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 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)
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. 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.
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
… excerpt ends here. Continue reading the full article.
