A hearing protection device, also known as an 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 use of the HPD without individual selection, training and fit testing link does not significantly reduce the risk of hearing loss. For example, one study covered more than 19 thousand workers, some of whom usually used hearing protective devices, and some did not use them at all. There was no statistically significant difference in the risk of noise-induced hearing loss.
Standards and regulations focused on preventing the effects of occupational noise vary across countries. Since companies can often operate in more than one country, health and safety professionals are expected to be informed of the different requirements and their implementation, we well as best practices and their effectiveness.
Exposure limits In the context of work, adequate hearing protection is that which reduces noise exposure to below 85 dBA over the course of an average work shift of eight hours.
When sounds exceed 80 dBA, it becomes dangerous to the ears. In the US, the National Institute for Occupational Safety and Health (NIOSH) has standards that show how long a person can be in different loudness levels before the person reaches their maximum daily dose and becomes damaging to their hearing. These standards can give individuals an idea of when hearing protection should be considered. The maximum daily dose with the corresponding decibel level is shown below.
8 hours at 85 dB(A) 2 hours at 91 dB(A) 15 minutes at 100 dB(A)
Noise,
dBA Time reaching maximum daily dose, hours : minutes OSHA,
TWA 90 dB(A),
exchange rate 5 dB NIOSH,
TWA 85 dB(A),
exchange rate 3 dB ISO 1999,
TWA 80 dB(A),
exchange rate 3 dB 80 – – 8 : 00 81 – 20 : 9.5 6 : 21 82 – 16 : 00 6 : 02 83 21 : 07 12 : 42 4 : 00 84 18 : 23 10 : 4.8 3 : 10 85 16 : 00 8 : 00 2 : 31 86 13 : 56 6 : 21 2 : 00 87 12 : 08 5 : 2.4 1 : 35 88 10 : 33 4 : 00 1 : 16 89 9 : 11 3 : 10 1 : 00 90 8 : 00 2 : 31 48 min 91 6 : 58 2 : 00 38 m 92 6 : 04 1 : 35 30 m 93 5 : 17 1 : 16 24 m 94 4 : 36 1 : 00 19 m 95 4 : 00 0 : 48 15 m 96 3 : 29 0 : 38 12 m 97 3 : 02 0 : 30 9.4 m 98 2 : 38 0 : 24 7.5 m 99 2 : 18 0 : 19 6 m 100 2 : 00 0 : 15 4 m 43 sec 101 1 : 44 0 : 12 3 m 45 s 102 1 : 31 9 min 24 sec 2 m 58 s 103 1 : 19 7 m 30 s 2 m 22 s 104 1 : 09 6 m 1 m 53 s 105 1 : 00 4 m 42 s 1 m 29 s 106 52 m 3 m 48 s 1 m 11 s 107 45 m 3 m 56 s 108 40 m 2 m 24 s 45 s 109 34 m 1 m 54 s 36 s 110 30 m 1 m 30 s 28 s Permissible noise levels in different countries Country TWA, dBA
(for an 8-hour shift) Level increase corresponding to doubling the dose
(Exchange rate) Argentina 90 3 Australia 85 3 Brazil 85 5 Canada 85 & 82 3 Chile 85 5 China 70–90 3 European Union countries 85 3 Finland 85 3 France 85 3 Germany 85, 70, 55For mental work 3 Hungary 85 3 India 90 – Israel 85 5 Italy 85 3 Netherlands 80 3 New Zealand 85 3 Norway 85, 55, 70 3 RF 80 3 Spain 85 3 Sweden 85 3 United Kingdom 85 3 USA 90 (100)* 5 Uruguay 90 3 OSHA issued a directive to inspectors in 1983. They are ordered to stop requiring employers to install engineering noise control if noise dose < 100 dBA. This decision is considered illegal, Commissioner Cleary's view but it is carried out in practice in most US states.Appendix H. Economic Feasiblity Analysis of Noise Engineering Controls These numerical values do not fully reflect the real situation. For example, the standard by the American Occupational Safety and Health Administration (OSHA) sets the Action Level 85 dBA, and the PEL 90 dBA. But in practice, the Compliance Safety and Health Officer must record the excess of these values with a margin, in order to take into account the potential measurement error. And, in fact, instead of PEL 90 dBA, it turns out 92 dBA, and instead of AL 85 dBA – 87 dBA.B.9 Extended Workshifts
Different types of hearing protection may be used to maximize hearing protection. OSHA regulations dictate whether hearing protection is required and if the company must participate in a hearing conservation program. But many employers are not implementing these programs effectively, and the risk of hearing loss is not reduced.
