Abstract: The propagation characteristics of sound waves in a closed cavity depends on viscosity of air. Based on acoustic perturbation theory, the air viscosity can be demonstrated to be measured by sonic interference using double cylindrical resonators. Electric signal, generated by sweep signal generator, is converted into acoustic signal through a speaker. The acoustic wave is reflected back and forth in the cavity to form a standing wave. The acoustic-electric conversion is performed by a microphone and then, the electric signal is input into frequency sweeper. Using a frequency sweeper, the actual resonance frequency of air can be measured and compared with theoretical resonance frequency. It also can be used to calculate the air viscosity. The air viscosity at 24.5℃ is measured to be 178×10-5pa·s, and the relative error is 2.94% when compared with the recognized value. In order to explore the effect of temperature on the air viscosity coefficient, the air viscosity coefficient at different temperature is carried out. The results show that the air viscosity coefficient increases with increasing temperature.

Key words: air viscosity, acoustic perturbation theory, double cylindrical resonator, resonance frequency