A NEW MESURING METHOD FOR SOUND PROPAGATION CONSTANT BY USING SOUND TUBE WITHOUT ANY AIR SPACES BACK OF A TEST MATERIAL

摘要

The conclusions of this study are as follows. (1) A new measuring method of sound propagation constant by using sound tube without necessity of any air space back of a test material could be proposed. (2) It is very simple as such as using only one transfer function between sound pressure on both surface of test material. (3) Even for soft and powdered material, which cannot keep its form and air space behind itself, measurement can be performed. (4) Deep depth appears in the measured result of many porous materials. The cause is the resonant vibration similar board vibration. (5) Resonant vibration makes large errors, and should be suppressed. (6) Introduced suppression method using fixed thin nails is very suitable to this measuring method having hard wall just behind the test material. (7) The new measuring method is effective for many kinds of materials including very soft and powdered materials.