Vibro-acoustic of Table Tennis Rackets. Influence of the Plywood Design Parameters. Experimental and Sensory Analyses.

The performances of a table tennis racket can be qualified with several adjectives like: fast, slow, stiff, adhesive, controllable, etc. These qualifications are subjective since they are relative to the sensory analysis made by each player. It appears that the noise produced at the ball impact on a racket has a great influence on the opinion that a player can give about a racket. Moreover, the sound emitted at the stroke can be appreciated differently among several players. Hence a good sound may give a positive a priori to the player abut the racket appreciation.The study is based on a previous work that demonstrated: the correlation between the acoustic frequency spectrum and the vibration frequency spectrum of a racket following the ball impact – two vibrations modes of the racket blade are responsible of the sound emitted. The influence of the blade plywood composition is studied. Several prototype racket blades have been specially realized with some differences between them on: the thickness of the plies, the wooden essences. The analysis is first performed on the racket blades without rubbers glued on. The vibro-acoustic of each racket is analyzed by experiments on a lab test bench. The results obtained permit to clearly state on the effectiveness of these design parameters on the impact sound.In the second part, the experimental observations obtained at the laboratory are compared with the results of a sensory analysis performed with the same prototype rackets by a panel of high level players which were asked to classify the sounds of the rackets. It is shown that the classification made by the players is consistent with the experimental laboratory observations.