![]() ![]() So, 3 is the magic number right? Well, not so fast. Conversely, a 3dB decrease means the sound is cut in half. ![]() ![]() Reality Physics tells us that for every doubling of acoustical energy, there is a 3dB increase. It yields a single-numbered result and gives us a good idea of the overall sound level (when, in reality, the sound is at many different noise levels all across the frequency spectrum). At any rate, the dBA scale gives us a good starting point from which to measure sound. Just remember that the most commonly used scale is dBA, and that’s what most people are referring to when they talk about decibels (whether they know it or not). To accommodate this, there are several different algorithms of decibel weightings that we call “scales.” Most commonly, you hear about the dBA scale (this is the one that applies to humans) and the dBC scale (but that’s for another blog). We “hear” some frequencies as being louder than others our ears do not have a very “flat” response. It is “weighted” because our ears do not treat all frequencies the same. To futher confuse matters, humans hear “weighted” noise levels. This means that we always talk about decibels in the positive sense, such as 50dB or 60dB we don’t say that some noise is -20dB. For humans, the reference level is the “threshold of hearing”. A decibel is a ratio of how much acoustical energy we hear compared to some “reference level”. Are we talking about physical sound levels or perceived sound levels? There is a big difference! It seems like everyone is talking about decibels these days: “5 dB of this” and “3 dB of that.” As acoustical consultants, we hear people using these metrics and often wonder to ourselves, “Do they really know what a decibel is?” Occasionally, someone is brave enough to ask the more important question, “Just how much is a decibel?” The answer to that question is, of course: well, it depends. ![]()
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