Hearing Protection Equipment: Passive and Communication-Enabled Versions

Mirey Bonfil - Technical Coordinator - 3M

In Turkey, the mentality of "I'll only be here for 5 minutes, I don't need to use hearing protection equipment" is unfortunately very widespread. However, even this brief exposure causes damage to hearing. This condition, naturally accepted especially in older individuals, has been shown by scientific studies to actually begin from age 40 onwards. However, it has been noted that hearing loss caused solely by aging does not significantly affect a person's daily life. To protect against hearing loss from industrial sources, the EN 352 standard series is used in Turkey and Europe. The EN 352 standard series (EN 352-1: Earmuffs, EN 352-2: Ear plugs, EN 352-3: Helmets with attached earmuffs) covers the manufacture, design, performance, marking and user information of hearing protection equipment. It does not provide information regarding the SNR (attenuation) value to be selected. In this case, the most appropriate selection can be made by referring to the EN 458 standard titled "Hearing Protectors – Selection, Use, Care and Maintenance – Guidance."

According to the "Regulation on Protection of Employees from Risks Related to Noise" published in Turkey, three different exposure values exist. According to the regulation, the lowest exposure action value is set at 80 dB(A), the highest exposure action value at 85 dB(A), and the exposure limit value at 87 dB(A).

Looking at their impact in our daily lives, if noise measurements taken during an 8-hour work shift in a work environment are reported as 80 dB(A) or above, the employer is required to provide hearing protection equipment at the workplace. At 85 dB(A) or above, employees are required to use the hearing protection equipment provided by the employer. However, regulations generally contain no guidance regarding the SNR values that occupational safety specialists should select. In this case, the EN 458 standard is particularly important. When examining noise measurements conducted in Turkey, 8-hour dB(A) values and peak values are generally provided in dB(C). However, when examining EN 458, the inclusion of frequency values in measurement results plays a very significant role in selecting the correct hearing protection equipment. For this reason, we recommend obtaining frequency-dependent measurements. Generally, there is a table on the packaging and/or in the user manual of all hearing protection equipment as follows.

When determining attenuation values for hearing protection equipment, attenuation values are measured at 8 different frequencies by fitting the hearing protection equipment on a group of 16 different individuals in a specially isolated acoustic environment.

As a result of repeated measurements, the average attenuation value obtained is called Mf, the standard deviation resulting from calculations is sf, and the minimum value found by subtracting the standard deviation from the average result is called APVf. The large table seen above is called the "octave band method" and is the method that determines the correct protection level, especially for workplaces with frequency-dependent measurements on hand. By looking at the H, M and L values shown below the table, calculations can be performed using the HML method. Here, starting from values for 63, 125, 250 and 500 Hz, L (noise at low frequencies), from values for 500, 1000 and 2000 Hz, M (noise at mid frequencies), and from values for 2000, 4000 and 8000 Hz, H (noise at high frequencies) values are indicated. Accordingly, the required calculations are performed using the formulas given in EN 458 standard to determine whether the selected hearing protection equipment is appropriate.    

The last and most common method in Turkey is to perform calculations using the SNR value calculated according to the logarithmic average of all frequencies. Based on the SNR value, whether hearing protection equipment is appropriate is determined using calculations found in EN 458.

However, the most commonly applied and practical method is that the noise level transmitted to the ear, as a result of subtracting the SNR value of the ear plug from the measured noise measurements, falls between 70-80 dB. Unfortunately, in this calculation, frequency values are not directly taken into account, meaning progress is made on average, making it the last preferred model in correct hearing protection selection. Besides passive earmuffs, another model is communication earmuffs. While these models fall into the personal protective equipment category, meaning they provide attenuation, they also enable mutual communication.

Especially on long routes, for workers such as crane operators who work at remote distances, such solutions are preferred to protect from noise, enable communication, and increase productivity. Another feature available in communication earmuffs is the "level dependent" function.

Thanks to this feature, environmental sounds such as human voice and forklift noise are delivered to people's ears more clearly, while sounds that could damage hearing are attenuated by the attenuation value. In this way, workers can continue their work without being isolated from ambient sounds even with earmuffs on. Communication earmuffs are generally divided into two categories internally. Some have their own radio transmitter, while others are connected via cables dedicated to radio systems. These features should be selected entirely according to the working environment. Hearing protection equipment, whether passive or communication-enabled, must have proper fit to the ear canal and/or be worn correctly after the attenuation value is determined, which is one of the most prioritized issues. There is only one way to understand this: EARFit. With the conformity test, which is mandatory in the United States and United Kingdom, after determining the correct attenuation value, the suitability of the selected hearing protection equipment for that individual is also determined.