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Official Journal of the Japan Wood Research Society

Table 1 Average sound absorption coefficient of three softwood species at 2000–5000 Hz before and after microwave treatment depending on anatomical direction

From: An experimental study on changes in sound absorption capability of spruce (Picea sitchensis), Douglas fir (Pseudotsuga menziesii), and larch (Larix kaempferi) after microwave treatment

  Spruce Douglas-fir Larch
Transverse Radial Tangential Transverse Radial Tangential Transverse Radial Tangential
Control 0.159 0.038 0.041 0.151 0.042 0.036 0.191 0.043 0.036
− 0.039 − 0.014 − 0.014 -0.036 − 0.013 − 0.014 − 0.043 − 0.013 − 0.014
Microwave treatment 0.17 0.046 0.054 0.187 0.05 0.054 0.223 0.059 0.05
− 0.043 − 0.014 − 0.013 − 0.043 − 0.014 − 0.013 0.05 − 0.013 − 0.013
ta − 33.6** − 21.2** − 29.4** − 70.8** − 21.3** − 42.0** − 63.9** − 35.1** − 33.2**
  1. Numbers in parentheses are standard deviations
  2. at value
  3. **p < 0.001