posted on Dec, 18 2003 @ 01:54 AM
You mentioned it's constant, more 'loud' when you lean against the door jam. Sounds vibrational. The constant thing is telling too.
Possibilities include: Attic fan vibration, WOOD BEES, TERMITES, RATS, MUD DOBBERS, etc.
Bugs is loud. Especially when there's lots of 'em chewing up stuff.