Abstract: [Objective]Decayed wood utilization is significantly important due to environment pressure be growing with increasing the quantity of decayed wood. Analysis of the relationship between sound absorption property and decayed degree was to provide a way for decayed wood utilization.[Method]The impedance tube was used to measure normal sound absorption coefficient of cross section for different decay degree woods and health wood. The changes in the microstructure of decayed wood were examined using field emission scanning electron microscope (SEM), and mercury intrusion porosimetry(MIP) was used to analyze pore size and distribution for decayed wood. According to the changes of micro-voids, the mechanism of improving sound absorption property was explained.[Result]The average of sound absorption coefficients for three kinds of decayed woods were 0.35, 0.27 and 0.24, and the maximum sound absorption coefficients were 0.58(1600 Hz), 0.45(3150 Hz) and 0.43(4000 Hz), respectively. With the increase of decay degree, the average and maximum of sound absorption coefficient were both larger,and the maximum sound absorption coefficient moved to low-frequency range. The phenomenon that the destroyed and reopened in pit membrane, the broken down in parenchyma cells and the crack in cell wall were observed for decayed wood. Those microstructure changes led to the porosity and pores connectivity increasing. So much more sound waves could enter into wood when sound wave impacted against the wood surface, and resulted in acoustic attenuation increasing.The results of mercury intrusion porosimetry measurement indicated that the range of 313-2513 nm pores of decayed wood was more than 1.25 mL·g^-1 compared with health wood, however, no significant difference in the range of 9535-45290 nm pores of decayed wood were found. The porosity was increased 24% in decayed wood and the inner pores specific surface areas were three times than those of health wood. The differences of pore distribution for decayed wood were ranged from several hundred nanometers to a few microns compared with health wood. Those micro-voids led to wood pores connectivity increasing,what's more, the pores specific surface area also increased, resulting in internal friction between sound wave and cell wall and acoustic attenuation increasing.[Conclusion]Those micro-voids because of microorganism decomposition improved the connectivity, porosity and pore specific surface area of wood inter-cells, and let more sound waves into wood, increased viscosity loss. So the sound absorption property of decayed wood was better than that of health wood.

Key words: decayed wood, sound absorption property