Schwartz Engineering & Design

The technology disclosed in U.S. Patent 7,580,533 is available for licensing.

In brief, PFD microphone technology is the first working method for creating an audio transducer without a diaphragm, plate, filiment, or any other mechanical part that vibrates in response to sound pressure waves. Instead, a thin ribbon of fast-moving smoke or vapor is directly exposed to pressure waves in the air. This ribbon is "written on" by the pressure waves, creating variations in the density and geometry of the ribbon.

A laser beam passing through the smoke or vapor ribbon is modulated by the variations in density and geometry caused by sound pressure waves. These modulations cause a photo detector's voltage output to vary linearly, producing an electrical signal analogous to the sound pressure waves passing through the smoke or vapor ribbon.