Hearing protection fit-testing

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Fit testing (MIRE) Sistema proizvodstvennogo kontrolia effektivnosti SIZ organa slukha.jpg
Fit testing (MIRE)

Hearing protector fit-testing is a method that measures the degree of noise reduction obtained from an individual wearing a particular hearing protection device (HPD) - for example, a noise canceling earplug or earmuff. Fit testing is necessary due to the fact that noise attenuation varies across individuals. It is important to note that attenuation can sometimes score as zero due to anatomical differences and inadequate training, as to the proper wear and use. [2] Labeled HPD attenuation values (for example, the Noise Reduction Rating, or NRR) are average values that cannot predict noise attenuation for an individual; in addition, they are based on laboratory measurements which may overestimate the noise reduction obtained in the real world. [3]

Contents

Hearing protection devices such as earplugs or earmuffs must be worn correctly for the wearer to be protected from noise. [4] Correct use of hearing protection includes:

Fit-testing hearing protection can facilitate an appropriate choice of hearing protection, and allow for the professional administering the fit-test to train users on proper techniques for wear. [8] [9] [10] [11] [12] [13]

Requirements and Recommendations for HPD Fit Testing

The Occupational Safety and Health Administration, National Hearing Conservation Association, and National Institute for Occupational Safety and Health recommend it for all workers used HPD as a best practice, [14] and describes existing testing methods and how to incorporate them in hearing conservation programs. [15]

Effective March 31, 2023, the Alberta Government added a requirement that employers fit test each employee who wears HPDs. [16] A trend towards recommending HPD fit-testing as a best practice is emerging in the European Union and the USA. [17] [18]

Fit-testing methods

Fit testing is typically carried out using one of the available fit-testing hardware and software systems (also known as field attenuation estimation system (FAES). [19] Although all fit-testing systems measure the amount of sound reduction provided by hearing protection devices, different systems use different approaches to making this measurement.

The different methods [20] used to measure the attenuation provided by HPDs are as follows:

Real-ear attenuation at threshold (REAT)

NIOSH mobile laboratory for REAT measuring (sound thresholds & real attenuation of earplugs) NIOSH shum mobil'nyi izmeritel' SIZOS 2.jpg
NIOSH mobile laboratory for REAT measuring (sound thresholds & real attenuation of earplugs)

REAT is the most commonly used type of fit-testing technology used in commercial systems. REAT systems are modeled on the "gold-standard" approach to measuring hearing protector attenuation as defined in acoustic standards such as ANSI/ASA S12.6 and the ISO 4869-1. This approach measures the difference in auditory (hearing) thresholds without hearing protection (unoccluded) and with hearing protection (occluded). Differences in occluded and unoccluded thresholds across one or more test frequencies are used to calculate the noise reduction. REAT systems rely on the subjective response of the person being tested to determine auditory thresholds much like a hearing test where the subject indicates when sound is heard at various frequencies.

According to the acoustic standards, REAT testing of hearing protection devices must be tested in an acoustic chamber with a diffuse sound field. Because such chambers are not mobile, portable fit-testing systems employing sound-isolating headphones have been developed to test earplugs. [22] For noncritical screening, REAT can be performed using a web browser and simple audio devices. [23]

Loudness balance

This method first has the subject listen to tones with headphones and "match" loudness between both ears until tones sound equally loud on both sides. Then an earplug is placed in one ear while the baseline procedure is repeated to match loudness in both ears. The increase in loudness required to balance represents the attenuation achieved in that ear. The second earplug is then placed in the other ear and the procedure is repeated a third time. The required increase in loudness this time represents the noise reduction achieved in the second ear. The loudness balance fit-testing approach provides individual personal attenuation ratings for each ear. [24]

Microphone-in-real-ear (MIRE)

Earplugs with probes for MIRE measurements. Vkladyshi Classic s zondom dlia zamera urovnia shuma za vkladyshem.jpg
Earplugs with probes for MIRE measurements.

