noise-induced hearing loss

By , November 17, 2014 1:14 am
“NIHL” redirects here. For the National Ice Hockey League, see English National Ice Hockey League.

Noise-induced hearing loss (NIHL) is hearing decrease caused by loud sound. Evidences of NIHL include a history of exposure to loud sound and a hearing loss in a narrow range of frequencies, such as those from gunfire, power tools, explosions and night club music. The best, first option for protecting hearing is lowering the volume at the source of the sound.[1]

Currently, hearing loss in mammals is permanent. While frogs, fish, and birds with hearing loss regain their hearing naturally, mammals lost that ability as much as 300 million years ago, and so far scientists have been unsuccessful in solving that problem.[2]

Mechanism

NIHL occurs when too much [3] They were not able to fully prevent it.

Damage ranges from exhaustion of the “hair” (hearing) cells in the ear to loss of those cells[4]

NIHL is therefore the consequence of overstimulation of the hair cells and supporting structures. Structural damage to hair cells (primarily the outer hair cells) will result in hearing loss that can be characterized by an attenuation and distortion of incoming auditory stimuli.

Types

The ear can be exposed to short periods in excess of 120 dB without permanent harm — albeit with discomfort and possibly pain; but long term exposure to sound levels over 80 dB can cause permanent hearing loss.[5]

There are two basic types of NIHL:

  • NIHL caused by acoustic trauma and
  • gradually developing NIHL.

Acoustic trauma

NIHL caused by acoustic trauma refers to permanent cochlear damage from a one-time exposure to excessive sound pressure. This form of NIHL commonly results from exposure to high-intensity sounds such as firecrackers.

Gradually developing NIHL

Gradually developing NIHL refers to permanent cochlear damage from repeated exposure to loud sounds over a period of time. Unlike NIHL from acoustic trauma, this form of NIHL does not occur from a single exposure to a high-intensity sound pressure level. Gradually developing NIHL can be caused by multiple exposures to any source of excessive volume, such as home and vehicle stereos, [7] Therefore, gradually developing NIHL occurs from the combination of sound intensity and duration of exposure.

Both NIHL caused by acoustic trauma and gradually developing NIHL can often be characterized by a specific pattern presented in audiological findings. NIHL is generally observed to affect a person’s hearing sensitivity in the higher frequencies, especially at 4000 Hz. “Noise-induced impairments are usually associated with a notch-shaped high-frequency sensorineural loss that is worst at 4000 Hz, although the notch often occurs at 3000 or 6000 Hz, as well”.[4]

Not all audiological results from patients with NIHL match the above description. Often a decline in hearing sensitivity will occur at frequencies other than at the typical 3000–6000 Hz range. Variations arise from differences in people’s ear canal resonance, the frequency of the harmful acoustic signal, and the length of exposure.[9]

Prevention

NIHL can easily be prevented through the use of some of the most simple, widely available and economical tools. This includes but is not limited to ear protection (i.e. earplugs and earmuffs), education, and hearing conservation programs. Earplugs and earmuffs can provide the wearer with at least 5 to 10 dB SPL of attenuation.[10]

Hearing protection programs have been hindered by people not wearing the protection for various reasons, including the desire to converse, uncomfortable devices, lack of concern about the need for protection, and social pressure against wearing protection.[12]

A systematic review of the effectiveness of interventions to promote the use of hearing protection devices such as earplugs and earmuffs among workers found that tailored interventions improve the average use of such devices when compared with no intervention.[13]

In the workplace

Further information: Industrial noise

About 30 million workers are exposed to hazardous [15]

The following is a list of occupations that are most susceptible to hearing loss:[14]

Among musicians

Musicians, from [19]

Music-induced hearing loss is still a [20]

Given the extensive research suggesting that [22]

Workplace standards

The United States Department of Defense (DoD) instruction 605512 has some differences from OSHA 1910.95 standard, for example, OSHA 1910.95 uses a 5 dB exchange rate and DoD instruction 605512 uses a 3 dB exchange rate.

