The PHB gives examples of specific active uses of perception.
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Perception. Your Wisdom (Perception) check lets you spot, hear, or otherwise detect the presence of something. It measures your general awareness of your surroundings and the keenness of your senses. For example, you might try to hear a conversation through a closed door, eavesdrop under an open window, or hear monsters moving stealthily in the forest. Or you might try to spot things that are obscured or easy to miss, whether they are ogres lying in ambush on a road, thugs hiding in the shadows of an alley, or candlelight under a closed secret door.
FINDING A HIDDEN OBJECT
When your character searches for a hidden object such as a secret door or a trap, the DM typically asks you to make a Wisdom (Perception) check. Such a check can be used to find hidden details or other information and clues that you might otherwise overlook.
In most cases, you need to describe where you are looking in order for the DM to determine your chance of success. For example, a key is hidden beneath a set of folded clothes in the top drawer of a bureau. If you tell the DM that you pace around the room, looking at the walls and furniture for clues, you have no chance of finding the key, regardless of your Wisdom ( Perception) check result. You would have to specify that you were opening the drawers or searching the bureau in order to have any chance of success.
Your senses of things you don't see that you are not specifically looking for is generally handled with passive perception.
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HIDING
The DM decides when circumstances are appropriate for hiding. When you try to hide, make a Dexterity (Stealth) check. Until you are discovered or you stop hiding, that check's total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence.
Passive Perception. When you hide, there's a chance someone will notice you even if they aren't searching. To determine whether such a creature notices you, the DM compares your Dexterity (Stealth) check with that creature's passive Wisdom (Perception) score, which equals 10 + the creature's Wisdom modifier, as well as any other bonuses or penalties. If the creature has advantage, add 5. For disadvantage, subtract 5.
If someone is putting their ear to the door and listening, I would give them a perception check. If appropriate to the scene I would also include the fact that they smell smoke wafting from under the door or that the door feels exceptionally cool or any number of other things.
If they go to listen at a door, I'll probably double check if they're actually putting their ear to the door if it matters (bad example because it would never matter because I think contact poison is dumb) since I'm not a gotcha DM. A lot of issues seem to come up because DMs will punish players for not being specific. I don't. I may ask for specifics in certain situations, zooming in on details.
But again, I have never seen this in an actual game. Yes, you may be attempting to hear a conversation through an open window but because you're paying close attention, you may feel the earth vibrate under your feet as a giant approaches.
If listening at a window meant I didn't get something my other senses would have picked up, I'll just start adding every other sense I can think of to the list of what I'm doing.