Also referred to as F-MIRE (field microphone in real ear). This method measures attenuation by placing a small microphone inside the ear canal while hearing protection is worn. Sound pressure levels (SPL) are measured inside and outside of the ear simultaneously and used to calculate a PAR. [24]

Fit test results

The effectiveness is typically measured as a personal attenuation rating (PAR) which is subtracted from the known noise exposure to estimate the total noise exposure a single person has when wearing the tested hearing protection device (HPD). [8] [25]

The outcome measure generated by hearing protector fit-test systems varies from a simple pass/fail to a quantitative personal attenuation rating (PAR). and can be interpreted differently to determine the effectiveness of hearing protection or calculate total noise exposure. [22]

Personal attenuation rating (PAR)

Similar to a noise reduction rating (NRR) required on hearing protection devices in the United States, a personal attenuation rating (PAR) is obtained from an attenuation measurement at one or more than one frequency. The effectiveness is typically measured as a personal attenuation rating (PAR) which is subtracted from the known noise exposure to estimate the total noise exposure a single person has when wearing the tested hearing protection device (HPD). [8] [25] However, the PAR is regarded as more accurate than the NRR because it is calculated per individual and per hearing protection device, while NRR is a generalized estimate of potential sound reduction based on the protection provided to a small population of people. Therefore, PAR gives the evaluator an estimate of the total noise exposure an individual is receiving when wearing hearing protection.

PAR is subtracted from the known noise exposure to estimate the total protected noise exposure a single person has when wearing the tested HPD. [8] [25] The method for estimating protected noise exposure based on the measured PAR may vary slightly across fit-test systems, so it is important to understand to use the PAR generated by a given fit test system [22]

Use of Fit-testing as a training tool

Evidence shows that including fit-testing as a part of employee training for correct hearing protection device use increases the user's ability to properly fit the device, and that this ability is often retained on follow-up. [9] [26] [13] [27] Fit testing provides the individual with immediate feedback regarding the noise reduction achieved, which helps them understand how the device should feel when it is properly fit. Investments in fit testing and training have been shown to be effective at reducing the rates of standard threshold shifts in industry. [27]

A systematic review published in 2024 investigated the effectiveness of hearing protection fit-testing systems and as well as any training occurring alongside the use of these systems in improving the amount of attenuation from noise these workers received. [28] This review included three different studies, which together totaled evaluations on 756 participants. The studies evaluated the impacts of either simple or extensive instructions provided to workers for inserting and fitting earplugs (foam or pre-molded). Extensive training included personalized instruction, while simple training lacked this one-on-instruction. Fit testing with extensive instructions was found to enhance workers’ protection against noise following the test and training sessions, while training with only simple instructions did not significantly improve personal attenuation ratings over the absence of instructions. Thus, fit testing system effectiveness may vary depending on the type of training methods employed in addition to the type of HPD used during fit testing. [28]

See also

Related Research Articles

<span class="mw-page-title-main">Noise</span> Unwanted sound

Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arises when the brain receives and perceives a sound.

<span class="mw-page-title-main">Hearing loss</span> Partial or total inability to hear

Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken language, and in adults it can create difficulties with social interaction and at work. Hearing loss can be temporary or permanent. Hearing loss related to age usually affects both ears and is due to cochlear hair cell loss. In some people, particularly older people, hearing loss can result in loneliness.

<span class="mw-page-title-main">Personal protective equipment</span> Equipment designed to help protect an individual from hazards

Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, electrical, heat, chemical, biohazards, and airborne particulate matter. Protective equipment may be worn for job-related occupational safety and health purposes, as well as for sports and other recreational activities. Protective clothing is applied to traditional categories of clothing, and protective gear applies to items such as pads, guards, shields, or masks, and others. PPE suits can be similar in appearance to a cleanroom suit.

<span class="mw-page-title-main">Noise-cancelling headphones</span> Headphones with active noise control

Noise-cancelling headphones are headphones that suppress unwanted ambient sounds using active noise control (ANC).

<span class="mw-page-title-main">National Institute for Occupational Safety and Health</span> US federal government agency

The National Institute for Occupational Safety and Health is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the Centers for Disease Control and Prevention (CDC) within the U.S. Department of Health and Human Services. Despite its name, it is not part of either the National Institutes of Health nor OSHA. Its current director is John Howard.

