Ear plugs and frequency

These wax ear plugs come with a note detailing the protection by frequency. It is good to note that the average noise reduction is bigger at higher frequencies. In class I have found that not all notes played with the same amplitude are heard as the same volume. Notes around 4000 Hz sound loudest and most likely to cause damage. APV stands for Assumed Protection Value. https://esselacoustics.com/news/assumed-protection-value-apv/ You'll notice that in this data APV = average noise reduction - standard deviation. This is explained in the link. What you actually hear with the ear plugs in is EXTERNAL NOISE - APV = EXTERNAL NOISE + STANDARD DEVIATION - AVERAGE NOISE REDUCTION. In other words, the uncertainty caused by the spread of the data across the population means that it is assumed that you will get less protection than average. More on standard deviation later.