Sometimes ticking can be causing by thermal expansion/contraction of dissimilar materials rubbing, like PVC against wood framing. I used to get something similar with my previous house when attic temperatures got to a certain point. I can't tell for sure from your video, though, if that is your issue.

@kudzu9 - how did you fix it?

Find what is making a ticking. Put pressure on it. If it stops ticking you have found the source. Try wedging a wooden shim between the pipe and a whatever it is rubbing against.

@mike_home - the sound sounds like it is coming from above the roof though, not where the pipe is visible. (I think maybe the pipe is carrying the sound down from the attic to the second floor)

Follow Mike's suggestions. If rubbing is the problem, a shim might fix it, or carefully shaving a little wood away at the rub point might work.

Thanks! I think the 2 contact points I can see from the attic are filled with canned spray foam though, which I imagine would prevent the rubbing if it was happening at one of the contact points (I'll take a close look though to see if they're fully surrounded by foam)

I can't say for certain that rubbing is the problem, but I see a point where a pipe goes out through a foamed penetration in the roof and it appears to be touching one side of the hole. The foam could even be locking the pipe in place. Just go around and strat applying pressure all along the pipe, not just those two points.

By the way: 1) is this noise continuous, and 2) does the interval between noises ever change?

the interval does not change, the noise only happens a few times a day, for about a few minutes at a time. (So it's hard to debug, as I have to wait to start hearing the noise).

I've uploaded more video and pictures of the noise and pipe: https://imgur.com/a/py8YqJJ

When you say "The foam could even be locking the pipe in place." - that would be a good thing, right? (could prevent the noise?)

thanks!

I was theorizing that, if it's locked in place, the pipe is resisting minute movement from thermal expansion at that location which is transferring stress which in turn makes a noise. But I'm just throwing out possibilities. Until you have a chance to see if pressing on the pipes alters anything, it's just speculation.