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Audio Technology



Frequency response
Polar Patterns
Proximity effect
Cabling and phantom power

Recording techniques

Recording environment
Microphone placement
Signal processing and special effects


Recording devices

Analog recorders
Digital recorders
DAT recorders
Minidisk recorders
PC card and CD-R recorders
Hard disk recorders


A-to-D conversion

Improving audio digitization
Digitization workflow

Analysis and Delivery

Preparing files for analysis and delivery
Digital restoration
LPC in acoustic analysis

Audio Technology / Recording / Microphones / Introduction...

Two basic microphone types are most typically used for recording speech. The dynamic microphone has a diaphragm that consists of Mylar plastic that has a finely wrapped coil of wire (so-called “voice coil”) attached to its inner face. This coil is suspended within a strong magnetic field. Whenever a sound wave hits the diaphragm, the coil is displaced in proportion to the amplitude of the wave, causing the coil to cut across the lines of magnetic flux supplied by the permanent magnet. Since the mass of the diaphragm and the coil is quite large, compared to the pressure changes in the sound wave, the dynamic microphone may not respond well to sharp transient sounds and it may fail to record minute changes in voice intensity. This does not mean that dynamic microphones should not be used for speech recording. On the contrary, there are several low-cost, rugged microphones, such as Shure SM58 or Shure SM48 (once recommended by Kay Elemetrics), that can be used successfully for many speech recording applications. PHOTO>>

Dynamic microphones do not require any external power supply, which makes them a good match to several field recorders (e.g., Marantz PMD 222). The condenser microphone works on a different principle. A thin plastic diaphragm coated on one side with
gold or nickel is placed at a close distance from a stationary backplate. Once a polarizing voltage (from a 48 V phantom power supply) is applied to these plates, the two surfaces create capacitance that varies as the diaphragm moves in response to a sound wave. Since the diaphragm is very light, the response of the condenser microphone is very accurate, often producing a recording that is extremely rich in both frequency and dynamic response. PHOTO>>

Condenser microphones are usually more fragile than dynamic microphones and require a 48 V phantom power supply. Some of them can use battery packs, but some rely on an external power source. This makes the condensern microphone a bit more cumbersome to use in the field, though several DAT and HDD recorders have an on-board phantom power supply.

Audio Technology
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Last updated: 2002