Basically its the echo

The simplist way to understand this is to get your sound card driver/software up and run an eax test. you should have a list with: off, generic, sewer, padded room, hall, cave, underwater and so on, click test and you will hear a sound (usually footsteps) with the EAX effect added. (muffled in padded room, big echo in sewer and cave, hall is very "light" echo, underwater is muffled watery sound)
OK: basically its an echo - i personally NEVER use it (MAJOR resource hog, and i prefer my bells rung without an echo
