Hearing preservation program

The OSHA standard contains a number of requirements for a hearing protection program:

• The use of technical means and organizational measures. The Management Standard in paragraph 29 of CFR 1910.95 (b) (1) requires that “... appropriate technical means and organizational arrangements” be used to protect against noise ^{[2] [3] [4] [5] [6] [7]} . And if they are not enough to reduce the impact of noise to an acceptable level, then "to reduce the impact of noise on workers they need to give out and they must use personal protective equipment for hearing organs."
• Monitoring The aforementioned standard in paragraph 29 of CFR 1910.95 (d) requires that when the average shift of 8 hours to any of the workers can exceed 85 dBA, the employer will monitor the effects of noise on the workers.
• Hearing test. In 29 CFR 1910.95 (g), the employer commits itself to conducting a hearing test ( audiometry ) for all workers if the average shift exposure to noise exceeds 85 dBA.
• Personal Protective Equipment (PPE) 29 CFR 1910.95 (i) requires the employer to provide all workers exposed to noise of more than 85 dBA with suitable hearing protection PPE at their own expense.
• Education and training 29 CFR 1910.95 (k) requires an annual program of education and training for all workers with an average exposure to noise of more than 85 dBA, and lists a number of requirements for such training. This includes: communication of the effects of noise on hearing; purpose, advantages and disadvantages of different PPE of the hearing organ, and their degree of noise attenuation; purpose of audiometry (hearing test) ^[8] .
• Storage of records (on the implementation of the hearing preservation program). 29 CFR 1910.95 (m) requires the employer to make accurate records of all noise measurements of workers.

To determine the impact of noise, it is often measured in different places of work, where (as expected) it can be large. Usually they use a sound level meter . There are three types of sound level meters. Type 0 is a high precision instrument commonly used in laboratories. Type 1 is an accurate instrument used in a production environment. And type 2 is a less accurate instrument than type 1, and it is often used to measure noise levels for different purposes. To determine the dose of exposure to the worker, a noise dosimeter is often used that integrates (summarizes) all noises — continuous, intermittent and pulsed — to determine the impact on the worker ^[9] .

If there has been a significant change in the process and / or equipment replacement so that a change in noise exposure can be expected, the determination of noise exposure must be repeated ^[10] .

Hearing impairment caused by excessive exposure to noise does not appear at the initial stages of development, and is practically untreatable (p. 173-182 ^[11] ). The best way to protect your hearing organ from noise is to reduce the impact of noise - through the use of technical means and organizational measures. The use of these measures does not require the use of PPE, and therefore they provide more reliable protection. But sometimes it is very difficult to prevent excessive exposure to noise using only these means. To avoid the use of PPE, the average shift of 8 hours should be reduced to 85 dBA or less. On October 19, the US Department of Labor gave the word “feasible” (technical and organizational methods ...) the following interpretation: “which can be done,” thereby giving the Labor Protection Administration more opportunities to force the employer to use them, and not PPE. ^[12] .

If the use of technical and organizational measures does not allow reducing the average shift exposure to noise to a value less than 85 dBA, the use of PPE of the hearing organ is required. Most often they use headphones or earbuds, and they have their own advantages and disadvantages. Usually, the selection of a suitable PPE is carried out by a specialist in industrial hygiene - so that the applied PPE provides the required noise attenuation ^[13] .

Inserts

There are four main types of inserts: prefabricated, elastic , made in-place individually for a particular worker, and not fully inserted.

• Pre-made earbuds do not need to be squeezed before being inserted into the ear canal. This avoids contamination of the liner before installation.
• Elastic liners are made from different materials, which should allow the worker to compress the liner before installation. An obvious drawback is that you need to squeeze the liner with clean hands, which is not always possible. And the advantage is that they take the form of an auditory canal, which can not always be said about pre-made earbuds.
• Individually made earbuds are made in place under the auditory canal and ear of a particular worker, and therefore they provide a snug fit for "your" worker.
• Not completely inserted earbuds are ordinary soft earbuds that are fixed to the ends of a rigid elastic arch that allows you to install them at the entrance to the auditory canal. The advantage is that they can be easily and quickly removed and installed.

