The mechanism to suppress the Aeolian tone of a pantograph horn with periodic holes is studied experimentally in a low noise wind tunnel. Three types of horn model, that is a simple cylinder, a cylinder with periodic holes, and a cylinder with a continuous slit, are used to compare aerodynamic noise characteristics and the flow field around them. Experimental results show that the shear layer of the wake of the cylinder with holes becomes stable due to the periodic jets emitted from the holes. This is the main reason to suppress the Aeolian tone. In the case of the cylinder with a slit, the Aeolian tone is also suppressed. But the interaction between the continuous jet and the shear layer causes another pure tone noise.

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