What is 'Noise Reduction Rating'?

How Does NRR Work?

Let's talk about decibels for a second. They're not like kilograms or meters - they're on a whole different scale. Think of it this way: if you add 3 kg to your weight, it's a small increase. But if you add 3 decibels to a sound? You've just doubled its intensity! Add another 3 decibels, and you've doubled it again. So 91 dB is twice as loud as 88 dB, and four times as loud as 85 dB.

This is why workplace safety rules are so strict about noise. They'll let you work in 85 dB noise for 8 hours, but only 4 hours at 88 dB, and a measly 2 hours at 91 dB. It's all about protecting your ears from that exponential growth in sound intensity.

Now, let's talk about those earplugs you see with NRR ratings. NRR 33 sounds impressive, doesn't it? In perfect conditions, these could turn a deafening 100 dB noise into a much more manageable 67 dB. But here's the kicker - we don't live in a perfect world. There are a bunch of factors that can affect how well your earplugs actually work. And remember, even a tiny 3 dB difference can mean double the noise hitting your ears. So it's crucial to get this right.

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Can We Trust NRR?

Here's the thing about NRR - it's not always what it seems. Sure, they test it in perfect conditions, but let's be real - when's the last time you wore earplugs in a lab? In the real world, like at a rock concert or in a noisy factory, things are a bit different.

So, what do we do? We derate the NRR. It just means we adjust it to be more realistic. Some organizations recommend an easier way of derating hearing protection—25% (OSHA) or 50% (NIOSH). However, the most common and likely most prudent practice involves a bit of math.

Let's say you've got earplugs with an NRR of 33, and you're in a place with 100 dB of noise. To derate it according to this procedure, you would go through the following steps:

• (NRR – 7) / 2. So in this case, it would be : (33 – 7) / 2 = 13
• Then subtract the above value from the noise level, which is 100 in our example. That would give you 100 – 13 = 87.

So those earplugs that claim to knock off 33 dB, in reality, they're probably only getting you down to about 87 dB. Still better than nothing, but not quite the protection you might have expected.

When shopping for earplugs, whether for personal use or your company, consider the noise levels you'll be exposed to. Check the NRR rating on the packaging, but don't forget to calculate the real-world NRR rating for a more accurate assessment of protection.

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