On a ruler the distance between markings is consistent all the way up and down the ruler. It’s a bit confusing, but if you think of it like a ruler it might help. The logarithmic scales also change as you move away from your reference point. Decibels are measured on a logarithmic scale, which is a way to express large data ranges in a compact way. That is to say that the difference from 1dB to 2dB is not equal to the difference between 10dB to 11dB, even though they are both represented by a 1 decibel change. So the first point to make is that decibels are not measured on a linear scale. Before we do, we need to understand something about scaling, and how it relates to decibel measurements. Fortunately for us, those that have come before us have done all the hard work of figuring out those references and how they all relate. So the reality is, when talking about decibels, we need to know what reference we’re dealing with, and what we’re actually measuring. Since the decibel is one-tenth of the Bel, it’s a simple way to measure smaller increments without all those nasty decimal places. It was named after Alexander Graham Bell (scientists and engineers like to name things after their heroes). A Bel is a unit of measurement that measures the ratio of a source against a known reference level. You see, the word decibel simply means one-tenth of a Bel. We’ve all said things like, “Hey, can we bring that down a dB or 2?” or, “Bring that up about 3dB,” but what do we really mean? Or, even more to the point, what does that really mean? I mean what is a decibel, really?
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