An Aeolian tone suppression mechanism of a perforated pantograph horn has been experimentally studied with an anechoic wind tunnel. Three types of horn models — a simple cylinder, a cylinder perforated with periodic holes and one with a continuous slit — were used to compare aerodynamic noise characteristics and the flow field around them. Experimental results showed that the wake shear layers of the perforated cylinder become stable due to the jets emitted from the holes at regular intervals, thus providing the optimal way of suppressing the Aeolian tone. In the case of the cylinder with a continuous slit, the Aeolian tone was also suppressed, but the interaction between the continuous jet and the shear layer caused another narrow-band noise.