Can pressure-field microphones perform in diffuse and free fields?

A free field is a sound field where sound waves can propagate freely without any disturbing objects. This means a space with no reflecting objects – the microphone is the only thing that disturbs the sound field. Understandably, ideal free fields are difficult, if not impossible to realize. Sound fields with a close resemblance to free field can be achieved in an anechoic chamber or emulated using a time-selective response (TSR) algorithm.

Free-field microphones are typically used to measure, for example, loudspeakers or outdoor sound.

A diffuse field has so many hard-reflecting surfaces that the sound waves arrive simultaneously from all directions with equal probability and level. Sound fields with a close resemblance to diffuse field are normal in environments such as buildings with hard walls, where many simultaneous sound or noise sources exist, for example, in-cabin measurements, churches and in test boxes that do not resemble anechoic conditions. 

Diffuse-field microphones, also known as random-incidence microphones, are designed to have a flat response when signals arrive from all directions and are typically used to measure vehicle interior noise, or building acoustics.

A pressure field is sound pressure that has the same magnitude and phase at any position within the field. Sound fields with a close resemblance to the pressure field can be achieved in small cavities (small compared to the wavelength) such as artificial ears, or when measuring very close to a sound port.

Pressure-field microphones are typically used in small, closed couplers, wind tunnels or for flush-mounted measurements.