Noise Monitoring: A Sound Strategy

Effective noise monitoring and control measures in the workplace are crucial to preventing noise-induced hearing loss and ensuring employee safety.

• By Tim Turney
• Sep 10, 2024

The world is getting louder. People cannot escape noise pollution in their everyday lives whether from traffic, infrastructure, music or more, but employees can and must be protected from excessive noise in the workplace. Exposure to loud noise kills the nerve endings in ears. 

When compounded over a long time, this can result in noise-induced hearing loss (NIHL), a permanent occupational illness that blights at least 10 million people in the U.S., according to the National Institute on Deafness and Other Communication Disorders.

Those with affected hearing are more likely to develop dementia, suffer from social isolation, have weakened processing abilities and are at a higher risk of physical injury due to a lack of awareness of immediate hazards. 

Under OSHA’s Noise Standard, the employer must reduce noise exposure through engineering controls, administrative controls or Hearing Protection Devices (HPDs) to attenuate the occupational noise received by the employee’s ears to within specified levels.

Terminology

Employees that are subjected to loud, instantaneous noise can suffer from immediate noise induced hearing loss that cannot be repaired. Similarly, lower levels of noise over the course of a working life can also cause similar damage, but due to the lengthy period of time this takes, this can often be ignored.

Workplace noise terminology can be difficult to understand for those that are not trained, as employers will often work with consultants or other experts to ensure compliance. It is just as important for employees to understand how noise is measured and the respective limits placed on noise levels to protect employees in the workplace. To improve employee engagement and awareness in understanding the risks of occupational deafness and other hearing related diseases, a better understanding of this terminology is the best place to start.

Sound is measured in decibels (dB), a logarithmic scale. With NIOSH standards, this means that every three-decibel increase equates to double the amount of sound energy. This doubling of noise energy also equates to a doubling of the risk of hearing damage, making relatively small increases in deciBels have a significant effect on employee health. Sound values will have a dBA unit attached to them, the ‘A’ refers to A-weighted sound levels which closely match the perception of loudness by the human ear.

It depends on the local legislation, but in the United States, there are two different types of “action levels” or values. OSHA implemented a permissible exposure limit (PEL) of 90dBA for all workers for an eight-hour day. The National Institute for Occupational Safety and Health (NIOSH) has recommended that all worker exposures to noise should be controlled below a level equivalent to 85 dBA over eight hours to minimize occupational noise-induced hearing loss.

The eight-hour exposure period is referred to as the Time Weighted Average (TWA). These exposures are all standardized to an eight-hour working day so that individuals with different exposure times and shift durations can all be compared to the same action values. 

With the eight-hour averaged action levels, employers must measure representative samples of employees’ exposure to noise. To do this, an average measurement must be taken which is known as the LAVG, a logarithmic average. This is done with a handheld sound level meter or a noise dosimeter which can be work throughout the day. In the case of the noise dosimeter, as it is worn through the day it will display the eight-hour noise exposure.

If the workplace in which the sample is taken is continuously noisy—and will remain so over the workers’ shift—then the measurement can be taken over the course of a few minutes, as this is a representative average of the conditions throughout the day. If the noise level fluctuates throughout the day, longer samples must be taken to achieve a representative average when using devices such as a sound level meter. A noise dosimeter is a bodily worn device that can be worn to measure exposure during a working day, which is especially useful if the worker is mobile and therefore it becomes increasingly difficult to measure exposure using a handheld sound level meter.

Controlling Noise 

Any sound over 85 decibels(dB) can damage hearing, meaning the operation of concrete mixers, forklifts, jackhammers, nail guns and masonry drills all pose a permanent risk to worker health if effective control measures are not put in place.

The hierarchy of controls should always be used with hearing protection being the last resort, or a first aid measure until noise can be controlled at the source. They are listed from the most to least effective and include elimination, substitution, engineering controls, administrative controls and personal protective equipment (PPE).

A noise survey can help employers determine which employees are at risk. For noise control and control of noise sources, a noise-control survey should be conducted to identify the source and determine its contribution to the area noise level and worker noise exposure so that businesses can identify at-risk employees and ensure they adhere to OSHA regulations. However, professionals who undertake the monitoring must be trained and prepared with the right equipment as minor errors in noise level estimates can lead to major errors in exposure calculations. This results in greater risks for employers and employees’ long-term ear health.

In 1981, OSHA implemented new requirements to protect all workers in general industry for employers to implement a Hearing Conservation Program where workers are exposed to a time-weighted average noise level of 85 dBA or higher over an eight-hour work shift. 

These programs require employers to evaluate noise levels regularly, offer hearing protection that has been determined as adequate for the noise in the workplace and train employees on managing noise. This is unless equipment and schedules are made so that they are less noisy and worker exposure to noise is less than the 85 dBA.

Noise assessors should ideally use both a sound level meter, primarily designed as a hand-held device used by an operator, and a noise dosimeter, which a staff member wears for their working shift. This ensures primary noise sources can be identified and, when exposure is occurring, to establish a noise control program.

Wear Hearing Protection: A Last Resort 

If noise levels are above safety regulations, workers must wear protection. When selecting the right makes and models, the attenuation level is critical and noise levels at the ear must be reduced so that exposure is below 85dB(A) TWA. NIOSH has published three methods for calculating the attenuation of hearing protectors. However, making sure people wear the protector for the entirety of their shift is essential to ensure real-world protection.

Despite the irreversible nature of NIHL, over half of noise-exposed workers report not wearing hearing protection.

Employers can take a proactive approach to encourage all-day wear by considering comfort, communication, the environment, the individual and the relationship with other PPE. Removing PPE, even for short periods, has a significant effect on exposure. Therefore, it is crucial that hearing protection is comfortable to increase worker acceptance and support the likelihood of all-day wear.

When working in an environment with airborne hazards present, for example, ensure the hearing protection that was provided is comfortable and unobtrusive to the respiratory protection worn.

Every worker on site will have unique physical characteristics that will affect how comfortable the chosen hearing protection is. Some will be more comfortable wearing ear defenders, others will be more suited to ear plugs. The more comfortable an individual is, the less likely they are to remove the PPE.

The interaction of hearing protection with other PPE is also a significant factor. For example, an employee wearing prescription or safety glasses will not obtain an adequate fit from a standard earmuff. So plugs or semi-inserts may be more suitable. 

The world is getting louder, employers must act now to implement a successful and effective noise control regime. However, skill and knowledge of measuring noise can take years to build, so this guidance is a starting point. If certain aspects of noise monitoring, protection and control are outside of an individual’s competencies then external consultancies, training and support should be sought to bridge knowledge gaps and ensure employees get the critical protection they need. When it comes to a permanent health issue like hearing loss, it’s never worth the risk.

This article originally appeared in the September 2024 issue of Occupational Health & Safety.