Editing Microphone (section)

===Boundary===
{{Main|Boundary microphone}}

Several approaches have been developed for effectively using a microphone in less-than-ideal acoustic spaces, which often suffer from excessive reflections from one or more of the surfaces (boundaries) that make up the space. If the microphone is placed in, or very close to, one of these boundaries, the reflections from that surface have the same timing as the direct sound, thus giving the microphone a hemispherical polar pattern and improved intelligibility. Initially, this was done by placing an ordinary microphone adjacent to the surface, sometimes in a block of acoustically transparent foam. Sound engineers Ed Long and Ron Wickersham developed the concept of placing the diaphragm parallel to and facing the boundary.<ref>{{Cite patent |country=US |number=4361736 |pubdate=1982-11-30 |title=Pressure recording process and device |inventor1-last=Long |inventor1-first=Edward M. |inventor2-last=Wickersham |inventor2-first=Ronald J. }}</ref> While the patent has expired, ''Pressure Zone Microphone'' and ''PZM'' are still active trademarks of [[Crown International]].

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. Crown's trademark on this approach is ''Phase Coherent Cardioid'' or ''PCC'', but there are other makers who employ this technique as well.