Acoustic Practical Advice

The main mechanism by which SAS systems absorb sound is the passage of sound waves through the perforated face of the ceiling tile, baffle, raft or wall panel, which then interacts with the sound absorptive media behind.

The higher the inherent sound absorption of this media, the better the level of sound absorption will be.

Depth of treatment can also be important, where thicker materials tend to absorb more sound with performance extending further down the frequency range. Thus an 18mm acoustic pad performs better than an 8mm pad – pad density also has an effect.

The size and pattern of perforations on the face of the system also contributes to the overall performance. An optimum free area range of between 15% to 22% is important– beyond this greater free area does not offer any worthwhile improvement. With regard to the actual perforation pattern, this is not important within rooms of normal proportion, and the sound absorption data for a particular product can be taken as published.

For open plan office spaces, the normal room acoustic rules do not strictly apply, and the concept of a reverberant field as occurs in normal rooms is not relevant. It is nevertheless important that the acoustic ceiling tile, baffles, rafts or panels, should provide as much sound absorption as possible, with as great a free area as possible. With small perforation patterns and/or a low free area, there is a risk of sound over long distances impinging upon the ceiling with “grazing incidence”, such that the sound is not absorbed, and there is less attenuation across the open plan office space that might otherwise have been expected.

The final reverberation time in a space will depend upon the total sound absorptive surface area for all surface finishes in relation to the volume of the space. It is self evident that the greater the surface area of the acoustic product/system, the lower the space reverberation time will be – the minimum area required can be assessed by an Acoustic Consultant.