A Silent World
You stroll along the verge, the grass silently folding under your feet. Not a birdsong around, the wind whips up nearby fallen leaves and scatters them, the moving air not whistling, the dry leaves soundlessly hitting the pavement.
As you walk along the street, no dogs bark; no cats howl; children play silently, a vehicle of some sort zips by without a whisper. Up in the sky, a jet trail from an aircraft forms, without the noise of any engine.
After a few moments you start to feel unnerved, you step from the grass to the concrete of the pavement. It too, makes nary a sound. Stepping harder, your heavy footfalls do not even raise a clack. Moving to the tarmac of the road, still nothing. Suddenly you sense it, and hurl yourself to the side just as a vehicle shoots silently by, straight through where you once stood.
Pain shoots through your head, from a sudden impact; your forehead struck the curb. No one comes to your aid, as no one heard you fall.
The world described above sounds freakish (pun intended), although very familiar to a deaf person. Moreover, it illustrates to those who can normally hear, something which so many forget when designing a virtual environment - sound matters.
Not simply background sound like music, but realistic, correct sounds, little things that add to the experience; the sound of the wind blowing through the trees, of birds singing, of grass flumping underfoot, leaves crackling, or a clomp of shoe on concrete. At night, the sounds change. Crickets chirp in the bushes, owl howls at odd intervals, widely spaced. Wind howls get louder, animals creep about. These are the things, which add atmosphere to a world, that bring it to life. We have more than just the visual sense, let's use those senses, feed them.
Localisation by sound
Often we hear things coming before we see them. Hearing is not that accurate, and can usually only tell right or left, never mind in front, behind, above or below. However, the very fact we can hear them, gives us valued clues to their existence, early. Removing the sound from the equation takes away one of our senses, abstracts the realism of the environment. How often have you heard a car coming up behind you, before you see it, been made aware of a police car, ambulance, or fire engine, long before you see it, by the siren? Listened to a television I another room? Each of these little things demonstrate how appropriate sounds attached to things that should be capable of those sounds, add much to the experience that sight alone cannot match.
It is no good just having one sound for footfalls within a world, as so many do. The sounds you make when you move change depending on what you walk on. A clip clop sound does not really sound right when travelling through mud - your eyes tell you the mud is soft, your ears tell you it is hard. Your brain feels queasy.
Likewise, a wet sloshing sound when walking on tiled stonework is going to drive you batty. The sounds of movement need to change to whatever you are walking on - snow, ice, flora deep flora, new wood, old wood, stone, mud, metal, et cetera.
Appropriate sounds and sound effects are all well and good, but they still serve little purpose if you are the only one who can hear them. Throwing a rock to distract a guard is pointless if only you can hear the clack as it hits that boulder. Dry twigs in the forest are nothing to be afraid of, as they break under your feet, and a siren is utterly pointless if only its operator can listen. Sounds need to be collaborative, heard from person to person - the action one person makes to trigger a sound, results in that sound projecting out to all within range, fading with distance, then being eliminated after it has faded to nothing. That way, interaction and noise bounce off of one another, enhancing one another, making the environment, more real.