Background and Objective: Perforated panels are one of the most common resonant absorbers for sound control. These types of absorbers are widely used due to their adjustable mechanical properties and ease of processing. This study was conducted to investigate the acoustic properties of non-flat perforated panels in oblique angle and diffusion field using both numerical and experimental methods.
Materials and Methods: To investigate the effect of surface shape on the performance of the perforated panel, three non-flat shapes were considered for the perforated panel and their absorption performance was compared with the usual shape of the perforated panel (i.e., flat) using the numerical method. Initially, the most appropriate shape was determined in terms of absorption coefficient. Afterward, the desired shape was constructed in the dimensions approved by the ISO 354 and subjected to a random incidence absorption coefficient test in the reverberation chamber.
Results: The results of numerical simulation indicated that the shapes defined in this research all could improve the absorption coefficient at the middle and high frequencies. Moreover, the shape C showed a higher absorption coefficient at the lower frequencies than the flat and the two defined shapes. Based on the measurement of a random incidence absorption coefficient, the highest absorption coefficient was obtained at a frequency of 160 Hz with a value of 0.77. These conditions were implemented in a numerical environment and the random incidence absorption coefficient was calculated according to the existing relationships.
Conclusion: It can be concluded that surface shape is effective in improving the absorption performance of these types of adsorbents. The comparison of numerical and laboratory results showed the acceptable agreement of these two methods and the numerical method is capable of predicting this quantity with good accuracy.