Hearing protection decibel rating

[Dave Lehnert]

Have a question on decibel ratings for hearing protection.

One model I am looking at has a rating of 30 decibels. Another model is rated at 25 decibels. Is this rating the amount the sound level is reduced to, or reduced by that amount.
For example, If I was using a tool that was rated at 100 decibels and I was using the 25 decibel hearing protection. would the new decibel rating at my ear be 75 or 25?
The question I am trying to answer is what model is better and is the difference 25 vs 30 a big deal?

[Morey St. Denis]

Provided those specs adhere to industry accepted standards for reporting Noise Reduction Rating, the hearing protection affording a NRR of 30 decibels is considerably better than a NRR of 25. Basically, if your power tool is generating around 95 dB and you are wearing hearing protection of 25 dB NRR, your exposure should likely be under 70 dB, but actual sound pressure numerical measurements greatly depend upon distance from the source and frequency to an extent. Generally, sustained noise above 85 dB over a prolonged period, can be considered hazardous and is certainly perceived as annoying. 70 dB is the EPA identified limit to protect against hearing loss and other disruptive effects from noise, such as sleep disturbance, stress, learning detriment, etc.

To further confuse you, keep in mind that the decibel scale is not linear, it is logarithmic in nature. Exploring the exponential math, you will no doubt see that a 5 dB difference in acoustic energy is substantial and likely well worth paying for; provided your comfort level in wearing each style of protective device is roughly perceived as equivalent. Hearing protection momentarily not worn due to convenience or discomfort does no good at all...

[Bob Coleman]

To give you a baseline for what Morey said above, a 3dB reduction is a 50% reduction in volume (really sound pressure level, but that's getting a bit technical)

[Jerry Bruette]

And remember the NRR on the packaging only applies if the hearing protection is used properly. If you're using plugs make sure they're inserted properly and far enough. If you're using muffs and safety glasses the NRR could be reduced by the muffs going over the bows of the glasses.

Jerry