So, what about wellbeing?
One of the most preventable workplace illnesses is hearing loss. The hazard we don’t see, but constantly hear, is noise.
Overview
The Centers for Disease Control (CDC) estimates that 22 million workers are exposed to potentially damaging noise each year. Whether you work at a sports venue, on a tarmac, or operate a jackhammer, hearing loss is preventable.
Know Your Workplace Noise Levels
If you need to raise your voice to speak to someone just three feet away, noise levels may exceed 85 decibels.
Fortunately, several instruments can measure workplace noise levels, including:
- Sound level meters
- Noise dosimeters
- Octave band analyzers
Noise may be a problem in your workplace if you:
- Hear ringing or humming in your ears after work.
- Must shout to be heard by a coworker an arm’s length away.
- Experience temporary hearing loss after leaving work.
The National Institute for Occupational Safety and Health (NIOSH) Sound Level Meter App is a free tool for iOS devices. It measures workplace sound levels and provides noise exposure information to help reduce occupational noise-induced hearing loss.
Health Effects
Exposure to high noise levels can cause permanent hearing loss. Unfortunately, surgery and hearing aids cannot restore this type of hearing loss.
Even short-term exposure to loud noise can temporarily affect your hearing. Your ears may feel plugged, or you may experience ringing, known as tinnitus. While these symptoms often disappear within a few minutes or hours, repeated exposure can eventually cause permanent tinnitus or hearing loss.
In addition, loud noise creates physical and psychological stress. It can reduce productivity, interfere with communication and concentration, and increase the risk of workplace accidents by making warning signals harder to hear.
Over time, noise-induced hearing loss can significantly reduce your ability to hear high-frequency sounds, understand speech, and communicate effectively.
How Does the Ear Work?
When sound waves enter the outer ear, they strike the eardrum. The vibrations then travel through the middle ear and into the inner ear.
Inside the middle ear, three small bones—the malleus (hammer), incus (anvil), and stapes (stirrup)—amplify the sound before passing it to the inner ear.
The inner ear contains the cochlea, a fluid-filled structure shaped like a snail shell. Tiny hair cells line the cochlea. As vibrations move through the fluid, these microscopic hairs bend and convert sound waves into nerve impulses. Your brain then interprets those impulses as sound.
Unfortunately, exposure to loud noise can destroy these delicate hair cells, leading to permanent hearing loss.
What Do I Need to Know About the Ear?
The ear is the organ responsible for hearing. It consists of three main sections:
- The external (outer) ear
- The air-filled middle ear
- The fluid-filled inner ear
Outer Ear
The outer ear consists of several important parts.
Pinna
The pinna is the visible portion commonly called “the ear.”
Its primary functions include:
- Locating the source of sound.
- Directing sound into the ear canal.
- Amplifying certain sound frequencies while reducing others.
- Creating a unique acoustic signature for each individual.
External Auditory Meatus (Ear Canal)
The ear canal extends from the pinna to the eardrum. It averages 26 millimeters long and 7 millimeters wide, although size varies from person to person. This variation is important when fitting hearing protection.
The ear canal also protects the eardrum and naturally amplifies sound by approximately 10 decibels around 3,300 Hertz.
As a result, sounds between 2,000 and 4,000 Hertz receive the greatest amplification. Unfortunately, this is also the frequency range most vulnerable to hearing damage.
Tympanic Membrane (Eardrum)
The eardrum separates the outer and middle ear. It protects the inner structures from foreign objects and measures about 17.5 millimeters in diameter.
When sound waves strike the eardrum, it vibrates. Although those vibrations move only about one-billionth of a centimeter, they begin the hearing process.
Middle Ear
The middle ear transfers sound from the outer ear to the inner ear. Three key structures make this possible.
Ossicles (Bones)
The malleus, incus, and stapes form the ossicles.
Together, they convert the eardrum’s vibrations into movement at the stapes. This process increases sound pressure in two important ways.
First, the eardrum is about 17 times larger than the oval window, increasing sound pressure.
Second, the ossicles create a lever action that further amplifies the sound.
Because of this system, most sound energy entering the ear reaches the inner ear efficiently. Without it, only about one-thousandth of the acoustic energy would reach the inner-ear fluids.
The malleus and incus move together, transmitting sound to the stapes. The stapes then pushes against the oval window.
Muscles
Two muscles—the tensor tympani and stapedius—help stabilize the ossicles.
When sound exceeds approximately 80 decibels, these muscles contract. This action reduces the amount of sound energy entering the inner ear.
However, this protective reflex has limitations. It reacts too slowly to protect against sudden impulse noises and cannot remain contracted long enough to protect against prolonged exposure.
Eustachian Tube
The eustachian tube connects the middle ear to the nasal passages.
It opens during swallowing and equalizes pressure on both sides of the eardrum. Without equal pressure, the eardrum cannot vibrate efficiently, reducing the amount of sound energy reaching the inner ear.
Inner Ear
The inner ear converts mechanical sound waves into electrical nerve impulses that the brain recognizes as sound.
The cochlea, a spiral-shaped structure resembling a snail shell, contains the sensory receptors responsible for hearing.
Inside the cochlea are three canals:
- Scala Vestibuli
- Scala Tympani
- Scala Media (cochlear duct)
The Scala Media houses the organ of Corti, the organ responsible for hearing.
The basilar membrane forms the floor of the cochlear duct, while Reissner’s membrane separates it from the Scala Vestibuli.
Hair Cells and Cilia
The basilar membrane supports the delicate hair cells within the organ of Corti.
Approximately 3,500 inner hair cells and 12,000 outer hair cells detect sound.
Tiny hair-like structures called cilia extend from these cells into the tectorial membrane.
Generally, hair cells at the base of the cochlea respond to high-frequency sounds. Those near the apex respond to lower frequencies.
Activity in the Cochlea
Movement of the stapes pushes on the oval window, creating fluid movement within the Scala Vestibuli.
That fluid movement shifts the cochlear duct, distorts Reissner’s membrane, and moves the organ of Corti.
The vibration then transfers through the basilar membrane into the Scala Tympani.
At the end of the cochlea, the round window acts as a pressure relief point.
As the basilar membrane vibrates, the hair cells bend against the tectorial membrane.
That movement activates nerve endings and converts sound into electrochemical signals.
Finally, those signals travel through the Vestibulocochlear nerve, where the brain interprets them as sound.
Protect Your Hearing
Workplace hearing loss is preventable. The right training, education, and hearing protection can preserve your hearing for years to come.
Do you hear me?