Attenuation in Earplugs

April 2, 2013

Consistency of Attenuation across Multiple Fittings of Custom and Non-custom Earplugs

Hearing protection devices (HPDs) play a significant role in protecting workers from occupational noise-induced hearing loss. Individual HPD fit-testing Noise Rating Attenuationestimates the amount of protection, or attenuation, that an individual achieves from a given hearing protection device as it is worn. Results from a single fit-test may not be representative of real-world hearing protection device performance over time, however, due to inconsistency in how the individual fits the hearing protection device from time to time. Jennifer B Tufts, Kelly N Jahn, and John P Byram conducted a study, the effects of hearing protection device type and user training on the consistency of attenuation achieved across multiple fittings were evaluated in a within-subjects design. To learn more or buy the study CLICK HERE.

In this study the subjects were initially naive to proper earplug insertion techniques and later received one-on-one training for the second half of the attenuation measurements. Consistency, or reliability, of fit was assessed using:

(i) the standard deviation of the ‘distance to ear mean attenuation’, a measure of fitting uncertainty, and

(ii) the standard deviation of the attenuation values across multiple fit-tests for each subject.

The custom earplug provided statistically significantly better consistency of attenuation than the non-custom earplug at 500, 1000, and 2000 Hz. Training effects were statistically significant at 250, 500, and 1000 Hz and at the Personal Attenuation Rating. No interactions were statistically significant. These results indicate that, in general, subjects obtained more consistent attenuation with the custom earplugs than with the non-custom earplugs and that consistency improved with training for both earplug types. CLICK HERE to buy article. REAT reliability training © The Author 2012. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

What is Attenuation

Attenuation measurements using a real-ear attenuation at threshold procedure were obtained on 30 participants wearing custom-molded and non-custom earplugs.

According to OSHA, for employees who have experienced a significant threshold shift, hearing protector attenuation must be sufficient to reduce employee exposure to a TWA of 85 dB. Employers must select one of the following methods by which to estimate the adequacy of hearing protector attenuation. The most Noise Reduction Rating convenient method is the Noise Reduction Rating (NRR) developed by the Environmental Protection Agency (EPA). According to EPA regulation, the NRR must be shown on the hearing protector package. The NRR is then related to an individual worker’s noise environment in order to assess the adequacy of the attenuation of a given hearing protector. This appendix describes four methods of using the NRR to determine whether a particular hearing protector provides adequate protection within a given exposure environment. Selection among the four procedures is dependent upon the employer’s noise measuring instruments.

Instead of using the NRR, employers may evaluate the adequacy of hearing protector attenuation by using one of the three methods developed by the National Institute for Occupational Safety and Health (NIOSH), which are described in the “List of Personal Hearing Protectors and Attenuation Data,” HEW Publication No. 76-120, 1975, pages 21-37. These methods are known as NIOSH methods No. 1, No. 2 and No. 3. The NRR described below is a simplification of NIOSH method No. 2. The most complex method is NIOSH method No. 1, which is probably the most accurate method since it uses the largest amount of spectral information from the individual employee’s noise environment. As in the case of the NRR method described below, if one of the NIOSH methods is used, the selected method must be applied to an individual’s noise environment to assess the adequacy of the attenuation. Employers should be careful to take a sufficient number of measurements in order to achieve a representative sample for each time segment.

NOTE: The employer must remember that calculated attenuation values reflect realistic values only to the extent that the protectors are properly fitted and worn.

Read more articles on Hearing Attenuation: 



Personal Hearing Conservation Noise Reduction Measures

Every human has their own limit of acceptance – according to their attitude to their own life and health, their family and their colleaques. This limit of acceptance varies a lot from human to human, but even if the limit is exceeded one will back away from the risk. The limit is rather vague and is related to workers’ traditions, possibilities of finding other less unhealthy jobs and the degree of influence at the workplace. The individual limit of acceptance thus might be either above or beneath what is considered healthy or legally justifiable.

Employees can make their own noise reduction measures by:

* Avoiding unnecessary noise at transport and handling – “don’t throw the things”.

* Stopping machines and equipment that is not in use at the moment

* Securing loose machine parts that rattle.

* Reducing occupation and staying in high noise areas to an absolutely minimum

* Using appropriate technical equipment, for example encapsulation and noise shields.

* Making their own routines for maintenance, adjusting and oiling machinery and equipment.

* Taking part in development and evaluation of new noise efforts.

* If anything else is impossible, and hearing protectors like dB Blockers must be used: Use them all the time!

* By taking any incipient hearing damage seriously, involve health personnel and have all damages properly investigated.

Learn more about Personal Hearing Conservation. 

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