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Audio Dual-System Sound

Have you ever wondered how they record audio for a motion picture? DVD bonus features clearly show the microphones, headphones, wireless packs and other audio goodies, but where does it all go? They don't have microphone inputs on film cameras, do they? While it is possible to record audio on film, virtually all film sound is recorded on separate devices. This technique adds a layer or two of complexity to the production, but it also has some powerful benefits. In the video production world, it's a technique you can use to improve the consistency and quality of your digital audio. Sounds like it's worth investigating (pun intended).

In the video world, this technique is called dual-system sound, because the audio is recorded on two devices: the camcorder and a separate audio recorder. I know what you're thinking: why go to the trouble of recording on another piece of equipment when my camera's got a mic input? Please be patient, because there is more than one answer.

First, not all camcorders have a microphone input. There are many perfectly adequate cameras that are locked into their tiny built-in microphones. As a content creator, you're probably leaving that camera on the shelf rather than risk the bad audio. With dual-system sound, that camera is now available - if not for your primary shot, at least as a B-roll camera.

Second, camcorder microphone preamps aren't always the highest quality. In fact, some of them stink. They often have limited headroom and increased noise, compared to a dedicated audio system. In addition, there are plenty of producers who don't like the compressed MPEG and AC3 audio of HDV and AVCHD cameras. Recording separately eliminates this concern.

Finally, dual-system sound forces you to pay close attention to your audio. It requires more setup, more operator involvement and some rec-ordkeeping. Extra work, yes, but the kind of extra effort that insures a quality produ…