This is archive material from Jay's popular Audio Solutions column in DV Magazine.
Most of this content is still valid and useful... but some of the specific information may have changed. You'll find newer, more comprehensive, better written tutorials in my books. The blatant ads on the right take you to downloadable samples, critical comments, and discount sales.
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by Jay Rose Published October, 2000
To find the best locations, use your ears as well as your eyes.I live in New England, where Autumns are particularly spectacular. You can point a camera almost anywhere and get a wonderful shot...
... unless you're shooting dialog. Even the prettiest location can have audio problems. If you don't know what to check for, that beautiful shot will cost you a lot of time and money in sound fixes.
The laws of acoustics are in full force every day of the year, indoors and out. Looping -- replacing noisy dialog in a studio session -- is an expensive and cumbersome process. So it makes sense to think sound while you're looking for settings. There are only three things you have to ask about a location to determine if it's sound-worthy:
• Is it quiet enough for dialog?
• Does it have the right acoustic properties?
• Can you use equipment without interference?
Other location issues -- access, electrical power, legal clearance, and the like -- are common to both audio and video, so you'll probably be checking them anyway.
NOISE IN EXTERIORS
The microphone is a lot less selective than the lens. To the camera, a city park may look as bucolic as a medieval pasture. But you can't point the mic to avoid traffic or crowd noises, and once they're on your track, you can't get rid of them. If you think a location looks good, stand where the talent will be and listen for a while. What you hear is what you'll get. A few tips can help you avoid unpleasant surprises.
• Scout at the same time of day you're planning to shoot. A suburban park that's quiet at five in the afternoon may be very noisy when school's in session. Noise patterns also change from day to day, sometimes in unexpected ways. I once got burned by an otherwise lovely exterior that was across the woods from a corporation's helicopter pad. The producer said it would be quiet... but he'd checked on a day when the executives were in a meeting instead of flying around.
• High frequencies are directional. Even if you've found what seems to be an okay location, check other alternatives in the same vicinity. They may be quieter. They might also be noisier, which is worth knowing before you set up a shot.
Watch out for very large buildings in the middle distance, like the apartment house peeking over the trees in figure 1. Those buildings don't make noise themselves, but mid- and high-pitched noise from nearby traffic or factories can bounce off them and into your shot. This is worst when a building's surface is mostly glass and it has two wings at an angle: it acts as a corner reflector, focusing the sound right at you.
Figure 1: That shack in the woods would make a great rural setting... but the apartment house behind it (inset) can reflect traffic noises all over the "farm".
Low-frequency sounds aren't as directional and will carry farther, but are easier to remove with filters.
• Ask neighbors what their experience has been with airplane traffic. This changes during the day and also as the wind shifts. It's usually not a good idea to shoot near airports because of the electronic interference, but runway patterns can affect locations miles away.
• If you're using generators, be sure they can be positioned far enough away to be quiet; ideally behind some solid structure to block the sound. And make sure there's enough extension cable.
NOISE IN INTERIORS
Indoor locations have fewer variables, but you still have to listen to them. Then check all the windows: do they overlook a potential noise source like a loading dock or trash compactor? Can you get these operations shut down while you're shooting?
If a window lets a small amount of noise through even though it's tightly shut, try hanging sound blankets over it. If the window is part of the shot, seal a piece of thick Lexan or Plexiglass to the frame. If all else fails, plan a point-of-view shot through the window showing the activity on the other side... that way, the viewer will at least understand where the sound is coming from.
Check every interior opening as well. Hollow-core doors don't stop sound, and even solid ones may have gaps around them. Built-in cabinets and media walls can be openings in disguise: sometimes, these open directly into another potentially noisy room. If there's a work area on the other side of an opening, make sure you'll be able to shut them down when the camera is rolling.
A common practice in office buildings is to build partial walls that stop at the suspended ceiling. The area above the ceiling is an open plenum -- sometimes extending completely across a building -- where ducts and cables can be run. It's also an open path for sounds to pass from one room to another. Check by lifting a tile near an interior wall. Special fiberglass ceiling blankets can absorb some noises, but installation is difficult and they're not totally effective. If you absolutely must shoot in a space with partial walls, you may have to wait until after the building closes.
Air-conditioning systems can be troublesome at interior shoots, particularly if you have to mic from a distance. Even if the system's motors are far enough away that you don't hear them, the moving air can make noise because of friction. This often happens at the vanes of a ventilation grill -- you can make HVAC systems a lot quieter if you remove the grills before you shoot. You'll also hear hiss if the duct has a sharp corner near the vent, but the only cure for this is to turn off the blowers.
Refrigerators, water coolers, and fish tanks also have motors that make noise. The best solution is to turn them off while you're rolling. Watch out for units that turn on and off automatically: if some shots have noise and others don't, the difference will be distracting. As a last resort, record additional room tone with the motor running, and mix it under the quieter shots.
Even if you've found an incredibly quiet interior, you still have to deal with room acoustics. While all practical rooms have some kind of reverberation, most people learn to ignore it when they're in the room. But on playback, those echoes can sound unnatural. Room reverb can be countered with absorption and close miking. But make a note of room reverb you're scouting, so you can bring appropriate equipment and materials to the shoot.
Reverberation is seldom a problem outdoors, unless there's a large wall nearby to cause reflections on voices. If the building is in the shot, viewers expect this and there's no problem. But if the building is outside camera range -- or if you're faking a location that shouldn't have buildings at all -- the echo will destroy your track's credibility. If you can't find another location, shoot the dialog as closeups so the mic can be very near the actor's mouth.
Wireless mics are subject to interference from TV stations, police radios, radar, and a lot of other things. Its tiny transmitters can't compete with those much larger cousins. Wireless can also be affected by those rectangular cellphone antennas planted all over the place (figure 2). While the phones themselves work on different frequencies than a wireless mic, the signals from the relay station can mix together in low-cost receivers to create unpredictable interference.
Figure 2: Those ubiquitous cellphone antennas can radiate combinations of signals that interfere with wireless mics.
If you're in doubt about a location's suitability for wireless, plan for a long test before the shoot. And always have a wired backup with adequate cables. For tips on dealing with wireless problems, see "Dialog Unplugged" in/on page [editor: I'm developing this feature article now. Jim will know if it's in this issue or the next.]
Some electronic sources can disturb wired mics. High-voltage transmission lines, power distribution transformers, medical equipment, and even lamp dimmers can radiate interference that's picked up by the mic or cable. Balanced wiring and a transformer adapter at the camera help a lot. Surprisingly, some interference that affects wired mics doesn't bother a wireless rig at all!
A little knowledge and thoughtful planning almost always results in finding locations that work better for dialog. Or, as the motto goes, a scout should be prepared.
Jay Rose is a Clio- and Emmy-winning sound designer who spent his early years as a location recordist. Visit his studio -- and learn about his books -- at www.JayRose.com.