Effect of Surface Shape on Perforated Acoustic Absorber Performance Using Numerical and Experimental Methods

Perforated panels are one of the most common resonant absorbers for sound control. In this study the acoustic properties of non-flat perforated panels in oblique angle and field diffusion were investigated in both numerical and laboratory methods at 1.3 octave frequencies.

3 non-flat shapes were considered for perforated panel and their absorption performance was compared with the usual shape of (flat) perforated panel. After determining the best shape in terms of absorption coefficient, it was constructed according to the standard  ISO 354at the approved dimensions and the desired structural properties and was subjected to absorption coefficient test in the reverberation chamber

Numerical simulation results showed that the shapes defined in this paper all improve the absorption coefficient at the mid and high frequencies and also the shape C has higher absorption coefficient at the lower frequencies than the flat and two defined shapes. The results of measurement of absorption coefficient showed that the highest absorption coefficient of 0.77 is observed at the frequency of 160 Hz. Also, to compare the results, these conditions were implemented in numerical environment and the absorption coefficient was calculated according to the existing relationships.

Surface shape is effective in improving the absorption performance of these adsorbents and comparison of the numerical and laboratory results showed that acceptable agreement for these two methods is found in most of the frequency spectrum and the numerical method is able to predict this quantity with good accuracy.