Elevated noise in the industrial setting has been shown to have long term detrimental effects on workers’ health and wellbeing. Here, Anthony Barnett, Technical Marketing Manager at Armacell, looks at why the source of the problem is not always as obvious as you may think.
Workers response to noise is well documented and even at a low levels it includes physiological responses, central nervous system reactions and biochemical changes in the body. In these situations it exacerbates stress and increases the risk of accidents. It can also hinder communication amongst workers and, more seriously, make safety and warning instructions inaudible.
When we think of noise in an industrial setting we automatically assume it is from machinery and processes, which is sometimes the case, although much work has been done over the years on attenuation and dampening these causes. A consequence is that noise disturbance from other sources, such as rainfall falling on metal profiled sheeting roofs and water rushing through guttering, downpipes and wastewater pipes have grown relative to these attenuated sources.
These sound waves, especially on large industrial buildings can reach elevated levels. The noise of this falling water is transferred via unprotected pipes to wall and ceiling elements and from there it can block out measures that are there to protect worker safety, for example, machine alarms, fork truck reversing signals and human voices.
The draft standard created by the BRE, BS EN ISO 140-18:2006, outlined the level of noise generated from a roof under certain conditions. It uses two types of rainfall: Intense and Heavy. A rainfall rate of 40mm per hour (mm/h) is classed as ‘intense’ and occurs once every 50 years. ‘Heavy’ rain has a rainfall rate of 15mm/hour and occurs once every two years. Often the most intense rain will fall for only a few minutes before easing off to heavy or gentle rain, and this is a much more common phenomenon that prolonged ‘intense’ or ‘heavy’ rain. Noise from rain water on the roof, guttering and downpipes regularly exceeds 70dB, which is comparable to typical street traffic.
Good acoustic design that is appropriate to industrial buildings can mitigate many of these issues. In practice this involves applying acoustic foam materials to rainwater and wastewater pipes. They have been show to achieve very good acoustic damping and acoustic isolation properties across the frequency range relevant to industrial buildings – irrespective of whether it is installed on aluminium or PVC rainwater and waste water pipes.
They also display very good fire behaviour, achieving the best fire class for organic products in the European SBI test. When supplied with a silver-coloured aluminium covering it complements metal-clad installations in industrial buildings where pipes are visible. Choosing a closed-cell insulation material also prevents condensation on the pipes, avoiding any deterioration over time.
The material should ideally consist of a 2mm thick foil faced acoustic EPDM-EVA barrier with 4kg/m2 weight and a 9mm elastomeric foam layer for decoupling. Independent tests by CSTB (Centre Scientifique et Technique du Bâtiment) confirmed that these acoustic foams are able to reduce the airborne sound pressure levels of a roof drainage system by 16 dB (A) at 2 l/s water flow. Similar tests on a PVC pipe, where the vibrations caused by flowing water are stronger because of the lighter weight PVC, achieved a noise reduction of 12 dB (A). The human ear perceives a reduction of 10 dB (A) as halving the volume. By choosing the correct flexible acoustic foam it is possible to achieve a weighted sound reduction index (Rw) up to 28 dB when pipe and pipe elbows are insulated.
As sound mitigation measures on specific industrial processes and machinery becomes ever more effective, noise disturbance from rainwater will grow relative to this. That means any materials that tackle this growing problem will be making an important contribution to workers’ occupational health and welfare. It is therefore essential that noise abatement measures in the form of thin acoustic lagging are consistently planned and properly carried out, both when constructing new buildings and when upgrading existing ones.
