CNC machining operations generate a significant amount of noise. It’s a consequence of machines operating as they are meant to do. However, excessive noise levels present serious health risks for employees in machine shops.
When the they are high enough, or are sustained over a long enough period, excessive noise can lead to hearing loss, as well as a range of other health conditions — like stress, depression, high blood pressure, and heart disease.
Soundproofing CNC machining is a great way to improve the comfort levels of shop workers and minimize the potential health risks they face.
When soundproofing a machine, the business has two options — either soundproofing the room that the machine is in, completely or partially, or building a soundproof enclosure for the machine. The enclosure may partially or totally surround the CNC machine. A sound barrier may be an option in place of a full enclosure.
Each of these soundproofing strategies relies on the same products to dampen sound — sound-absorbing surfaces like baffles and panels that will absorb the noise generated by a CNC machine or other types of loud equipment.
The right choice for any machine shop will depend upon the level of noise reduction you aim to achieve and the amount of money you spend on your soundproofing strategy.
Soundproofing the room
These soundproofing strategies will allow the business to add soundproofing without any inconvenience to workers or significant changes to plant workflow. A barrier or enclosure can make working around a CNC machine more challenging, especially if an enclosure is too small or a barrier interrupts a path that workers take to or from the machine.
Soundproofing an entire room can be expensive, however. While it is possible to soundproof just the wall behind the machine — if the machine is positioned closest to one wall — it is much more difficult to achieve significant noise reduction with limited soundproofing.
The level of noise reduction possible with either approach will depend on the sound transmission class (STC) and noise reduction coefficient (NRC) of the soundproofing materials that are used. A wide variety of materials are available and acoustic engineers are pioneering new materials all the time.
Right now, however, your business will likely need a combination of soundproofing products like quilted fiberglass sound absorption (QFA) products, barrier-backed composite (BBC) and barrier-septum composite (BSC).
Because the noise level in a machining shop is generally between 80 and 110 decibels, this soundproofing will provide a modest-but-noticeable decrease in noise levels. Combined with ear protection equipment, full-room soundproofing is a good way to protect workers from hearing loss in loud machining shops.
Partial-room soundproofing will provide less noise reduction, between one to six decibels depending on the position of the machine, the location of the soundproofing, and the direction of the machine’s noise.
For better soundproofing, it’s possible to build a barrier or partial or complete soundproof enclosure. Any of these options will offer better soundproofing than full- or partial-room soundproofing, but they can be inconvenient to workers, depending on the design.
Enclosures that are too small also may be unsafe if workers do not have the space to use the enclosed CNC machine or equipment properly.
Barriers or partial enclosures do not fully enclose the machine being soundproofed. Instead, they provide sound absorption and reflection on one or more sides of the machine. The best barriers will be at least twice the height of the noise source and positioned in the direction of the noise.
Depending on the location of a barrier or partial enclosure in the workspace, it may require access panels or windows for safety and accessibility purposes. Perforated metal screens can soundproof the equipment without sacrificing accessibility and airflow to the equipment.
These barriers and partial enclosures can offer a noise level reduction of between 6 and 15 decibels. Depending on a machine’s noise level, 15 decibels may be enough to allow workers outside of the barrier or enclosure to work safely without hearing protection.
Full enclosures will enclose the machine on all sides. These provide greater noise level reduction — up to 20 to 30 decibels — but can be more challenging to design. A full enclosure will probably require windows and access panels to be both safe and usable.
An effective full enclosure often may allow workers outside the enclosure to work safely, even without hearing protection.
Monitoring shop noise
Once soundproofing is installed, the business will need to monitor shop noise levels to ensure they are at safe levels (and that their soundproofing is working properly.)
Businesses have a few different options for monitoring shop noise levels.
It can be practical to monitor shop noise levels intermittently and use continuous noise-level monitors. Continuous monitors will constantly monitor noise levels in the shop and can alert staff or managers if noise levels become dangerously high.
Also, networked and IoT noise monitors can create digital records of shop-noise levels over time and use the internet to deliver alerts to staff. Intermittent noise monitoring will not provide the same quality of information as continuous monitoring but it can be an effective way to keep track of shop noise levels.
Businesses that adopt this strategy should schedule regular noise-level checks using sound level meters and noise dosimeters. The sound level meters will provide readings on current sound levels, while the dosimeters will help the business estimate its workers’ noise exposure over time.
It is important to conduct these noise checks are ;y frequently. Otherwise, workers could be exposed to dangerously high levels of noise when soundproofing fails or shop equipment changes.
Safe machine shop noise
Though common in machining shops, excessive noise can lead to serious health problems. Soundproofing, combined with the right hearing protection, will help keep workers safe.
Both full-room soundproofing and soundproofing enclosures are options for businesses. Enclosures can be harder to design and implement but will provide better shop soundproofing.
Emily Newton is the Editor-in-Chief of Revolutionized, an online magazine exploring the latest industrial innovations.