Composite Acoustic Barriers

Acoustic barriers are generally made from panels of different acoustic performance.

A single layer barrier between 2 rooms that is made up of 2 different materials.

If a partition is made up from different areas with different transmission loss performances the total transmission loss for the partition may be calculated given the following formula:

Where

S_i = area of i^th panel in barrier [m²]
R_i = transmission loss of i^th panel in barrier [dB]
S_tot = total area of the barrier [m²]

When the panels are the same area the transmission loss of the panel with the lowest transmission loss controls the overall performance of the partition.

Panel 1 and Panel 2 equal in area.

Panel 2 is 10% of the total area.

The above graph shows the transmission loss of two panels and the combined transmission loss. The area of Panel 2 is 10% of the total area. From this it can be seen that the transmission loss of the weaker area dominates, even when it is a small percentage of the total area.

From this it can be seen that when developing the transmission loss performance of a partition it is important to understand the complete system and if possible to improve the weakest areas first.

See also: Double Acoustic Barrier, Holes in Acoustic Barriers, Single Acoustic Barrier.