27th January 2022
How to design a bespoke
Author: Wakefield Acoustics – Noise Control Specialists | Last Updated: April 2023
An acoustic enclosure houses noisy equipment to protect nearby operatives or noise-sensitive receptors (usually neighbouring properties).
For best level of acoustic performance, the exterior of the enclosure must be constructed of dense material such as galvanised steel. The interior must be covered by absorbent material such as mineral wool, fibreglass, or acoustically absorbent foams.
There are several steps to be considered when designing and selecting an acoustic enclosure.
The sound produced by machinery is measured with a sound level meter. Ideally, the acoustic enclosure would reduce noise levels below 80 dB (A), which is the lower exposure action value of the current Control of Noise at Work Regulations in the UK. The required level of reduction will determine the type of engineered noise control solution.
For an acoustic reduction of only 5 to 10 dB, an acoustic screen will often be sufficient.
For a higher performance, a complete enclosure is recommended, where reductions of >40dBA can be realised with a single panel system (subject to frequency content of the source noise). Panels forming the enclosure can be formed with a number of thicknesses, infill materials and outer shell in order to determine the most effective noise reduction.
The usage of the enclosure will determine the overall dimensions. The following items are usually considered:
For the best acoustic performance, it is essential that the enclosure is supported separately from reciprocating machinery to avoid structure borne noise transfer, often known as ‘flanking transmission’. Where this can not be avoided, suitable vibration isolation measures should be employed into the design.
It is crucial that every opening is assessed in order to prevent noise leakage from the enclosure. Service apertures such as pipework and ducts will require sealing plates to fit tightly around, with additional consideration to be given to noise breakout from the pipe/duct wall.
Apertures around conveyor systems are usually more difficult to treat, especially if large openings are needed for materials to pass through. In these cases, an acoustically lined ‘tunnel’ section will need to be installed to the external wall or roof of the enclosure, in order to limit the noise passing through the aperture.
Whilst the acoustic enclosure is providing a vital solution in protecting employees and the environment, it can restrict access to a process or machine. A fully engineered acoustic enclosure will allow appropriate access for maintenance and general operation of machinery.
Enclosures can allow partial or complete disassembly if required. Different types of access panels, doors and apertures are available for maintenance.
Most machinery items will generate some form of heat, which requires removal to prevent overheating and damage to drive motors and other components.
For design purposes, the amount of heat generated needs to be taken into account (the heat load from the machine), in order to size suitable warm air extraction ventilation fans and associated attenuators – not forgetting to leave an attenuated air path for inlet air make-up!
Noise is not always the only harmful element in many industrial plants. For example, high levels of humidity and dust, intense heat, and chemical exposure can be present, and hence the materials of construction for the enclosure need to be carefully considered during the design stage.
Wakefield Acoustics have extensive experience providing bespoke solutions for general industrial applications: