Hi,

All of sudden, I started hearing a noise from my condo's washer/dryer closet. The closest I can describe it is that it sounds like the tail end of a toilet flush cycle. I'm still not certain where exactly it's coming from, but I've made the following observations:

1. Pretty sure it's not the machines. I turned off power to both washer and dryer, and the noise persists.

2. I've run both machines. The noise is still there unchanged both during operation and after.

3. Putting my hand on the dryer's exhaust vent hose (with machine off) I can feel a vibration.

It almost feels like something has changed with what I imagine is the building exhaust that leads from my dryer vent to the exterior? As if someone has installed a fan or some kind of machinery that is either causing noise, or doing something to the airflow that is causing noise and vibration?

I've contacted building management and they've told me they have not heard any complaints from other units.

Any clue what this could be?