Cavemen should have enhanced hearing compared to other roles: non-silent monsters you can’t see appear on the map with a warning-style symbol showing not their severity, but the amount of volume they are making. Possibly, having too many monsters in one place would confuse this system.

Zombies and possibly mummies have a new sound MS_GROAN instead of MS_SILENT. This would not do anything at the moment except give you “The zombie groans.” when chatted to.