AIBU to think 8.45pm is too early to expect quiet?

Or maybe after a few weeks of noisy teenagers till quite late in the evening and many weeks of unsettled infant in this heat they're losing their minds and just thought they'd ask.
We still don't know what the actual noise is. If they're asking if the teenager can turn their music down in the garden at 8.45pm I don't think that's unreasonable.
The OP is a bit confusing because she says her older teen only has friends over every couple of weeks. So what noise are we talking about?

How did they let you know they were unhappy about the noise. Did they catch you off guard, as you could have told them that you used to use background noise of a radio or white noise when you had your babies, so they would not hear external noise.
Its bad enough that you would have to be quiet for your own kids when they were small, never mind the next door neighbours, years later. I would not be happy telling my own grown up kids to be quiet because someone else has a baby (in another house)

It depends on how noisy and how often tbh. It’s impossible to say.

dont wake until atleast 11am just has his usual group of 5 friends in the garden music just chatting, all respectful kids who are very aware of the baby next door

OP says it's 9pm during term time (which seems really, really early for everyone to be in bed..but that's another thread).

OP, you need to tell us what sort of noise? Are there a bunch of teenagers playing music under the infant's window? Are they playing basket ball?

If I'm having people over in the evening, we'll use our garden but just for talking, I would let my teenager be too loud out there past about 9.30pm I suppose - just how I didn't let them out in the garden before 9am when they were little. I am in a terrace.

This so the question isn't it? If they are asking for silence they are being unreasonable, if they're asking that 10 teenagers aren't playing aloud music in the garden then they're very reasonable. Op needs to return and explain

I think it depends on what kind of noise you’re making, I wouldn’t complain that early but things like mowing a lawn/drilling/anything with a chainsaw etc in the evening would be irritating when you have young children you’ve put to bed.

If it’s just that you’re sitting outside talking and especially if it’s the weekend then they are definitely being unreasonable and that’s the sort of noise I’d hope my children would sleep through, if not I’d close their windows.

What noise are your teens making or can you hear noise through the walls? Have they got radios blaring outside or through windows? Is it general chatter in the garden? How quiet do they expect you to be?

in answer to your question, 8.45pm is too early, especially in the summer. Do you hear their baby cry a lot when it awakens?

It's ridiculous. There is still noise outside my house at 9pm . People getting in from work, people laughing in the garden, neighbours kids still playing out, my teens in the garden with friends, neighbours mowing the lawn. Inside the house In watching TV, teens often chatting with friends, playing video games, teens coming and going. That's normal noise for 9 pm. It's summer. My teens don't go to bed untill 1 am during the summer but do keep the noise down from 10 pm.

Have they tried white noise in their baby’s room, to mask outdoor sounds?

Or maybe after a few weeks of noisy teenagers till quite late in the evening and many weeks of unsettled infant in this heat they're losing their minds and just thought they'd ask.
We still don't know what the actual noise is. If they're asking if the teenager can turn their music down in the garden at 8.45pm I don't think that's unreasonable.
The OP is a bit confusing because she says her older teen only has friends over every couple of weeks. So what noise are we talking about?

Generally quiet time
legally is 11pm to 7am in the UK.

What kind of noise is it? If it’s just daily life then that’s unreasonable but if it’s huge noise I can see their point?

I would laugh and carry on. 8.45 pm is ridiculous to expect other people to turn out the lights and be 100% quite because of a baby. And we are not a noisy family but 8.45?

Camp sites and hostels and similar usually say either 10 or 11.

if the baby is waking at noise from next door then unless you are having a full on rap battle or something it’s unreasonable to be completely quiet from 8:45

Can they not socialise indoors?

YANBU
Babies need to get used to noise. They are being unreasonable. They need to move to a house with no neighbours!
Is it detached?

What's the noise though? There's a big difference between sitting and chatting outside vs. loud music and shouting every single evening.

I don’t think you're unreasonable, but your post implies you’d be happy to be quiet from 9pm - not sure 15 minutes makes that much difference.