When you're taping outside the studio environment, it seems that every new location presents an infinite number of possibilities and even more potential for problems. Once you've gotten past the ability of the camera mike to deal with them, you need to use the proper external mikes and mixer combination to pick up clean tracks. The most common problem-solver in the soundperson's kit is the lavalier microphone, also called the lav, body or lapel mike. Their sound is always clear and their perspective uniform in spite of different camera angles. Since lavs are usually close to the talent's mouth, the high ratio of direct to reverberant sound keeps background sounds to a minimum. While they come in a variety of sizes and construction, there are several tips that apply to all of them. Note: as we explore the techniques of using lavalier mikes, I'll frequently refer you to other articles in Videomaker for additional useful info. So grab your back issues, and let's get started.
Placement is Everything
The most obvious common tip for lavalier mike usage is placement. All body mikes work well placed somewhere on the chest, but this does not mean that they will all sound the same. Each brand interacts with resonance from the chest cavity, and a difference of two inches can radically alter the frequency response and sound quality of the mike. In order to get the best results, you need to start by placing the lav approximately eight inches below your talent's chin. In profile, you should see that the mike is not being shadowed by the chin and has a clear path to the mouth. From this point, raise or lower the capsule until you have balanced sound in your headphones (see "Headphone Lessons," March '95).
You should hear a full range of high and low frequencies, without any noticeable bass boost or excessive sibilance. At this point, check to see if you will need to use a windscreen to prevent breath noises. Unfortunately, many screens add significantly to the on-camera bulk of the mike, but they will always give you a cleaner sound and prevent that nasty plosive hit in the middle of the perfect take.
Mike placement is often a matter of compromise. The one spot that sounds best may also create mouth noises that a windscreen can't cure. Putting the capsule farther down the chest can cause severe rumble from the chest cavity and stomach, as well as let too much studio noise into the balance of direct- to-room sound. Furthermore, take care to center the microphone on your talent as much as possible. When put on a lapel, the capsule is more sensitive to sound coming from that direction. In other words, turning the head for different camera shots will cause the dialog to come in and out of acoustic focus. Camera angles can also dictate mike placement. If your wide shot allows the microphone to blend into the talent's clothing, you may want to keep the element below the frame line of the close-up, so it looks like there are no microphones on the set.
Another important factor in the use of lav mikes is your talent's wardrobe. If you have any control over the shooting situation, ask your on-screen help to wear clothing made of natural fibers such as cotton, wool or some blends. Pure synthetics--and other fabrics like silk--can cause rustling noises made even louder by the close proximity of the microphone element. They can also cause sparks of static electricity that sound like large clicks on tape. Anti-static sprays from your neighborhood grocery store can actually eliminate some of these noises, but test them first to make sure they won't stain or give your talent an allergic reaction.
Don't forget to ask for clothing that will allow you to hang a microphone in the first place. The business suit is your safest bet, since the gentleman's tie gives you a central location for the capsule. Run the cable under the label on the back, which holds the cord firmly in place and out of sight. If the look is casual and there is no tie, remember to figure out which way the talent will be looking towards camera. Place the mike on that lapel and dress the cable under the jacket with a quality gaffer tape like Permacel, which leaves no sticky residue on someone's expensive wardrobe.
If female talent is wearing some kind of bow-shaped neckwear, be on the lookout for clothing noise or static discharge, since this neckwear is usually made of Rayon or silk. Open shirts and sweaters present a different problem. Dangling cables look ugly and make noise, but you have to be something of a diplomat to get your talent to run a capsule and cable up their clothing so you can anchor it to the top of the sweater or the area around the second button of the shirt. If the sweater has a high neck, you'll need to audition the sound, since the mike will be under the chin. Moving it an inch either way on the neckline can make a big change in the tone quality of the voice. Use the microphone clip to route the cable behind the mike and under the clothing. It gives you a cleaner look and extra strain relief on the cable.
If you have to hide the microphone, almost all rules go by the wayside. The only objective is to get reasonable sound without too much clothing noise. Picking a wardrobe made of natural fibers is almost a given; any other combination is sure to cause problems. Since a good portion of the rustling comes from different layers of clothing moving over each other, hold them together with double-faced tape. If none is available, take strips of Permacel gaffer tape and twist them with the sticky side out. You'll end up with long thin tubes of tape that can hold a tie together or anchor a suit lapel to a shirt.
Try wrapping the edges of the capsule in moleskin, a soft cloth available from your local drugstore. Then mount the mike under the tie, shirt or lapel with double-faced tape or Permacel. You can fold the gaffer tape into small triangles, sticky side out; then put the mike between them and use the outside surfaces to sandwich the capsule between the clothing. If you're lucky, you can hide a small lav directly underneath a sweater or loose weave shirt by taping a 2-inch-by-4-inch strip of Permacel to the mike so it sits between the tape and the cloth. Be careful to keep the microphone diaphragm open, and watch for telltale bulges. Burying the mike in a small chunk of acoustic foam can sometimes help in a high wind situation, but you lose some highs and may add noise from the foam itself.
