Occupational Noise-Induced Hearing Loss: Definition, Causes, and Prevention

Employee safety must always be the top priority in the workplace. When the risk of occupational hazards increases in certain professions, preventative measures to protect employees become increasingly crucial. The risks increase significantly when employees are exposed to consistent loud noise as part of their daily roles. Occupational hearing loss is damage to the inner ear from noise or vibrations due to certain types of jobs. Fortunately, occupational hearing loss can nearly always be prevented.

This guide will walk employers and safety professionals step by step through the basics of creating a safer, quieter workplace and protecting workers from noise-induced hearing loss. This guide follows the structure of a Hearing Loss Prevention Program (HLPP), while incorporating the best practices such as the hierarchy of controls.

Understanding Hearing Loss

While there are varying degrees of hearing loss, there are three main types of hearing loss:

Conductive Hearing Loss: Conductive hearing loss occurs when sound cannot make it through the outer and middle ear to reach the inner ear. With this type of hearing loss, it becomes harder to hear soft sounds and louder sounds may be muffled.
Sensorineural Hearing Loss: Sensorineural hearing loss is caused by inner ear damage, such as problems with the nerve pathways from the inner ear to the brain. This is the most common type of hearing loss and is oftentimes permanent. However, hearing aids may help with this type of degradation. This type of hearing loss can occur when working in loud or extreme noise environments.
Mixed Hearing Loss: Mixed hearing loss happens when conductive hearing loss and sensorineural hearing loss occur at the same time. This means that there is damage in the outer or middle ear and in the inner ear. This happens when working in loud-noise environments. Together, conductive hearing loss and sensorineural hearing loss can make hearing worse than with only one problem.

Whereas age-related hearing loss happens naturally and gradually over time, noise-induced hearing loss occurs with regular exposure to loud noises. Noise-induced hearing loss occurs due to damage to the cochlea. The cochlea is a coiled, spiral tube section in the inner ear where sensitive hair cells become damaged. Loud noises commonly cause hearing loss over time. Specifically, the inner compartments of the ear easily become damaged when the ear is exposed to repeated, regular loud noises over a long period of time.

Causes of Noise-Induced Hearing Loss

Over time, repeated exposure to loud noise or music can cause hearing loss. There are many different recognized causes of hearing loss. Certain medications, otologic medical conditions, head trauma, age, and noise exposure are all possible reasons for the loss of hearing. As a result, there are some occupations or fields of work that put people at greater risk of experiencing noise induced hearing loss-particularly if the individual finds themself in a field of work where they are frequently exposed to loud noises as part of their daily occupation.

Sounds above 80 decibels (dB, a measurement of the loudness or strength of sound vibration) may cause vibrations intense enough to damage the inner ear. This is more likely to happen if the sound continues for a long time.

Examples of sound intensity are:

90 dB -- a large truck 5 yards (4.5 meters) away (motorcycles, snowmobiles, and similar engines range from 85 to 90 dB)
100 dB -- some rock concerts
120 dB -- a jackhammer about 3 feet (1 meter) away
130 dB -- a jet engine from 100 feet (30 meters) away

A general rule of thumb is that if you need to shout to be heard, the sound is in the range that can damage hearing.

Some jobs carry a high risk for hearing loss, such as:

Airline ground maintenance
Construction
Farming
Jobs involving loud music or machinery
Military jobs that involve combat, aircraft noise, or other posts with loud noises

These industries are regulated by safety agencies like the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH). workers are exposed to hazardous levels of occupational noise, potentially leading to occupational noise induced hearing loss.

Exposure to loud noise and ototoxic chemicals can lead to more than just hearing damage. Research shows that hearing loss is associated with cognitive decline and heart problems. Hearing loss can impact safety at home and on the job. The sound of a smoke detector, the warning beep as a forklift backs up, and the engine of an oncoming car may be missed. Working in a noisy job when you're pregnant can increase your stress levels which can impact the health of your developing baby. Very loud sounds may also affect your baby's hearing.

Occupational hearing loss is permanent but preventable. Employers and health and safety professionals can measure noise, implement noise controls, and establish hearing loss prevention programs. Workers can learn more about ways to protect themselves from hazardous noise and chemicals. Workers should have a yearly hearing test if exposed to hazardous noise or ototoxic chemicals. Get your hearing tested if you notice a change in your hearing or develop tinnitus.

How to Prevent Noise-Induced Hearing Loss at Work

Mechanisms of Noise-Induced Hearing Loss

Noise induced hearing loss occurs when several important functions within the auditory system are damaged. The ear and auditory system are complicated little structures, with many different well-balanced, well-oiled parts. When one or several of these parts are damaged or not functioning, the processes described below are interrupted, and temporary or permanent hearing loss can result.

