Noise control strategies are the first line of defense against excessive noise exposure. The use of these controls should aim to reduce, eliminate, or replace the sources of excessive noise and to reduce exposure to noise hazards to the point the risk to hearing is eliminated or minimized.
With the reduction of even a few decibels, the hazard to hearing is reduced, communication is improved, and noise-related annoyance is reduced. There are several ways to control and reduce worker exposure to noise in the workplace.
Reduce the Hazard and Exposure
OSHA’s hierarchy of controls for noise can be summarized as:
- Engineering controls to eliminate or contain the escape of the hazardous noise at its source;
- Administrative controls to control exposure by changing work schedules to reduce the amount of time any one worker spends in the hazard area; and
- Personal protective equipment (PPE) to control the exposure with barriers between the worker and the hazard.
This hierarchy highlights the principle that the best prevention strategy is to eliminate the source of hazardous noise levels, and if that is not successful, manage exposure to those hazards through scheduling and the use of PPE. When it is not possible to eliminate the noise hazard or relocate the worker to a safe area, the worker must be protected with personal protective equipment.
The use of these controls should reduce hazardous exposure to the point where the risk to hearing is eliminated or at least more manageable.
For hearing loss prevention purposes, “engineering controls” is defined as any modification or replacement of equipment, or related physical change at the noise source or along the transmission path (with the exception of hearing protectors), that reduces the noise level at the employee’s ear.
Typical engineering controls involve:
- Reducing noise at the source
- Interrupting the noise path
- Reducing reverberation
- Reducing structure-borne vibration
Simple engineering noise control solutions can reduce the noise hazard to the extent that audiometric testing, a hearing conservation program, and the use of hearing protectors are not necessary. Examples of inexpensive, effective engineering controls that can be applied include:
- Choosing low-noise tools and machinery (e.g., compressors, grinders, etc.)
- Maintaining and lubricating machinery and equipment (e.g., oil bearings)
- Placing a barrier between the noise source and employee (e.g., sound walls or curtains)
- Enclosing or isolating the noise source
Engineering Control Examples
The diagram below shows how installing softer bends in the pipe and increasing the distance between the valves will reduce the turbulence in the line and, consequently, reduce the noise generated. Often, large pressure drops across valves, which cause noise, can be prevented with
in-line diffuser silencers, which reduce the pressure upstream of the valve. Installing a muffler on the end of the nozzle is another option. All these methods can help reduce noise from compressed air sources.
Common examples of the implementation of such controls are:
- Installing a muffler
- Erecting acoustical enclosures and barriers
- Installing sound-absorbing material
- Installing vibration mounts and providing proper lubrication
Administrative controls, defined as “management involvement, training of workers, and changes in the work schedule or operations that reduce noise exposure,” may also effectively reduce noise exposure for workers. Examples include:
- Operating noisy machines during shifts when fewer people are exposed.
- Limiting the amount of time a person spends at a noise source. This is probably the most common administrative control being used today in the workplace.
- Providing quiet areas where workers can gain relief from hazardous noise sources (e.g., construct a soundproof room where workers’ hearing can recover – depending upon their individual noise level and duration of exposure, and time spent in the quiet area).
- Restricting worker presence to a suitable distance away from noisy equipment.
Controlling noise exposure through distance is often an effective, yet simple and inexpensive administrative control. This control may be applicable when workers are present but are not actually working with a noise source or equipment. In open space, for every doubling of the distance between the source of noise and the worker, the sound level of the noise is decreased by 6.02 decibels. No matter what the scale of measurement, you will get a 6.02 decibels sound level drop for every doubling of distance.
Personal protective equipment (PPE)
There are many different types of personal protective equipment (PPE) that can be used to control noise at work. Some of the most common types of PPE include earplugs, earmuffs, and noise-cancelling headphones.
- Earplugs are small devices that are inserted into the ear canal to help reduce the amount of noise that enters the ear. Earplugs are available in both disposable and reusable varieties. Disposable earplugs should be thrown away after each use, while reusable earplugs can be cleaned and reused multiple times.
- Earmuffs are devices that fit over the ears and help to reduce the amount of noise that enters the ear. Earmuffs are available in both passive and active varieties. Passive earmuffs work by simply blocking out noise, while active earmuffs use batteries to create a sound-cancelling effect.
- Noise-cancelling headphones are designed to reduce the amount of noise that enters the ear. These headphones work by creating a sound-cancelling effect that helps to reduce the amount of noise that is heard. Noise-cancelling headphones are available in both over-the-ear and in-ear varieties.
When choosing PPE to control noise at work, it is important to select the type of PPE that will best fit your needs. If you are exposed to high levels of noise, you may need to use more than one type of PPE to adequately protect your hearing.