Occupational noise is the amount of acoustic energy received by an employee's auditory system when they are working in the industry. Occupational noise, or industrial noise, is often a term used in occupational safety and health, as sustained exposure can cause permanent hearing damage. Occupational noise is considered an occupational hazard traditionally linked to loud industries such as ship-building, mining, railroad work, welding, and construction, but can be present in any workplace where hazardous noise is present.

The permissible exposure limit is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits were established by the Occupational Safety and Health Administration (OSHA). Most of OSHA's PELs were issued shortly after adoption of the Occupational Safety and Health (OSH) Act in 1970.

<span class="mw-page-title-main">Earplug</span> Device to protect ears from loud noises

An earplug is a device that is inserted in the ear canal to protect the user's ears from loud noises, intrusion of water, foreign bodies, dust or excessive wind. Since they reduce the sound volume, earplugs may prevent hearing loss and tinnitus, in some cases.

<span class="mw-page-title-main">Earmuffs</span> Ear-protecting headgear worn over ears to protect from cold or loud noise

Earmuffs refer to two different items. Both items consist of a thermoplastic or metal head-band that fits over the top or back of the head, and a cushion or cup at each end to usually cover both ears. The cups can either be clothing accessories designed to cover a person's ears for warmth or personal protective equipment designed to cover a person's ears for hearing protection.

<span class="mw-page-title-main">Noise control</span> Strategies to reduce noise pollution or its impact

Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors.

<span class="mw-page-title-main">Sound level meter</span> Device for acoustic measurements

A sound level meter is used for acoustic measurements. It is commonly a hand-held instrument with a microphone. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. The diaphragm of the microphone responds to changes in air pressure caused by sound waves. That is why the instrument is sometimes referred to as a sound pressure level meter (SPL). This movement of the diaphragm, i.e. the sound pressure, is converted into an electrical signal. While describing sound in terms of sound pressure, a logarithmic conversion is usually applied and the sound pressure level is stated instead, in decibels (dB), with 0 dB SPL equal to 20 micropascals.

<span class="mw-page-title-main">Health effects from noise</span> Health consequences of exposure to elevated sound levels

Noise health effects are the physical and psychological health consequences of regular exposure to consistent elevated sound levels. Noise from traffic, in particular, is considered by the World Health Organization to be one of the worst environmental stressors for humans, second only to air pollution. Elevated workplace or environmental noise can cause hearing impairment, tinnitus, hypertension, ischemic heart disease, annoyance, and sleep disturbance. Changes in the immune system and birth defects have been also attributed to noise exposure.

<span class="mw-page-title-main">Noise-induced hearing loss</span> Medical condition

Noise-induced hearing loss (NIHL) is a hearing impairment resulting from exposure to loud sound. People may have a loss of perception of a narrow range of frequencies or impaired perception of sound including sensitivity to sound or ringing in the ears. When exposure to hazards such as noise occur at work and is associated with hearing loss, it is referred to as occupational hearing loss.

<span class="mw-page-title-main">Hearing conservation program</span>

Hearing conservation programs are programs that should reduce the risk of hearing loss due to hazardous noise exposure, if implemented correctly and with high quality. Hearing conservation programs require knowledge about risk factors such as noise and ototoxicity, hearing, hearing loss, protective measures to prevent hearing loss at home, in school, at work, in the military and, and at social/recreational events, and legislative requirements. Regarding occupational exposures to noise, a hearing conservation program is required by the Occupational Safety and Health Administration (OSHA) "whenever employee noise exposures equal or exceed an 8-hour time-weighted average sound level (TWA) of 85 decibels (dB) measured on the A scale or, equivalently, a dose of fifty percent." This 8-hour time-weighted average is known as an exposure action value. While the Mine Safety and Health Administration (MSHA) also requires a hearing conservation program, MSHA does not require a written hearing conservation program. MSHA's hearing conservation program requirement can be found in 30 CFR § 62.150, and is very similar to the OSHA hearing conservation program requirements. Therefore, only the OSHA standard 29 CFR 1910.95 will be discussed in detail.

An Exposure Action Value (EAV) or Action Value (AV) is a limit set on occupational exposure to noise where, when those values are exceeded, employers must take steps to monitor the exposure levels. These levels are measured in decibels. The American Occupational Safety and Health Administration (OSHA) set the EAV to 85 dB(A). When the eight-hour time-weighted average (TWA) reaches 85 dB(A), employers are required to administer a continuing, effective hearing conservation program. The program consists of monitoring, employee notification, observation, an audiometric testing program, hearing protectors, training programs, and record-keeping requirements.

