ABS pipe noise

After taking a warm shower, I hear these intermittent, sharp, loud, annoying thud like noises below my shower, for about 5-15 mins. It has been going on for years and I decided to take a look by removing part of my ceiling to look at the abs pipe below the shower pan. It looks like the noise is due to expansion and contraction, and the ABS pipe is probably hitting something in the wall as it goes from 2nd story to 1st story. I believe the shower pan acts like an amplifier of any noise transmitted thru the pipe.

Is there any way I can dull the noise so I won't hear it? It is quite loud and very annoying. I do have access to about 2-3 feet of the abs pipe below the shower pan. I don't see the ABS pipe touching wood in the accessible area, thus I believe the source of the noise is in inaccessible areas.

Thanks

All of the plastic pipes expand and contract a fair amount. It is likely that the pipe is constrained in an area where it goes through the floor. Release that restriction, and most of the noise will go away. Insulation might help a little, but probably not much.

Most of the time, it's where the ABS goes through a hole in the wood plates.
If they bind, crooked hole, or even just tension, you will get those annoying clicking sounds.
Sometimes the cure, is to cut drywall and make the hole a little bigger around the pipe.
Either that or ear plugs.

My house, makes all kinds of night time sounds. When I first moved in a year ago, I would even wake up and look around to see if someone was walking through the house.