boundary microphone

The boundary microphone can be used as a piano mic or on hockey boards for body check sound effects.

PZM is the trademark for Crown International's line of omnidirectional boundary microphones.

A boundary microphone is a small omnidirectional condenser mic capsule positioned near or flush with a boundary (surface).

A directional boundary microphone is a boundary microphone with a directional polar pattern such as cardioid or supercardioid.

Other microphones introduced by Crown included the PCC-166 directional boundary microphone in 1986, the tiny GLM series and the patented differoid CM300 in 1987.

While the patent has expired, "Pressure Zone Microphone" and "PZM" are still active trademarks of Crown International, and the generic term "boundary microphone" is preferred.

The predecessor of the directional boundary microphone was a directional microphone placed in an Electrovoice Mic Mouse, a foam block that suspended a conventional microphone horizontally just above a surface.

While a boundary microphone was initially implemented using an omnidirectional element, it is also possible to mount a directional microphone close enough to the surface to gain some of the benefits of this technique while retaining the directional properties of the element.

When used to record a soloist or small musical ensemble along with the room acoustics, a boundary microphone prevents phase interference between direct and reflected sound, resulting in a natural sound with a flatter frequency response than can be obtained with a stand-mounted microphone at the same distance (explanation below).