We have a regular (every few seconds or so) noise that sounds like "boing" coming from what seems like inside the walls between our house and the townhouse adjacent on the second floor. The noise is audible on the first floor and basement but much less loud. It usually lasts for 20-60 minutes at a time then stops. I feel like it is probably a pipe of some sort. I also thought it seemed to go away when you flush the toilet a couple times, although that only seems to coorelate sometimes. I only notice it at night or early morning. My husband says he's been hearing it for almost a year, I only noticed it a couple months ago. We looked in the attic to see if it was water dripping on a vent or pipe, but no evidence of that. It drives me crazy when I'm trying to sleep! Help!

I'd ask the neighbor if he has anything mounted on the wall that could account for the noise, maybe a clock.

Did you ever get an answer to this? We are having the same issue. You can email me direct at [email protected]. Thank you!