Auditory System Hearing Disorders Noise Induced Tinnitus

Human hearing is designed to perceive sound in a wide range of intensities (loudness levels), measured on the decibel scale. However, prolonged exposure to loud noise can cause a specific type of hearing damage known as noise-induced hearing loss (NIHL). Noise-induced deafness is even possible with sudden exposure to extremely loud noise. Proper precautions can help you to avoid hearing damage from noise exposure.

How Can Noise Damage My Hearing?

Constant exposure to high-intensity noise can damage the hair cells in the cochlea, affecting sound transmission to the auditory nerve and leading to sensorineural hearing loss. NIHL is generally characterized by a hearing loss in the frequencies of 4000-6000 Hz. Noise-induced tinnitus (a constant feeling of ringing in the ears) is also possible. 80-90 dB is a general measurement for sound that begins to pose a permanent threat to hearing. Examples of activities with noise levels 80 to 90 dB or greater include:

  • Garbage disposal, dishwasher (80 dB)
  • Blender, busy street (90 dB)
  • Motorcycle, jackhammer (100 dB)
  • Chainsaw, car horn at 1m (110 dB).

120 dB is about the volume of a jet takeoff or nearby thunderclap, and is generally considered to be the threshold for pain for sound exposure. However, hearing damage can begin at levels much lower than those that will cause pain.

How Can I Protect My Hearing from Noise Damage?

You can take several measures to protect your hearing from excessive noise:

  • Take care not to use personal music devices too loudly, or for long periods of time. Take care when listening to headphones in the presence of background noise. You may feel the need to turn your headphones up in order to drown out the background, sometimes without realizing how loud it is.
  • Wear hearing protection, such as earmuffs or earplugs, when you know you will be exposed to loud noise, such as at construction sites or concerts.

If you are consistently exposed to noise at work, the Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) enforce rules for maximum noise exposure for workplace hearing safety. Each organization has its own exposure recommendations; however, the NIOSH recommendations are most conservative.

The decibel scale is logarithmic (that is, based on base ten), meaning that an increase of only three decibels is very significant. As a general rule, for every 3 dB increase, the permissible exposure time is halved. The NIOSH noise exposure limits are as follows:

Decibel Level Permissible Time Exposure
85 dB 8 hours
88 dB 4 hours
91 dB 2 hours
94 dB 1 hour
97 dB 30 min
100 dB 15 min
103 dB 7 min
106 dB 3 min
109 dB 1 min
112 dB 56 sec
115 dB 28 sec

Noise exposure can be less noticeable than other hearing loss causes, and can occur gradually; therefore it is important to be vigilant about protective measures in order to reduce the chances of occupational hearing loss.

Resources

American Speech-Language-Hearing Association (n.d.). Noise and hearing loss. Retrieved February 10, 2010, from American Speech-Language-Hearing Association Web site: http://www.asha.org/public/hearing/disorders/noise.htm.

National Institute for Occupational Safety and Health (n.d.). Criteria for a recommended standard: occupational noise exposure. Retrieved February 15, 2010, from CDC Web site: http://www.cdc.gov/niosh/docs/98-126/chap1.html#11.

Dangerous Decibels (2005). Decibel scale of common sounds. Retrieved February 10, 2010, from Dangerous Decibels Web site: http://www.dangerousdecibels.org/teachers_guide/DDB_TRG_Appendices_3.pdf.

National Institute on Deafness and Other Communication Disorders (n.d.). The noise in your ears: facts about tinnitus. Retrieved February 10, 2010, from National Institute on Deafness and Other Communication Disorders Web site: http://www.nidcd.nih.gov/health/hearing/noiseinear.asp.

Neitzel, R. (2008). NIOSH and OSHA permissible noise exposure limits. Retrieved February 10, 2010, from Audiology Online Web site: http://www.audiologyonline.com/askexpert/display_question.asp?question_id=573.