Researches On The Acoustic Properties Of A Composite Material Based On The Periodical Structure

To enhance the quality of life, people put forward new requirements of vibration damping and noise reduction. Periodic structure, as a new noise damping structure, is widely used in rigid thin plate structure to enhance its acoustic properties. Composite structure is commonly used in aerospace engineering and transportation. Recent years, structural damping composite material as a new type of composite materials has good performance in vibration and noise reduction. This thesis analyzes the acoustic properties of two-dimensional periodically perforated rigid thin plate embedded in the acoustic material, and discusses the influence of periodic thin medium layer on sound pressure characteristics.First, the acoustic properties of rigid periodic thin plate in the infinite medium is analyzed. According to the acoustic balance condition theory and boundary conditions, the balance equation for particle in one hole is established under the plane wave incidence. Based on the theory of Rayleigh integral formula, the distribution of particle velocity amplitude within one hole is got by meshing the surface, which is transformed to the problem about the solution of linear equations. Solving the linear equations so that the approximate distribution of particle velocity amplitude within one hole is obtained. In order to analyze the acoustic properties of the composite material with rigid periodic plate embedded in, this thesis further obtains transmitted acoustic pressure of the plate, and discusses the influence of different structural parameters on the transmission of sound pressure. Finally, based on the transmission line theory, this thesis analyzes the acoustic properties of the composite material, and discusses the influence of different structural parameters on the transmission sound pressure.In order to make the results more intuitive, plate structure with and without the medium layer are analyzed respectively. The effects of different parameters on the reflection and transmission sound pressure of the structure in both cases are calculated, as well as the acoustic characteristics of two structures are compared.