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.
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.
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||Example|
|0||Faintest sound heard by human ear.|
|30||Whisper, quiet library.|
|60||Normal conversation, sewing machine, typewriter.|
|90||Lawnmower, shop tools, truck traffic; 8 hours per day is the maximum exposure to protect 90% of people.|
|100||Chainsaw, pneumatic drill, snowmobile; 2 hours per day is the maximum exposure without protection.|
|115||Sandblasting, loud rock concert, auto horn; 15 minutes per day is the maximum exposure without protection.|
|140||Gun muzzle blast, jet engine; noise causes pain and even brief exposure injures unprotected ears. Maximum allowed noise with hearing protectors.|
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.
Difficulty inunderstanding in noisy area
Sense of fullness the ear
Noises, ringing in the ear
Bleeding from the ear
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.
Person working in noise above 85 db should use noise protection devices-ear plugs and ear muffs. It is as simple a concept as using goggles to protect your eyes from UV rays of sun. It is for Musicians also.
People with occupations involving noise exposure should undergo periodic hearing screening (audiometry test).
On earliest sign of noise trauma like irritability, buzzing sound in ear or difficulty in hearing, visit your physician.
Turn down the volume of television and MP3 players
Do not stand directly near to the source of noise.
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.
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.