The Sound dialog allows you to control how quickly the sound engine adapts to the variations in volume and displays the current volume levels and types so that you can evaluate the impact of your changes.
If you are looking for tips and tricks on how to use the screen
saver with sound, be sure to read FAQ item #1.
Raw - this represents the current system-wide volume level
Expanded - this represents the current volume scaled to a percentage of the loudest sound detected. The scale will expand if and when higher amplitude sounds are detected.
Dynamic - this represents the current volume level after amplitude homing is applied. If amplitude homing is set to "None" this will be similar to (or the same as) the Expanded volume level.
Simulated - this is the volume level that the visual generators use. If the sound engine detects sound then this level will be similar to the Expanded volume level. If no sound has been detected for several seconds then this level will revert to a simulated volume level until sound is detected again. The purpose of this is to keep Displays that have been authored to use sound interesting when no sound is present to drive them.