Industrial sound reduction often refers to preventing noise from becoming a hazard that could be harmful to the health and well being of a person or persons within a specified area or location. Industrial applications tend to require sound reduction measures to either comply with The Noise at Work Act or to meet environmental noise requirements.
Typically the main acoustic issues when reviewing industrial sound reduction requirements include identifying the risks and causes of excessive noise and implementing solutions to reduce environmental, plant or machinery noise to acceptable limits. Where this is not possible measures can be put in place to protect employees and the public.
Reducing Noise Levels
Enclosures & Canopies
Sound reduction is the acoustic technique used for reducing sound being transmitted from one area to another similar to how a wall or floor is utilised within residential dwellings.
The Noise at Work Act has strict requirements on acceptable noise levels and actions that need to be taken where levels exceed safe limits. Where industrial (or environmental) noise is an issue then environmental health, planning officers or other similar body may request that as part of the solution suitable measures should be put in place to limit and reduce the exposure of noise on others.
Generally the main issue encountered is with airborne noise although vibration. Impact noise can compound the effect especially when machinery such as repetitive stroke punches or presses are in use.
– Airborne Noise – Sound that is passed through the atmosphere as a result of sound generated through actions such as speaking, television, music etc
– Impact Noise – Caused by a single source impacting direct on to the floor
– Vibration – Noise caused as a result of the source shaking back and forth causing the vibrations to become audible.
Unlike sound reduction in architectural applications, in industrial applications the key measure for suitable products is Rw (Sound reduction value tested under laboratory conditions). This should have a dB value attached to it (the larger the value the better the performance).
In each industry there will be one or more areas that need to individually assessed and treated (if required) including:
Fixed machinery – when sound cannot be controlled through the machinery’s own housing and enclosure, a screen can be placed around it to ensure the noise is controlled and isolated at the source
Portable machinery – if needed to be moved then portable screens or temporary barriers can be erected around equipment to provide the sound reduction performance needed.
Fixed Plant – Can be treated with screens or enclosures, like machinery, but may need to include acoustic louvres or attenuation to ensure required air flows are maintained.
Noisy environments – foundries or other heavy industry cannot treat the issue at source and therefore sound havens and acoustic control cabins can be used to provide a safe controlled working environment.
Reducing Noise Levels
Achieved by adding mass to a structure. By applying the principles of the Mass Law a structure can increase the performance levels by 5dB if the mass is doubled. The Mass Law does have diminishing returns and therefore care needs to be taken when applying the rule. Ways of adding mass to a structure include:
– Dense block or brick
– Plasterboard or other type of Gypsum based lining material
– Polymeric, metal or other heavy sheet material
– Timber, plywood, MDF
Different sources of noise may require different methods of treatment including isolation. Isolation may also be referred to as an independent layer, resilient layer and as a decoupling item. Adding isolation can be achieved through:
– Adding resilient bars to a wall or ceiling structure
– Using decoupling products to isolate individual elements
– Using a flexible layer between hard surfaces (assists mainly with impact noise)
– Adding a damping material to steel panels to help alleviate vibration.
Typical examples of systems used in an industrial environment are:
Enclosures and Canopies
Forming an acoustic room (more commonly referred to as an acoustic enclosure) around a fixed piece of machinery (or other noise source) that includes a roof structure. These enclosures can be manufactured to bespoke sizes and specifications to suit most applications.
The enclosures are normally manufactured using a steel outer skin with an acoustic absorption mineral wool core and perforated steel inner skin to help retain the mineral wool in place. The thickness of the steel outer skin will dictate the majority of the mass and therefore what the performance levels for sound reduction will be. The overall panel thickness will also have an effect on performance levels by assisting with sound absorption.
Enclosures and canopies can also include acoustic ducts and attenuated ventilation systems to ensure the machinery can function correctly within the enclosure whilst maintaining the acoustic performance required.
Acoustic screens are similar to enclosures with the exception that they do not have a roof. Sound may, therefore, travel over the top of the screen if not designed correctly.
Acoustic screens may consist of louvre type sections and can commonly be seen fitted around roof top plant areas to both attenuate noise and provide an aesthetic finish to the building. They can also be fitted as a dividing wall between two areas to isolate areas from each other.
Similar to an acoustic screen, an acoustic barrier is designed to run alongside a line of communication or noise source (industrial premises, estate, airport etc) to prevent noise from becoming a nuisance to local residents (or employees) within the local area.
Barriers can be seen along the sides of roads and railways and may look like fencing. Where timber is used then attention must be given to the mass of the structure and that no gaps or weak points are left between panels or slats.
Portable barriers can include any type of heavy material that is capable of providing temporary solutions to reducing noise levels to acceptable limits. These systems tend to be easily installed and removed and are usually reusable.
Such systems may include heavy quilts that can be fixed to fencing (Heras fencing for example) or scaffolding. They usually consist of a weatherproof outer layer and heavy mass loaded vinyl inner layer with additional layers of mineral fibre between each section.