<span class="mw-page-title-main">Safe-in-Sound Award</span>

The Safe-in-Sound Excellence in Hearing Loss Prevention Award is an occupational health and safety award that was established in 2007 through a partnership between the National Institute for Occupational Safety and Health (NIOSH) and the National Hearing Conservation Association (NHCA). In 2018, the partnership was extended to include the Council for Accreditation in Occupational Hearing Conservation (CAOHC).

<span class="mw-page-title-main">Occupational hearing loss</span> Form of hearing loss

Occupational hearing loss (OHL) is hearing loss that occurs as a result of occupational hazards, such as excessive noise and ototoxic chemicals. Noise is a common workplace hazard, and recognized as the risk factor for noise-induced hearing loss and tinnitus but it is not the only risk factor that can result in a work-related hearing loss. Also, noise-induced hearing loss can result from exposures that are not restricted to the occupational setting.

<span class="mw-page-title-main">Hearing protection device</span> Protection device for auditory organs

A hearing protection device, also known as a HPD, is an ear protection device worn in or over the ears while exposed to hazardous noise and provide hearing protection to help prevent noise-induced hearing loss. HPDs reduce the level of the noise entering the ear. HPDs can also protect against other effects of noise exposure such as tinnitus and hyperacusis. There are many different types of HPDs available for use, including earmuffs, earplugs, electronic hearing protection devices, and semi-insert devices.

The Auditory Hazard Assessment Algorithm for Humans (AHAAH) is a mathematical model of the human auditory system that calculates the risk to human hearing caused by exposure to impulse sounds, such as gunfire and airbag deployment. It was developed by the U.S. Army Research Laboratory (ARL) to assess the effectiveness of hearing protection devices and aid the design of machinery and weapons to make them safer for the user.

<span class="mw-page-title-main">Safe listening</span> Avoiding hearing damage from intentionally heard sounds

Safe listening is a framework for health promotion actions to ensure that sound-related recreational activities do not pose a risk to hearing.

