چكيده به لاتين
Porous materials are known as a key tool in passive noise control due to various factors such as price, shape, easy scalability, easy implementation and the ability to reduce sound transmission, especially at high frequencies. For this reason, they have many applications, including in the aerospace and automotive industries. Its expansion is due to different environmental and border conditions and the removal of basic constraints with the aim of getting closer to reality. The purpose of this study is to expand the recent studies of Dr. Talebi and his innovative method, which is based on the assumption of isotropic matter. Now we are looking to apply this method in anisotropic materials to be able to achieve the amount of sound transmission loss by having the acoustic and structural properties of the material and to assess the impact of each of these properties on the material, which is a type of industrial porous material. Which of the properties, the preference of porous material and other materials in terms of acoustic properties and assess the validity of the resulting method. After the positive results of the validation of the method, according to previous studies, we came to the conclusion that the flow resistance and shell thickness of porous cylinders are directly related to the decrease in sound transmission. The angle of impact on the drop in sound transmission is inversely proportional. Increased porosity of the material causes an unexpected decrease in sound transmission loss due to the poor alignment of the two sides of the shell. The properties related to the fluid part of the material, the characteristics of the external flow and the impact wave, including Mach number and the angle of impact do not affect the values of the ring and critical frequencies, while increasing the Mach number has an adverse effect on sound loss over a wide frequency range.
