PZM (Pressure Zone) Microphones are a special type of condenser microphone. Also known as a boundary microphone, this type of microphone uses a sound phenomena called the boundary effect.
PZM mics are quite unusual-looking. They are flat and don't really look like microphones at all. They work best when placed against a hard, flat surface at least one meter square; for example, a tabletop or wall.
These mics are often used in conference situations, where they can be placed conveniently and unobtrusively in the middle of the table.
How PZM Microphones Work
A small condenser microphone is mounted face-down a short distance from the reflective boundary plate. This creates a pressure zone between the plate and the mic. The microphone detects changes in this pressure zone, rather than the conventional method of detecting changes in the surrounding air pressure (i.e. sound waves).
Advantages of PZM Microphones
The main advantage of this technology is the elimination of interference from reflected sound waves. A normal microphone will pick up sound waves from the primary source and also any reverberations, which can result in unnatural sound reproduction. In the pressure zone microphone, sound waves are always in phase and there is no interference.
PZM mics also tend to have a smooth frequency response, good off-axis consistency and strong output levels.