Hearing protection fit-testing

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]

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:

• Choosing the most appropriate hearing protection device, both with appropriate level of attenuation and appropriate fit for the individual.^[5] 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.^[6]
• Wearing or inserting the hearing protection device correctly so it seals the wearer's ear canal, using the "roll-pull-hold" method for foam earplugs, and ensuring earmuffs create an unbroken seal around each ear.^[7]

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]}