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 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.

Types

Earmuffs

style hearing protection devices are designed to fit over the outer ear, or pinna. Earmuff HPDs typically consist of two ear cups and a head band. Ear cups are usually lined with a sound-absorbing material, such as foam. The cups should be fit so that the center of the ear canal aligns with the ear canal opening. The soft cushions seal around the pinna of the ears. The head band, centered at the top of the head, applies force/pressure to seal the ear cups over the ears.

Earplugs

style hearing protection devices are designed to fit in the ear canal. Earplugs come in a variety of different subtypes. The attenuation offered by these devices can be measured through hearing protection fit testing.
Some HPDs reduce the sound reaching the eardrum through a combination of electronic and structural components. Electronic HPDs are available in both earmuff and custom earplug styles. Electronic microphones, circuitry, and receivers perform active noise reduction, also known as noise-cancelling, in which a signal that is 180-degrees out-of-phase of the noise is presented, which in theory cancels the noise.
Some electronic HPDs, known as Hearing Enhancement Protection Systems, provide hearing protection from high-level sounds while allowing transmission of other sounds like speech. Some also have the ability to amplify low-level sounds. This type may be beneficial for users who are in noisy environments, but still need access to lower level sounds. For example, soldiers who need to protect their hearing but also need to be able to identify enemy forces and communicate in noise, hunters who rely on detecting and localizing soft sounds of wildlife but still wish to protect their hearing from recreational firearm blasts, as well as users with pre-existing hearing loss who are in noisy environments may all benefit from Hearing Enhancement Protection Systems.
Electronic HPDs require the use of batteries and are typically more expensive than non-electronic types.

Semi-insert devices (canal caps)

Canal caps are similar to earplugs in that they consists of soft tip that is inserted into the opening of the ear canal. Some styles are inserted slightly into the ear canal while others sit in place at the opening of the ear canal. In this case, the tips or caps are connected by a lightweight band which also serves to hold them in position.

Dual hearing protection

Dual hearing protection refers to the use of earplugs under ear muffs. This type of hearing protection is particularly recommended for workers in the mining industry because they are exposed to extremely high noise levels, such as an 105 dBA TWA. Fortunately, there is an option of adding electronic features to dual hearing protectors. These features help with communication by making speech more clear, especially for those workers who already have hearing loss.

Hygiene and care

In order to prevent irritation or infection of the ear, reusable HPDs should be cleaned on a regular basis. Before using any HPD, it should be inspected for damage or dirt to ensure that it is safe to use. Single-use, disposable earplugs are available in addition to reusable options. Earplugs intended for single-use should not be washed for reuse as this degrades the material and reduces effectiveness.
Most reusable earplugs can be cleaned using mild soap and warm water between uses and should be replaced every 2–4 weeks. Earmuff cups and cushions should be cleaned regularly with soap and water, and be replaced if they become cracked or otherwise compromised. Ear cushions can last from 3–8 months depending on use. Use of a clean, protective case to store HPDs when not in use is recommended to prevent damage or contamination.
Any damage to a HPD can compromise its integrity, thus reducing its effectiveness. Damaged HPDs should not be used.

Recommended use

Many countries require several interventions to control risks from exposures to loud noise in the workplace. In the US, the Occupational Safety and Health Administration requires hearing conservation programs which include the provision of hearing protection devices. It is also recommended by the U.S. National Institute for Occupational Safety and Health, audiologists and other hearing healthcare professionals when one works exposed to noise levels that exceed 85 dB. NIOSH and OSHA base their recommendations for use of hearing protection by a calculation called time-weighted average. A time-weighted average is the average noise level a worker is exposed to over a period of time. NIOSH recommends that OSHA use an 85 dBA time-weighted average during an 8 hour period as their exposure limit. An 85 dBA time-weighted average means that HPD use is recommended if an employee is exposed to an average noise level of 85 dBA or more during an 8-hour work day. NIOSH also uses a 3 dB exchange rate for time-weighted averages. A 3 dB exchange rate means that for every 3 dB increase in the average level of noise the recommended time being exposed to that level of noise is cut in half. For example, for a worker who is exposed to 88 dBA, it's recommended he/she only be exposed to that level of noise for 4 hours. These levels of noise may be encountered in both occupational and recreational settings. HPDs are recommended for use in settings where it is difficult to control the noise level, and the person exposed to the noise cannot be removed from the environment.
The amount of protection from noise can vary based on the physical fit of the device. Hearing protection devices with accurate placement and/or accurate insertion will provide the most attenuation of noise. There are many challenges to achieving the needed protection from the device, from barriers to adequate use, to issues related to comfort, convenience, lack of training, to beliefs and attitudes towards its use.

Noise reduction ratings

Hearing protection device manufacturers in the United States are required by the EPA to label HPDs with a noise reduction rating, or NRR. The NRR estimates how much noise is reduced by a hearing protection device, measured in decibels.
The NRR is measured by manufacturers using American National Standards Institute specified procedures in a laboratory environment. The NRR tends to overestimate the amount of protection the HPDs provide in real-world conditions. These differences are most likely attributed to incorrect insertion or poor earplug fit. Because the actual amount of attenuation is typically less than the labeled NRR, the U.S. Department of Labor/OSHA suggest "derating" or reducing the NRR when using it to evaluate total noise exposure when wearing the HPD. OSHA's training manual has uses a 7 dBA correction factor: NRR- 7dBA= estimated noise exposure
in the late 1990s the US National Institute for Occupational Health and Safety recommended a different derating scheme for HPDs but now encourages the hearing protection fit-testing. Hearing protection fit-testing has been developed in order to determine the actual attenuation of the device as it is worn for an individual. These tests for checking attenuation values summarize the real-world attenuation in a personal attenuation rating. The PAR is unique to the HPD tested and the individual wearing the protection. When obtaining a PAR, it is recommended to test both ears individually as there may be asymmetry between ears. This asymmetry can be caused by anatomical differences between ears or improper fit of the HPD and could lead to a unilateral threshold shift. A PAR can be reported as C-weighted values, A-weighted values, or attenuation values for specific frequencies. The PAR can then be used to determine if the HPD is providing adequate attenuation so that an individual's noise exposure does not exceed the recommended limits set forth by regulatory agencies such as the Occupational Safety and Health Administration.

Regulations and standards

United States