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Audio Advice: Hidden Microphone

Audio Advice: Hidden Microphone

The art of recording audio in a manner inconspicuous to the viewer. In other words, you're hiding the microphone from the "eye" of the viewfinder.

Invisible miking is the art of recording audio in a manner inconspicuous to the viewer. In other words, you're hiding the microphone from the "eye" of the viewfinder. But why would you want or need to hide a microphone?
Let's say you are shooting a wedding. The bride and groom want to hear their vows on the tape, however a visible microphone is distracting and undesirable to them. Unfortunately, the on-camera microphone isn't a good option. There are few things that sound worse than the microphone included with most camcorders. These mikes pick up a lot of background noise. At 75 feet, your bride and groom's exchange of love will sound like little more than a mumbled whisper. So what can you do? Try hiding an external microphone. With proper placement, the mike "invisible" on to the eye is able to pick up the dialogue of the bride, groom and minister in a clean and intelligible manner.
Weddings aren't the only occasion demanding invisible miking. Been to a movie lately? Watch any sitcoms? Seen any commercials? Anytime you hear audio, whether it's dialogue or other sounds, there is a mike in the vicinity. And more often than not, the mike is invisible to the camera. Fortunately, there are many options available to the video producer wanting to employ this technique. By using invisible miking techniques to record your sound, you can dramatically improve audio quality while adding aesthetic professionalism to your videos.

Lapel Microphones

Also known as "lavaliere mikes" or "lavs," these miniature microphones are usually worn on clothing - clipped to a shirt, jacket or tie. While they are not completely invisible, lav mikes are more inconspicuous than other external microphones. Lapel mikes are the workhorses of the news industry. Tune in to any news show and, if you look long enough, you will see one clipped to the anchor's clothing. These microphones are extremely small (some are smaller than a pencil eraser) and are easily concealed. Also popular in theatrical applications, these mikes weave into hair or a veil (think weddings), with just enough of the mike sticking out to obtain good sound.
Most lapel microphones are omni-directional, meaning they pick up sound from all directions. The biggest advantage to a lapel mike is that it is always the same distance from the subject's mouth, ensuring consistent sound quality. One disadvantage to using an omni-directional lavaliere is that they pick up extraneous background noises (machinery, vehicles, airplanes, wind, etc).
Lapel microphones can be hard-wired (meaning they plug directly into your camcorder's microphone jack) or wireless. Obviously, using a wireless microphone presents a better opportunity for invisible miking.
With wireless models, the mike itself is wired to a transmitter that is worn on the belt or carried in a pocket. A receiver plugs into the camcorder and the sound transmits between the two devices. This is the ideal set-up for invisible, long-distance recording such as a wedding. It also is a good choice for production of an instructional tape, where the subject needs free hands for uninhibited movement.
If you are going to be physically close to your subject such as in a sit-down interview hard-wired lavalier mikes can also be invisible. Simply run the wires through the talent's clothing, exiting through the back of a shirt or pant leg. Use caution though, lavaliere mikes are prone to mechanical noise (brushing against clothing, etc.).

Sonic Boom

A "boom" is a pole that holds a microphone. The mikes most often used with booms are highly unidirectional (hypercardioid) "shotgun mikes" which tend to pick up sound from the direction in which you aim them. A boom lets you position a mike close to your talent (usually above the head) just out of the frame. An extendable boom pole adjusts for height and angle, allowing the operator to capture sound from above or beside the subject.
Many daytime talk shows like Oprah, Montel and Ricki Lake use large booms that roll on stands. Occasionally, you may see the devices when the camera goes to a wide shot before commercials. Soap operas and sitcoms also use them.
For non-controlled situations, or should we say most situations, the portable "fishpole" version is used. These light, telescoping poles are common on many shoots. Fishpoles are easy to use and manipulate and compact down to just a few feet for storing. Many extend up to 20 feet. This kind of invisible miking allows for exceptional sound recording. Since a shotgun on a boom stand or fishpole is highly directional, this kind of mike picks up very little background noise. And, because they are not held by or attached to the talent in any way, there is a minimum of interfering noise.
The only disadvantages when working with a mike on a fishpole is that it must be carefully positioned just outside the video frame to capture optimum sound without entering into the shot. During heated news event coverage, of say, ten city blocks exploding, it may be acceptable for the microphone to momentarily peek into the frame. But when producing an instructional video, a mike dipping into the frame for even a second is unacceptable.
Using a boom usually means that you will have to have an assistant at the shoot - a "boom operator." This person's responsibility is to keep the microphone aimed at the talent and close enough to record clean audio, while keeping the rig out of the visible shooting frame.

Boundary Microphones

Another kind of mike that allows for invisible audio recording is the boundary microphone. Also known as a PZM (pressure zone microphone), the boundary mike is unconventional in that it lays on a table or floor (or attaches to a wall) and effectively uses the entire surface that it rests on for pickup.
Boundary microphones are excellent at picking up large groups of people, background ambience and crowd noises (applause, laughter, etc.) in a non-intrusive or visible manner. On the other hand, these mikes also excel at picking up noisy bystanders, air-conditioning rattles and the hum of fluorescent lights. Though you can't use pressure zone microphones in every situation, they are valuable when recording projects such as corporate meetings, a panel of speakers or courtroom video. By laying one or two microphones on a conference table or desk, and framing the shot properly, you can capture clear audio from a number of subjects without ruining the aesthetics of the image.

Some Final Tips

You may find yourself in a situation that calls for hiding a mike on something other than a table or person. Get creative. Is there a plant or vase on the set that would hold a mike? How about the edge of a picture frame or door? All of these are good options for hiding a lav. Run any hard wires under carpets and along furniture legs. In an outdoor setting, try a tree limb, down spouting or a fence post for supporting a boom microphone. Try using some sand on the beach to conceal wiring. The possibilities are only limited by your imagination.
Recording good sound for your video doesn't necessarily mean showing the mike. Next time you shoot, evaluate whether the mike should be heard and not seen, then use the tools and tips in this article to get great sound without having those unsightly microphones clutter up your shot.

Tags:  April 2001
Hal
Robertson
Sun, 04/01/2001 - 12:00am