Hunting and firearms
The shooting of guns for recreational use can lead to hearing loss in the high frequencies. The shooting of firearms can cause damage to a variety of cochlear structures due to the high peak sound pressure levels that they generate. This can range from 140 to 175 dB.
Along with the passive noise reduction options usually used vocationally (such as earmuffs and earplugs) there are also active noise reduction devices available. Active noise reduction technology is used to provide noise protection like passive options, but also use circuitry to give audibility to sounds that are below a dangerous level (about 85 dB) and try to limit the average output level to about 82 to 85 dB to keep the exposure at a safe level.
Strategies to help protect one's hearing from firearms also include using muzzle brakes and suppressors, shooting fewer rounds, and avoiding using a firearm with a short barrel. It is recommended to shoot outdoors or in a sound-treated environment, rather than a reverberant environment (an enclosed area with sound-reflecting surfaces). If there are multiple people shooting, make sure there is a large distance between the shooters and that they are not firing at the same time.
Types
Types of ear protection include: Earmuffs, external: This ear protection fits snug around the person's external ear. With this type of equipment, the ear is completely enclosed by a hard plastic shell, which is padded at the point of contact and otherwise lined with sound-absorbing and cushioning foam. Earplugs, internal: These are ear protection that fit inside of the person's ear canal. There are many different types of ear plugs. The most commonly known are foam, musician, or custom earplugs that are made from a mold of a person's ear. Helmet, covering various parts of the head, including the ears
In some occasions, multiple types of ear protection can be used together to increase the NRR. For example, foam earplugs can be worn in-conjunction with earmuffs.
Each type of ear protection has what is called a noise reduction rating (NRR). This gives the consumer an estimate of how much noise is being reduced before reaching the individual's ear. It is important for the consumer to know that this is only a single number estimate derived from a laboratory experiment, and the NRR will vary per individual wearing the hearing protection. NIOSH and OSHA have derating values to help give the person an idea of how much sound is being attenuated while wearing the hearing protection. OSHA uses a half derating, while NIOSH uses 70% for pre-formed earplugs, 50% for formable earplugs, and 25% for earmuffs.
But all such derating are not consistent with each other, and do not take into account the individual characteristics of the worker. Country,
organization Earplugs Earmuffs formable pre-formed USA, OSHA Decrease by 2 times Decrease by 2 times Decrease by 2 times USA, NIOSH Decrease by 2 times Decrease by 3.3 times Decrease by 1.33 times Italy Decrease by 2 times Decrease by 3.3 times Decrease by 1.33 times Great Britain 4 dB reduction 4 dB reduction 4 dB reduction France 10 dB reduction 10 dB reduction 5–7 dB reduction Germany 9 dB reduction 5 dB reduction 5 dB reduction Therefore, no derating allows the specialist to predict the noise attenuation of a particular model for a particular worker. That is, the use of laboratory test results (NRR, SNR, HML, ets.) does not predict the effectiveness of the protection of a particular worker, at all. The range of actual values may be, for example, from 0 to 35 decibels.
Earmuffs Earmuff 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
Earplug 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.
Pre-molded earplugs have a preformed shape and a push-to-fit design. Formable earplugs are pliable and take the form of an individual's ear canal. Roll-down foam earplugs are one of the most commonly used earplugs, and are made from slow recovery foam which expands after it has been "rolled-down" and inserted in the ear canal, creating a tighter seal. Custom earplugs are made individually for each user following earmold impressions. Typically custom earplugs are purchased from an audiology clinic or hearing healthcare professional.
Electronic hearing protection devices 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 In Ear Electronic 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.