The ear is split into three separate parts: the outer ear, middle ear, and inner ear. The outer ear collects sound waves in the air, and effectively funnels those sounds toward the middle ear. The middle ear functions as a mechanical sound booster, and helps to increase the audibility of soft sounds as they travel along the middle ear bones to reach the inner ear for sound processing.

The inner ear, or cochlea, is the organ of hearing and is full of fluid rich in potassium, sodium and calcium which help to transform the mechanical energy of sound into electrical energy along the sensory hair cells and auditory neurons so that the brain can interpret it as sound.

Occupational hearing loss, often caused by exposure to loud noise, involves complex molecular mechanisms beyond the simple notion that loud sounds damage the inner ear’s tiny hair cells. The reality is that multiple pathways contribute to hearing impairment. Some of these involve the auditory system’s metabolic processes, where various receptors may change, hindering the inner ear’s function. Others result from the direct physical harm to the hair cells.

The outcome can range from temporary to permanent hearing loss, with the former typically associated with transient inhibition of metabolic pathways, while the latter results in enduring noise-induced hearing damage.

Conditions Leading to Noise-Induced Hearing Loss

As briefly discussed above, noise induced hearing loss is not always a simple matter, with clear-cut causes and triggers. While loud noise is obviously the culprit in this type of hearing loss, the noise exposure itself can significantly impact the reach of noise induced hearing loss. To understand how noise exposure and decibel level impact hearing and hearing health, you must first understand the manner in which sound is measured.

While measures frequently operate on a linear scale-think 1, 2, 3, 4-sound is measured in terms of logarithmic scales, or scales with a more complicated rating or measuring system than a simple stack of addition or subtraction. This is important largely because of the way that the auditory system takes in and interprets sound; while one sound may be technically similar to another in terms of sound, the way that our brain measures, takes in, and processes those loud noises will determine whether it seems like excessive noise and leads to hearing issues, or whether it easily fades into the background.

One way to more fully understand how excessive noise is calculated in the human auditory system is to look at it in terms of a time/intensity tradeoff.

When looking at the trade off of time and intensity, consider the following questions:

How loud is the sound? Is the sound a deafening one? Whether a jackhammer or a loud sound system, the louder the sound, the greater the likelihood that hearing damage will occur (though the nature of the noise can also come into play).
How long are you listening to it? Are you listening to the sound all day, every day? Loud noise that continues for hours each day is far more likely to lead to occupational hearing loss than a loud noise exposure that is only experienced periodically.

These two things together determine your noise dose. There are “allowable” amounts that are determined to be safe, and some amounts of sound cross the threshold for what is safe and are known to cause a greater risk for occupational hearing loss that can affect one or both ears. Occupational noise induced hearing does not guarantee complete hearing loss or permanent hearing impairment; instead, you can take a close look at the loud sounds and how frequently you are being exposed to them to determine how great the likelihood is that you will experience hearing impairment as a result of occupational noise exposure.

Regulations Regarding Occupational Noise-Induced Hearing Loss

The ability of loud noises to jeopardize hearing has not gone unnoticed by healthcare professionals and those in leadership positions. In the United States, laws regulate the maximum job noise exposure that it is allowed. Both the length of exposure and decibel level are considered. If the sound is at or greater than the maximum levels recommended, you need to take steps to protect your hearing. Ultimately, OSHA developed a hearing conservation program that is mandated for workers exposed to sounds at or above 85 dB averaged over 8 hours. The same exposure limit recommendations exist through NIOSH, in order to reduce the likelihood of experiencing damage to the auditory nerve pathway that leads to hearing loss and preserving remaining hearing ability.

As we discussed above, the way that sound is measured differs from standard linear measurements. That means that the way sound is looked at to determine the maximum job noise exposure levels takes more than one measure into account; instead, the safety limits are developed only after weighing the average of sound over time and its subsequent impact on the hearing system. These safety limits were developed to reduce the likelihood of occupational noise exposures leading to hearing loss, and to prevent excessive noise exposure in situations in which loud noises are unavoidable.

Primary Characteristics of Noise-Induced Hearing Loss (NIHL)

There are many varieties of hearing loss, and each of them is characterized by different causes, configurations, and severities of those losses. NIHL is characterized by bilateral sensorineural hearing loss, with a notched pattern, typically around 3000-4000-6000 Hz. What this means is that in the initial stages of this type of hearing loss, changes may only be readily distinguishable at certain Hz, making it difficult to detect. Many people with this type of hearing loss incorrectly assume they may be experiencing changes to hearing primarily as a result of aging. This means that a proper diagnosis can go undetected, until the loss progresses past this initial threshold. Although NIHL is often detected in both ears, there can be asymmetries if noise exposure is consistently greater on one side. This should also be noted in any consultations or meetings with hearing health professionals, along with any ringing in the ears (called tinnitus), as noise exposure is a risk factor for tinnitus development.

