Acoustic characteristics of unidirectionally fiber-reinforced polyurethane foam composites for musical instrument soundboards

Unidirectionally fiber-reinforced composites for the soundboard of musical instruments were made using glass fiber or carbon fiber and light-weighted hard polyurethane foam. The vibrational properties and frequency response characteristic of the composites were investigated by changing fibers, volume fraction of fibers and fiber distribution, and the results obtained were compared with those of Sitka spruce for soundboard. The composites, which had 5 to 6 volume percent of carbon fiber filaments distributed uniformly, exhibited almost the same acoustic property as Sitka spruce for soundboard. The results indicated that the acoustic characteristic of wood for soundboard in all audible frequency range could be mostly represented using a simple wood model composed of unidirectionally oriented fibers and porous matrix foam.