抄録
The "Magic Ball", newly developed by Moritex Co. in Japan, is considered to be an excellent advertising medium. The "Magic Ball" is composed of a vertical plate with radiation elements, a horizontal basic plate and a balancing weight. The radiation elements are controlled electronically using a computer to project advertising letters and figures on the sorrounding globe. The aerodynamic drag forces of the composed parts are measured using a wind tunnel. The sound noise level, caused by high-speed rotation of the composed parts in the "Magic Ball", is measured and discussed for various forms of the composed parts. It is found that the attachment of small cylinders decreases aerodynamic noise sharply. The optimum forms of the composed parts realize the reduction of sound noise level by 3dB comparing with the prototype "Magic Ball".
