This paper replies to Dr. Matsumoto's doubts on the authros' claims. The experimental results showed that the separated shear layer on the stationary model had a broad-band spectrum with a peak, the characteristics of which mean the periodic vortices were shedding on the model, and that the inverse of vortex shedding frequencies corresponded to the onset wind speed of the excitation. Therefore, it can be concluded that the excitation is due to vortex shedding.
