This paper deals with the experimental determination of the acoustical properties, that is, the sound absorption coefficient and the transmission loss, of wood-base mater ials in Reverberation Rooms. Descriptions of all materials measured are given in Table 2.
The characteristics of sound absorption for the materials tested are shown in Fig.3 and those for transmission loss are shown in Fig. 4.
From these measurements of accoustical properties for wood-base materials, the following conclusions can be drawn ;
On the sound absorption coefficient ;
1) The sound absorptions of materials depend upon the surface state of panels. All of the roughed-, perforated-, fissured-, and holed-faced panel materials studied have relatively high absorption coefficients as shown in Fig. 3.
2) Smooth-faced panels, such as particleboard, particleboard-core-plywood, hardboard, and insulation board with glued printed paper, are shown to have relatively low absorption coefficients and behave as vibrating panels.
3) Acoustical materials with absorption properties, that is, the insulation board with no-holes or holes and the mineral fiberboard, have a low level sound absorption coefficient in the low frequency range, but this increases at higher frequencies.
On transmission loss ;
1) The transmission loss pattern for the wood-base materials increases with an increase in frequency.
2) It seems likely that the phenomenon of the dropping tendency was due to the coincidence-effect ranging from one to three KHz(arrow marks in Fig. 4) in wood base materials.
3) Wood-base materials show a tendency to follow the equation of the mass law, but the wood-base materials tested, except plywood, exhibited greater transmission loss properties than the values calculated from the mass law(at500Hz). This means that wood-base construction materials are more effective in sound isolation than a similar weight of other materials. Wood-base materials offer advantages to the user in light frame and other wooden constructions.