Willie The Wimp wrote:
Little brick bungalow in midwest US, built in 1954. Mostly original
stuff. Floor-boards creak a good bit. I'm alone here.

Every night, in bed, I hear a CLUNK from the direction of the kitchen.
Often a second one, not too long after the first. I've heard it while in
the dining room as well. Never while I was in the kitchen.

I orignally figgered it was in the studs or rafters, possibly
where they attach to the forced-air ductwork. If so, I may never
find the cause.

Fridge is an Amana built around 1984. Has given very good service.

It sometimes sounds like it is coming from the fridge, but I can't
tell for sure. Do they CLUNK when the compressor shuts off?

Any other ideas?

Thx,
Willie

Another possibility is if the fridge has a condenser fan underneath.
When the thrust washers/bearings wear, the shaft will pop back and
fourth when power is applied or removed from the motor. It can make
a clunking sound. As far as the compressor goes, hermetic compressors
have the motor and pump actually suspended or sitting on springs inside
the can. Over the years, the springs can weaken and allow the compressor
to bang against the inside of the can when it starts or stops. There can
also be bearing wear in the compressor itself much like what happens
with a fan motor, the shaft can move longitudinally and make a thumping
sound when the compressor motor cuts off. I found a PDF file that has
an exploded view of a small hermetic on page 71 that shows the springs:

http://eprints.utm.my/2627/1/71811.pdf

Here's a link to an excellent video about small hermetic compressors:

http://www.youtube.com/watch?v=bAZGkny8g64

TDD