Just as there are regulations dictating the amount of time a worker may be exposed to chemicals, there are also standards regarding the amount and level of noise a worker can endure in an industrial environment. In order to manage noise levels, the noise can be either controlled at the source or noise reverberations minimized. Because it is often difficult to eliminate a noise at its source (many machines are, by nature, quite loud), attempts to limit noise reverberation through the addition of noise absorbent material is often necessary. However, odd factory dimensions can make the reverberation of sound uneven, and thus prevention is more complex.
To understand how reverberation differs from source noise and how best to minimize internal factory sound, it’s helpful to examine the terms associated with the relay of sound. Essentially, there are three points at which a noise can be controlled: the source, the transmission path, or the receiver. A noise’s source, or point of origin, is not always singular. In a busy factory, there could be countless noise sources all operating simultaneously. Additionally, some machines may contain several noise sources, which can further complicate the issue of identifying a source.
The next stage, the transmission path, refers to wave transmission and the manner in which sound and vibration travel from the source to the final receiver. Transmission paths can range in form and content, from direct airborne sound transmission to reverberated sound delivery. Additionally, sound can be transmitted through the ground, ducts, liquid, surrounding structures, or a combination of means, making it sometimes difficult to trace a noise’s direct path.
Once the sound has travelled along its transmission path, it reaches a receiver, the end person or structure that receives, absorbs, or hears the sound. The recipient of noise is the party most affected by it—be it an instrument recording sound waves or a worker—and is therefore the primary consideration in noise control. Regardless of who or what receives the final transmitted sound, it’s possible to control the noise so that it falls within a predetermined acceptable range.
Noise control can occur at the source, along the path of transmission, or at the receiver. If possible, noise control should occur at the source. However, in many cases this isn’t possible, and therefore control along the transmission path must be tried next, although this is often more expensive and more complicated than controlling the sound at the source. Controlling noise at the receiver can be cost-effective, but is also complicated.
Noise Control Methods
Depending on what stage of transmission a sound is controlled, there are several methods for minimizing noise. Controlling sound at its source can be accomplished several ways. First, examine the work machine to see if the mechanics or process can be altered to decrease the sound level. Dampening treatments can be applied to processes that create ringing and large sounds, such as anvils and hammers. Additionally, a dampening pad can be used underneath the work piece to further absorb noise. If possible, place the machine within an enclosure to further reduce the spread of noise.
When seeking to minimize noise along the transmission path, other methods may apply. Re arranging the layout of the floor so that the source is farther from the receiver, or so the transmission path is softened, can be a good place to start. Using absorbent padding along the walls and ceiling can further reduce reverberations.
If the receiver of the noise is a person, employing more than one machine operator can help reduce noise exposure, as can the use of ear plugs or ear phones to block out sound. Reducing machining duration can also help. If a noise problem persists once these methods have been exhausted, the next step requires close examination and the possible revamping of the acoustic properties of the workplace.