It seems reasonable to assume that an alchemist's bomb (normal fiery version) causes light and noise when it impacts.
The question is how much noise. Making this a fairly easy check seems the most realistic option but may also unduly penalise the alchemist. It also opens up a whole can of worms in relation to his other bombs. Eg How much noise for a cold bomb? More or less than an acid bomb? Does a force bomb make noise at all?
How have other people dealt with this?
The DC for Battle in general is -10. I'd just go with that.
It seems reasonable to assume that an alchemist's bomb (normal fiery version) causes light and noise when it impacts.
The question is how much noise. Making this a fairly easy check seems the most realistic option but may also unduly penalise the alchemist. It also opens up a whole can of worms in relation to his other bombs. Eg How much noise for a cold bomb? More or less than an acid bomb? Does a force bomb make noise at all?
How have other people dealt with this?
Just use the normal rules for perception and combat. Combat takes a DC -10 perception check to notice. the DC goes up by 1 for every 10 feet, and is modified by walls and doors as well.
I don't see that different energy types would modify the DC significantly (maybe raise the DC by 5 or so).
edit: what steve said