The Martlet

Have you ever played your iPod at full volume or gone to a rock concert without hearing protection? If you answered yes, you’re at risk of developing noise-induced hearing loss.

May is Speech and Hearing Awareness Month, a fine time to evaluate how well you protect your hearing against this condition, which can make it difficult or impossible to understand speech.

“The danger of exposure to noise is a function of the volume and the time exposure,” said Monica Pozer, director of audiology at Island Hearing. “The louder the sound, the shorter the duration of [safe] listening.”

At an 85-decibel level, which is roughly the amount of sound a blender generates, an eight-hour exposure is the most someone should have, according to Island Hearing.

But Health Canada suggests that 45 minutes of unprotected exposure at 85 decibels is more appropriate, while the Canadian Hearing Society states that this should not be considered a safe level for unprotected hearing.

With every three-decibel increase, the sound energy doubles, so the time of unprotected exposure must be halved. In industrial settings, for example, only four hours should be spent at 88 decibels and two hours at 91 decibels.

Experts seem to agree that unprotected exposure to sounds above 140 decibels is dangerous. Rock concerts typically deliver 120 to 150 decibels.

“Afterwards, people [without hearing protection] can experience a temporary threshold shift,” said Pozer. “ Hearing seems to decline; there may be a muffled feeling or ringing in the ears, then by the next day it seems to resolve.”

With repetition, though, the damage becomes permanent by harming the hair cells in the inner ear, which are responsible for passing messages via the auditory nerve to the brain where they are interpreted as sound. Pozer likens hair cells to grass: walk across a healthy lawn, and within a short time the grass springs back. Keep walking until you wear a path, and the grass dies.

A temporary threshold shift, or ear pain following exposure to noise, is a warning that your hearing is at risk. But not everyone gets a warning.

iPods used at too high a volume for too long are one of the most severe potential causes of hearing loss in children and young adults. Twelve per cent of six to 19-year-olds in the United States have noise-induced hearing loss.

“Individuals can use iPods at 50 per cent volume or less for eight hours a day, but the moment they turn them above this, they are at risk,” said Pozer. For every 10 per cent rise in volume level on the dial they should halve the time. Another hazard is to try to drown out background noise, or to use earphones other than those that came with the iPod.

“The music is too loud if others can hear it, or if the person listening cannot hear you when you speak to them from two meters,” said Pozer.

There are a variety of jobs where workers should protect their hearing, ranging from industrial sites to nightclubs, orchestras and dentists’ offices.

“Employers should provide hearing protection in these situations. If they don’t, there are a number of routes workers can follow,” said Tek Manhas, manager of Island Hearing’s industrial division.

These routes include talking to their workplace industrial first aid attendant or safety officer about their concerns. If the issue remains unresolved they can request a noise assessment from the Workers’ Compensation Board, or buy their own hearing protection. Safety supply stores have a full range of protection from earmuffs to earplugs.

“Foam-rubber ear plugs can be bought from drug stores, and will provide good protection even on industrial sites,” said Manhas. People with normal hearing should be able to hold conversations with others while wearing them.

Custom-molded ear protection is another option. Differing according to the situations it will be used in, it costs about $160 and lasts about 10 years. It’s often more comfortable than off-the-shelf protection.

Noise-induced hearing loss is irreversible and initially imperceptible. Consonants become hard to discriminate, and speech sounds muffled and difficult or impossible to understand, especially in noisy places. Hearing aids help by amplifying sounds, but do not make hearing normal — listening becomes work and is no longer effortless. The condition is preventable.