Hearing protection

SNR is the single-number rating under EN 352 and NRR is the US equivalent; both are measured in a lab with ideal fitting. Real-world attenuation is usually lower, so guidance commonly derates the figure, for example the OSHA method of (NRR minus 7) divided by 2 for dBA measurements. The aim is an at-ear level of roughly 70 to 80 dB.

Not necessarily. Overprotection stops workers hearing alarms, forklift signals and speech, and often leads them to remove the protector mid-shift. Measure the noise at the workstation and choose a rating that just brings the at-ear level under the limit, which in Vietnam is 85 dBA over 8 hours under QCVN 24:2016/BYT.

Earplugs (EN 352-2) are light and cool, suited to hot environments, but their performance depends heavily on insertion. Earmuffs (EN 352-1) are easy to fit correctly and easy to check visually, but they are warm and leak when worn over thick spectacle arms. Helmet-mounted earmuffs fall under EN 352-3 and must only be used with the helmet models listed in their instructions.

At very high noise levels, typically around 100 dBA and above, double protection increases attenuation. The combined reduction is not the sum of the two ratings; it adds only a few dB over the better device. Such cases should be assessed by a specialist together with limits on exposure time.

Disposable foam plugs should be discarded after each shift or when dirty; reusable plugs are washed and replaced when hard, cracked or misshapen. Manufacturers commonly advise replacing earmuff cushions periodically, around every six months with regular use, or sooner if they harden or tear. A headband that has lost its clamping force also reduces protection.

Measure noise at the workstation with a sound level meter or a noise dosimeter, expressed as an 8-hour average. A practical rule: if you have to raise your voice to be heard at one metre, the limit is probably exceeded. The measurement also tells you how much attenuation to select and whether noise should be reduced at the source.

With clean hands, roll the plug into a thin cylinder, pull the ear up and back with the other hand, insert the plug and hold it for about 20 to 30 seconds while it expands. When fitted well, most of the plug sits inside the ear canal and your own voice sounds deeper. A plug resting loosely at the canal entrance can give far less attenuation than the rating on the pack.

It can, especially when the attenuation chosen is much higher than the actual noise requires. Aim for a level at the ear of roughly 70 to 80 dB, and consider flat-response protectors or level-dependent earmuffs where signals must be heard. Alarm systems in very noisy areas should also use flashing beacons.