LF Equalizing Tube/Vent

A pressure microphone, in principle, consists of a diaphragm in front of a closed chamber. A small housing hole (capillary tube) allows for pressure equalization to prevent the microphones from recording the static pressure or extremely low frequencies. This small hole, or leak, is sometimes designed as a small-diameter tube or hose. In some cases (miniature microphones), the hole is cut in the diaphragm.