中文摘要：

应用时频分析方法对气动装置的非稳态排气噪声进行研究，分析了该排气噪声频谱随时间变化的规律，揭示出该排气噪声具有的脉冲冲击特性的产生机理，非稳态质量流引起的单极子声源和湍流四极子声源在排气过程中的变化规律及辐射特性。

英文摘要：

The time-frequency analysis method has been applied to study on the radiated noise of unsteady pneumatic exhaust. The variation law of noise spectrum with time has been analyzed. The generation mechanism of impulsive and shocked exhaust noise has been revealed. The variation law of mono-pole source generated by unsteady mass flow and quadrupole source generated by turbulence during the exhaust process has been put forward, as well as the radiation characteristic.