Hearing protector fit-testing is a method that measures the degree of noise reduction obtained from an individual wearing a particular

hearing protection device 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 no ...

(HPD) - for example, a

noise canceling 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 vibratio ...

earplug 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. Earplugs may be used as well to improve sleep quality or focus in noisy environments ...

earmuff Earmuffs are accessories designed to cover a person's ears either for warmth or for hearing protection. Both types of earmuff 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 ...

. Fit testing is necessary because 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. 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. Hearing protection devices such as

s or

earmuffs Earmuffs are accessories designed to cover a person's ears either for warmth or for Hearing protection device, hearing protection. Both types of earmuff consist of a plastic, thermoplastic or metal head-band that fits over the top or back of the ...

must be worn correctly for the wearer to be protected from noise. Correct use of hearing protection includes: * Choosing the most appropriate hearing protection device, both with appropriate level of attenuation and appropriate fit for the individual. Ideally, the device should limit the sound intensity that reaches the ear to levels below 85 dBA. If the attenuation does not limit the noise levels to that level, other alternatives should be sought. If the attenuation is greater than that, it can also interfere with the HPD use by making it difficult to hear important sounds. * Wearing or inserting the hearing protection device correctly so it seals the wearer's

ear canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the auricle to the eardrum and is about in length and in diameter. S ...

, using the "roll-pull-hold" method for foam earplugs, and ensuring earmuffs create an unbroken seal around each ear. 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.

Requirements and recommendations for HPD fit testing

The

Occupational Safety and Health Administration The Occupational Safety and Health Administration (OSHA; ) is a regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. The United States Congress established ...

, National Hearing Conservation Association, and

National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the List of United States federal agencies, United States federal agency responsible for conducting research and making recommendations for the prevention of work-related occ ...

(NIOSH) recommend it for all workers used HPD as a best practice, and describes existing testing methods and how to incorporate them in

hearing conservation program Hearing conservation programs''Larry H. Royster & Julia D. Royster''Hearing Conservation Programmes In: Vol. 2Chapter 47. Noise/Encyclopedia of Occupational Health and Safety/ Michel Hansenne ed. — 4th ed. — Geneva: International Labour Office, ...

s.PDF
/ref> Countries that have published standards recommending the use of fit testing as part of hearing conservation interventions include Argentina, Australia, Brazil, Italy, Russia, Uruguay, and Venezuela. A few other countries (Canada, Germany, Malaysia) and the US Department o
Defense
are regulating its use as part of hearing conservation interventions. Effective March 31, 2023, the

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

Government added a requirement that employers fit test each employee who wears HPDs. A trend towards recommending HPD fit-testing as a best practice is emerging in the European Union and the USA.link
/ref> On January 2025 NIOSH published a Science Policy Update recommending employers use individual, quantitative fit testing to evaluate the attenuation received by workers from their hearing protection devices.

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). 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 used to measure the attenuation provided by HPDs are as follows:

Real-ear attenuation at threshold (REAT)

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 The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...

ASA Asa may refer to: People and fictional characters * Asa (given name), a given name, including a list of people and fictional characters so named * Asa people, an ethnic group based in Tanzania * Aṣa, Nigerian-French singer, songwriter, and reco ...

S12.6 and the

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

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. For noncritical screening, REAT can be performed using a web browser and simple audio devices. + onlin
test tool
/ref>

Loudness balance

This method first has the subject listen to tones with headphones and "match"

loudness In acoustics, loudness is the subjectivity, subjective perception of sound pressure. More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relat ...

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.

Microphone-in-real-ear (MIRE)

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 level Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone ...

s (SPL) are measured inside and outside of the ear simultaneously and used to calculate a PAR.

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

(HPD). 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.

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

(HPD). 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 peopl

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. 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

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. 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. 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. 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.

References

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External links

OSHA's Letter of interpretation on hearing protection fit-testing
*

NIOSH The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury, illness, disability, and death. It ...

Provide Hearing Protection

DOD, 2024 policy on hearing protection fit-testing
US Department of Defense * Video:
he importance of hearing protection fit testingHearing Center of Excellence
Occupational safety and health Hearing loss Audiology Acoustics Hearing Protective gear