it's summer; people like to sleep with their windows open. If your balcony is anywhere near his bedroom window, you need to move your conversations indoors after 10pm.

It may seem like a normal conversation to you, but it may be particularly disturbing to him--and it IS after 10pm, and it's an apartment, not a house.

And, is it a NORMAL conversation, or a HUSHED conversation? Normal is out of line, in my opinion, if your balcony is near his bedroom--which is must be. Hushed might be OK, but normal is not.

I know that in my own case, noise AS I'm trying to go to sleep is really hard. AFTER I'm asleep, I may sleep through all sorts of stuff. So a quiet conversation at 11:30, I won't hear. But at 10, it might disturb me a lot.

You might also speak w/ the actual landlord or building manager, to get a clarification from the authoritative source (and to discreetly sound out how much they value him; they may be more likely to side w/ him in a genuine, i.e. no unreasonable, dispute).

I'm sorry to say, I don't think his request is out of line. Before 10, yes. After 10, no. I think you should move your conversation indoors after 10.

At the VERY least, you should keep your voices way down after 10.

I agree with Taley. But I'll take it a step further and say conversations of ANY sound level should be kept indoors after 10 p.m. I live in a condo and never let my friends go on the lanai after 10 p.m. We have neighbors up, down, and on both sides. You have to respect their quiet.