EN 352-3 covers ear-muffs that clip into the side slots of a helmet. This is the standard arrangement in construction, forestry and industry, where head, hearing and often face protection are needed at the same time.
The critical detail: the compatibility list
The attenuation of a helmet-mounted muff depends on how the cushion presses against the head, which in turn depends on the geometry of the helmet. An EN 352-3 certificate is therefore always issued against specific helmet models — the manufacturer must supply the list of compatible helmets and separate attenuation data for each.
Mounted on any other helmet, the muff is no longer a certified assembly and its declared SNR no longer applies. This is one of the most commonly overlooked rules on site.
Attenuation compared with the headband version
The helmet-mounted version of the same model typically attenuates 2–4 dB less than the headband version, because the mounting arm reduces cushion pressure. Allow for that when assessing noise exposure.