In the case of people trying to be quiet, the DCs given on the table could be replaced by
Move Silently checks, in which case the indicated DC would be their average
check result.
Action: Varies. Every time you have a chance to hear something in a reactive manner (such as when someone makes a noise or you move into a new area), you can make a Listen
check without using an
action. Trying to hear something you failed to hear previously is a
move action.
A fascinated creature takes a -4 penalty on Listen checks made as reactions.
A half-elf has a +1 racial bonus on Listen checks..