Can't get audio reverb to work.

Hi all. I posted this question elsewhere but i’ll ask again.

I intend to teach Unreal for a sound for computer games unit on a music tech course. I have most areas covered but adding reverb seems to be an issue.

An easy question to answer no doubt but how can i create reverb in an environment? I create a BSP of a cube and set the brush type to subtractive (to make it invisible) and set the overall type to audio volume. By doing this i get the tab to enable attachment of reverb. i add a reverb but it has no affect on the in-game sounds. What am I missing in getting the reverb to work?

Many Thanks,