The sound system in TDM version 2.06 has been switched to OpenAL on all platforms.
It means that the environmental effects (formerly known as EAX) can now be used by everyone with no requirements on sound hardware.
This wiki page explains generic pipeline about setting EFX in your map.
Also see this Judith's post for some ready-to-use presets.
For now the best approach perhaps is to copy/paste these presets into EFX file.
If you have any problems or questions regarding EFX, the most suitable people to ask are: me and Judith.
The Judith's topic is the recommended place for discussing EFX presets and properties.
P.S. Do not forget to enable OpenAL EFX in the main menu