Pneumatic servo valves play a significant role in power transmission and system control using a pressurized gas. When pressurized air passes through servo valves, noise and pressure fluctuations are often experienced at the downstream side, and such fluctuations limit the value’s efficiency. In this paper, a novel four-port nozzle-flapper-type servo valve using a slit structure instead of an orifice plate is proposed. The slit structure maintains a laminar flow condition, and this provides an opportunity for the minimization of the noise and pressure fluctuations. The slit structure is fabricated using etching technology. The flow characteristics of the slit are investigated theoretically and experimentally in order to evaluate the design specifications and characteristics of the valve. The experimental results indicated that the noise level decreased by approximately $15dB$ and could reduce the pressure fluctuation by 75%, compared with the previous valve. It is felt that the valve is more effective than many current valves.

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