There are even tricks to cabling the microphone which can come in handy. Tie a single loose overhand knot in the feed cable about 2 inches below the capsule. This prevents mechanical vibrations from working their way up the cord and into the housing. Politely ask to run the microphone's power supply down a talent's trousers so you won't see the cable unless there's a full cover shot. Use an ace bandage to hold the supply to their ankle.
There are times when even the close perspective of an non-directional lavalier lets in too much background noise. If you can't move the mike closer, you need to switch to a body mike with a cardioid (directional) pick-up pattern. These capsules are usually larger than normal, and have ports on the side of the mike barrel that must remain uncovered. You can't really hide these mikes, and they are very sensitive to mouth noises and breath pops. Even so, they can make all the difference in getting usable dialogue from a crowded street scene or a noisy factory environment.
When it comes time to put some lavaliers in your location kit, review Glenn Calderone's excellent microphone survey in the July '94 issue of Videomaker. He lists several models from Audio Technica, Sony and Shure that list for under $100. As the price goes up, so does the sound quality. On the other hand, the size of the capsule gets smaller as you get into the professional range. The Sony ECM-77, Sennheiser MKE-2, and the Sanken COS 11 are tiny barrel mikes that aren't a whole lot bigger than the diameter of the mike cable. Specialty mikes like the TRAM, Crown GLM series and Millimic have flat capsules which make them much easier to hide without losing high frequencies. They can cost more than $300 apiece, but their usefulness and durability often justify their price.
You can use any of these microphones with a wireless transmitter and receiver, but there are some tricks to get the best possible use out of them. The capsules that come with inexpensive transmitters aren't the best from a sound standpoint. Get your dealer to insert male/female connections near the base of your microphone power supplies. You can then plug the mike element into the hard wire supply or the transmitter. Since the microphone gets its power from the transmitter battery, you need to have this done by someone with access to the right tools and service schematics.
In normal use, all of the placement techniques will still work, but you have to be even more cautious with cable dressing. Keep the mike cord away from the transmitter antenna, and don't just bunch up any extra length in the talent's pocket. This can turn the cord into an unwanted source of radio pick-up. Put the transmitter where it can be "seen" by your receiver, because the human body can absorb the low- powered radio energy from a wireless body pack. By the way, don't put the unit where talent can accidentally lean or sit on it; use an accessory pouch if the wardrobe has no safe place to hold the unit. Make sure you provide strain relief for the connector cable, since most failures occur at the point where the cable enters the unit. If your transmitter has a long length of antenna cable, use an alligator clip and rubber band to hold it at full length. This allows the talent to move freely without pulling it out of the box.
Always check your transmitter batteries; they will invariably quit in the middle of a production if they are not in top shape. Use an alkaline brand for longer life, and change them at the first hint of an audio problem. Keep your wireless receiver as close to the action as possible; it's much safer to send audio down a balanced cable from a distant receiver to your camcorder than to play at the edges of wireless reception. Since objects, people and structural steel can all create false sources of reflected radio waves, your cleanest signal will always the close one.
Wired for Sound
Once you've got your talent wired, the real fun begins. If there is more than one person on the set, the "three times rule" comes into play. Essentially, a speaker's mouth needs to be three times closer to his or her microphone that to another active mike. If your talent are too close together, they will bleed into each others' microphones, and the sound will suffer from a nasty effect called "phase cancellation" Basically, phase cancellation occurs when a sound is arriving at multiple mikes at slightly different times. If the sound is of a similar strength in each mike, certain frequencies will cancel out.
There are two ways out of this situation. If you have a separate soundperson, have him or her keep all of the mike channels open about a third of the way. As each person speaks, bring the mike up to full level. This makes it easier to reach full volume without missing any of the speaker's words, and keeps the background at a more even level.
The body mike can also come in handy under more unusual circumstances. Suppose, for example, that you don't have enough microphones to cover the number of talent. Listen to the volume of the people who will be speaking. Put a mike on the person who is the softest spoken, but don't get it too close to the mouth. The stronger voice will come across at almost the same level as the weaker one. With some rehearsal, you can get an overall sound that will sound somewhat like an overhead boom mike held just out of frame. However, this will only work if you have control over the talent's actions; it wouldn't do to have your "human mike" stand and walk away from the rest of the cast.
Lavaliers also make good hidden mikes on the set. You can hide them in plants, under telephones, behind books, and even suspend them overhead outside of camera range. Since you don't mount the mike on a person, it will have a much "thinner" sound. But this technique is very useful when an overhead boom can't get into a tight corner.
As you can see, you shouldn't let the small size of the lavalier mike fool you. It may just be the number one tool in your audio toolbox.