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Did You Hear That?
Microphones may be very simple, yet very complex.
By Douglas Spotted Eagle - VASST Trainer/Sundance Media Group
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 It’s been often said that a picture is worth a thousand words, but just try watching the news without the volume turned up on the television. One of the worst fears of any broadcaster is to lose audio transmission. Even a static picture with a voice over is generally preferable to a moving image with no descriptive narration or explanation, or even simple music or background sound to set the tone of the image environment. Audio is arguably the more important portion of any visual presentation, yet is often overlooked by most videographers. In fact, until the advent of Sonic Foundry’s Vegas Video 2.0, not a single NLE system had audio tools worth mentioning. Most still don’t even today. For some unspoken reason, video geeks are frightened of audio geeks. And guess what folks? Audio geeks are frightened of video as well. But the day of reckoning is close at hand. Videographers are doing audio and audio engineers and producers are doing video. And soon it will just be one big multimedia family. Learning the basics of audio is easy; Something makes a sound, a microphone hears it, and sends a signal to the camera or recording deck. But learning to get good audio, audio worth listening to, goes far beyond that. Perhaps that’s part of the fear of audio on the video side of the multimedia world.[an error occurred while processing this directive]
 | | It's not easy holding a boom without moving. Find an experienced boom operator. | Most all DV and other cameras come equipped with a mic. The mic on these cameras do exactly what they are supposed to do; pick up everything that’s close to the camera. Zoom noise, motor noise, fingers clicking on/off buttons, breathing of the cameraperson, tripod clinks and clanks, noise from the generator that’s hidden behind 3 buildings 50 feet away, etc. To get good audio with a camera mic is next to impossible in all but the most unique situations. Camera mics are good for family soccer games, vacation videos where the audio is being narrated by the person at the camera, or at a shoot where ambient audio is needed, but will not be used as a primary source of audio. Even for the simple vacation video, a head-worn boom mic such as those worn by cell phone users is better than an on-camera mic. Microphones may be very simple, yet very complex. On the simpler side of the microphone, it’s basically a speaker in reverse. If you apply voltage to a speaker, it makes sound that you can hear. If you apply sound to a microphone, it generates voltage that the receiving device can hear. Speakers are often used as microphones, even today. One of the best ways to get a big bass sound is to take a large speaker and wire it with microphone connections, place it in front of a big bass rig or kick drum, and use it in combination with other mics or direct boxes to record the bass or kick drum. For the moment, we’ll focus on more average mics.There are 4 basic types of mics that we’ll examine in this article.
Dynamic mics are mics that generate their own power. These mics are found everywhere in every situation, from rock stages to cheap computer microphones. Some types of dynamic mics have been around for years. The Shure SM 58 for instance, is a common dynamic mic. Far from fragile, the running joke in the rock music industry is that you can drive nails with one. Dynamics are by far the most common and familiar type of mic. The dynamic mic works by having plates inside, that when pressed upon by air pressure, the plates move, creating voltage as a result of magnets coupled with the plates. This voltage is passed from the mic to a preamplifier, usually found in a mixer or camera, and amplified to a level where the voltage is sufficient for a mixer or camera to process and record or reproduce.
Condenser mics use an auxiliary power system, sometimes built into the mic in the form of a battery compartment, and others use an external source. The external source may be a camera, mixer, or powered box that sends voltage down the line. This is known as "Phantom Power." The auxiliary voltage allows the plates to be more sensitive, and typically capable of outputting higher voltage from the mic, reducing the need for a high amount of preamplifier gain, cutting down on the noise generated by the preamplifier, and typically providing a cleaner, more accurate sound.
Source: © 2003 Sundance Media Group
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