"Quiet on the set" is a clich we’ve all heard before. A movie director typically sounded the command before the microphones and video cameras were set in motion. After all, the audio about to be acquired was needed for the final production, and whatever got on tape, good or bad, was "part of the picture," so to speak. Hollywood of today doesn’t have to worry about this as much as it used to. Most, if not all audio in a modern production has been recreated in a sound studio. So, what’s a poor amateur camera operator with a mike or two to do?
Listening is Critical
If you are like most videographers, you are a visual person who thinks about light, color, texture and composition. When evaluating the environment where you will be shooting, take note of available light. What is the light temperature daylight, indoor or a combination? If you will be capturing audio, you have added to your job description. You have to also wear the hat (or headphones) of the audio engineer and evaluate or critically listen to the given environment. The easiest way to begin to tune your senses for critical listening is to don those phones, turn on your mike and amplify the noise. Noise is any unwanted sound, and when you crank up those personal audio monitors the unwanted noise will be all too apparent to your ears.
The Usual Suspects
When shooting outdoors, noise can come from an infinite number of sources that are, more likely than not, beyond your control. If you can steer the shoot away from busy streets, flight paths of aircraft or other machinery, do so. If you must deal with relatively high levels of noise, like that from traffic, your recording techniques are your only salvation.
Reach for the Directional
Use a directional mike, like a shotgun or hand-held cardioid pattern. The back of the mike should face the offending noise. A directional mike will tend to reject sound that comes from the rear of the mike. In addition, the mike should be close to your desired sound source. Battling high ambient noise levels becomes a case of ratios. In simple terms, it’s a shouting contest, and the physics of sound can work to your advantage. The further away a sound is from a mike, the lower its intensity, agreed? Then, the converse must also be true; the closer the sound source is to the mike, the greater its intensity. So, get that mike close to your subject and as far away from the noise in question as possible.
Low frequency noise is much more difficult to get rid of than high frequency noise. High frequencies are directional in nature, while low frequencies tend to ooze all around. For example, we have all heard the muffled sound of voices talking behind a door. When the door opens, the voices become clear. Close the door and they muffle. The closing of a door is basically the effect you get when turning the directional mike away from an offending sound source. The high frequencies tend to be rejected, but the lows or muffled sounds will trickle around to the front of the mike.
A wind sock is a must for hand-held mikes used in the field. These foam guards reduce the thumping noise caused when wind blows on the pickup element. In most situations, a foam wind sock will provide all the protection you need on a windy day.
A low-frequency cutoff is a tool that any field mike worth carrying should have and one that is showing up in many DV cam menus. It is referred to as the Wind setting. Settings such as this are known as high pass or low cut filters and they cut off frequencies below a given point, only letting the frequencies above the cutoff pass. This helps greatly to mitigate wind noise and the low rumble of machinery and does not significantly affect the range of the human voice.
When a shoot moves indoors, a new pallet of noise hazards adds to the mix. Air-conditioning, refrigerators, computers and more can seem innocuous when you are in the room with them. Your ears tend to block out sound that is repetitive when you are in the environment, but when you get the footage home, the air-conditioner that didn’t seem like such a big deal may now sound like a freight train roaring through your sound track. This prompts another call for action. Listen to the environment through headphones and crank it up before you shoot. Now, start turning off switches, shutting down hard drives and pulling plugs. When the room falls silent and the only sound is granny creaking in her rocker, plop her down on the couch and roll tape.
The Crackle, Buzz and Hum
Many times, the noise that you may hear in your headphones doesn’t come from an actual sound sources but from electrical interference. Bad audio cables could be one cause, so verify your connections before you arrive at the shoot and always bring backups. Need we state it again? Sure, why not? Listening with phones is the best way to ferret out a bad plug, jack or wire. If you are plugged into the AC of a building, you can pick up 60-cycle buzz, which can be exacerbated by dimmer lights.
If you find these ghosts creeping into your audio, try changing outlets in an attempt to find a different circuit. And always run audio cables and AC power perpendicular to each other, not parallel.
As if all the other trials of audio acquisition were not enough, wireless mike transmitters can also cause radio interference. You may not be ready to break the bank to buy a top-of-the-line, true diversity UHF wireless system that costs as much as your camcorder. Therefore, you’ll probably have to deal with some audio interference and drop-out. Radio frequencies can bounce around off metal surfaces and arrive at the receiver out of phase, causing dropouts. If you encounter this, try moving the receiver closer to the transmitter. This may mean running a cable from the receiver back to the video camera after it has been placed as close to the transmitter as possible. Ensure that all the units have fresh batteries and that the transmitter and receiver remain in each other’s line of sight.