The purpose of this study was to determine the optimal sound absorption conditions by comparing the sound absorption characteristics of fresh and air-dried leaves of Quercus glauca, the main species of evergreen broadleaf trees (EBLT) in southern Korea. The sound absorption coefficients (SACs) obtained under 18 conditions were comparatively analyzed. The SAC of air-dried leaves improved significantly with increasing leaf layer thickness. The highest average SAC in the fresh leaf group was 0.617, which was observed under the condition of a leaf specimen size of 0.5 × 0.5 cm2 and a leaf layer thickness of 1.75 cm. In a group of air-dried leaves, this was 0.615 under the condition of a leaf specimen size of 0.5 × 0.5 cm2 and a leaf layer thickness of 2.50 cm. The maximum value of SAC for each wavelength was observed under the condition of a leaf layer thickness of 2.50 cm consisting of 0.5 × 0.5 cm2 leaf specimens, ranging from 1,400 Hz to 1,500 Hz.

Abstract
1. Introduction
2. Materials and Methods
    2.1. Processing of sound absorbing materials
    2.2. Estimation of sound absorption coefficient
3. Results and Discussion
    3.1. Effect of leaf layer thickness on the soundabsorption coefficient
    3.2. Effect of leaf specimen unit size on the soundabsorption coefficient
    3.3. Sound absorption properties by frequencyband
4. Conclusions
Acknowledgments
REFERENCES

• Su Young Jung(Warm-Temperate and Subtropical Forest Research Center, National Institute of Forest Science, Jeju 63582, Korea)
• Hee-Seop Byeon(College of Agriculture & Life Science, Institute of Agriculture & Life Science, Gyeongsang National University, Jinju 52828, Korea) Corresponding author
• Kwang-Soo Lee(Warm-Temperate and Subtropical Forest Research Center, National Institute of Forest Science, Jeju 63582, Korea)
• Hyun-Soo Kim(Warm-Temperate and Subtropical Forest Research Center, National Institute of Forest Science, Jeju 63582, Korea)