Effect of extraction on the acoustic vibrational properties of Picea jezoensis var. microsperma (Lindl.) W.C.Cheng & L.K.Fu

Abstract

The specific dynamic elastic modulus, acoustic radiation, logarithmic decrement, sound transmission parameter, and acoustic conversion efficiency of spruce wood (Picea jezoensis var. microsperma (Lindl.) W.C.Cheng & L.K.Fu) were improved by extraction treatment with deionized water, dichloromethane, benzyl alcohol, and ethanol. A larger improvement was achieved after extraction with benzoyl alcohol and dichloromethane extraction than by using ethanol and deionized water. It is necessary to improve the acoustic vibrational properties of wood to solve the problem of resource shortage of wood with excellent acoustic vibrational properties for the soundboards of musical instruments and to improve the use value of wood. The effects of extraction treatment with deionized water, dichloromethane, benzyl alcohol, and ethanol on the acoustic vibrational properties of spruce wood were evaluated. After the acoustic vibrational properties of untreated wood samples were measured using the free-free flexural vibration test method with a fast Fourier transform spectrum analyzer (FFT, CF-5220Z), extraction treatment of the wood samples was separately performed with deionized water, dichloromethane, benzyl alcohol, and ethanol for 15 days at room temperature and pressure, followed by drying. The acoustic vibrational properties of the treated wood samples were then measured, and the effect of extraction treatment on the acoustic vibrational properties was analyzed. The increase in the specific dynamic elastic modulus was highest (14.5%) after the benzyl alcohol treatment. The acoustic radiation clearly improved after the ethanol treatment (18.1%). The acoustic impedance of the wood treated by dichloromethane extraction decreased significantly (−4.35%), while the logarithmic decrement was significantly reduced (−52.0%) by benzyl alcohol treatment. From the viewpoint of energy utilization, with benzyl alcohol treatment, the acoustic conversion efficiency and transmission parameter increased by 124% and 125%, respectively. The degree of improvement in the acoustic vibrational properties of wood differed depending on the solvent used. Greater improvement was observed after extraction with benzoyl alcohol and dichloromethane as compared to ethanol and deionized water.