Although the process of extruding plastic sections does not normally generate significant noise levels, terminal cut-off saws operating for a few seconds every five minutes can emit very high noise levels.
One company had up to 20 such saws operating in an open production area with employees on the lines being regularly exposed to A-weighted levels of 100 dB when all the lines were working.
The saws themselves were adequately protected by safety guards. However, as these were all in open steel mesh, they offered no attenuation of sound radiation from the saw blades.
The sound radiation was effectively impeded by replacing the mesh guards with solid panels, lined on the saw side with acoustically absorptive material. These were fitted both above and below the saw bench. An acoustic strip curtain was hung along the product out-feed, so achieving further attenuation.
The method has since been extended to cut-off saws on new lines, incorporating an acoustically-lined hood to swing into place over a solid base.
About £650 per hood. (1995)
A noise reduction of 15 dB without having either to alter the machine itself or prevent access to the saw.
Photographs courtesy of Caradon Duraplus Limited.