Knock to join room permission

The only issue I see for this is someone going around 'knocking' on every user in the channel, bothering people or when they just wanna hang out with a couple of people. Personally I wouldn't want a noise played and I might not see the pop-up if I have it hidden behind a video or smth. So maybe a way to set the channel to a do not disturb mode so nobody can try joining it if they don't want anyone to. People could still ask in a text channel if they want to join or in a dm if you are fine with them doing that.