Acoustic vibration performance of birch veneer-metal copper mesh composites

  Objective  The selection and use of traditional solid wood musical instrument soundboards are very strict. However, at present, there is a shortage of high-quality wood resources in our country, and the pressure on resource demand is relatively high. The development of composite materials that can be used as musical instrument soundboards is an effective way to alleviate the pressure on wood demand.

  Method  2-layer and 5-layer birch veneer composite materials with two thicknesses and metal copper meshes were prepared in the experiment. On the basis of analyzing the dimensional stability of composite, the acoustic vibration performance of the composite was tested by the dual channel Fast Fourier Transform Spectrum Analyzer (FFT), and the effects of the direction of birch veneer pavement, the location and number of layers of metal copper mesh on the acoustic vibration performance were studied. The acoustic performance of the composite was compared with that of Sitka spruce by the comprehensive scoring method.

  Result  The highest coefficient of moisture expansion resistance of double layer and five layer birch veneer composites prepared with metal mesh was 80.00% and 88.09%, respectively. The increase of bonding interface improved the coefficient of moisture expansion resistance of the composites. The direction of birch veneer pavement affected the E_L/E_R value of composite materials. The E_L/E_R value of double-layer veneer composite materials paved with parallel veneer texture was 29.09, and the E_L/E_R value of double-layer veneer composite materials paved with interlaced veneer texture was 0.99. The 5-layer composite added with two layers of metal copper mesh had a vibration efficiency quality close to that of Sitka spruce and a better timbre. Its moisture resistance coefficient reached 87.61%, the longitudinal specific dynamic modulus of elasticity reached 20.02 GPa, the sound radiation quality constant reached 6.13 m/(Pa·s³), the sound impedance was 3.29 Pa·s/m, and the E/G value reached 29.63.

  Conclusion  The comparison with Sitka spruce shows that the acoustic vibration performance of the composite material can basically meet the requirements of general musical instruments, and it has good dimensional stability, which is a good substitute for traditional solid wood soundboards.