Week 5 – AA1 – Introduction to Microphones

Microphones are a form of transducer. That means it turns an acoustic energy into electrical energy. The four microphone types we were introduced to were dynamic, condenser, ribbon and PZM.

Dynamic microphones are a passive device. A diaphragm is attached to a moving coil of wire suspended in a magnet. They are extremely durable but not as sensitive to transients and higher frequencies. Examples of dynamic microphones are Shure SM58, SM57 and Sennheiser MD421.

Ribbon microphones have a thin ‘ribbon’ made from a small strip of aluminium thinner than a human hair placed between polar opposites of a magnet. They always have a figure 8 polar pattern. Popular models are made by Royer and Coles.

Condensers work by sound pressure vibrating two charged plates. A preamp is needed to bring the level up to a usable volume. A DC voltage (commonly called phantom power) is needed to charge the plates. Common condenser models are Neumann U87, AKG 414 and RODE NT3.

PZM (pressure zone microphone) are boundary condenser microphones. They work by having an omni directional capsule covered by a plate which creates a hemispherical polar pattern.[1]

I found a horrible buzz on the radio to use as the continuous sound source.

Sound1 : MD421 5cm away from speaker slowly brought to 0cm away to judge proximity effect. I probably should have had a sound with lower frequency content for these examples.

Sound2: KM841 Same position as Sound 1 but judging with a condenser.

Sound3: KM841 but I start the mic at 90 degrees and go through 0 degrees to 270 degrees to judge the polar pattern. The mic is 5cm away from the speaker.

Sound4: C414 same test as Sound 3 but with an omnidirectional polar pattern. There is no difference in pickup.

Sound5: C414 same test again but with a figure 8 polar pattern.

Sound6: PZM starting 20cm away from the speaker and moved within 0cm. There is distinct phase shifting happening as the mic is moved closer and further away.

Fieldhouse, Steve. 2007. “Audio Arts 1 Seminar – Introduction to Microphones.” Seminar presented at the University of Adelaide, 28 March.

[1]paraphrased from: random trout “Audio Production I Notebook - Microphones” http://govguru.com/random/default.aspx (10 April 2007)