Headphones

The main difference between headphones and earbuds is that the headphones do not fit into the ear canal. Instead, they form a tight end connection with the head around the ear so that the sound does not pass into the inner ear. Headphones are easy to use, and they often allow a snug fit than the earbuds. Headphones have also been developed that actively reduce the effects of noise . But people who use glasses, or who have whiskers may have difficulty wearing, and some people find them simply uncomfortable ^[14] .

Effectiveness of PPE

In the United States, PPE is certified by the Environmental Protection Agency (EPA). It does this in accordance with the standard () and it requires that all PPE of the hearing organ have a mark indicating the degree of noise attenuation - noise reduction coefficient noise reduction rating (NRR) ^[15] . In the EU and the Russian Federation, the noise attenuation coefficient SNR is used. These ratios are different.

The values ​​of the degree of noise attenuation measured in the laboratory strongly depend on the individual characteristics of people (the shape and size of the auditory canal, etc.), and on how well the earbuds are inserted / put on. Therefore, after measurements, a group of testers obtain a variety of attenuation coefficients. In order to evaluate the effectiveness of the tested PPE on the basis of these different values ​​with one number, it is assumed that the results correspond to a log-normal, and take the lower 95% confidence limit (in the USA) and the lower 84% limit (in the EU).

A specific example: Laser lite (Sperian) inserts after certification in the United States obtained NRR = 32 dB, and SNR = 35 dB. Also, the NRR measurement can be carried out with C-correction, or with A-correction, and SNR measurement is carried out only with A-correction. It can be seen that, due to differences in the requirements of certification standards, the percentage of cases where the noise attenuation is less than that specified in the coefficient, American requirements are tougher than European ones. But in practice, not in the laboratory, the real attenuation of noise can be significantly less than specified by the manufacturer ^{[16] [17]} .

Already in the middle of the last century, practice showed that the degrees of noise attenuation measured in the laboratory are noticeably higher than those obtained in actual use ^[18] . Since the US often measures NRR with C-correction, the Office recommends subtracting 7 dB from the NRR to obtain the degree of noise attenuation with A-correction. Then, the Office recommends dividing the result (subtraction) in half for a rough account of the differences between real efficiency and laboratory ^[19] .

The Scientific Research Institute of Occupational Medicine believes that the effectiveness of PPE of the hearing organs is lower than laboratory at least 2 times (10-15 dB or more) ^{[20] [21]} . Studies by specialists of the National Institute of Occupational Safety (NIOSH) showed that in the practical use of inserts, their effectiveness is significantly lower than in the laboratory ^[22] . The liners of seven different designs were studied (see diagram to the right).

A new standard is being developed with requirements for certification of PPE for the hearing organ, which should eliminate the shortcomings of the existing one (ignoring the difference between real efficiency and laboratory efficiency in certification, ignoring the effectiveness of protective equipment using active noise suppression, etc.) ^[23] .

Checking PPE for workers

Noise attenuation depends not only on the PPE and on its attenuation coefficient, but also on the individual characteristics of the worker and on his skills to correctly insert the earbuds / put on the headphones. Therefore, to check how much noise attenuation is obtained when PPE is worn by a specific worker, special devices have been developed and used (for example, INTEGRAfit, VeriPro, EARfit, Fit Check, QuietDos and QuickFit ). They can use a miniature microphone installed in the ear canal deeper than the PPE, and measure the actual attenuation of noise at different frequencies. The duration of all measurements can be several minutes. This allows you to objectively assess how much PPE is suitable for specific workers, taking into account their ability to properly insert earbuds / put on headphones.

Developed a new simple and inexpensive device QuickFit .

1. Timeliness of application

If PPE for the hearing organ is technically very effective, but will not be used in practice, this will not help protect workers from exposure to noise. Experts recommend taking into account the opinion of workers, and when choosing a pre-trial detention center for a particular worker, give him the opportunity to choose the most convenient one from several different ones. At the same time, it is necessary that sufficiently (technically) effective SIZOS be offered. If an employee wears glasses, the glasses bow may interfere with the snug fit of the headphones to the head. When working in contaminated conditions, and the need to periodically interrupt the use of SIZOS, the earbuds will be difficult to use - re-insertion into the ear after compression with dirty hands will cause dirt to enter the ear canal, which will cause irritation. When using earbuds, there are no two people with the same ear canals, and even in one person they are different in the right and left ear. It is advisable to use only suitable inserts that are appropriate for the person (but we do not have on sale liners of the same model in different sizes in order to choose the right size).

