Microphone Fundamentals: Technology and Applications
What you need to know about installing microphones in audio systems.
I recently had the good fortune to attend a class taught by John Born of Shure, one of the big names in microphone technology.
Born did a great job of clarifying lots of the terminology and technology with regards to microphones. Hopefully, this translation will help you understand the topic better.
All microphones are transducers. A transducer is a device that takes one type of energy and converts it to another type. A microphone takes acoustic energy and converts it to electrical energy.
A loudspeaker does the opposite, taking electrical energy and converting it back to acoustic energy.
Microphones are available in many different options, depending on things like the form factor, the technology involved and the application needed. The two primary types are called dynamic and condenser.
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A dynamic microphone uses a Mylar diaphragm pushing against a voice coil in a magnet to produce its signal.
A condenser microphone uses a diaphragm pushing against a charged back plate to produce its signal. The condenser style requires a certain amount of voltage to make it work.
On occasion, you’ll find a battery powering a condenser microphone, but most of the time the mixer or mixer/amplifier will provide power so the microphone cable can energize the circuit.
One of the concerns that sound engineers deal with around microphones is feedback. Feedback occurs when a microphone picks up an amplified signal from that microphone—very annoying.
One microphone characteristic that is important, especially in relation to feedback, is the polar pattern. This is what the microphone will pick up or not pick up.
If you can imagine a pencil with a tennis ball stuck on the end of it, you are imagining an omni-directional pick-up pattern. An omni-directional microphone will pick up signals from all around it, reproducing the louder sounds more than the quieter sounds.
This type of microphone is not appropriate for live music vocal reproduction because the stage monitors will be picked up.
Another style of microphone polar pattern is called cardoid. It’s named after its heart-shaped pick-up pattern. This type of microphone is adept at picking up sound in front of it while not picking up sound behind it.
It’s very appropriate for amplified music, since it will only pick up what the singer is saying and not what’s coming out of the stage monitors.
Fred Harding is in sales and technical support at Capitol Sales, a full service distributor of electronic installation hardware. He is a frequent contributor to CE Pro, writing hands-on product reviews and technical tips. Have a suggestion or a topic you want to read more about? Email Fred at email@example.com
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