Standards and testing methods
European EN 352 standards define testing methods for hearing protectors which satisfy the basic requirements of European legislation based on the New Approach. The basic requirements for the design, manufacture and use of hearing protectors against the harmful effects of noise are in Directive 89/686/EEC on Personal Protective Equipment of 21 December 1989. Directive 2003/10/EEC of 6 February 2003 defines the minimum health and safety requirements for workers regarding noise exposure.
The existence of product and testing standards is a prerequisite for the effective implementation of the directive. There was a need to develop several standards in a very short time period and the basic standards for hearing protectors have already been revised once.
The first three parts of EN 352 standards are the basic parts and they define passive performance requirements for hearing protectors. Parts other than 1, 2, and 3 incorporate the safety requirements and associated test procedures of additional functions manufactured into hearing protectors. Today additional functions include electronic devices in hearing protectors.
EN 352 standard series for hearing protectors
EN 352-1, -2, and -3 are the basic parts of EN 352 standard of the hearing protectors. Testing and safety requirements for ear-muffs are in EN 352-1 and those for earplugs are described in EN 352-2. Testing methods for ear-muffs attached to industrial safety helmets are covered in EN 352-3.
The instructions of the testing methods are not directly described in these three basic parts but instead the reader of the parts is referred to another standard; EN 13819 deals with the testing methods common to all types of hearing protectors covered by EN 352 series and is in two parts; Part 1: Physical test methods, and Part 2: Acoustic test methods. An associated standard EN 458 is often cited in EN 352 standards and it covers selection, use, care and maintenance of hearing protectors.
The limits of the test results from the measurements according to those described in EN 13819 are given in the basic parts of EN 352. For instance, headband force must not be too strong; according to EN 352-1 the headband force of ear-muff shall not be more than 14 N and cites to test methods in EN 13819-1 which tells the test dimensions and gives a number for the amount of specimens to test. EN 13819-1 also suggests a mounting device for the measurement of the head band force. Another example would be the minimum sound attenuation whose requirements at different frequencies are in EN 352-1, 2 and 3 parts but whose testing method is described in EN 13819-2.
All terms and definitions involved to hearing protectors, like “cup”, “cushion”, “liner” etc., are in parts EN 352-1, -2, and -3. Also it defines all related passive characteristics, non-electronically working functions, e.g., minimum sound attenuation (see Figure 1.). Moreover, the requirements for size, materials and constructions of hearing protectors are given in these three parts of EN 352.
A tabular guide to&nbsp;EN 352
|Some important hearing protector standards|
|EN 352-1:2002 Hearing Protectors||General requirements||Ear-muffs|
|EN 352-2:2002 Hearing Protectors||General requirements||Ear-plugs|
|EN 352-3:2002 Hearing Protectors||Ear-muffs attached to an industrial safety helmet||General requirements|
|EN 352-4:2001 Hearing Protectors||Safety requirements and testing||Part 4: Level-dependent ear-muffs|
|EN 352-5:2002 Hearing Protectors||Safety requirements and testing||Part 5: Active noise reduction ear-muffs|
|EN 352-6:2002 Hearing Protectors||Safety requirements and testing||Part 6: Ear-muffs with electrical audio input|
|EN 352-7:2002, Hearing protectors||Safety requirements and testing||Part 7: Level¬dependent ear-plugs|
|prEN 352-11, Hearing Protectors||Safety requirements and testing||Part 11: Two -way communication ear-muffs|
|EN 458:2004, Hearing Protectors||Recommendations for selection, use, care and maintenance||Guidance document|
|EN 13819-1:2002 Hearing Protectors||Testing||Part 1: Physical test methods|
|EN 13819-2:2002 Hearing Protectors||Testing||Part 2: Acoustic test methods|
Generally speaking, parts 1, 2 and 3 of EN 352 define hearing protectors and tell the performance requirement, whilst parts of EN 13819 describe how the hearing protectors must be tested in order to satisfy the requirements of the basic parts of EN 352 standard.
From Part 4 onwards the EN 352 standard series deals with safety and testing methods of additional functions build into a hearing protector. One example of additional function incorporated to a hearing protector is the so-called level-dependent function of hearing protectors. For instance, a level-dependent ear-muff is designed to provide restoration of external sounds, while providing attenuation of sound at high sound pressure levels. The safety requirements and associated test procedures for the level-dependent ear-muffs are contained in EN 352-4.
