Pipe expansion sound

[Bob from accounting]

So I don't want to assume anything as I am not a plumber. However, when I turn on my hot-water side of a bathroom faucet I hear what sounds like creaking or pinging in an uniform way. Frequent in the first few seconds that then taper off eventually.
My mind is set on this must be the hot-water pipe expansing in a wood hole as it passes through a stud or wall? Yes the sound is coming from inside a wall in the bathroom where the pipe is.
The cold water side has not sounds and the drain line exist a diff way so I don't think it is that.
So I am open to any other suggestions as to isolating what this sound might also be before I naively make up my mind it must be a hot-water line (3/4" copper)
If I run hot water into a bowl I still hear it, so most likely not the drain line. When I run Hot-water into the bath which uses the same line the bath may be too loud as it fills so I don't recall hearing it then? But I will listen more carefully.
So is it OK if I leave it like this or do I need to make room for it to breath and expand in the studs? I never have heard it before until this last month?
I would prefer to leave it as it is not a big bother to us?
Thoughts?

 

[Terry]

Creaking, popping, ticking sounds are pretty normal when pipes, both supply and drain are tight to wood. Sometimes on a drainline, the hole might have been drilled a little crooked, which makes for a tight fit. I wouldn't worry about it.