This paper reports an experimental investigation of the acoustic field in a duct due to vortex shedding from multiple restrictors. The spacing between two restrictors was varied very closely in these experiments. It was observed that high amplitude acoustic field was established in the duct when the restrictors were closely spaced and that the highest amplitude of acoustic oscillations occurred for a certain specific spacing of the restrictors depending upon other conditions. It was also observed that the dominant freq uencies locked on to the different possible natural acoustic modes that could be established in the duct. © 2000 by B. Karthik, B. V. R. Kowsik, N. Venkateswarulu, R. I. Sujith and S. R Chakravarthy.