WOOD RESEARCH Volume 62, Number 4, 2017
Dong Wang, Li Min Peng, Feng Fu, Bo Qi Song, and Mei Hong Liu

Changes of microscopic structures and sound absorption properties of decayed wood

Utilizing waste decayed wood is an effective method of conservation woodresourceand protection environment.In this paper, the sound absorption property of decayed poplar wood (Populus tomentosa) was investigated by analyzed the changes of microscopic structure, pore characteristics and sound absorption properties. Experimental results indicated that the sound absorption coefficientof decayed poplar woodwas significantly improved compared with the health wood. The components of cell wall were decomposed after decayed resulting in the pit membrane being disappeared, even the cell wall are decomposed and formed new pores. In addition, the pore size and connectivity increased, flow resistivity and sound impedance decreasing for the decayed poplar wood. Those results revealed that propagation path and internal friction between sound wave and cell wall increased, resulting in the acoustic attenuation increasing. The decayed waste woods as a sound absorption material would become possible.

WOOD RESEARCH Volume 63, Number 4, 2018
Limin Peng, Meihong Liu, Dong Wang, and Boqi Song

Sound absorption properties of wooden perforated plates

Wooden perforated plates are used to control noise and optimize the indoor sound environment. In the paper, the effects of structure factors on the sound absorption properties, such as the absorption peak, resonant frequencies, and frequency bandwidth, were analyzed using the impedance tube transfer function method and SAS (Data analysis software) significant analysis. Experimental results showed that with the thickness of the medium density fiberboard (MDF) perforated plate increasing from 10 to 20 mm, the resonance absorption frequency shifts to the lower frequency. The depth of hole increased, the absorption peak reinforced. With the pore size increased, the resonance absorption frequency reduced and meanwhile the resonance peak absorption coefficient shrunk. The resonance frequency moves toward the high frequency direction and the sound absorption coefficient decreased when the perforation rate was increased from 3.14% to 7.07%. After increasing the air gap thickness from 25 to 100 mm, the resonance absorption frequency reduced and the sound absorption bandwidth remained relatively constant as the acoustic impedance of the MDF perforated plate did not vary in spite of the variation in the air gap thickness. But the absorption coefficient decreased. This paper may provide a certain theoretical basis for wooden perforated plate design and research.

WOOD RESEARCH Volume 64, Number 4, 2019
Meihong Liu, Limin Peng, Zhengqiang Fan, and Dong Wang

Sound insulation and mechanical properties of wood damping composites

The sound insulation performance and mechanical properties of medium density fiberboard (MDF) and rubber multilayer panels were studied. The MDF and rubber materials were compounded under certain conditions of hot pressing, temperature and amount of glue. The weighted sound reduction was 28.0 dB for 6 mm MDF, while it was 37.4 dB for 6 mm wood composite damping material, increased by 25.1%. Compared to the monolayer MDF, the composite panels showed increased sound insulation at the resonant frequency, and the critical frequency moved to a higher frequency. The coincidence valley became shallow, effectively suppressing the anastomosis effect. As the rubber thickness increased, the multilayer composite material exhibited enhanced sound insulation efficiency and mechanical properties, and the damping properties of the composite increased, making the composite resistant to bending deformations caused by incident sound waves.