What is noise-induced hearing loss?

Every day we experience sound in our environment. Normally, we hear these sounds at safe levels that do not affect our hearing. However, when we are exposed to harmful noise - sounds that are too loud or loud sounds that last a long time - sensitive structures in our inner ear can be damaged, causing noise-induced hearing loss (NIHL). These sensitive structures, called hair cells, are small sensory cells in the inner ear that convert sound energy into electrical signals that travel to the brain. Once damaged, our hair cells cannot grow back.

What are the effects of NIHL?

Exposure to harmful sounds causes damage to the hair cells as well as the auditory, or hearing, nerve. Impulse sound can result in immediate hearing loss that may be permanent. This kind of hearing loss may be accompanied by tinnitus - a hissing, ringing, buzzing, or roaring in the ears or head - which may subside over time. Hearing loss and tinnitus can occur in one or both ears, and tinnitus may continue constantly or occasionally throughout a lifetime. Continuous exposure to loud noise can also damage the structure of hair cells, resulting in hearing loss and tinnitus, although the process occurs more gradually than for impulse noise. Exposure to impulse and continuous noise may cause only temporary hearing loss. If a person regains hearing, the temporary hearing loss is called a temporary threshold shift. This mostly disappears 16 to 48 hours after exposure to loud noise. Those at risk can prevent NIHL from both impulse and continuous noise by regularly using hearing protectors such as earplugs and/or earmuffs.

What are the symptoms of NIHL?

Over time, the sounds a person hears may become distorted or muffled, and it may be difficult for the person to understand speech. Someone with NIHL may not even be aware of the loss, but it can be detected with a hearing test.

Can NIHL be prevented?

NIHL is 100% preventable. All individuals should understand the hazards of noise and how to practise good hearing health in everyday life. To protect your hearing:

• know which noises can cause damage (those at or above 85 decibels)
• wear earplugs or other hearing protective devices when involved in a loud activity
• be alert to hazardous noise in the environment
• protect the ears of children who are too young to protect their own
• make family, friends, and colleagues aware of the hazards of noise
• if you suspect hearing loss, visit an otolaryngologist (a physician who specialises in diseases of the ears, nose, throat, head, and neck) and request a hearing test by an audiologist (a health professional trained to measure and help individuals deal with hearing loss)