The Dynamic Microphone • A microphone is an acoustic-to-electronic transducer or sensor that converts sound into an electric signal. • The Dynamic Microphone, in principle, operates by using electromagnetic induction to generate an output signal. • Electromagnetic induction is the production of a potential difference across a conductor when it is exposed to a varying magnetic field.
The Dynamic Microphone • Dynamic microphones are robust, relatively inexpensive and resistant to moisture. • This, coupled with their potentially high gain before feedback, makes them ideal for on-stage use. • They use the same dynamic principle that is used in a loud speaker only it’s reversed.
The Dynamic Microphone • There is a small and moveable induction coil, positioned in the magnetic field of a permanent magnet and it is attached to the diaphragm (the inside part of the microphone above the magnet). • When sound enters through the windscreen (the outer covering of the microphone) of the microphone, the sound wave moves the diaphragm. • When the diaphragm vibrates, the coil moves in the magnetic field, producing a varying current in the coil through electromagnetic induction. • Also, a typical stage dynamic microphone has a “cardioid” pickup pattern so it picks up sound better from a single direction.
The Dynamic Microphone • A typical budget dynamic microphone has an upper frequency-response limit around 16kHz. • Most dynamic microphones don’t do justice to very high-frequency sounds such as symbols, bells, or upper harmonics of the acoustic guitar or piano. • High-frequency detail reproduction isn’t as good as with a capacitor microphone so, in audio engineering, several kinds of microphones are used at the same time to get the best result. • Dynamic microphones are generally more useful when the sound source is close and reasonably loud.
The Dynamic Microphone • Dynamic microphones have the benefit of being tough and relatively inexpensive, and they don’t require batteries for their power. • The more expensive dynamic microphones have the best sensitivity, the smoothest frequency response, and the most natural sound. • . However, no two models are the same.
The Dynamic Microphone • The final shortcoming of the dynamic microphone is its restricted sensitivity; the less sensitive a microphone is, the more amplification you need to get the sound up to a useful level.
The Dynamic Microphone • http://www.youtube.com/watch?v=fqZYwhStcKI • Start video at 1:02 • End video at 1:59