Investigation of sound transmission in composite rectangular panels under the incidence wave with two various angles

Nowadays, composite panels are widely used in various industries, and the study of the behavior of these panels under acoustic vibrations is one of the important cases in engineering analysis. Also, the effects of incidence and azimuthal angles and Mach number are investigated and the calculated critical frequency and sound transmission loss are validated with other works. The results show that the critical and coincidence frequencies and sound transmission loss are influenced by factors such as the orthotropic behavior of the panel and its thickness, incidence and azimuthal angles, sound wave Mach number, and transverse shear flexibility. Based on the resulting graphs, increasing the incidence and azimuthal angles causes the enhancement of the critical frequency and sound transmission loss, while the orthotropic parameter has the opposite effect. On the other hand, increasing the Mach number and decreasing the thickness of the panel reduces the sound transmission loss and increases the critical frequency of the panel. Also, with the increase of the transverse shear flexibility of the panel, the critical frequency is increased. The trends of coincidence frequency changes are also similar to the mentioned trends of critical frequency with respect to the effective parameters except for the incidence angle. According to the presented results, the coincidence frequency of the panel, unlike the critical frequency, decreases with the increase of the incidence angle.