Hearing protection devices (HPDs) are worn for the purpose of reducing noise. From construction to food processing to manufacturing, HPDs can help reduce noise exposure and thereby could help reduce noise-induced hearing loss (NIHL). Traditionally, earplug manufacturers instruct the wearer to use a two-handed insertion method. But what about one-handed insertion? Let’s learn more….
But How Do You Know How Effective HPDs are?
Single number ratings such as the U.S. Environmental Protection Agency (EPA) Noise Reduction Rating (NRR) are indicators of how much noise attenuation or noise reduction HPDs are capable of under ideal conditions.
However, research suggests that users may receive less noise reduction on the job than indicated by the NRR printed on the package due to many factors such as:
- Differences in the size and shape of ear canals
- Not following the user instructions
- Variation between fittings
- Fitting skill
- Motivation of the user
To account for variability among real-world workers in real job conditions, various NRR derating schemes have been recommended. For example, as an alternative to enforcing engineering noise control requirements, U.S. OSHA allows employers to derate the NRR by 50 percent.
How well suited the earplug is to the size and shape of the ear canal and how well the earplug is fitted can affect the level of attenuation achieved, both during NRR testing in an acoustical laboratory, and when fitted and used by the user in the workplace.
The Important Role of HPD User Instructions
The test method for measuring NRR, ANSI S3.19-1974, requires hearing protectors to be inserted “in accordance with instructions from the manufacturer.” Manufacturers have typically specified in their earplug instructions that the opposite hand should be used to pull the pinna (outer ear) outward to help straighten the ear canal prior to inserting the earplug with the other hand. This is known as a two-handed insertion method.
Using a fitting technique that is not consistent with the manufacturer’s instructions means the attenuation rating or class cannot be applied for that fitting. In countries where regulations require the use of such ratings or classes to select hearing protectors with appropriate attenuation, employers may have compliance concerns if employees don’t follow the manufacturer’s fitting instructions. Users may also put themselves at risk of hearing damage and NIHL if they don’t adhere to proper user instructions.
Recently, innovative earplugs with fitting stems that are used to push the foam ear tips into the ears have been tested using two distinct methods of insertion—the traditional two-hand method and a one-hand insertion method that does not include the pinna pull.
It is important to note that the NRR values obtained from the two insertion methods are different. This validates the one-hand instruction as an acceptable insertion method. This dual NRR approach gives users more flexibility in choosing the best insertion method for their situation and maintains a valid NRR when calculating protected noise exposure.
These new earplugs have been tested for both one-hand AND two-hand insertion methods using manufacturer’s instructions that specify both methods of insertion. So, the user should closely follow the instructions for the insertion method that is aligned with the most appropriate NRR for the individual’s situation.
For all earplugs, regardless of method(s) of insertion specified in the manufacturer’s instructions, individual fit testing is recommended before using hearing protection in hazardous noise. In addition, periodic checks should be made to determine if training is needed on how to more effectively insert the earplugs to help improve the fit. These are vital components of an effective hearing conservation program.