Acoustics FAQ

 

Acoustic Performance of Metal

It is a common misconception that perforated metal is a poor sound absorbing material, outperformed by alternatives such as mineral fibre. Through careful specification of the size and number of perforations, metal tiles with mineral wool infills offer sound absorption equal to or greater than other commonly specified materials.


Test Data

The acoustic tests undertaken by SAS quantify the performance of the tiles, not the complete system. The reason for this is that it is unfeasible to test the multiplicious combinations of tile and suspension system. It is the perforation type, infill and cavity depth that govern the acoustic performance of a system – other variables have very little affect.


Change in Ceiling Void Depth

Most SAS systems are laboratory tested using a 400mm void depth. If other void depths are used then the sound absorption performance will change at the low frequencies. As the cavity depth decreases, so the low frequency limit of sound absorption increases. For example, the sound absorption at 800Hz associated with a 100mm cavity is the same as the absorption at 200Hz due to a 400mm cavity. The effect of not employing a cavity can be seen by considering the performance of a tile backed with plasterboard or a steel plate.


Effect of Borders Around Perforated Area

There are options for different border widths around the perforated tile area. Whilst a larger border will theoretically result in less sound absorption, the effect in practice is minimal.


Effect of Tile Size

Larger tiles provide greater sound absorption at low frequencies. This is because they exhibit lower stiffness and as such support flexural waves, also termed panel absorption.