How do you stereo record sound of moving vehicles?

K

Kevin Kelly

Active member
I know there are different setups to stereo record sound, but what about when the sound source is moving (i.e. autos, trains, planes, etc.) Would the microphone setup be different if the camera was locked down verses panned with the action? Would your setup change if the vehicle was passing close-by the camera, or at a distance? I only have two audio channels and options for omni, cardiod, hypercardiod, and shotgun microphones.

So, what are your suggestions?

Kevin
 
This is actually a really good question, and the answer is "it depends".

If it were me, I would record the card in lots of different ways, but most of the recordings would be done with a matched stereo pair of cardioid mics. If you know you need certain perspectives, get those first, and then move in for all the other stuff that you may not need right now but should grab while you can, like door opens, engine idle...basically any noise the car makes. Record all those things individually. You could easily have over 100 different stereo recordings off of one car.
 
+1 with Dave on coverage, record EVERYTHING you can while you have the car.

I think there is something on recording cars in the stickies. If not you should search the forum because I know it has come up before.

An important point though is that a camera "sees" very differently than a mic "hears". A car passing on screen is usually seen and followed by the camera. You need to do that also with your stereo pair. If you just plant them the car will just zip through and you won't have nearly the length you need.
The second BIG point is that "speed" in sound has to do with how fast the engine is going and if it is straining.

You never want to record a car going fast to match a car filmed going fast, they won't match at all.

If the filmed car is going 80 your recorded car should be going maybe 30. But since you need a fairly high RPM and you need the engine to be doing some work you need the car to be going up hill a bit. If you are recording an automatic stick it in one of the lower gears so you can get the RPM up at slower speeds.

A side benefit is it's a LOT safer.
 
+11 Dave.
It depends. I would normally use a number of mics, interior, exhaust, engine compartment.
For drive-bys, a single stereo mic would be the simplest and most fool-proof. (with a proper shock mount and wind protection of course)
 
A lovely stereo drive past with Doppler sound great, but is a swine to edit because it's very much a complete start to finish effect, and I usually go with David's technique above.
 
Speaking of doppler. As long as your out there recording get a few doppler horn bys.

In case you don't know what we are talking about the "doppler" effect is the pitch shift that happens when something moving rapidly and making noise changes from coming at you to going away. Coming at you the sound is compressed and the pitch is higher, as it passes you the sound is stretched out and shifts lower.

So if the car honks it's horn as it passes you get a really noticeable shift in sound that communicates "speed".
 
Maybe I'm beyond my depth here…..

Is stereo really needed? Could you do a single track, following the sound with an appropriate mic, and then simply pan the track left to right (or right to left) during the edit? Maybe this isn't as elegant, but it sure seems more simple and reliable.

Grant
 
ggrantly said:
Maybe I'm beyond my depth here…..

Is stereo really needed? Could you do a single track, following the sound with an appropriate mic, and then simply pan the track left to right (or right to left) during the edit? Maybe this isn't as elegant, but it sure seems more simple and reliable.

Grant
Click to expand...

Well, that's what I'm trying to figure out. I'm mostly involved with the video side of recording, but I would like to get better sound. Most stereo sound techniques I've read about seem to be ideal for stationary sound sources. So, using a fixed pair of near coincident microphones would work.

If the camera is panning with the movement, I think the simplest solution would be to pan a microphone (mono or stereo) with the moving sound source, and than panning the sound in post. Would mixing a track from a stationary omni microphone with a panned mono microphone, give the sound a better/realistic/etc. quality?

But what if the camera is stationary and the sound source enters and exits the frame? Would your mic setup change if the moving sound is close-by the camera, far away? This situation would seem to be ideal for a spaced pair of omni microphones.

Whether the camera is panning or not, some of the setups I'm considering are stationary or panning: a mono microphone, X-Y pair, ORTF, perhaps even a Jecklin Disk.

