BTW, the suction noise at the end appears to be a vacuum line of sorts, de-compressing. You can see the DISA valve change in position when that noise occurs. Almost like a "pop-off" valve sound, except when the engine is turned off.
I also verified I get a buzzing noise  if I leave the climate on and shut the car off. The higher the temperature on the panel, the longer it takes the buzzing noise in the "DISA area" to stop buzzing.  the buzzing noise will be shorter if I had the climate control turned off already well before the car is shut down.
Hope this bit of discovery helps. But I'm curious to find out the source of this annoying noise is (for your and my engine). Don't like the sound of it and not sure its proper.
2004 325Cic, ZSP, ZPP, ZCW, Owned since 12/1/12
E46 Merit Badges: OFHG, WP, ET, AT-T, ICV, CCV, Fluids (5)