I'm posting this in the General Forum, as opposed to the plumbing forum, because I am not convinced that it is a plumbing issue, although at first glance it would appear so.

I live in a house that was built 6 months ago (I live in Ohio). About 3 months ago, I began hearing a jackhammer noise in one wall in my bedroom on the 2nd floor. You cannot hear the noise anywhere else in the house. The noise lasts about 3-4 seconds and goes away. It is never louder or softer and always lasts the same amount of time.

There is absolutely no consistency to this noise. It began 3 months ago and stuck around for a few weeks. Then it went away...then it comes back. It seems to happen more often at night - however, it may happen 75 times a day and it may never happen. There is not pattern to it at all. It is going off like crazy right now, but I hadn't heard it in a few days, and before that I hadn't heard it in a few weeks.

In the past few days, the noise has picked up a lot more. I have not noticed any patterns with regards to the temperature outside (it has happened whether it's 35, 55 or 75 degrees out.) However, it does seem to happen more at night. I also have not noticed any patterns as to whether or not my Heat/AC is on or off.

AND...it does not happen when the water is on or off or recently been on or off. It's happening like crazy as I write this (about every minute) and I haven't had the water on in hours.

The builder has agreed to rip open the wall and take a look at it, but I'd like to avoid that.

ANYONE?????

You seem to be sure its not water hammer since the water has not been turned on or off, but even if it hasn't been turned on or off maybe it actually went on on its own due to a bad toilet valve, maybe some water leaked into the toilet bowl and the toilet turned on to replenish the lost water. Maybe a bad valve on a washing machine or dishwasher caused the water to turn on? Any dripping faucets?
Based on the layout of the plumbing do you think that there are any pipes in that wall?
It is possible for an electrical fault to cause the wires to rattle before a breaker can trip. I heard a direct fault cause the wires to bang against the walls of the conduit.
Is this wall an exterior wall? If so is there a possibility the noise is coming from outside the house?

thanks for the reply....a few things...

1. it IS an exterior wall. however, i have been outside when the noise it at its peak and I hear nothing.

2. You brought up the toilets/washing machine. Interesting - I had considered the toilets, however, never the washing machine. My wife did a heckuva lot of laundry tonight - i'm wondering if I can investigate that further. However, the last load was probably 2 hours ago, and the noise is still currently going off a few times a minute.

3. i am unaware of any electrical issues, and I have never had any breakers go off.

4. not sure if there is plumbing in this wall.

as i think about the washing machine scenario more (or dishwasher for that matter, since it ran tonight as well) - the wall that this noise is coming from is about as far away from these appliances as it could possibly be. they are on complete opposite sides of the house. i can't thin that water would travel through the pipes from these appliances to this area of the house.

i fear that there is no way to figure this out except for tearing out the wall.

Did you turn off the main water valve to the house and wait for hammering? If no noise, you need to shut off any and all valves in the house and one by one open them to isolate which valve/fixture is the problem.
To me it sounds like a usual toilet slowly leaking and refilling sporatically.

The only other suggestion is that you have a family of woodpeckers dining on your bedroom siding or living in your attic.

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Does it sound like this?

Intermittent rapping....

http://www.youtube.com/watch?feature=endscreen&NR=1&v=7Ju7Ng-gIqc

Good question! However this statement would tend to negate the possibility of woodpeckers...

"...i have been outside when the noise it at its peak and I hear nothing."

I would think that there will not be any water pipes in an outside wall in a bedroom.
Anything on the roof near that area such as a mechanical roof vent?, maybe the bearings are bad and its vibrating, I doubt you will have one in a newer house but I just wanted to mention it.
Please let us know when the mystery is solved.

True, but the OP doesn't state where they are located, and southern locations sometimes DO have outside wall pipes.

I still like Jeffy's thought on a critter out there...

You can get banging as a hot water pipe
heats up or cools, if a long stretch of
pipe is hanging from metal hangers.
Plastic hangers or padding help.
My dad's hot water pipes once sounded like
a team of dwarf carpenters.

1-pipe steam radiators make a terrible
ruckus when the radiator isn't level, too.