Machinery Noise Control: The First Step
Before time and money are invested in implementation of noise controls, the first step should be to ensure the noise concern is not due to improper equipment setup and/or maintenance related. The recommended step here is to meet with engineering and maintenance representatives to ascertain their opinions on the matter as it relates to elevated noise levels.
Most manufacturing equipment is computer-driven, using programmable-logic controllers (PLC) to actuate various component input and output devices. These devices include servomechanisms (e.g., servo-drives and motors), relay switches, logic relays and other software-controlled mechanisms. When the timing is optimized, the motion of the machine is smooth and relatively impact-free, and compressed air cylinders or solenoids are effectively managed to prevent wasted energy through excessive or extended blowing cycles—all of which results in the lowest noise output potentially available for the machine. For example, Fig 1 shows the “retracted” and “extended” positions of a push bar used to help form cases. Initially, due to excessive driving force, the push bar experienced a hard impact at each end of its stroke (extension and retraction), resulting in a noise level of 94 dBA. After the PLC was optimized to deliver slightly less air pressure, the noise level dropped by 10 dBA, as exhibited in Fig 2.
One of the most significant and cost-effective noise control measures can be to review with facility engineering the parameters used to operate these PLC devices. When necessary, modify the logic to keep equipment functioning within its “sweet spot.” This process alone will yield significant benefits in both the long-term life of the equipment and in minimizing noise exposure risk to employees.
“Listen Up!” is an exclusive column provided by the National Hearing Conservation Association (NHCA) [https://www.
Dennis P. Driscoll, P.E. (retired), Board Cert. Noise Control Engineer, Driscoll Acoustics LLC