AIBU to be freaking out

[Lucieaew]

I've been hearing the odd noise coming from the chimney through the day. When the kids went to bed and things quietened down the noise from the chimney increased. I can't describe the noise, it's not flapping or scrapping or any noise you can liken to an animal it's just a metal noise coming from the chimney. Almost like a metal expanding type of noise. Clank.
Anyway I'm freaking out about it and my husband is acting like I'm crazy. AIBU? talk me down people? I've tried to tape a bin bag over the fire place so nothing could come through but was jumping out of my skin every time I heard a noise so husband very grudgingly took over to shut me up. He says there is no way there would enough room for an animal to fit through to be able to get in to our front room, but as he isn't any kind of chimney expert or fire expert I place no faith in his opinion.

Is it actually metal expanding and contracting? We've had some large temperature swings recently.

And increasing once the kids are in bed, as it's dark and cooling down more quickly.

Bird on top of chimney?
Kids/neighbour moving something upstairs near chimney grate?
Wind?
Nearby noise outside?
Could be lots of things, nothing exactly dangerous though.

When birds perching on our aerial (which is attached to the chimney) fly away, it twangs. It proper freaked me out when we first moved in... Could it be that? Or is your aerial loose and blowing in the wind?

Thanks for the replies, I does sound like metal contracting and expanding but I've lived her for two years and we've never heard these noises before. I do keep thinking I should be hearing some flapping or scraping. Next door is empty and has been the whole time we have lived here, so it's not anything coming from there.