Noise Induced Hearing Loss

A teenage girl visited ENT clinic with her mother with ringing in the ear and felt like cotton in the ear. Previous night,  Diwali Night she had spent several hours setting off the fire crackers.

Her ear were normal on video otoscopy and Audiogram showed  35 db at 4000 and 8000 hertz, Several days later, her hearing had returned to normal.

This patient is an example of a “temporary threshold shift.” Or Reversible Hearing Loss by exposure to an intense “impulse” sound such as fireworks or loud rock concert.

If sound is too loud or duration of exposure is long enough, such as noise generated in a woodworking shop it may lead to permanent threshold shift.  This condition is called Noise Induced Hearing Loss which has no cure.

Acoustic trauma occurs when excessive sound energy strikes inner ear. When we are exposed sounds that are too loud or loud sounds that last a long time—small sensitive structures in our inner ear, called hair cells, can be damaged, Hair cells convert sound energy into electrical signals that travel to the brain. The louder the sound, the shorter the time period before NIHL can occur.

Sound is measured in units called decibels. Continual exposure to more than 85 decibels (dB) is dangerous to the ears. Firecrackers emit sounds from 120 to 160 decibels. Sound with 140dB can cause ear ache. A very high intensity sound (above 160 dB) may also damage the ear drum and can cause dislocation of middle ear ossicles.

An even higher intensity may cause leakage of inner ear fluid leading to permanent hearing loss associated with dizziness.

Symptoms

• Hearing loss
• Sense of fullness  the ear
• Noises, ringing in the ear
• Earache
• Bleeding from the are
• Dizziness,

Signs and tests

Acoustic trauma is suspected if hearing loss occurs after noise exposure. Audiometry may determine how much hearing has been lost. Audiogram has typical “notch” at 4000 hz, with better hearing at both lower and higher frequencies. Otoacoustic Emisson (OAE) testing is very sensitive to noise induced hearing loss.

Treatment

The hearing loss may not be treatable. The goal of treatment is to protect the ear from further damage. Hearing aid is prescribed for communication needs. If ear Drum is ruptured, surgery to repair ear drum may be needed.

Ear protection using noise protector ear plugs or ear muffs may prevent the hearing loss from getting worse.

Noise exposure, whether occupational or recreational, is the leading preventable cause of hearing loss. It can be prevented by avoiding “too loud” or “too long” Noise exposure and use of hearing protection when necessary.

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It’s a Noisy Planet. Protect Their Hearing campaign, a program of the National Institute on Deafness and Other Communication Disorders (NIDCD).