There are programs that seek to increase compliance and therefore effectiveness of hearing protection rules; the programs include the use of hearing tests and educating people that loud sound is dangerous[11]

Employees are required to wear hearing protection when it is identified that their eight-hour time weighted average (TWA) is above the exposure action value of 90 dB. If subsequent monitoring shows that 85 dB is not surpassed for an eight-hour TWA, the employee is no longer required to wear hearing protection.[6]

In the European Union, directive 2003/10/EC mandates that employers shall provide hearing protection at noise levels exceeding 80 dB(A), and that hearing protection is mandatory for noise levels exceeding 85 dB(A).[23] Both values are based on 8 hours per day, with a 3 dB exchange rate.

Mitigation

For people living with NIHL, there are several management options that can improve the ability to hear and effectively communicate. Management programs for people with NIHL include counseling and the use of clarification needed] With proper amplification and counseling, the prognosis is excellent for people with NIHL. The prognosis has improved with the recent advancements in digital hearing aid technology, such as directional microphones, open-fit hearing aids, and more advanced algorithms. Annual audiological evaluations are recommended to monitor any changes in a patient’s hearing and to modify hearing-aid prescriptions.

There is evidence that hearing loss can be minimized by taking megadoses of magnesium for a few days, starting as soon as possible after exposure to the loud noise.[27]

There are currently no medical options for NIHL from noise-exposure which occurred more than a week previously. However, current research for the possible use of drug and genetic therapies look hopeful.[28]

See also

Mitigation:

General:

References

  1. ^ Mestayer, Kathi. 2014. Caution Noise at Work. Hearing Health Magazine, Vol. 30, No. 1, p. 31. ISSN: 0888-2517
  2. ^ Mestayer, Kathi. 2014. Caution Noise at Work. Hearing Health Magazine, Vol. 30, No. 1, pp. 16 – 17. ISSN: 0888-2517
  3. 9518561. 
  4. ^ f Gelfand, S. (2001). Auditory System and Related Disorders. Essentials of Audiology (2nd ed.). New York: Thieme. p. 202. 
  5. ^ http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9735 OSHA 29 CFR 1910.95(b)(2)
  6. ^ Occupational Safety & Health Administration. 2002. 
  7. ^ “Hearing Protection”. Retrieved 21 February 2014. 
  8. 8184280. 
  9. 12747520. 
  10. 3436923. 
  11. ^ 16470464. 
  12. ^ http://www.cdc.gov/niosh/topics/buyquiet/default.html
  13. ^ 22513929. 
  14. ^ National Institute for Occupational Safety and Health. 2001. 
  15. help)
  16. 6648318. 
  17. 18408864. 
  18. ^ “Rock and Roll Hard of Hearing Hall of Fame”. Guitar Player. 2006. Archived from the original on 2009-03-04. 
  19. ^ Ostri, B.; Eller, N.; Dahlin, E.; Skylv, G. (1989). “Hearing Impairment in Orchestral Musicians”. International Journal of Audiology 18 (4): 243–9. doi:10.3109/14992028909042202. 
  20. ^ 17365063. 
  21. ^ Fligor, B. J. (2009). “Risk for Noise-Induced Hearing Loss from Use of Portable Media Players: A Summary of Evidence Through 2008”. Perspectives on Audiology 5: 10. doi:10.1044/poa5.1.10. 
  22. 16011051. 
  23. ^ Directive 2003/10/EC of the European Parliament and of the Council of 6 February 2003 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise)
  24. 12170143. 
  25. self-published source?]
  26. 12030420. 
  27. ^ “Magnesium”. A.D.A.M., Inc. June 17, 2011. 
  28. ^ “Noise-Induced Hearing Loss”. National Institute on Deafness and Other Communication Disorders. October 2008. 

External links



This article uses material from the Wikipedia article noise-induced hearing loss, which is released under the Creative Commons Attribution-Share-Alike License 3.0.

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