'97 E36: Odd Noise After Turning Off Ignition

I recently bought a 1997 328ic with 87K and it has been performing admirably.
However, I just noticed an odd sound seeming to come from the dash area after I turn the car off.
It sounds a bit mechanical and a bit like static/buzzing from the radio and seems to last for more than a minute or so. There are no other obvious symptoms.
What might continue running after the ignition is turned off to make that noise?
Any ideas?
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wrote:

If it's got A/C it could be the system settling down otherwise it could be the trap doors on the heating ventilation system closing to the "rest" position.
Sir Hugh of Bognor
The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it!
Hugh Gundersen snipped-for-privacy@h-gee.co.uk Bognor Regis, W.Sussex, England, UK
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I'm with Sir Hugh, it's the trap doors on the life support system reverting to their Park position. Do not be concerned, grasshopper,
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