2. Technical efficiency

The legislation obliges the manufacturer to put efficiency data on the package of the SIZOS - the degree of noise attenuation. But this information refers to the results of tests during certification in the laboratory, and may not correspond to real effectiveness in practical application. The reasons for the discrepancy: the testers in the laboratory insert / put on the SIZOS more accurately and leisurely; in the laboratory, there is less likelihood of headphone creeping in, earbud displacement (than during the performance of various work), etc. Studies of the effectiveness of the SIZOS directly during work were conducted. For this, for example, a miniature microphone was inserted under the headphone / earpiece, and two noise levels were measured simultaneously - outside, near the head, and behind the SIZOS ^[24]

After analyzing the results of 19 studies in which more than 1030 people participated, the specialists of the National Institute of Labor Protection came to the conclusion that to take into account much less efficiency in practice compared to laboratory conditions, you can do this:

• Headphones reduce performance by 25%.
• In elastic earbuds, which are compressed before insertion into the ear, and after compression, slowly restore their previous size ( so that you can manage to insert them before they “swell” - to the full depth ) - reduce by 2 times.
• In all other SIZOS (earbuds on the arch that cover only the entrance to the ear; hard earbuds; elastic earbuds that quickly acquire their original shape after compression, etc.) - reduce efficiency by 70% (~ 3 times).

The efficiency values ​​obtained by such methods are average for a preliminary assessment of the effectiveness of the initial selection of an SIZO; they may differ from actual values ​​due to differences in a particular model; and because of the different dressing skills of different workers. Since the United States uses the noise attenuation coefficient NRR, which is slightly less than the European and Russian SNRs, these recommendations can be used in the Russian Federation, slightly reducing the result to take into account the differences between SNR and NRR. If you have access to the Internet, you can use the free online program to roughly check the ability of a particular worker to correctly insert a specific model of inserts (a link to the program is in the QuickFit description of the device ), because of all the SIZOS, the inserts have the most unstable efficiency, which greatly depends on the correct insertion.

A document has been developed in the European Union - a standard that defines the procedure for the employer's choice of hearing aid for a known level of noise at the workplace. This document ^[25] contains detailed guidelines that allow you to take into account the specific effectiveness of noise attenuation (if there is data on the noise level at low, medium and high frequencies) with a specific model of PPE for the hearing organ, that is, its technical effectiveness (without taking into account the skills of the application worker) . Unfortunately, the document does not allow one to at least approximately determine how much this calculated efficiency can decrease in practice for a particular type of PPE. In this regard, the recommendations of American experts ( see above ) - look more practical and feasible.

An important place in the hearing preservation program is occupied by audiometry . It allows you to identify those employees who have had a significant hearing impairment, and those who have this impairment at the initial stage. Audiometry is especially important for identifying those who have changed the threshold for sound perception (NIPTS) ^[26] . The initial deterioration occurs mainly at high frequencies, and therefore does not appear in everyday life, remaining unnoticed.

In addition, different people have different “individual survivability” with the same harmful effects, and in combination with the unstable and unpredictable effectiveness of PPE, only timely initial and periodic medical examinations, including audiometry, can reliably prevent the development of hearing loss in all workers.

To prevent hearing impairment, it is important to train and train those employees who are exposed to excessive noise. If workers learned the right way to implement a hearing preservation program, then the risk of hearing loss is lower. Management requires training and education annually. This is important because "even a small briefing can significantly improve hearing retention." ^{[27] [28]} .

Management requires the employer to record noise exposure measurements and hearing tests. Such records should contain the following information: full name and specialty / position of the worker; date of audiometry; Name of the inspector; instrument calibration date; the results of measuring the impact on this worker are the most recent; and background noise level in the room where audiometry was performed.

