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Hanging Mics

Mics can be hung to record large groups of people or presentations. Typically, an omnidirectional or cardioid mic is best, and you might need more than one if you’re covering a large area. You usually need a lot of cable when hanging a mic, so you’ll need balanced mics and connectors. Alternatively, a high-quality, omnidirectional wireless lavalier can be used— obviating the need for lots of cable—if you’re not miking an area that’s too large.

Multiple Mics

If your subjects are too far apart to reach with one boom, consider using multiple mics. Some sound people like to use multiple mics as backups. For example, you can feed a lavalier mic into the left channel and a boom mic covering the same actor into the right channel. When mixing and editing, you can select between channels to get the best sound.

Think Batteries

Accept it right now: at some point in your moviemaking career, a mic battery will die in the middle of the best take you’ve ever shot. Your sound will be useless. Although frustrating, the situation will be more frustrating if you don’t have any extra batteries! Always pack several extra batteries for each type of mic you plan on using, and be sure to test your mics throughout the day to make sure their batteries haven’t died. For shots where you only get one take—pyrotechnic or other special effects shots—consider using more than one mic so that if a battery dies in one mic, you’ll still get sound from the other.

Using Your Mixer

If you’re feeding multiple mics through a mixer, then you might want to consider “arranging” the different mics onto the separate left and right channels that you’re feeding to your camera. This will allow you to keep different actors (or groups of actors) on separate channels. If there are two people who have a lot of overlapping dialogue, then consider using your mixer’s pan control to place one person at the extreme left and the other person at the extreme right. This will help you maintain separation during overlapping dialogue, which will ease your audio editing chores.

Getting the Right Sound for the Picture

No matter which type of microphone you use, it’s important to consider what the audio “feel” of the shot should be. An extreme wide shot, for example, should sound far away, while a close-up should have a more intimate sound. Consider this when selecting the type of mic to use for a shot.

When using an overhead mic, you’ll tend to automatically compensate for these types of shot changes. Since the mic will have to be farther away from its subject during wider shots, but can afford to be brought in closer during close-ups, your audio recording will have a natural shift of audio “space.”

The bass response of any microphone drops off over distance. Consequently, handheld mics and lavalier mics often have a richer, bassier tone—sometimes too rich and bassy—than an overhead mic. This difference in bass tone is called the proximity effect, and some microphones have special filters to reduce the amount of bass response in the mic. It’s important to be aware of the proximity effect while miking so that you don’t create mixing hassles in postproduction.

If a bass-heavy lavalier is used in a close-up, but a less-bassy overhead mic is used in a cutaway, the actor’s voice will sound distractingly different from shot to shot. A good pair of headphones and careful attention to EQ while shooting will help you prevent such problems.

Testing Sound

After connecting your mics, you’ll want to do a mic check to ensure that the microphones are working and that their input levels are set properly. Your camera might not have manual control of input levels, in which case, there’s little you can do in the way of testing and preparing to record. Simply connect the mic to your camera, attach headphones to your camera, ask the subject to speak, and make sure you can hear her in your headphones. If her voice is too quiet, consider moving the microphone closer to her mouth, and then test again.

Hopefully, you’re running your audio through a mixer. A mixer will not only allow you to use multiple microphones, but will also provide you with level controls—for adjusting the volume of each microphone. Level adjustment is crucial to getting good audio. If the record levels for a mic are too low, then the resulting sound will be too quiet. If they’re too high, however, then distortion and noise can be introduced, and the resulting sound will be ugly and unintelligible.

Sound is measured in decibels, although there are two types of decibel scales. dBSPL (or decibel sound pressure loudness) is a measure of the actual acoustic power of a sound. This is the sound that we hear with our ears. A faint whisper from a few feet away might register at about 30 decibels, while a jackhammer usually meters at about 85 decibels. You should know that 135dB is considered painful, and is the point at which permanent hearing damage can occur.

A dBm (or decibel milliwatt) measures sound as units of electrical power and is measured using a VU meter that is displayed on your camera, record deck, or mixer. Through careful use of a meter, you can ensure that your audio level is set properly (see Figure 8.17).

Figure 8.17

An Edirol 4-channel portable mixer with a display featuring digital level meters.

196 The Digital Filmmaking Handbook, 4E

Analog audio meters—the type you’ll usually find on a video camera or deck—can seem a little strange at first, because they place “0” in the middle of the scale. The zero point does not mean no sound, but rather, ideal sound. Your goal when setting a level is to keep the VU meter readout as close to the ideal as possible. Using your mixer controls, you’ll set the level when you test the mic, and then ride the level during your production (but not too much!), adjusting the level control to compensate for changes in the loudness of your subject.

With digital audio, the ideal level is somewhere between –12 and –20dB. This is the point where you’ll want your audio level to peak on your VU meter. Try to set the level so that any spikes in the audio level don’t go beyond this point. When digital audio peaks, the parts of the signal that go into the red are clipped out of the signal altogether. (If you’re recording on an analog recording device, such as an analog video camera or tape deck, then you’ll want the audio to peak a bit higher, at 0dB.)

It is during the mic test that you’ll also perform any sweetening of the subject using a graphic equalizer (if your mixer has one). We’ll discuss this type of EQ in detail in Chapter 15, “Sound Editing.”

Reference Tone

Not all pieces of hardware and software use the exact same scales and meters for measuring the loudness of audio. Consequently, “ideal” sound on your camera might be too quiet on your editing system. Fortunately, there’s a simple way to work around this. Just as you record color bars on your videotape to help calibrate color when editing, you should record some 60Hz audio reference tone on your videotape before you start shooting. You can then use this tone in postproduction to set your audio levels (more on this in Chapter 13, “Preparing to Edit”).

Any camera that can generate color bars should be able to generate reference tone as well. If you’re shooting double-system sound, you’ll also need to record tone with your DAT or miniDisc recorder. If your camera can’t generate bars and tone, then you can use your editing software to prerecord the tapes with bars and tone before you shoot.

Managing Your Set

Although it is possible to edit your sound in postproduction, you simply can’t do many things. For example, you’re not going to be able to remove the sound of a passing semitruck or of that obnoxious couple that was having an argument across the street from your shoot. Consequently, you’re going to have to pay close attention to what your set sounds like.

This involves more than just yelling “Quiet on the set!” and then waiting for everyone to stop talking. Your ears have an incredible ability to adjust to—and eventually tune out—sounds that might ruin an otherwise good shoot. You’ll need to stop and listen to—as well as look at—the set to pick out any potential audio troubles. Once you start paying attention, you might be surprised at all the “white noise” you didn’t hear before: air conditioners, refrigerators, fans from computers and equipment. Any one of these things can render a soundtrack muddy and useless.