A few weeks ago I was sitting in 9C on an A321 when during takeoff and landing I kept hearing this loud "thud...thud" from underneath the door. It repeated itself every 2 minutes or so during climb, then stopped when we reached cruising altitude. Then it started up again on decent. Fortunately this was only CLT-TPA, but I couldn't wait to get off the plane. The F/A dismissed it as not being a problem, but everyone in the row had a look of concern.

I know the Airbuses make weird noises (my favorite being the hydrolics when they taxi on 1 engine, that freaks out everyone in the wing section), but I've never heard this one before.

Anyone else?