![]() ![]() To me, that sounds like a job for an logarithmic unit. If our goal is to create a system that measures sound loudness, one of the key things we need is that the unit we use can comfortably cover a large range of values. Several orders of magnitude, actually. Unless you love counting zeros, that doesn't look very convenient, does it? Note how using Pascals is not very confortable with quiet sounds while mPa (a thousandth of a Pascal) doesn't work very well with loud ones. OK, with those three properties in mind, let's sum up what a decibel is. ![]() Some examples are electronics, video or optics. Decibels are used in all sort of industries, not only audio. ![]() These properties can be related to audio (like air pressure or voltage) or they may have little or nothing to do with audio (like light or reflectivity on a radar). 20% percent of what? 20dB respect to what? So, what kind of reference value could we use? This brings me to the third reason: 3: A Versatile UnitĪlthough most people associate decibels with sound, they can be used to measure ratios of values of any physical property. Just saying 20dB is incomplete in the same way that just saying 20% is incomplete. We need to specify the reference value we are using. In other words, they are a comparative unit. This is the second reason why decibels are odd, let me elaborate:ĭecibels are really the ratio between a certain measured value and a reference value. Well, is not that simple. When we say something is 65dB, we are not just making a direct measurement, we are always comparing two values. Great, so we have now an easy to use scale to measure anything from a whisper to a jet engine, we just need to stick our sound level meter out of the window and check the number. So the take away here is that we use a logarithmic scale for convenience and because it gives us a more accurate model of nature. ![]()
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