Would you mention it or not?

How often and how long does it last?

I'm only wondering because if it's just on the odd occasion and not prolonged you might just want to invest in a pair of headphones and leave them to it.

You could try turning up your music very very loud

The walls must be quite thin, making me think twice about moving to a retirement complex

Presumably your complex has a manager, resident or visiting. Why not discuss this problem with them and leave them to deal with it for you?

go with MOnica I say!!! Otherwise you might have to say something to them like - do you hear much noise from my flat? - or gosh aren't these walls thin? - can you maybe add more sound insulation?

Go for the headphones or make it a competition! !

Reach for the ear plugs and a good book, it should all be over in a few minutes...

Anya Usually Wednesday and Sunday! Sometimes Saturday afternoon.
M0nica No, no manager. We just get someone every 4 months to check the alarm system.
We don't own the property so can't make changes like adding sound insulation.
I sound like a right misery don't I!! But it makes me think twice about our own love life!!

Clap loudly when they finish. That should get the message across ( only joking) I would agree with MOnica

No real suggestions but your situation reminds me of the landlord's son in our first rented flat. He brought a young bride from Cyprus, after a short visit home, and they indulged in rapturous sex thrice nightly in the room above us! We were only newly together ourselves but the effect was demoralising in the extreme. I couldn't look either of them in the eye.

It should be interesting chatting over the garden fence, can you look them in the eye?

What is so special about Wednesday and Sunday? Nothing on telly? Or is it Poldark that gives them inspiration?

Do what we did. We were spending a short break in a quite large hotel in the Highlands, and were in a room in a very quiet and under-occupied part of it. The room next door was supposedly empty, but I assume that staff members congregated there in the off hours to socialise.

The door was very busy with people arriving far into the night, lots of chatter, and lots of thumping the bedhead against the wall - our bedhead was just a wall-thickness away so we got no sleep until 3 or 4 in the morning. Then it started again at 6 am. So we retaliated in kind. There was a muffled exclamation, and silence and stillness from then on.

You could try that. Be sure to be noisily vocal in your appreciation of the experience. Then when you next meet them, mention how thin the walls are.

Guess you too will have to go to bed early on Wed and Sunday!! I'm feeling very inadequate!!

No, don't go to bed early, wait until early next morning, when they are trying to catch up on their sleep.

Sing loud hymns?

You could put on some music that you know they dislike at top volume, then go off down to the pub.

I like the idea of clapping! - or bang in the wall!

I love Elegran's suggestion. Sounds like fun.... If you can't beat them, join them!

Good idea Elegran but they'll have to get up and go into the sitting room !

When the bedhead starts banging. Start saying loudly things like "Oh no, up a bit" "Yes, that's good" "Slower darling"
Seriously I would just say "I hope our TV/music/radio didn't disturb you last night as these walls are notoriously thin" said with a knowing smile.

Thank you all, you have made me smile. It is very hard to look her in the eye when i see her!!

When I was doing my house jobs preregistration, the bedroom above the lounge in the doctor's mess was occupied by the obs and gynae SHO Many lunchtimes she was joined by the obs and gynae registrar in the very squeaky bed.
The faces of the senior consultants had to be seen to be believed! We juniors had difficulty containing our giggles.
We used a system of coloured lights as a call system ( before modern bleeps)
The call sign for the registrar was a a steady orange! He was known as forever amber!
And no, they were not married. He was married to someone else!
I think that came from tv series that was current at the time

Bolero by Ravel might be a good choice of music!

My friend made me giggle when she told me this was playing loudly in the room next to theirs when they were on their honeymoon:
www.youtube.com/watch?v=9fWeBZTfrQI

Wow! Respect, 3/4 times a week!
Seriously though, I would do what others advise and say innocently, ' hope our noise doesn't bother you, the walls here are so very thin!'