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Noise Induced Hearing Loss

What is Acoustic Trauma or Noise Induced Hearing Loss (NIHL)?

Exposure to loud noise can cause damage to hearing temporary or permanent. 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.

  • Noise level goes up with celebrations, social gatherings, party, music, rock-concert and fire works, and so does people visiting E.N.T. and audiology clinics with hearing problems or ringing in the ear (tinnitus).

  • Children and teens listening to loud music are also more prone to develop hearing loss later in life.

  • People with occupations involving exposure to noise above 85 decibel over an 8 hour period daily are also at risk. These includes industries like mining, construction, drilling and agriculture, music.

How Noise Causes Hearing Loss?

Too loud noise damages sensitive nerve endings in inner ear (delicate cells called cillia) and cause sensorineural loss. Sensitivity to sound is different for each person.
Sudden exposure to loud noise such as firework or loud rock concert may cause temporary sensorineural hearing loss which usually recovers over 24 to 48 hours.

But if sound is too loud, or loud sound is too close or loud sound is exposed over a long period of time(more than 85 db), permanent sensorineural hearing loss can occur.

And 85 decibels is not as loud as you will think. Sound from an ipod shuffle is usually 115 db, and with fireworks it goes at 150 db.

Tinnitus may be presenting complaint for some person.

Types of Ear Protectors

Hearing protection devices decrease the intensity of sound that reaches the eardrum. They come in two forms: earplugs and earmuffs.

Earplugs are small inserts that fit into the outer ear canal. They must be snugly sealed so the entire circumference of the ear canal is blocked. They are available in a variety of shapes and sizes and can be custom made.
Earmuffs fit over the entire outer ear to form an air seal so the entire circumference of the ear canal is blocked, and they are held in place by an adjustable band.

Properly fitted earplugs or muffs reduce noise 15 to 30 dB.

Simultaneous use of earplugs and muffs usually adds 10 to 15dB more protection than either used alone. Combined use should be considered when noise exceeds 105 dB.

Cotton balls or tissue paper wads stuffed into the ear canals are very poor protectors.

What is Dangerous Level of Noise?

Sensitivity to sound is different for each person.

Noise may damage your hearing if you have to shout over background noise to make yourself heard, the noise hurts your ears, it makes your ears ring, or you have difficulty hearing for several hours after exposure to the noise.

Sound is measured in units called decibels. Continual exposure to more than 85 decibels (dB) is dangerous to the ears.

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.

Approx. Decibel Level



Faintest sound heard by human ear.


Whisper, quiet library


Normal conversation, sewing machine, typewriter


Lawnmower, shop tools, truck traffic; 8 hours per day is the maximum exposure to protect 90% of people.


Chainsaw, pneumatic drill, snowmobile; 2 hours per day is the maximum exposure without protection


Sandblasting, loud rock concert, auto horn; 15 minutes per day is the maximum exposure without protection.


Gun muzzle blast, jet engine; noise causes pain and even brief exposure injures unprotected ears. Maximum allowed noise with hearing protectors

Occupational Exposure to Noise
People with occupations involving exposure to noise above 85 decibel over an 8 hour period daily are also at risk. These include industries like mining, construction, drilling and agriculture.

For unprotected ears, the allowed exposure time decreases by one-half for each 5 dB increase in the average noise level. For instance, exposure is limited to 8 hours at 90 dB, 4 hours at 95 dB, and 2 hours at 100 dB

The highest permissible noise exposure for the unprotected ear is 115 dB for 15 minutes/day. Any noise above 140 dB is not permitted.

Noise exposure is cumulative. So the noise at home or at play must be counted in the total exposure during any one day.

Symptoms : Earliest symptoms of hearing loss may be irritation or buzzing in ear.
  • Hearing Loss

  • Difficulty inunderstanding in noisy area

  • Sense of fullness the ear

  • Noises, ringing in the ear

  • Earache

  • Bleeding from the ear

  • Dizziness

How to Diagnose ? Hearning Tests
How to Prevent Noise Induced Hearing Loss?
What is Treatment of Noise Induced Hearing Loss?