The most common dynamic microphone is the Shure SM57. This microphone is relatively inexpensive and extremely versatile in application. Nevertheless, we're not here to discuss particular microphones, we're here to examine what a dynamic microphone is in relation to transduction. A dynamic microphone converts sound into an electrical signal through electromagnetism. Dynamic microphones fall into two categories, moving coil and ribbon. The ribbon microphone, on a practical standpoint is viewed as a separate group of microphones even though it falls under the same category because both types use electromagnetism to transduce sound into electrical energy.
"Moving coil microphones are probably easiest to understand, because they are basically built like a loudspeaker: A coil is glued to the rear of a membrane, and there is a strong magnet surrounding this coil. When sound waves hit the microphone, the membrane moves to the rhythm of the sound waves, and the coil on its back moves along with it. The relative movement of the coil within its (stationary) magnetic gap induces a small signal voltage in this coil. There’s your microphone, a device that converts sound into an electrical signal. (a)"
These microphones work on the same principle of electromagnetic induction. Rather than using a membrane and coil they use a narrow strip of thin aluminum foil to transduce sound into an electrical signal. This design allows the microphone to follow the movement of the sound waves more accurately making it a much better replicator of sound. So if you're looking for a more analogous microphone, then ribbons are the way to go! However, ribbon microphones produce a much lower output and thereby contain a step-up transformer to increase the output voltage. Having a lower sensitivity to a sound source, ribbons also require a low noise preamp with lots of gain.
"Ribbon mics are very fragile and must be treated with great care. Another drawback is that the treble response of most ribbon mics is quite limited. Today, ribbon mics are used for special applications, only, where extended top end is not required, e.g. for guitar cabinets, or not wanted, e.g. to tame overly bright brass instruments. (a)"
The use of a stretched conductive membrane suspended above a fixed conductive plate, are two key components that make up the condenser microphone. This particular kind of microphone heeds great results when capturing sound. When variations in air pressure, otherwise known as sound, move the membrane closer or farther from the backplate, also known as the capsule, it varies the voltage and converts it into electrical audio.
"This is the major electromechanical contributor to the sound of the mic, as it is where acoustic energy is converted to electrical energy. This now electrical audio is amplified by an amplifier inside the mic which raises the electrical level of signal high enough and noiselessly enough to be sent to the mic preamplifier, another piece of gear required before it reaches line level and can be mixed or modified with signal processing. It is important to note that all three components — membrane, backplate and electrical amplifier — have a profound effect on the sound of a microphone. (b)"
Every microphone has a specific function, color, and distinct characteristic. Understanding microphones is essential in order to properly record music and speech. In this blog, we've only discussed a very small portion of the subject. For a more in depth look into microphone techniques, function, and design, ask Google. Google knows everything!
a: WHAT IS A DYNAMIC MICROPHONE?
b: Microphones: Understanding Classic Condenser Microphone Capsules