The main symptom is partial or complete hearing loss. The hearing loss will likely get worse over time with continued exposure. Noise in the ear (tinnitus) may accompany hearing loss.

Prevention of Noise-Induced Hearing Loss

Prevention is key when risk factors for NIHL are present. Regardless of the type of hearing loss experienced by an individual, hearing healthcare professionals unanimously agree that reducing loud noise exposure is a good way to protect yourself from further hearing damage. Although not all noise exposure can be prevented, as in the case of sudden loud noise exposures, many recreational and occupational noise exposures can be avoided or at least reduced with the use of hearing protective devices like earplugs and earmuffs.

OSHA has implemented a hearing conservation program for people with regular exposure to loud noises at work-think those working in construction, those with regular exposure to aircraft noise as might be the case with air force workers, and more. Hearing conservation programs typically include at least some of the following components:

Audiometric monitoring (baseline testing + subsequent monitoring on an annual basis)
Measurements of noise levels
Hearing protection devices (including assessments related to their effectiveness)
Education and training related to how to reduce the impacts of hazardous noise exposure
Scheduling to account for maximum noise doses

While these cannot, of course, guarantee that occupational hearing loss does not occur, it does significantly lessen the likelihood of acoustic trauma in response to loud noise exposure. Taking care in personal pursuits and hobbies to avoid noise exposure is also recommended for anyone, but especially those at risk of developing occupational hearing loss.

To decrease the risk of hearing loss in such circumstances, individuals need to get in the habit of using the right kind of ear protection. Protective earplugs and headsets can make an important difference in protecting the ear health of employees. Most protective equipment does not work effectively for hearing-impaired individuals using hearing aids and can cause more harm than good if they remove these devices in high-noise environments.

If your Hearing Protection Devices (HPDs) are not providing the correct level of hearing protection for your workers, choose the right hearing protection and prevent hearing loss.

The following steps can help prevent hearing loss.

Protect your ears when you are exposed to loud noises. Wear proper protective ear plugs or earmuffs when you are around loud equipment.
Be aware of the risks to hearing from recreational activities such as shooting a gun or driving snowmobiles.
DO NOT listen to loud music for long periods of time, including using headphones.

Sensear’s SENS® Technology

Sensear’s SENS® Technology in our Digital Communication Headsets suppresses noise in the surrounding environment while allowing users to still communicate with each other. The innovative SENS® Technology works by limiting loud background noises while processing and separating speech, allowing the wearer to hear speech, alarms, or other important sounds. This is perfect for potentially dangerous environments such as factories, heavy industrial sites, etc. Use our Hearing Protection Calculator to calculate the sound level at the ear when wearing hearing protection.

Treatment of Noise-Induced Hearing Loss

Whether NIHL develops as a result of occupational hearing loss or damage to the inner ear of one or both ears following recreational noise exposure, occupational work exposures, or accidental noise exposure, there are ways to address hearing loss and resulting tinnitus. Tinnitus treatment and hearing loss treatment can differ, but often intersect, including the following:

Hearing aids. Hearing aids are often considered one of the first interventions for damages to hearing health, including hearing loss caused by occupational noise exposure and tinnitus.
Cognitive Behavioral Therapy (CBT). When hearing loss is not repairable, CBT can be useful to address the emotional effects of losing hearing and the potential fallout, including difficulty in social situations.
Cochlear implants. Cochlear implants can be used to address hearing loss from occupational noise exposure when standard interventions like hearing aids are not sufficient to successfully amplify hearing.

Treating NIHL focuses on restoring missing input to the brain through the use of devices like hearing aids, to help facilitate better communication and improve quality of life. Unfortunately, there is no treatment to restore the permanent damage to the delicate inner ear structures that has occurred. However, with modern hearing aid technology, and the support of a hearing health care provider thousands of those with NIHL are hearing the world around them again, and experiencing tinnitus relief.

You may need to learn to live with hearing loss. There are techniques you can learn to improve communication and avoid stress. Many things in your surroundings can affect how well you hear and understand what others are saying.

Using a hearing aid may help you understand speech. You can also use other devices to help with hearing loss. If the hearing loss is severe enough, a cochlear implant may help.

Protecting your ears from any further damage and hearing loss is a key part of treatment. Protect your ears when you are exposed to loud noises. Wear ear plugs or earmuffs to protect against damage from loud equipment.

Be aware of risks connected with recreation such as shooting a gun, driving snowmobiles, or other similar activities.

Learn how to protect your ears when listening to music at home or concerts.

This means that preventive measures, like wearing hearing protection and adhering to OSHA guidelines, and supportive measures, like hearing aids, are the primary means used to address NIHL and successfully mitigate the effects of hearing loss caused by regular or severe exposure to loud sounds.