The dynamics of an isolator shock train with forced downstream pressure perturbations at different frequencies is experimentally investigated. Experiments are performed in an isolator test rig, in which an oblique shock train is formed at an incoming Mach number of 2.2. The oblique shock train’s behavior is manipulated by an elliptical shaft positioned in the downstream diffuser section. Experimental investigations are conducted using high-speed flow visualization techniques and time-resolved pressure measurements. The results showed that, under the condition without the effect of downstream perturbations ( \(f_b\) \(\approx \) 0 Hz), the shock train exhibits large scale periodic oscillations at a dominant frequency of 76 Hz. It was observed that the amplitude of shock train oscillation decreased upon the introduction of the back pressure fluctuations in the isolator; the frequencies of oscillations were observed to be the forcing frequencies and/or their harmonics. The shock motion is found to be well correlated with back pressure fluctuations.