Sound Advice: Gaining Control of Your Volume

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This fledgling video producer bought the best equipment his meager budget would allow, and, fueled by his creative drive, flew headlong into his first production shoot. Back home in his edit suite/living room, the images he captured were stunning - but what was that awful whirring in the audio? He tried everything, but alas, the noise would not go away. He would have to either re-shoot the segment or live with the poor audio - neither of which would make his client happy. What to do? Our young friend had fallen prey to the evils of AGC, also known as automatic gain control.

Actually, this story is played out all over the world as more and more people discover desktop video production. Most beginners and hobbyists can't afford a $5,000-plus professional video camera with all the bells and whistles, so they buy something that better suits their budget, usually a Mini DV or Digital8 consumer-grade camcorder. These cams have excellent images and digital video effects. They represent a complete production studio in the palm of your hand except for the audio features. Specifically, the inclusion of AGC instead of an adjustable audio input.

How Does it Work?
The automatic gain control circuit in your camcorder "listens" to the incoming audio and keeps the loud sounds from getting too loud and the soft sounds from getting too soft. It's a great idea on paper but, in application, the results are often unpredictable, even under the best of circu…