Study On Testing And Selection Of Vibration Properties Of Wood For Piano Resonance Board

The piano acoustical quality is decided by the soundboard to a great extent, and the soundboard acoustical quality is decided by the wood. In the producing, wood selection for piano soundboard is depending on the subjective evaluation of technician for the moment. This method of wood selection is inefficient. It does not satisfy the requirement to produce the excellent piano soundboard.This research selected nine Picea wood and provided technique parameters by measuring the sound vibration data of the instrument wood. In order to establish the objective method of wood selection for piano soundboard and objective evaluation method of vibration properties of piano resonant board, this research analyzed and differentiated the comprehensive vibration properties of the samples of Picea glehnii, Picea jezoensis, Picea likiangensis var. linzhiensis, and Picea sitchensis by the comprehensive coordinate method and comprehensive marking method. According to the results of differentiation, it selected two groups of samples used for producing the resonant boards from every species respecitvely, and the distinction between the both groups of every species was obvious. It analyzed the vibration properties base on the vibration theory of resonant board.The results were summarized as follows:(1) According to the vibration parameters of experiments, the relationship between small-size and full-size instrument wood samples were analyzed. The results showed that if theibration parameters of small-size were large, the corresponding parameters of full-size were large. The vibration parameters of full-size instrument wood can be forecasted by the small-size samples.(2) On the basis of studying exploringly on the vibration properties measurement of full-size wood samples, it measured the vibration properties of full-size wood used for resonant board of piano. The comprehensive vibration properties of samples of Picea glehnii, Picea jezoensis, Picea likiangensis var. linzhiensis, and Picea sitchensis were analyzed and differentiated by comprehensive analysis methods. And finally, it selected two groups of samples for producing the resonant board of piano, and that the distinction of vibration properties between the first groups and the second groups was obvious in every species.(3) It analyzed the foundation theory of vibration of piano resonant board, and the frequency equation of free vibration was acquired. The MOE, velocity of longitudinal wave of resonant board on the length direction (MOE_x, V_Lx) and the width direction (MOE_y, V_Ly) direction were computed on the basis of the frequency equaion and longitudinal wave transmittal equation. And the results were: the MOE_x, MOE_y, V_Lx, V_Ly of the first resonant board are larger than the second in every species; for all resonant boards, the MOE_y, V_Ly are larger than MOE_x, V_Lx.(4) The objective selection method of wood used for piano soundboard is the comprehensive vibration properties of wood used for piano soundboard were computed by comprehensive coordinate method and comprehensive marking method, and the indexes include not only wood radial but also wood longitudinal vibration properties.