抄録
Very high noise generated during thermal spraying is disadvantageous for the working environment. If operators are exposed to the noise with high sound pressure, they may suffer damage. In addition, in areas surrounded with congested buildings, the effect of noise on the environment may cause problems. For the purpose of abating the noise of thermal spraying, the authors measured the characteristic impedance and propagation constant of various materials including waste materials.
The results obtained were summarized as follows. The acoustic absorption coefficient is nearly the same even through their densities were different because granular materials with the same diameter had nearly the same characteristic impedance and propagation constant. As the grain diameter is large, a sound is able to incident to material but the sound damping becomes small. Granular materials with nearly the characteristic impedance and the propagation constant of rockwool is larger sound absorption than another granular materials in a wide range of frequency. These results are very effective for searching a better material. By adopting a multi-layer structure with diverse granule diameters, stable high acoustic absorption coefficient was obtained in a wide range of frequency.
