How are helmet mounted ear defenders tested?
Mounted ear defenders must be tested with compatible helmets. Both physical and acoustic tests are required to make sure they perform at the intended level. Ear defenders and helmets also need to be certified together as a combination, allowing a notified body to monitor ongoing compliance.
Physical tests
Adjustability
Mounted ear defenders are tested to make sure they fit the designated size range. The ear defenders are attached to the helmet then fitted on test headforms of different sizes.
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Cup rotation
Testing is carried out to ensure the cups enable sufficient rotation, so the ear defender can be adjusted to create an effective seal.
The ear defenders and helmet are fitted to a mounting fixture with plates that rotate the cups in different directions. During the test, the cushions must maintain continuous contact with the plates.
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Headband force
This test assesses the force exerted by the ear defenders and helmet working together. The force must be high enough to create a tight seal without exceeding a set limit required for wearer comfort.
Ear defenders are attached to the helmet then fitted on a test fixture designed to measure force. The headband force must not exceed 14N.
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Cushion pressure
Cushion area is measured on the same test fixture. The headband force reading from the previous test is divided by the cushion area to calculate cushion pressure, which must not exceed 4500 Pa.
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Resistance to damage when dropped
The helmet and ear defenders are attached to a test rig and dropped from a height of 1m to swing into a vertically positioned steel plate. The ear defender and attachments must remain intact and fully functional.
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Change in headband force
This test assesses change in headband force after flexing to simulate repeated use. Mounted ear defenders are attached to the helmet then fitted on a test fixture which flexes the supporting arms 1000 times – opening and closing the mechanism, switching from the ‘standby’ to ‘in use’ position.
After 1000 cycles, headband force is measured again. The final reading must not exceed 14N and must fall within 15% of the original measurement.
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Resistance to leakage
Fluid-filled cushions are tested for resistance to leakage. The cups are placed horizontally on a flat surface and subjected to a vertical load of 28N, after which the cushions are inspected for rupture and leakage.
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Ignitability
All parts of the ear defender and supporting arms are tested for ignitability using a steel rod heated to 650°C. The components must not ignite or continue to glow after the rod is removed.
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Acoustic tests
Insertion loss
Insertion loss testing uses a microphone to measure sound levels at various frequencies with and without ear defenders fitted. For this test, the ear defenders are attached to the helmet and fitted on a test fixture using a supporting pad.
Standard deviation must not exceed 4dB in four or more adjacent one-third-octave-bands, or 7dB in any individual one-third-octave-band.
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Sound attenuation
Sound attenuation testing is carried out with people wearing the helmet and ear defenders, listening for a test noise in a controlled chamber.
Trial sound attenuation tests are first carried out without wearing hearing protection. Then, with the helmet and ear defenders fitted, test subjects indicate when they can hear the test noise.
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Supplementary combinations
After an ear defender has been tested with one helmet, additional helmet models can be tested as supplementary combinations.
Supplementary combinations are assessed for adjustability and headband force. Sound attenuation testing is not required unless the headband force falls outside of set limits.
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Why is certification important?
In addition to being tested together, mounted ear defenders must also be certified in combination with compatible helmets.
As a category III product under the PPE Regulation, hearing protection is subject to ongoing monitoring by a notified body. Compliance is reassessed annually through audits or independent testing. Any changes to the products or production process are captured, and the notified body advise what additional testing is needed to verify performance. This ensures the same level of performance is maintained or, if it changes, makes sure user information is updated accordingly.
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Mounted ear defenders must be tested with compatible helmet models to verify the performance of each combination. Ear defenders are fitted to the helmet for physical and acoustic testing, assessing how the items work together. Testing a helmet and ear defenders together once provides a snapshot of performance at that moment in time, however certification is needed to make sure the combination continues to perform at the intended performance level.
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