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Ear Protectors and Their Action in Protecting Hearing System of Workers against Occupational Noise

Authors: F. Forouharmajd, S. Pourabdian, N. Ziayi Ghahnavieh


For many years, the ear protectors have been used to preventing the audio and non-audio effects of received noise from occupation environments. Despite performing hearing protection programs, there are many people which still suffer from noise-induced hearing loss. This study was conducted with the aim of determination of human hearing system response to received noise and the effectiveness of ear protectors on preventing of noise-induced hearing loss. Sound pressure microphones were placed in a simulated ear canal. The severity of noise measured inside and outside of ear canal. The noise reduction values due to installing ear protectors were calculated in the octave band frequencies and LabVIEW programmer. The results of noise measurement inside and outside of ear canal showed a different in received sound levels by ear canal. The effectiveness of ear protectors has been considerably reduced for the low frequency limits. A change in resonance frequency also was observed after using ear protectors. The study indicated the ear canal structure may affect the received noise and it may lead a difference between the received sound from the measured sound by a sound level meter, and hearing system. It means the human hearing system may probably respond different from a sound level meter. Hearing protectors’ efficiency declines by increasing the noise levels, and thus, they are not suitable to protect workers against industrial noise particularly low frequency noise. Hearing protectors may be solely a reason to damaging of hearing system in a special frequency via changing of human hearing system acoustical structure. We need developing the subjective method of hearing protectors testing, because their evaluation is not designed based on industrial noise or in the field.

Keywords: Ear protector, hearing system, occupational noise, workers.

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[1] Alam N, Sinha V, Jalvi R, Suryanarayan A, Gurnani D, Barot DA. Comparative study of attenuation measurement of hearing protection devices by real ear attenuation at threshold method. Indian Journal of Otology. 2013;19(3):127.
[2] Lokki T, Huhtakallio I. Measurements on active earplugs and effect of ear canal resonance on spectral balance. EuroNoise 2015. 2015:21.
[3] Tufts JB, Chen S, Marshall L. Attenuation as a function of the canal length of custom-molded earplugs: A pilot study. The Journal of the Acoustical Society of America. 2013;133(6):EL446-EL51.
[4] Hiipakka M. Measurement apparatus and modelling techniques of ear canal acoustics: Helsinki University Of Technology; 2008.
[5] Hong O, Kerr MJ, Poling GL, Dhar S. Understanding and preventing noise-induced hearing loss. Dis Mon. 2013;59(4):110-8.
[6] Nodoushan MS, Mehrparvar A, Jahromi MT, Safaei S, Mollasadeghi A. Training in using earplugs or using earplugs with a higher than necessary noise reduction rating? A randomized clinical trial. The international journal of occupational and environmental medicine. 2014;5(4 October):479-187-93.
[7] Kabe I, Kochi T, Tsuruoka H, Tonegawa T, Denda I, Nonogi M, et al. Noise attenuation of earplugs as measured by hREAT and F-MIRE methods in a Japanese metal manufacturing plant. Journal of occupational health. 2012;54(4):310-5.
[8] NĂ©lisse H, Le Cocq C, Boutin J, Voix J, Laville F. Systematic evaluation of the relationship between subjective and objective measurement methods of hearing protector devices attenuation. 2015
[9] ISO4869-1. Acoustics -hearing protectors -part 1: subjective method for the measurement of sound attenuation. Switzerland: Geneva; 1990.
[10] Cheng JT, Ravicz M, Guignard J, Furlong C, Rosowski JJ. The effect of ear canal orientation on tympanic membrane motion and the sound field near the tympanic membrane. Journal of the Association for Research in Otolaryngology. 2015;16(4):413-32.
[11] Forouharmajd F, Mohammadi Z, Ahmadvand M, Forouharmajd F. Sound pressure level tools design used in occupational health by means of Labview software. International Journal of Environmental Health Engineering. 2015;4(1):41.(in persian).
[12] Agarwal M. International Journal of Chemical, Environmental and. Pharmaceutical Research. 2014;5(1):1-7.
[13] Mirzakhani A, Monazzam M, Monazzam M. Noise Exposure and Hearing Status among the Registered Locksmiths in Tehran, Iran. International Journal of Occupational Hygiene. 2015;6(2):56-60.
[14] Chang T-Y, Liu C-S, Huang K-H, Chen R-Y, Lai J-S, Bao B-Y. High-frequency hearing loss, occupational noise exposure and hypertension: a cross-sectional study in male workers. Environmental Health. 2011;10(1):35.
[15] R G. Noise and vibration engineering. Medical university of Hamedan: student; 2015(in persian).
[16] Hohmann BW, editor. Assessment of impulse noise regarding harmfulness to hearing. PACS; 2015.
[17] May JJ. Occupational hearing loss. American Journal of Industrial Medicine. 2000;37(1):112-20.
[18] Lehtomaki K. Noise attenuation of hearing protectors against heavy weapon noise. Military medicine. 2000;165(9):678.