Do you have a kind of system for placing things like barking dogs, carbys, ringing phones, etc in the background of a scene? How do you decide what to place?
Also, do you ever use backgrounds that are emotional backgrounds that the audience won't pick up on rather than a recording of the real things? Such as a convolved voice as roomtone or forest ambience at a certain level during an interview.
For me, it's simply a matter of not thinking about it - i shoot from the hip on on this stuff, gut intuition. I play the scene segments over and over (as I move along the timeline with my editing duties) and drop things in and shuffle them around, replay a section here or there, tweak it etc. There's an innate musicality and rhythm to doing spotted effects. Great places are spots between dialogue where they can be massaged in, other times it's fun to play off of dialogue (or a funny offstage sound right after somebody shuts the other person down with a joke), and usually at the top or tail of scene when there's that brief moment of no dialogue there's golden moments to squeeze something in.
Also, they can be a saving grace with ADR lines - pop a spotted effect between the production line and ADR lines (or better yet, slightly overlapping naturally into the ADR line itself), and it helps detract the ears from focusing on a bad ADR match. BG phone rings in "ring-and-half" and "2-rings-and-half" style edits are great for this. Computer beep sequences/devices work well too for this, for exterior situations OS car horns or a car by of some nature (even dog barks) work. Just something to slightly distract.
Almost always I stretch reality in BGz for emotive content and richness, and sometimes you have to for fixing visual continuity or establishing a precedent. Honestly, sonic reality equates to the word "boring" for my ears. It's all about being tasteful and rich, whether the situation call for dense or minimal BGz.
A common situation with this is moaning winds inside scary spaces, albeit edited at very subtle levels so that it weaves in and out of the roomtone. I cut BGz on Killer Joe and during the final scene (a 20+ minute scene) we were inside a house during a rainstorm - yes, literally, 20+ minutes within the same one room. It's a very stong scene for dialogue/story so it actually holds its own very well. Now I could just play a steady, light rain like we see at the top of the scene's establishing shot - but 20 minutes of it would be boring and leave the sonical landscape incredibly flat. So instead, to push the emotive envelope of the scene, I gradually started with a light pitter-patter and over about 8 minutes built up a gale-force storm with windows rattling and wind blowing internally, stronger rain tracks. It builds up over such a long duration you aren't even aware of the change in BGz. Then after the climax of the scene, I gently pulled back the energy of the rainstorm to a middle level, while still retaining some of intensity of the strongest moment. It's one way to give a dynamic flow to especially long scenes and reinforce the story/emotive content (because even to some audiences, painfully obvious moments still need a gentle support by other non-dialogue means to sell effectively).
EDIT: Eventually I heard the mix and they didn't end up going with the storm build up. Oh well, unfortunate, but thats the way these things go sometimes.
Kind of a broad, high-level answer, but I hope this helps...
A mixer/sound designer up here at VFS (Brad Hillman) likes to use the E.A.T. acronym for background edits - Entertaining, Accurate and Technical.
I've found that helpful. So to bastardize his intentions, here's my interpretation of that:
Entertaining backgrounds are, in your example, those sorts of whispers, low drones, radically pitch-shifted elements that speak to an emotion or sense of eerieness without being an identifiable object in the scene, but nevertheless clue the audience in to what the story is saying somehow. Or, they are the comically distant tire squeal or bit of walla that manage to poke through when there's a lull in the dialogue. They are the parts of the background that get a tiny bit of space to speak without stealing the listener's focus, just subtly supporting the scene.
Accurate being, cut the precise right version of the thing you're seeing. If you're outside and it's raining, don't just grab any rain. How close is the camera perspective? How dense is the rain? Is it slappy and fat, with just the occasional spatters? Just kind of misting? Is it a torrential downpour? Is the rain hitting puddles, cars, etc.? Same thing with winds. If you can't see a visual reference of what the wind's doing, you might not want to cut in excessively howling winds. If you're cutting in a ringing phone, what era are you in? Don't give me an iPhone ring if I'm watching Madmen, etc.
Technical... I think of this as, choosing sounds on the basis of how that sound would be heard in the reality of the scene, and not just because it's a good-sounding background. So if you cut in a residential neighborhood dog bark, don't be afraid to filter that a little bit and try to give it a bit of distance. A mixer on a condensed schedule probably doesn't have time to rolloff and pre-send verb to properly place every single element you throw at them, and you will save them some time by taking them halfway there with tastefully baked-in effects in these cases. Outside traffic shouldn't have a bunch of really crisp highs on it. Rain, if you're indoors, should sound like it's hitting something (a roof) instead of gushing down in front of you.
In terms of speaker placement...
Backgrounds are really, really tough and require a ton of imagination and careful selection. I find them incredibly difficult and creatively challenging, even moreso than hard FX sometimes.
Remember that like a lot of cinema sound, their purpose is to serve the goal of the story and scene rather than to purely sound cool. Unless the scene's focus IS on the backgrounds of course!
There was an amazing interview with Tim Nielsen on Designing Sound re: backgrounds a month or two ago - http://designingsound.org/2011/08/tim-nielsen-special-interview-on-backgrounds/. Some good stuff in there.
Adding my $0.02 from an academic institution's standpoint, I learn here at SCAD from David Stone, a veteran supervising sound editor. He talks about separating the way you think of backgrounds in terms of broadband noise (or what he'll call "the mushy, whooshy, air tone, room tone, that sort of thing") and more specific sounds (bird layers, car bys, walla). This may seem to be a simple concept, but it helps me in terms of how I think about my layers.
I avoid grabbing too many sounds that contain air - you just get mud that way. The "mush", whether it's made of traffic beds, AC sound, computer sounds, is going to support your dialogue track.
Specific sounds and the like can be for creating the environment (the density of birds and walla, etc) and for affecting the pacing (in terms of spot BGs). An appropriately timed carby can both compress and expand an awkward pause. We feel that more time has passed, but it also feels much less awkward. Different carbys vary in their emotional content. Some can be very imposing, while other more distant car sounds, especially over wet roads, sound peaceful.
I use a lot of editing techniques that come from DX editing. Frequently with a very busy stereo ambience recording, I'll create some fill, and then begin pulling certain sounds (a voice here, a car or bird there) to customize my track.
Ultimately, start listening to movies really loud (closer to theater level) if you don't already. I discovered that when you do that, you actually hear the backgrounds. Se7en, Super 8, Social Network are a few that come to mind with awesome BGs.
As with so many things related to film/TV/game audio, there's no real answer...
Wherever you feel is appropriate, or makes sense, or helps the story, or helps put the viewer in the right mood or environment, where it makes them feel sad, where it is really bloody annoying, where it won't interfere with dialog, where it will mess up a line of dialog so bad so you are certain that the viewer cant understand what really is beeing said, and of course wherever the boss/director tells you to.
Theres really only one basic thing that should be avoided. Do not place it there if it doesn't actually do anything. Unless it does something there's no point in spending the time to put it there. Use your time wisely.
I have no system, but each project and scene will dictate what, how and where I choose to put a sound. That's in the best of worlds... In the worst of worlds, as soon as you find something that moves the scene along you just kick it in there just to do something to try to make the scene come alive, but with no time to actually contribute anything to the story. And then you move on to the next scene or you wont make the deadline.
Don't quite understand what you mean by system? placing effects is all relative to the scene?
I tend to have a stereo ambience track and then a couple tracks which are mono/stereo where I can place spot effects for the ambience. They're then placed relative to the camera shot.
