In order to explore the application of glottis’ deformable modulation model, used to simulate the human phonation process, in high power pneumatic speaker, a simulation model was established to model the flow field in the time-dependent shape vocal tract of air-modulated speaker. Characteristics of unsteady flow field in duct under typical working conditions were analyzed. The evolution process of pulsating sound source in the vocal tract was presented. The speaker’s characteristic parameters with different chamber pressures and modulated frequencies were investigated. The simulation results provided an useful guidance for possible application of improving the acoustic characteristics of pneumatic speaker.