Hearing protectors come with different attenuation data to match different noise environments. Here we explain some of the concepts and acronyms you might encounter when looking at hearing protector table data.
Let’s open the Sordin Sharp brochure and walk through the table data for the headband version of the flagship electronic hearing protector. The first concept we run into is SNR, which stands for Single Number Rating (not to be confused with signal-to-noise ratio, another common SNR acronym in acoustics and audiology).
SNR is the expected attenuation value for the hearing protector. The higher the value, the higher the attenuation. We can see that our model has an SNR value of 30 dB (A). Given an average maximum noise limit of 85 dB (A) over a workday, we can tell Sordin Share is approved for use at a noise level of 115 dB (A) next to the ear.
A concept related to SNR is NRR (Noise Reduction Rating), which is more commonly used in North America. NRR is a few decibels lower than SNR. There is no exact conversion rate, but SNR values are typically about 3–5 dB higher. For example, a hearing protector with an NRR of 25 dB will have an SNR of appr. 28 dB.
SNR is complemented by H, M or L values, which are used to weight the attenuation level depending on frequency – where H is the expected attenuation of high-frequency noise, M of medium-frequency noise and L of low-frequency noise. The data can be used as a guide e.g. to select the right hearing protector for workers in different noise types.
We can see that Sordin Share’s SNR value is higher in the high-frequency range. This is true for most hearing protectors as high frequencies are easier to attenuate than low. Since we humans are more sensitive to high-pitch noise, we also experience a higher sound comfort with this weighting.
Moving on through the data tables, we come to APV, or the Assumed Protection Value, which is the expected protective level in different frequency bands (subtracted by one standard deviation to improve the accuracy of the actual attenuation value).
The actual noise in the ear is the difference between the noise level outside the cup and the APV value in each respective frequency band. Just like with SNR, we can see that the APV values generally increases with higher frequencies.
Note: Contact Sordin for noise data relevant in Australia and New Zealand.
Sordin is a Swedish company with more than 30 years' experience of developing, manufacturing and selling professional hearing protection equipment.