Experimental study on impulse exhaust noise related to the dynamic flow characteristics of pneumatic directional valve

Impulse exhaust noise generated by a sudden switch of directional valve exists commonly in pneumatic systems. The acoustical properties of such transient exhaust noise have a close relationship to the dynamic flow characteristics of valve during the opening process. The aim of this paper is to study the influences of various flow characteristics of valve on the impulse exhaust noise. A novel directional valve driven by a servo-motor was assembled in a typical pneumatic exhaust system to simulate various valve opening regularities and effective flow areas. The valve opening curves related to three kinds of common flow characteristics including linearizing, percentile and rapid opening forms were designed to test the impulse exhaust noises. Both the temporal waveforms and spectrums of transient noises were measured and analyzed in time-frequency domain to evaluate the noise radiation properties. An appropriate dynamic flow characteristic of pneumatic directional valve generating lower radiated exhaust noise was found out among the mentioned characteristics.