You can see the video of our conversation at: Industrial Enclosure Video
Recently, Noise Engineers installed a hard metal acoustical enclosure at a factory in Aguascalientes, México. The noise from a press causes worker noise exposure levels to exceed the Mexican limits. The noise from the press is more than 20 dBA higher than the noise from any other equipment in the area of concern.
Types of Enclosures
There are two main types of enclosures: rigid metal and flexible MLV. Metal enclosures consist of 16 gage solid metal on the outside, perforated 22 gage metal on the inside and mineral wool (or fiberglass) in between. The exterior blocks noise from getting out and the interior insulation absorbs the noise inside to reduce levels. Metal barriers can reduce the radiated noise by equipment by 30-40 dBA. These enclosures are extremely heavy and not easily adapted to changes.
Flexible barriers are constructed of extruded metal frames with heavy mass loaded vinyl (MLV) connected to the exterior of the frame with mineral wool (or fiberglass) attached on the inside. MLV is flexible and weighs 1 or 2 pounds per square foot. MLV is attached to the frame using bolts through grommets in the MLV. Transparent vinyl can be used in sections to provide exterior light to come in and visibility. MLV enclosures are easily adaptable to changes in operation and provide 10-20 dBA noise reduction.
The background noise level must be considered in designing and enclosure. The total noise reduction may not be realized if there is noise from other equipment in the area.
Openings should be kept to a minimum. Openings will greatly reduce the defectiveness of an enclosure.
Other components in the enclosures are extremely important in the overall noise control. The doors and windows must seal well and provide adequate noise reduction. Ventilation is usually needed. Ventilation can include forced air or acoustical louver openings. Lighting and cable access may be needed as well.
Wash-ability may be a factor. If the enclosure is installed over a machine that produces significant amounts of contamination, the insulation in the enclosure may need to be regularly replaces or it can be enclosed in an acoustically transparent milar.
Other Noise Mitigation Treatments
In addition to an enclosure, acoustical absorption and/or barriers can be applied to an industrial space. This can further reduce the noise level in a space.