References

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  3. ↑ Berger, Elliott H.; Voix, Jérémie (2018). "Chapter 11: Hearing Protection Devices". In D.K. Meinke; E.H. Berger; R. Neitzel; D.P. Driscoll; K. Bright (eds.). The Noise Manual (6th ed.). Falls Church, Virginia: American Industrial Hygiene Association. pp. 255–308. Retrieved 10 August 2022.
  4. ↑ Ntlhakana L, Kanji A, Khoza-Shangase K (2015). "The use of hearing protection devices in South Africa: exploring the current status in a gold and a non-ferrous mine". Occupational Health Southern Africa. 21: 10–15.
  5. ↑ Murphy WJ, Themann CL, Kardous CA, Byrne DC (2018-10-24). "Three Tips for Choosing the Right Hearing Protector". NIOSH Science Blog. Retrieved 2018-12-28.
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  9. 1 2 Murphy WJ, Themann CL, Murata TK (November 2016). "Hearing protector fit testing with off-shore oil-rig inspectors in Louisiana and Texas". International Journal of Audiology. 55 (11): 688–98. doi:10.1080/14992027.2016.1204470. PMC   5333758 . PMID   27414471.
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  13. 1 2 Gong W, Liu X, Liu Y, Li L (May 2019). "Evaluating the effect of training along with fit testing on foam earplug users in four factories in China". International Journal of Audiology. 58 (5): 269–277. doi:10.1080/14992027.2018.1563307. PMID   30880506. S2CID   81978766.
  14. ↑ OSHA (July 6, 2022). "OSHA Technical Manual (OTM) Section III: Chapter 5. Noise". www.osha.gov. US Occupational Safety and Health Administration. Retrieved 18 January 2023. ... has recommended HPD fit-testing as a best practice and valuable training tool that can help in training the worker to achieve an optimal fit
  15. ↑ NHCA/OSHA/NIOSH Alliance (2008). "Hearing Protection-Emerging Trends: Individual Fit Testing". NHCA Alliance Best Practice Bulletin: 3. Retrieved 18 January 2023. PDF
  16. ↑ "Change highlights: Noise exposure – Part 16 in the OHS Code". ohs-pubstore.labour.alberta.ca/. Alberta (Canada): Government of Alberta. December 2022. p. 3. Retrieved 11 February 2023. A new requirement has been added for employers to ensure workers are fit tested for the hearing protection devices they use and wear. ... This change is intended to prevent noise induced hearing loss. The effectiveness of hearing protection is greatly reduced if the equipment does not fit correctly or is not inserted or worn correctly.
  17. ↑ Technical Committee CEN/TC 159 “Hearing protectors” (17 November 2021). EN 17479-2021. Hearing protectors - Guidance on selection of individual fit testing methods. Brussels: European Committee for Standardization. p. 46. ISBN   978-0-539-04746-2.{{cite book}}: CS1 maint: numeric names: authors list (link) link
  18. ↑ Accredited Standards Committee S12, Noise (2018). ANSI/ASA S12.71-2018. Performance Criteria for Systems that Estimate the Attenuation of Passive Hearing Protectors for Individual Users. Melville, New York: Acoustical Society of America. p. 54. Retrieved 25 October 2023.{{cite book}}: CS1 maint: numeric names: authors list (link)
  19. ↑ Voix, Jérémie; Smith, Pegeen; Berger, Elliott H. (2018). "Chapter 12: Field Fit-Testing and Attenuation-Estimation Procedures". In D.K. Meinke; E.H. Berger; R. Neitzel; D.P. Driscoll; K. Bright (eds.). The Noise Manual (6th ed.). Falls Church, Virginia: American Industrial Hygiene Association. pp. 309–329. Retrieved 10 August 2022.
  20. ↑ John R. Franks, William J. Murphy, Dave A. Harris, Jennifer L. Johnson & Peter B. Shaw (2003). "Alternative Field Methods for Measuring Hearing Protector Performance" (PDF). American Industrial Hygiene Association Journal. 64 (4). Akron, Ohio: Taylor & Francis: 501–509. doi:10.1080/15428110308984846. ISSN   0002-8894. PMID   12908866 . Retrieved 16 February 2023.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  21. ↑ Kwitowski, August J.; Carilli, Angela M.; Randolph, Robert F. (September 2010). "MultiFit4: An Improved System for Insert-Type". Spectrum. 27 (2). National Hearing Conservation Association: 17–25. Retrieved 6 January 2023.
  22. 1 2 3 "ANSI/ASA S12.71-2018 – Performance Criteria for Systems that Estimate the Attenuation of Passive Hearing Protectors for Individual Users". American National Standards Institute. 2016-11-21. Retrieved 2024-03-04.
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  25. 1 2 3 Trompette N, Kusy A, Ducourneau J (2015-04-01). "Suitability of commercial systems for earplug individual fit testing". Applied Acoustics. 90: 88–94. doi:10.1016/j.apacoust.2014.11.010.
  26. ↑ Assunção CH, Trabanco JC, Gomes RF, Moreira RR, Samelli AG (August 2019). "Longitudinal evaluation of a hearing protector fit training program". La Medicina del Lavoro. 110 (4): 304–311. doi:10.23749/mdl.v110i4.8214. PMC   7809996 . PMID   31475692.
  27. 1 2 Sayler, Stephanie K.; Rabinowitz, Peter M.; Cantley, Linda F.; Galusha, Deron; Neitzel, Richard L. (2018-01-26). "Costs and effectiveness of hearing conservation programs at 14 US metal manufacturing facilities". International Journal of Audiology. 57 (sup1): S3–S11. doi:10.1080/14992027.2017.1410237. ISSN   1499-2027. PMC   6188788 . PMID   29216778.
  28. 1 2 Morata, Thais C.; Gong, Wei; Tikka, Christina; Samelli, Alessandra G.; Verbeek, Jos H. (2024-05-17). "Hearing protection field attenuation estimation systems and associated training for reducing workers' exposure to noise". The Cochrane Database of Systematic Reviews. 5 (5): CD015066. doi:10.1002/14651858.CD015066.pub2. ISSN   1469-493X. PMID   38757544.
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