Metal Sound from Walls/Vents

[hiphippie]

I live in a rather new townhouse in Florida. It was only built about 3 years ago, and I've only heard this sound in the last couple months.

Every morning around 7am-8am, I hear a loud metal clinking sound coming from the walls. It sounds like someone is dropping marbles on a tile floor. It makes a metal clinking sound like the marble is bouncing on the floor and then repeats. This continues for a few hours and then comes back the next morning.

I'm not sure, but I assume it's coming from the air conditioning vents. We haven't had the air on lately because of the weather, so could that be the reason? And because I live in a townhouse, could it be the neighbor?

It's been waking me up every morning. I'd like to figure out how to make it stop so I can continue to sleep!

Thanks!

[HayZee518]

Ductwork if it isn't cross creased when manufactured willsnap and buckle when air is drawn through it. If there is a difference in temperature between the inside and outside condensation will form and drip inside it.