First, I stifle laughter from the 'sex-talk' example .. Then,

I say 'vocal' would imply actual vocalizations, including but not limited to onomatopoeia. That means the "oooohs, eeks, aahh aahs, a oh, yes yes, fuck me" are all considered 'vocalizing'
So, by definition of the English language I say "All of The Above" on this one, Alex. And yes, that is my final answer!

I know a guy who used to want me to bark while in doggy style... now THATS vocal. Lmfao  

PS I couldn't bring myself to do it without laughing lol

While she is facing the wall, that hotel security is called.  Happened to me in Boston in an older hotel with some thinner walls.

volume. Loud or just a purr, it's the intensity  
of the moment. And the reality. IMHO anyway

...from the soft moans of pleasure and almost sub-vocal purring, to where her neighbors know my name

I have had an experience or two with a provider who gave me almost NO feedback vocally and it was rather disturbing, kinda threw me off my game. There wasn't much movement on her part, either -- guess I was having flashbacks to married life!

The auditory equivalent of an involuntary muscle spasm.  Not something you consciously did, but a sound your body gave up in the heat of the moment.

In general, I do love to hear a gal moan, groan, and (if a highly secure area) scream with delight.  I don't care if it is genuine or not as long as she can pull it off convincingly.  This is after all audience participation theater, is it not?

Vocal can also describe a gal who coaxes me along with soothing yet alluring commentary about our encounter.  I have a tantrika (Who actually is also a semi-professional actress!) that does this and I just love it to death.

There was also one gal I met a long time ago who created an entire story that ran the whole hour of our encounter that was so erotic and so mesmerizing that it could have won a Tony.  Sadly I could never find her again.  She was able to incorporate elements that she picked up on like the sound of the maid in the hotel corridor and work it into the scenario.  

But then there are the gals that prate on about either trivial or even noxious subjects while they ought to be focusing on me.  Even my attempts to refocus their attention are rebuffed.  Customer oriented, they are not.

For me being vocal means telling the client I like what he is doing and moaning and yessss that feels amazing. If he is not doing it correctly I will guide him through what feels good for me particularly also if the client is happy I want him to show some sort of response so I am pleasing him or guiding me through what might work for him. I think it goes both ways to pleasuring the client and the provider.

vocal is usually faked. Screaming, biting on pillows, none of it seemed real.  I have no doubt that some providers actually do have orgasms and get vocal when they do. But I've had providers start to scream or make other loud noises one minute after we start intercourse.  

I now ask every provider I see to not fake orgasms, but instead tell me what to do to make her feel good. It makes for pretty quiet sessions, but the noises I hear are ones I believe are for real. It's nothing like the screaming I heard from my ex decades ago, but then again I'm not 25.

...i feel there should always be that intimate vocal exchange..sometimes it might even get loud...but i HATE that fake OMG!! loudness that some girls do because they think its what guys like and thats want do in porn vids..nothing makes my cock shrink like that first OMGGGG...