of that door closing as your visitors navigate through rooms. Think about ambient sounds, like the ones you heard when you stood listening in the quiet room with your eyes closed.
The VRML Sound node creates a sound emitter, like the speakers connected to your computer or home stereo system. The emitted sounds are provided by a sound source, like your computer or the CD or radio-tuner components of your home stereo, and these sources are defined with the AudioClip and MovieTexture nodes. You can hear the emitted sound within an ellipsoidal region, as shown in
Figure 1, that you define using fields of the Sound node. With the Sound node, you can create ambient or triggered sounds. This column focuses on ambient sounds; in future columns, I'll discuss triggering events (like causing a sound to play) and triggered sounds.
