Many workers are exposed to excessive noise levels while in their workplace. From working on construction sites to warehouses, these levels of excessive noise result in many workers experiencing work-related hearing loss, tinnitus or other hearing conditions. DIN EN 352 standard sets the general requirements for hearing protectors, ensuring the wearer is protected from excessive noise levels.
The EN 352 standard
DIN EN 352 standard regulates the general requirements for hearing protection as part of protective workwear. This is an extensive safety standard that covers many types of hearing protectors including ear muffs, ear plugs, and industry safety helmets with hearing protection:
- EN 352-1 – Ear-muffs
- EN 352-2 – Ear plugs and ear moulds
- EN 352-3 – Ear muffs attached to industrial safety helmets
- EN 352-4 – Level-dependent ear-muffs
- EN 352-5 – Active noise-reduction ear-muffs
- EN 352-6 – Ear-muffswith electrical audio input
- EN 352-7 – Level-dependent ear plugs
- EN 352-8 – Entertainment ear-muffs
The EN 352 safety standard has been developed to ensure hearing protection provided is fit-for-purpose and designed in line with The Control of Noise at Work Regulations 2005 requirements. By aligning with The Control of Noise at Work Regulations 2004, this standard ensures workers’ hearing is protected from excessive noise.
While DIN EN 352 is an extensive standard, this article will focus on Part 1: Ear-muffs exposed to noise.
EN 352-1:2002 - Hearing protectors - Ear muffs
DIN EN 352-1:2002 is the latest standard revision for ear-muff hearing protectors. This part of EN 352 sets the requirements for ear muffs that are tested in accordance with the EN 352 general requirements.
Ear muffs refer to a type of hearing protector that have external cups that fit firmly over the ears and are connected by a tensioned headband worn over or behind the head, ensuring the ear muffs remain in place. Ear-muff hearing protectors are easy to frequently put on and take off making them suitable for work environments with variable noise levels.
As DIN EN 352-1 sets the general requirements for ear muffs, this section also regulates the following sections of EN 352:
- EN 352-3 – Ear-muffs attached to industrial safety helmets
- EN 352-4 – Level-dependent ear-muffs
- EN 352-5 – Active noise-reduction ear-muffs
- EN 352-6 – Hearing protection with electrical audio input
EN 352-1:2002 - Requirements for ear muffs
EN 352-1:2002 sets many general requirements that ear-muffs must be tested against to ensure they offer suitable hearing protection.
Materials and construction
Any materials used to make the product that will come into contact with the skin must be non-staining and not likely to cause skin irritation, allergic reaction, or other adverse effects on health. The hearing protection device must be free from sharp edges to be considered safe for use. The cleaning and disinfection methods specified should not cause damage or impairment to the hearing protection. The extensive materials and construction assessment ensures the ear-muffs are safe for wear.
Sizing and adjustability
The sizing and adjustability of the ear-muffs is tested to ensure that the hearing protection device is suitable for the range of head sizes specified by the manufacturer. EN 352-1:2002 compliant products should provide an adequate fit for the intended wearer. The sizing and adjustability of the ear-muffs is tested using a fitting rig.
Cup rotation
The rotation of the ear-muff cups is measured to assess whether it offers sufficient movement. There must be enough rotation available for the wearer to adjust the hearing protection device for the best fit.
Headband force
The headband force is assessed to ensure there is no excessive pressure exerted on the wearer’s head. The headband force of the ear-muffs is tested using a force rig.
Cushion pressure
The cushion pressure is assessed to ensure there is no excessive pressure exerted on the wearer’s head. The cushion pressure of the ear-muffs is tested using a force rig.
Resistance to damage when dropped
Resistance to damage is assessed by dropping the hearing protection ear-muffs from a specified height onto a solid steel plate. If any part of the sample cracks or breaks, the device will fail the test. Hearing protection devices designed for use in colder environments will also be assessed with an optional resistance to damage test conducted at -20°C temperature.
Change in headband force
After the above tests have been performed, the headband of the ear-muffs are subjected to a second headband force test. During this assessment, the headband is flexed for 1,000 cycles using a flexing rig before being conditioned in a water bath at 50°C for 24 hours. Once complete, the headband force is assessed for a second time, with a maximum deviation between the two measurements being used to determine the pass criteria.
Insertion loss
The insertion loss assessment is used to measure the algebraic difference between the sound pressure level with and without the ear-muff fitted to a test fixture. This test does not use human subjects. Instead, it uses an acoustic test fixture to simulate the approximate dimensions of a human head. This test does not set a limit on the minimum attenuation which should be achieved. The insertion loss assessment is conducted to assess the standard deviation of the attenuation values to ensure there is not a major variation in performance between 10 samples of the same ear-muff device.
Resistance to leakage
If the ear-muffs being tested feature fluid-filled cushions then a resistance to leakage assessment should be performed. This test assesses the leakage resistance of the ear-muffs by applying a vertical load of 28±1 Newtons to the cushion for 15 minutes. If any leakage occurs, this would be determined a test failure.
Ignitability
The ignitability of the ear-muff hearing protectors is tested by applying a steel rod that has been heated to approximately 650°C to the device. If any part of the device ignites or continues to glow after the removal of the road, the ear-muff hearing protection device will be determined to be a test failure.
Minimum attenuation
The minimum attenuation assessment uses human subjects to determine the performance of the hearing protection device. The results of this test method will be published for the model when it is placed on sale and will be supplied to the wearers. This test uses 16 human test subjects with and without the hearing protection worm to measure the threshold of hearing and the lowest sound pressure level perceivable by the ear. The results from this test are then used to calculate the performance of the device tested.
EN 352 markings
The test methods conducted in line with the DIN EN 352-1 general requirements will be used to determine the markings.
In accordance with DIN EN 352, all hearing protectors that have received EN 352 certification must feature markings for:
- Name, trademark, or other mark of the manufacturer
- Manufacturer’s postal address
- Number of the standard i.e. “EN 352”
- Model designation
- Type, batch, or serial number
- Date of production and/or obsolescence (including statement of which)
- instructions on insertion, application and wearing (as necessary)
- nominal size
- CE marking
- In the case of earmuffs intended to be worn only in a specific orientation, "FRONT" and/or "TOP" markings, and/or "RIGHT" and "LEFT" on the cups
- CE marking with identification number of the notified body (PPE Regulation, Article 17(3))
How to choose hearing protection based on hearing protection requirements
When choosing the most suitable hearing protection, it is important to look out for the EN 352 markings. Any hearing protection device with an EN 352 marking will have been tested in accordance with the European standards for protection against excessive noise.
You will need to understand the noise exposure levels of your work environment in order to determine which hearing protection device will be most suitable for your needs. This can be done using a decibel meter to measure the noise levels.
The decibel (dB) rating can be used to work out the Single Number Rating (SNR) required to ensure compliance with The Control of Noise at Work Regulations 2005.
|
Noise level |
Minimum SNR |
Ideal SNR |
Maximum SNR |
|
85 dB |
5 |
9 – 14 |
18 |
|
90 dB |
10 |
14 – 19 |
23 |
|
95 dB |
15 |
19 – 24 |
28 |
|
100 dB |
20 |
24 – 29 |
33 |
|
105 dB |
25 |
29 – 34 |
38 |
|
110 dB |
30 |
34 – 39 |
43 |
The SNR value (Single Number Rating) provides information about the protective effect of hearing protection products and will be stated on the hearing protection device packaging and product. The SNR is an average insulation value which is calculated from all relevant frequencies.
