In this thesis, sound radiation from the impact of balls on elastic plates with various velocities have been examined by the theoretical and experimental works.
In order to obtain the characteristics of the contact force, dynamic response and sound field from the impact of a ball on elastic circular plates, a theoretical approach and some experiments have been performed. In the theoretical development the Hertz contact theory, plate vibration and acoustics were employed. Sound generation are due to radiation from the suddenly accelerated ball-sphere and radiation from the vibrating plate.
The experimental studies have been made of the sound generated by the impact of balls onto plates, ranging in radius of the circular plates from 7 to 14 cm and in their thickness from 1.2 to 3 mm. Steel balls, ranging in size from 1.502 to 2.84 cm in diameter, were used in a series of experiments in which the balls were impacted on to the center of the plate with various velocities. Momentum change and plate motions were also measured to aid in identification of the mechanisms of sound generation.
The experimental results of the momentum change, contact force, transient vibratory motion and maximum sound pressure from the impact were compared with theoretical results. It was found that experimental results were well matched with theories.
Momentum of the ball can be transfered to the plate by not only one contact but also two or three contacts. Such a multi-contact occured during one impact are appeared predominantly when large balls impact thin plates.
The major contribution on the peak sound pressure radiated from the impact of a ball on an elastic plate is due to the flexural vibration of the plate but not of the acceleration of the ball.
