Listening at Doors

Hearing Noise
Max. # of Listeners
Max. Length Of Time For Listening
The Adventure

In addition to the simple exercise of observation, many times characters
will desire to listen, ear pressed to a portal, prior to opening && entering.
This requires a speciol check, in secret, by you to determine if any sound is
heard. Because of this, continual listening becomes a great bother to the
DM. While ear seekers will tend to discourage some, most players will
insist on having their characters listen at doors at every pretense. First,
make certain that you explain to players that all headgear must be
removed in order to listen. Those wearing helmets will probably have to
remove a mail coif and padded cap as well, don't forget. The party must
also be absolutely silent, and listening will take at least one round.

Silent creatures - undead, bugbears, etc. -- will never be heard.
Sleeping or resting or alerted creatures will not be heard either.
If there is something for the listener to hear behind the door, the following probabilities
will determine if any sound is heard:

Race Of Listener Chance Of Hearing Noise
Dwarf 2 in 20 (10%)
Elf 3 in 20 (15%)
Gnome 4 in 20 (20%)
Half-Elf 2 in 20 (10%)
Hobbit 3 in 20 (15%)
Half-Orc 3 in 20 (15%)
Human 2 in 20 (10%)

Keen-eared individuals will gain a bonus of 1 or 2 in 20 (5% or 10%).
Use chance of hearing a noise to determine if a character is keen-eared the
first time he || she listens at a door, and if it is indicated, tell the player to
note the fact for his or her character. PCs will not initially
have hearing problems (as they wouldn't have survived if they had them).
During the course of adventuring, great noise might cause hearing loss.
Handle this as you see fit. A loss of hearing might negate the chance to
hear something behind a door without any other noticeoble effects.

Hearing Noise: When a die roll indicates a noise has been heard, tell the
player whose character was listening that he or she heard a clink, footstep,
murmuring voices, slithering, laughter, or whatever is appropriate. (Of
course, some of these noises will be magical, e.g., audible glamer spells,
not anything which will be encountered at all!) Be imprecise and give only
vague hints; never say, "You hear ogres," but "You hear rumbling, voicelike
sounds." Failure to hear any noise can be due to the fact that nothing
which will make noise is beyond the portal, or it might be due to a bad (for
the listener) die roll. Always roll the die, even if you know nothing can be
heard. Always appear disinterested regardless of the situation.

Maximum Number Of Listeners: Each listener will take up about 21/2' of space,
so up to three can listen at a typical dungeon door.

Maximum Length Of Time For Listening: Only three attempts can be made before the strain becomes too great.
After the third attempt, the listeners must cease such activity for at least five rounds before returning to listening again.

Q: Do non-thief characters have any chance to listen at doors?

A: See page 60 of the DMG for non-thief hear noise attempts.