Loud Music.

[SteakKnife68]

How do I let a hipster colleague know its not OK to play loud music on his turntable in his classroom while I'm trying to teach next door?

[Barmaid]

Approach him as an adult and ask him if he could keep the volume down a little since it impacts on your students.

[douglas9401]

Have you considered reporting him? 😐

[davebro3]

a brick through the window often works wonders🤣

[smurfchops]

Douglas that would be Cindy

[Old_Geezer]

Demonstrate the use of a hammer ?

[Untitled]

Hi excuse me. Can I talk to you about something quickly? Is now a good time? Great. 
 

it's about your music. i teach next door between x time and y time and i'm afraid the noise is disrupting my class. could you possibly turn it down?

if he says yes: great. 

if he says no:

look, this is a problem for my students and i'm asking you nicely. i'd really hate to involve anybody else in this but i will if i have to. 

[PsalmEquipt]

Dale Carnegie discussed Ways to Change People Without Giving Offense or Arousing Resentment in his book How To Win Friends and Influence People, which was first published in 1936. https://archive.org/details/howtowinfriendsi00dale