I would think the guy sitting next to me was joking if he suggested doing a PA about extending the spoilers...load of bollocks really.

And more in line with the sterile cockpit rule, if you need speedbrakes it means you 'screwed' up somewhere, or you are surprised by ATC vectors, or the airspace is challenging. In other words, time get busy, no time for public relations.

DC8 series aircraft with P&W JT3 engines could use inboard engine reverse while airborne for the same purpopse we use spoilers/speedbrakes. I remember crew warning about their use on Finnair flights and they where impressive in generating noise and vibration that was clearly out of the norm. I never flew the DC8 as pilot so I have no idea how effective this procedure was for what it was intended for.

dear janne!
it was very effective, and was used to get to the bar quickly.
when i suggested to use it once,the captain told me he would kill me first,because in his words the machine would fall apart,since it was over forty years old.
shame really,have thought about using it on the 47,damn thing couldnt do it....... all the best, see you, alex

There used to be informative brochures in the seatback pocket telling SLF all about these geewhiz gadgets.

Myself, I never bother with inflight PA about spoilers and gear. Of course, I'm flying a Piper J-3. :}

"Ladys and gentlemen, each of the wings is about to fall apart. The back edges
will start sliding back and hang down like shirts flapping on the clothesline. The
front bits will separate themselves from the front of the wing, and they realy
looked cool when I was on 727s. Once this is all done youll see bloodey great
gaping holes all over the front and aft sections of the wing. On landing large
chunks of metal will come apart from the top of the wing to further bamboozle
any armchair thoughts of aerodynamics you might have, as well as a huge
noisey revving of the engines to add to your confusion as to why Im throttling
them up when at the same time Im trying to stop on the runway. Im not paid
enough to teach you airfoil theory and landing performance so just google it.
Thank you."