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Hearing protector testing and certification
Tests to ensure that hearing protectors meet European standards.
Hearing protectors – often referred to as ‘hearing defenders’ – are used in a wide range of industries and situations where occupational limits for noise exposure are exceeded. In Europe, they fall within the scope of the Personal Protective Equipment Regulation, so must be tested and CE-marked before being placed on the market. To facilitate this, CEN (the European standards body) has developed a number of harmonised European standards, each relevant to a particular type of hearing defender – for instance, EN 352-1 for basic earmuffs, EN 352-2 for earplugs or EN 352-3 for helmet-mounted earmuffs. In fact, there are eight parts to EN 352, covering passive and active devices.
Devices meeting only EN 352 parts 1, 2 or 3 are examples of passive products – without any features for controlling the level of sound attenuation. A range of more sophisticated devices is available which may feature electrical and/or mechanical systems to control the level of sound attenuation or, in some cases, the level of sound attenuation at specific frequencies so that some sounds are cancelled out but the user can still hear speech. For example, EN 352-4 covers level-dependent earmuffs and introduces additional tests to be used alongside
Assessment of hearing protectors includes two basic tests – sound attenuation and insertion loss. These establish whether the basic requirements are met for reducing harmful levels of noise to acceptable levels at the ear.
The sound attenuation test is a subjective assessment using human wearers and is carried out on both earplugs and earmuffs of all types. This testing is carried out in a chamber with closely defined acoustic properties. The human subjects undergo initial trial sound attenuation tests and then, while wearing the hearing protectors, the human subjects will indicate the sound level at which they become aware of the test sound which fills the chamber for the duration of the assessment.
The other commonly used noise reduction test is ‘insertion loss’. This is an electro-acoustic method which compares the level of noise received by a microphone placed in a special test fixture, with and without the hearing protector fitted (human subjects are not used). Insertion loss is not carried out for standard earplugs.
For active devices (such as level-dependent earmuffs or level-dependent earplugs), more complex test procedures are used and are specified in the appropriate product standard.
A range of physical and mechanical tests is also carried out on hearing protectors to assess their basic performance. For example, initial testing on any earmuff begins with assessing whether it will fit the size of head claimed and whether it has the adjustment claimed. Three sizes of earmuff are specified – small, medium and large. Assessment is carried out using one of three appropriately-sized head forms. Other tests include assessing properties such as headband force and the change in headband force after mechanical flexing, cushion pressure, resistance to damage when dropped and ignitability.
However, in the case of aural earplugs, a smaller range of physical tests is used. This includes measurement of diameter (not required for custom moulded or semi-aural earplugs), resistance to damage when dropped and ignitability. Headband earplugs, like earmuffs, must also be checked for size using standard head forms.
For active hearing protectors, it will be also necessary to show that any electronic systems fitted meet specified additional requirements – such as intrinsic safety and electromagnetic compatibility.
Further information on SATRA's PPE certification and testing services is available at www.satra.com/ppe
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