Records of the effects of noise should be kept for at least two years, and records of the results of the audit of hearing - as long as the employee will work in the enterprise. These records should be available to workers, to those who worked earlier, to their representatives and to state inspectors ^[29] .

Proper evaluation of the effectiveness of a hearing conservation program is essential to protect workers. The National Institute for Occupational Safety and Health (NIOSH) has developed a list of questions whose answers will help determine the effectiveness of a hearing conservation program. These questions are on the website of the institute. ^[30] . The Institute recommends that less than 5% of workers have a bias perception threshold of 15 dB for the same ear and the same sound frequency.

The Institute considers it more important to implement a program to prevent hearing impairment, rather than a program to preserve hearing. The difference between the names may look insignificant, but it exists, and gives advantages. Prevention implies an impact on working conditions when the first signs of hearing impairment appear, rather than developing a new policy (for example, “Buy low noise”) or changing workers' training through training and training.

The Buy Low Noise policy ^[31] is an easy way to improve working conditions. Now a lot of new low-noise equipment and tools have been developed, which are similar to the noisier old ones. The purchase of such equipment usually does not require a change in technology and mode of operation ^[32] . Participating in the Buy Low Noise campaign, the New York Environmental Protection Agency has developed a list of suppliers' products (low noise equipment and tools) to help suppliers meet labor safety requirements.

In order to successfully preserve the hearing of employees, both workers and the administration must understand the prevention of hearing impairment when exposed to noise. Sound sources must also be studied before noise reduction may be required to prevent possible hearing impairment. The National Institute for Occupational Safety and Health conducted a study and developed the Power Tools Database, a hand-held power tool database that helps control noise levels and prevent workers from hearing loss.

The OSH Standard for Work in Excessive Noise Conditions 29 CFR 1910.95 was developed by OSHA in its original version in 1972 based on the relevant recommendations of the National Institute of Occupational Safety (NIOSH) . Later, after analyzing the scientific information received (both American and foreign), and repeatedly in-depth analyzing the information that was used to prepare the first recommendations (for the 1972 standard), the institute developed more reasonable and rigorous recommendations. Specifically, the institute recommended reducing the maximum permissible noise level from 90 to 85 dBA (and consider doubling the dose of noise exposure by increasing the sound pressure level by 3 dB, rather than 5 dB); change the criteria for evaluating which hearing impairment should be considered significant (so that the detection of hearing impairment becomes more accurate and sensitive); recommended a first hearing test for people working in conditions of noise above 100 dB after six months maximum, and repeat them 2 times a year (since people with increased individual sensitivity can experience significant hearing loss in a matter of months); stop adjusting the results of measuring the state of sensitivity of the organ of hearing for natural age-related deterioration ; when choosing personal protective equipment for the hearing organ, select them individually for the worker and check the device for real noise attenuation (taking into account the individual characteristics of the worker, his skills in wearing headphones or inserting earbuds, and real noise attenuation - technically achievable - a specific model of PPE for the hearing organ); and consider that the effectiveness of headphones, which can be achieved in practice, is 25% lower than laboratory certification, elastic earbuds (which slowly restore shape after compression) are 50% lower than laboratory ones, and all other types of PPE for the hearing organ are 70% lower laboratory (applied now to the packaging according to the results of certification tests).

These recommendations bring the requirements for American employers closer to the sanitary requirements that establish the maximum permissible noise level in the USSR and the Russian Federation of 80 dBA (and consider that the dose of noise doubles when the sound pressure level is increased by 3 dB); and with the international standard ISO 1999, where zero risk of hearing loss corresponds to a noise level of 80 dBA.

• Health effects of industrial noise
• Audiometry
• Hearing impairment
• NIOSH noise protection recommendations (new)
• QuickFit In-Ear Performance Tester
• Exposure Action Value
• Noise-induced hearing loss
• Safe-In-Sound Award
• List of occupational health and safety awards

• Occupational Health & Safety Administration
• National Hearing Conservation Association
• NIOSH Power Tools Database
• NIOSH Hearing Protector Compendium
• New York City Contractor Vendor List Guidelines