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Thread: please explain it to me

  1. #1 please explain it to me 
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    Dec 2005
    i know its really basic but how exactly does a micro-phone work.

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  3. #2 Re: please explain it to me 
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    Jan 2006
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    Quote Originally Posted by krishna
    i know its really basic but how exactly does a micro-phone work.
    Essentially there two kinds of microphones used in audiovisual production; electromagnetic ones and piezoelectric ones.

    Both type work by transforming mechanical energy (the pressure waves for sound) into a electrical fluctuation.

    Electromagnetic microphones consist of a magnet able to vibrate freely inside a lop of conductive wire. Usually the magnet is mechanically connected to a membrane that amplifies the oscillaltions caused by sound waves. Whenever the magnet moves inside the loop of wire, it wil generate a little electrical current (due to the electromagnetical effect)which will oscillate with a intensity and amplitude proportional to the movements of the magnet. Usually the loop of wire is already carrying some electrical current in order to strengthen the effect of the magnet's movement. The electrical current from the loop of wire is then amplified so it can be of use. The point is that this current will vibrate and strengthen or fade as do the movements of the magnet, and the magnet will move accordingly to the sound waves hitting the membrane and causing the magnet to move.

    Piezoelectrical microphones look for the same result, a electrcila current which oscillates at the same rythm and intensity as the sound waves; but they do it using a small crystal of quartz. Quartz crystals do have the property to vibrate when they're subject to a electrical current, and they will also generate a electrical pulse when they're under pressure. This is called the "piezoelectrical effect". So what piezoelectric microphone does is to feed a little electrical current to a quartz crystal, which then will vibrate in a well-known frequency. Anyway, the crystal is linked to a membrane which vibartes with sound waves, and this vibration causes little pressure waves in the quartz crystal. This little pressure waves generate their own electricity, which then adds to the current already being carried through the crystal. This vibrating current wll reflect the pressure waves hitting the crystal an thus the sound; then it's just a matter to pick this vibrating electrical current and amplify it.

    Also thee are a third kind of sound devices based on a laser whose return time can be measured with great precisison; this devices measure the distance betwen the emitter and a reflectign surface, like a glass, and pick the little vibrations of the surface... for an isnatnce, sound waves from a room behind the glass. This devices are used mostly for spying as they have a low quality of sound, but nonetheless they usually are useful to know what people is saying behind a distant window, door or even a wall.

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