One example is the PZM for Pressure Zone Microphone.

Crown International owns the trademark on the term "Pressure Zone Microphone" and PZM.

Mr. Thaler found a solution by buying a pressure zone microphone (PZM), which is omni-directional, capturing closeup-quality sound from anywhere in the room.

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.