Description of Secondary Sound Field Around a SphericalObstacle

摘要

Scattering and diffraction are phenomena still frequently discussed in acoustics. In his book ”Theory of Sound” published in 1877 Lord Rayleigh provided the analyticaldescription of a secondary sound field for a spherical obstacle and the approximate descriptionfor a cylindrical shaped obstacle. Yet since his time, no analytical solution for an obstacle ofany other shape has been published. For these obstacles, only the numerical description of thesecondary sound field based on experimental results is possible. We are preparing a methodfor creating mathematical models of a secondary sound field for different shaped bodies. Forpreparation of this method, a spherical body was chosen because the comparison between experimentaland analytical results is feasible. A concave spherical body made of glass was used for our experiments. Measurements were performed in an anechoic room, which is the model of a free field. The obtained numerical description of secondary sound field was compared to description calculated on the basis of analytical formula. A mathematical model of the secondary sound field measured is being prepared, and measurements with differently shaped bodies and their mathematical models with respect to our experiences obtained up to now will be prepared.