Controlling noise problems in commercial areas, hallways, large conference rooms, gymnasiums, etc. is often a complex task. Many customers believe that the installation of acoustic ceiling tiles or carpeting will resolve noise problems, but in most cases, these kinds of corrective measures will have a limited effect. The ‘root-causes’ of noise problems will be highly dependent on many factors:
- The size and geometry of the room(s)
- The type of walls, ceilings and floors that exist (plasterboard, cement, etc.)
- The location and sound pressure levels of the existing noise sources (talking, machinery, HVAC equipment, etc.)
The solution approaches that may be considered depend on a number of important criteria:
- Restrictions on appearance or layout (no carpeting allowed, walls or ceilings must remain aesthetically unchanged, etc.)
- Limitations on allowable architectural or configuration changes (no added walls or baffles, offices must remain ‘open space’, extensive use of large windows or glass dividers, etc.)
- Desired outcome (reduced background noise, less echo, etc.)
- Budgetary limitations
All of these points must be considered before a noise control plan can be established. In many instances, customers may not know the location or sources of unwanted, or may have no idea of what degree of noise reduction should be ‘targeted’ to reduce subjective annoyance or to improve communication
As one example, a large office area such as seen in Figure 1 may have excessive background noise or reverberation, which causes problems with employee concentration and creates difficulties in communicating clearly. See Figure 1 as an example.
As an example, a large restaurant may have an unwanted degree of background noise, clatter, reverberation, etc., which requires that patrons must raise their voices to speak.
In this example, the walls, floors and ceilings are all constructed of hard, acoustically reflective material. The blue arrows denote a ‘direct noise path’, which is emanating from localized noise sources (employees) and the dotted red arrows are just a few of the thousands of noise reflection points. The room itself may be very reverberant, but the vast amount of noise being radiated to the ‘boss’ in this picture is from direct paths. without any barrier between them. This is almost always the highest contributor to employee noise exposure, since there is very little distance between the noise source and the operator. If the machine hypothetically produces 90 dBA Time Weighted Average (TWA) when in operation, it is quite likely that the operator is being exposed to 90 dBA exposure levels as well.
Reflections can be significant in the propagation of ambient noise at a distance from the machines. Reflections often contribute to the ‘din’ and high ambient noise readings away from the machines. Sound reflection can be reduced by the use of noise absorbing materials covering a majority of these hard surfaces as shown in Figure 2. Sound waves striking these walls are now absorbed. This will certainly reduce the noise being reflected around the plant and into the office areas, but the overall results may be less than expected, since we still have strong direct and indirect noise paths present from the machinery. These wall treatments would make a very minimal difference to the machine operators, who are still being exposed to the direct and indirect noise paths in their immediate area. It may decrease their noise exposure by a few tenths of a decibel, but will make very little difference. Plus the office workers are still being exposed to higher than desired noise levels (now estimated at 75 dBA) due to these direct and/or distant noise paths.
If we care only about the office area, the next step would be to place acoustic barriers or walls between the equipment and the offices (as seen in Figure 3), which would serve to attenuate the direct noise paths, and in combination with the wall treatments will significantly reduce noise levels in the offices. The noise baffles serve to block sound paths from the equipment, as well as to absorb sound to prevent sound reflections back into the plant area. But this step has done virtually nothing to reduce noise exposure for the machine operators.
Another step that could be undertaken would be to place barriers around the machine operators, or to ‘compartmentalize’ their work spaces as seen in Figure 4. This approach will certainly reduce noise levels in nearby areas, but the fact that each operator is still is the direct noise path from each individual machine, his/her noise exposure level would be reduced by only 1.5 dBA, still resulting in a potential concern.
In most situations such as these, the only viable alternatives are to either:
- Enclose the machines with an effective noise-blocking material such that the direct path of noise to the operator is reduced or eliminated. This can be a problematic process, as issues of part entry/exit from the machine, or difficulties with operational control may make enclosures impractical. In addition, good quality acoustic enclosures are often expensive and can make maintenance difficult.
- Implement design changes to the machinery such that noise sources are reduced, or that certain noisy components (only) are enclosed. These types of corrective actions can involve stiffening certain frame elements or rotating components, installation of low-noise drive belts or VFD motors, use of improved tooling, etc.
In any situation, it is critical that the customer determine the desired goals before a noise control study is undertaken. If the goal is simply to reduce noise in offices or surrounding areas (and the machine operators are consistently using hearing protection), then the first two noise correction steps noted above should suffice. If the intent is to reduce the noise exposure levels of the machine operators, then a much more comprehensive and design-focused effort must be taken to minimize noise at the source(s).
BASIC RULE OF THUMB: If the direct noise path to an operator isn’t blocked, or the if noise source levels aren’t reduced via engineered improvements, then other noise control measures are unlikely to have any effect on employee noise exposure when working in close proximity to the noise source (machine) itself.
There are instances, such as are often found with large presses, grinding operations or similar situations where high-force impacts or major metal removing operations are in use, it is often not economically practical to reduce noise at the sources, and the use of hearing protection becomes the only viable solution.
Memtech Acoustics has the expertise to identify noise sources, analyze sound transmission paths, and develop cost-effective engineering solutions to address complex noise challenges in commercial environments. Our integrated approach includes acoustic measurement, evaluation of sound propagation and reflection paths, development of targeted noise control strategies, and implementation of appropriate mitigation measures such as engineered materials, acoustic treatments, or structural systems.
As an integrator, Memtech can manage the entire process, from initial assessment and diagnostic testing through system design, material procurement, and installation coordination. We also perform legally compliant noise monitoring and testing for employee noise exposure and environmental sound levels to support workplace standards, communication clarity, occupant comfort, and regulatory documentation.
