This is the sort of thing that a DM must adjudicate for themselves. The SRD lists a number of DCs for the listen skill for various circumstances.
Note that the DC of 10 equates to the average roll of an untrained individal with no dex bonus attempting to move silently. DC 15 equates to the average roll of a rogue with some skill ranks in move silent and a dex bonus. DC 5 equates to an individual attempting to move silently untrained with a armor check penalty. So you'd have to eyeball this yourself. For me I'd put it somewhere higher than 5 but lower than 10, and closer to 5. But this is rule 0 territory (DM Adjudication) and while rule 0 is RAW, the exact number is outside the scope of the thread.Originally Posted by SRD