Moderating:
Implicitly calling a poster an asshole by linking to a site that suggests it is insulting other posters. This is not the pit. You know better.
Posting as a poster: I endorse software or an appropriate headset to dampen background noises. In my experience, that works really well to hide background noises from people at the other end of the phone. Most headsets will do the trick – the microphone is usually designed to selectively pick up nearby sounds and not quieter sounds that aren’t right in front of it. But I notice that zoom and other audio sharing apps also tend to erase background noise. In fact, Discord has a toggle to let you control the extent to which it does so, and I’ve been on a call where we couldn’t hear the (loud) music of one of the participants due to it.
(That was actually a problem. He was trying to share the music. After he flipped one of the toggles, we heard it just fine.)
Have you considered putting a couple of nails into the top of the doorframe and hanging a comforter over it? Maybe fold it double?
That could/might go a long way to dampening the sounds to a more manageable level.
Failing that, bring them candies and ask them to move away from your door, you have an important meeting! It may well turn out you only need do this once.
It’s generous and kind, instead of a Shut Up sign! Much more likely to garner their cooperation, in my opinion.
Good Luck!
The noise canceling headphones may be your best bet.
But why not try a simple sign in English, chances are the teenagers know the language to some degree.
Quiet Please - work in progress
With the universal sign for sshhhh.
They’ll get the message but will they care?
You don’t need “noise cancelling headphones”, which are designed to shield you from noise. Most headsets with a microphone are designed to selectively pick up sounds close to it, and to cancel out background noise. And they typically work really well.
I considered that. But, I’m very worried ‘strange single man offering girls candy for a favor’ will not go over well.
Given that you describe the girls as pre-teens, my expectation was that they have parents, that it’s the parents that you would talk with, and that you’d by bringing over treats to the parents that would be enjoyed by the whole family.
(For the record)
I did not actually say that they had to suppress laughter. I only suggested explaining the situation to a responsible adult (rather than decorating one’s abode with passive aggressive signs or yelling at kids). If you would respond in a hostile fashion to polite conversation, it might explain why your kids were wreaking havoc on common public spaces. Anywhere I have lived, there was already a general understanding that apartment hallways are not the place for outdoor voices.