Main benefits & How to install the OSMA Acoustic Coupler. Find out how the NEW Osma Acoustic Coupler 4S125 can help you limit unwanted noise in soil stacks from expansion and structural borne sound. This video covers: Main Benefits: • Limiting the effect of noise transfer between separating walls and floors. • Managing expansion, so there's no stress on the pipework from thermal movement. • Ability to check the expansion gap is present after the first fix is complete (if installed with an access pipe) Design Detail: Using the Acoustic Coupler as a fixed point or non fixed point Installation: Step by Step installation and visual checking that the expansion gap has been maintained post installation.