I once had a player that wanted a Decanter of Endless Water just to waterboard people 😳
Idk, that feels a bit too technical. Trying to apply real world physics to D&D breaks way more things than just this, so we gotta be careful when to do it. Gotta keep just enough believability and consistency, without letting it ruin the feel.
For me, the fact that “starwars lasers go pew pew” is enough reason to disregard how sound actually works in real life, lol.
To be fair I’d just rule in favour of the players the first time it comes up. If they want it as a silencer with the prerequisite of putting it over someone’s head, that’s cool because the enemy will struggle and make it difficult.
If it’s debut was from an enemy doing it to a PC who said they’d yell extra hard to call for help, I’d probably ask for a skill check and say the sound does pass through.
From then on, I’d just keep that ruling.