Any thoughts, opinions, website links, etc. to help me narrow down my options?

Thanks.


Kevin
 
You can go either. All the stuff about proper stereo mic placement and such is essentially not considered in FX recording. With FX recording you are not trying to "document an event" you are trying to get some usable raw material for post.

So it almost doesn't mater if you go stereo or mono. Stereo might give the editors some options that mono doesn't and will pick up more nuance in doppler elements. But it's entirely possible that post will just use one side anyway so... YMMV.

I would guess that most are recorded in stereo, but that may partly because they are carting around a stereo rig and so why not use it. Plus they know it may just get used as mono in post. But while you can just use one side of a stereo recording there is no way to get to stereo with a mono recording.

Long camera lenses shrink perspective and the camera movement also messes with perceived time. Recording with a fixed mic is like sooting with a telephoto lense aimed straight across the road. The car goes in and out so fast you don't know what happened.

So you need to stretch out that car by so it will match visually. A follow pan with the mic is a good way to do that.
 
BTW this is not speculation on my part. I have recorded for a fair number of small and big films and we did tons of national auto spots. I have recorded, maybe not hundreds but close, of cars and trucks and race cars etc.
 
davefisk said:
this is not possible. You can create dual mono, but you can not create proper stereo from a mono file.
Click to expand...

I wasn't looking for 'proper stereo'. I was looking for the effect of a vehicle passing from one camera position to another, which is easily done by using two mono channels -- a left and right, both identical -- and then properly adjusting the balance envelope from heavier on one channel to heavier on the other. This is done all the time with dialogue as well, though in all instances subtlety is the key.
 
Sounds are 'placed' in a soundscape all the time. Let's consider an example.

I've got a scene at night. Crickets chirping. Establishing shot is outside the house, so I want the cricket sounds all around, pretty much evenly. Then I cut to inside the house, in a bedroom. Volume of the crickets is lower, obviously, and less high frequencies. But on one side of the camera is an exterior wall and a window. On the other side of the camera is an interior wall and several other rooms of the house between camera position and the great outdoors. Clearly I want the cricket sounds heavier (just a bit) on one side of the camera than on the other, because that's the way they would be heard in reality.

If the crickets are naturally-occurring, then the balance will (more or less) be automatic. But what if there were no crickets chirping when we shot the scene? Or they were too muffled or too intermittent? In that case I will use a sound effect in editing. Even if I use a stereo sound effect, the odds are it's not going to be balanced to match my scene and camera positions. So whether the sound effect is stereo or mono, I'm still going to manipulate the perceived position of those crickets by adjusting channel levels. Especially if I'm working with surround sound.
 
davefisk said:
this is not possible. You can create dual mono, but you can not create proper stereo from a mono file.
Click to expand...
Maybe, of course you would have to define "proper stereo". In the real world "stereo" doesn't exist. It's a construct of playback meant to simulate the "real" experience better than mono.

Sounds are almost all point sources that then go out and react to the world. If you stick a human in that world with two good ears they will hear with both and get interesting placement and distance information from the phase differences.

One can certainly take a point source (mono) sound and send it out into an artificial "world" and then "listen" to it in that artificial world and end up with "stereo" that is as valid if not more so than something recorded in the "real" world. More valid in that it is "stereo" in the "world" of the film and not an imported "stereo" sound from another "world".

Maybe more to the point nobody will ever be able to tell which "stereo" sound was created and which was recorded.

You do have to do more than just pan it though. For the car by I would look into one of the doppler plugins.
 
David W. Richardson said:
Sounds are 'placed' in a soundscape all the time. Let's consider an example.

I've got a scene at night.
...
So whether the sound effect is stereo or mono, I'm still going to manipulate the perceived position of those crickets by adjusting channel levels. Especially if I'm working with surround sound.
Click to expand...

On top of which humans tune out anything that isn't important or a danger, so in "real life" the crickets will mostly disappear from perception after a few minutes.
 
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