Everyone knows how to use a mic. After all, they're just the mechanical equivalent of our ears, right? Wrong.
Like the human tympanic membrane (or "ear drum"), a microphone reacts to fluctuations in air pressure and converts those fluctuations into electrical signals. However, that's where the similarity ends. Our ears work with our brain
to convert those signals into what we perceive as sound, but a mic has no such "intelligence." So we're stuck with a different mic type for every different application.
Myriad mic types create just as many ways to misuse them, a problem especially when the user is not a professional performer. Here's a summary of the different types of microphones you're likely to encounter, with tips on using them in their intended application.
The angled desk surface of a lectern can reflect sound from the talker back into the microphone. These reflections can negatively affect sound quality.
Make sure the mic is close to the talker's mouth. This will limit the amount of room noise picked up by the mic, and increase gain before feedback in live sound applications. A " gooseneck " mount can help.
Tabletop or surface-mounted boundary mics work great for tele- or videoconferencing or recording meetings. But they can be so unobtrusive that people place papers or book right on top of them, severely impeding their performance. Position mics directly along the centerline of the table, and make sure the table itself is wide enough to allow room for meeting attendees' documents and papers. Mics with trailing cables can also create a nuisance for attendees - use wireless mics or a conference table that allows cable to be feed through the tabletop.
Talkers may hold the mic too close or too far from their mouths. With dynamic mics, speaking too close can result in the "proximity effect," which creates a boomy, bass-heavy sound. Speaking too closely into a condenser mic can overload it, creating distorted sound. Also, be aware of on/off switches - users may inadvertently turn a mic off. A bit of tape over a switch in the "on" position prevents this.
Inexperienced mic users sometimes assume that the closer the mic is to the mouth, the better. Lavalier mics,
especially condenser types, are designed to pick up sound from 8 or more inches from the mouth. Above all: don't let users hold the mic up to their mouth! Besides defeating the purpose of a lav mic, this will almost certainly overload the mic, causing distortion and bad sound.
You've seen it dozens of times: the presenter approaches the lectern or sits at the conference table, pulls out their cellphone, PDA, or BlackBerry, and plunks it down right next to the microphone. Each time the device receives an incoming signal, the microphone picks up a loud, annoying sporadic buzz.
Any type of RF signal can create this problem. Several microphone manufactures have developed advanced electromagnetic interference (EMI) shielding techniques to minimize these disturbances. Be sure to ask your microphone vendor about their product's susceptibility to RF and other types of EMI.
[Sources: Audio-Technica, Crown, Shure.]