Moreover, there already exists additional functions in hearing protectors and respective standardised testing methods at least for active noise reduction in EN 352-5, hearing protectors with audio communications in EN 352-6 and for level-dependent ear-plugs that shall to be tested according to EN 352-7.
The number of additional functions is clearly increasing due to today’s development of embedded systems in electronics which is reflected to hearing protector technology. The number of EN 352 parts is also increasing and new standards are needed in order to ensure the safety of hearing protectors. In fact, there are several unfinished parts of EN 352 series and Part 7 is not the last one of EN 352 series.
Adopted EN standards have served as a reference for CE certification of hundreds of hearing protectors. These are under constant evaluation and a review of standards is made at least every five years. Due to limited resources, the validation of the test methods, especially for additional functions (electronic hearing protectors), is still lacking. There is also limited co-operation between test laboratories creating a problem in further refining existing standards or preparing new ones for new types of hearing protectors. Therefore, it is important to continue the validation of the standardised testing methods and their requirements. This needs good collaboration and research between test laboratories and research institutes.
In Europe, CEN/TC 159 (European Committee for Standardization, Technical Committee 159, Hearing Protectors) is responsible for the standardisation for hearing protectors but the acoustical test methods are set out by ISO/TC 43/SC1 (International Organisation for Standardisation, Technical Committee 43, Acoustics, Sub-Committee 1, Noise).
Real world attenuation
Despite the fact that the wearer information of a hearing protector gives its detailed characteristics, the optimal protection is not always achieved. One reason for this is that the protectors were selected incorrectly for the noise environment: protectors may have ineffective sound attenuation of the noise or they may be over-protective. Over-protection is imminent when, e.g., warning signals are not heard which, on the other hand, raises other safety hazards, which unfortunately can be more serious than those for hearing.
Hearing protectors may also feel unpleasant and, consequently, the user easily removes the protectors when danger from noise is not over. Protectors are subject to ageing and their protective effect decreases in time. Harmful noise easily leaks inside ear-muffs whose cushions are broken and perished due to ageing. In fact recent studies have shown that the laboratory made test results over estimate the real life protection of hearing protectors (See, e.g., Starck et al., 2002; Toppila et al., 2005).
As much as warning signals are important also communication is. Essential work related communications with emphasize on speech intelligibly are important together with the easiness of the use of the protector. For example, many present-day people carry cell phones and are reachable during noisy working day. Luckily there are some additional (electronic) functions in today’s ear-muffs for answering the telephone call without removing the hearing protectors. These additional functions transfer communication and other signals via, e.g., Bluetooth or auxiliary input connection. It is worth mentioning in this context that these two connections are tested according to standards prEN 352-11 and EN 352-6, respectively. Earlier when these devices were not implemented to hearing protectors the real world attenuation must really have suffered a decline when compared to the results measured in laboratories.
Good selection of hearing protector
For a good selection of hearing protector the standard EN 458 is useful with the wearer information of a particular hearing protector. As already mentioned, standard EN 458 is a guiding document for selection, use, care and maintenance of hearing protectors. Currently, the standard is in revision. As one very important tool for modern selection of hearing protector the revised EN 458 will contain a flow chart for selection according to noise environmental situation. This new user friendly approach makes the choosing of hearing protector much easier and brings more attention to the electronic devices (additional functions) of hearing protectors
The basic EN 352-1, -2, -3 standards will stay necessary and fortunately the additional electronic functions (sound restoration, active noise reduction, two-way communication…) are not confusing the issue but helping the selection of hearing protectors for a specific noise environment with revised EN 458.
Directive 89/686/EEC of 21 December 1989 on the approximation of the laws of the Member States relating to personal protective equipment, Official Journal L 399, 30/12/1989
Directive 2003/10/EC of the European Parliament and of the Council of 6 February 2003 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise)
Starck J, Toppila E, Laitinen H, Suvorov G, Haritonov V, Grishina T. The attenuation of hearing protectors against high-level industrial impulse noise; comparison of predicted and in situ results. Applied Acoustics 2002;63:1-8.
Toppila E, Pyykkö I, Starck J, The use of hearing protectors among forest, shipyard and paper mill workers in Finland – a longitudinal study. Noise and Health, 2005;7(26):3-9.
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Published: 10th July 2007 in Health and Safety International