We rely on microphones to get sound into our camcorders and while we use them often, we rarely stop and think about how they work. We explain how mikes function so you can get the best sound into your camcorder.
In our quest for good images, we often forget how important sound is to our production. Even the greatest sound can't salvage bad visuals but good audio can enhance almost any scene. On the other hand, bad sound can ruin any image. We rely on microphones to get sound into our camcorders and while we use them often, we rarely stop to think about how they work.
The first sound recordings were made without microphone at all. The person spoke or made music into a horn that had a flexible diaphragm at the other end. A needle attached to the diaphragm traced out a wavy line in the recording medium as the diaphragm vibrated in response to the sound.
The first successful application of a device we would call a microphone was made in 1876 by Alexander Graham Bell as the pickup device for his telephone, although he didn't call it that. The word microphone was coined a little later in reference to the carbon microphone. These mikes used carbon granules packed between two conductive membranes as the sensing element. From this, the entire array of modern microphones developed.
In order to understand how microphones work, we'll need to review a few basics. An electric current is simply a flow of electrons. If the flow varies in such a way as to convey information, it's called a signal. It can vary randomly or in response to something we don't want. We call this noise.
Think of your garden hose as a wire and the flowing water as electrons. Just as a pump pushes water through the hose, voltage pushes electrons through a wire. The water moves only in response to a pressure or, more properly, a pressure difference. Voltage is analogous to pressure; it's necessary to move electrons.