August 31, 2010
If seeing is believing, then hearing is understanding. Here are some guidelines for recording clean, intelligible sound.
- Trust your camera’s automatic level control (ALC) anytime you're moving too fast to pay close attention to audio levels. Once anathema to usable recordings, ALC circuits have evolved into a useful aid for anyone shooting without a dedicated sound recordist. Just remember to turn off ALC when shooting live shots and stand-ups; the extended period of silence while the talent awaits a cue will cause even the most passive ALC to boost the gain and pump up the background sound so it can be heard on air before the talent begins speaking.
- Always, always monitor the audio you are recording with an earpiece or headphones. ALC can't tell you that your mic is unplugged or that you're picking up interference on your wireless receiver.
- When using a hand mic for an interview, allowing the person asking questions to move the mic back and forth can result in missing the interviewee’s first words if they begin speaking while the mic is still aimed in the direction of the interviewer. It's better to have the question off-mic to ensure the entire response is well recorded. This is especially a problem with shotgun and cardioid mics. (Omni-directional mics don’t really need to be moved; they’ll pick up both sides of a conversation just fine.) This stationary mic technique also prevents voice level variations caused when interviewers hold the mic closer to their own mouths than the subject’s.
- When using multiple mics, extra care must be taken to avoid a gremlin called “phase cancellation” that can cause erratic levels and tonal changes when the same source is picked up by two microphones. The rule of thumb is to make sure the distance between mics is at least three times the distance between the source and the primary mic. Phase cancellation can also occur if a double-mic’ed lectern is improperly set up with a mic on either side instead of co-locating both mics in the center.
- An excellent but often overlooked tool to pick up the voices of people sitting around a conference table is a pressure zone microphone (PZM). The PZM, also known as a boundary mic, uses a large flat surface as an audio reflector. Placed on a table, or even a wall, the PZM is an inexpensive, quick, and surprisingly efficient way to mic a group.
Next month’s Sharpshooters Tips will zoom in on the videographer’s best audio friend, the lavaliere microphone.