The speed brakes do make a 'descending howl' when deployed. I've heard it several times from the flightdeck. Most noticable in the A319 but I can't recall hearing it on an A320 or 321, probably because the wing is further from the cockpit.
I've also noticed a similar noise when Flaps 1 is selected, this time when seated in the cabin near the leading edge of the wing.
If you lived in Slough instead of Swindon, you might be forgiven for worrying that it was the sound of the bomb-doors opening:
Come, friendly bombs, and fall on Slough!
It isn't fit for humans now....
(J Betjeman, 1937)
Last edited by eckhard; 22nd Aug 2012 at 15:41.