Method for measuring the constraint force of acoustically excited sound absorbent material

Abstract

Sound absorbing materials used in automobiles are usually attached to a vibrating structure. Here, a method of measuring the ratio of the velocity on the structure side to the velocity on the sound field side is examined. Since the velocity of the surface of the sound absorbing material is affected by the acoustic characteristics of the sound field in contact with it, the sound pressure on the surface of the sound absorbing material and the reaction force of the constraining point on the structure side are measured under acoustically excited condition, we proposed a method to obtain the velocity ratio using the reciprocal relation between structure and acoustics. By comparison with the calculation result of the finite element method, it is shown that there is a possibility to evaluate the characteristics of the sound absorbing material and the sound insulating material in which the sound absorbing material is combined.