Acoustic-Pneumatic Element

a device for converting acoustic signals into pneumatic signals. Such an element is used in the design of multichannel acoustic control systems, electropneumatic transducers, and the like. The element is operated by an acoustic signal of any frequency (Figure la); it consists of a cylindrical capillary supply line (from a source) which forms a laminar jet, a pickup tube, and a pressure recorder. When an acoustic signal is introduced, the sound acts on the free-flowing

Figure 1. (a) Acoustic-pneumatic element operated by a signal of any frequency, (b) Acoustic-pneumatic element with a selective signal pickup.

laminar jet, causing a disturbance in it; the pressure at the pickup tube then drops. In order to make the element responsive to a particular frequency, the supply capillary and the pickup tube are connected to an acoustic resonator (Figure lb). The laminar jet becomes turbulent only when the acoustic signal frequency coincides with the natural frequency of the resonator. The frequency tuning of the element is adjusted by varying the volume of the resonator.