Theres also the equal loudness contour, which tells us that we hear an increase in volume differently accourding to the frequency of the sound, so each frequency has a different "double volume" level.Īll in all, it's complicated and I'm not pretending to understand all of it and I certainly oversimplified parts of it, but that's what I can tell you. Therefore, the louder your initial sound is, the even louder your "double" volume sound has to be. The Weber-Fechner law says that the more you increase a "signal", the less apparent an identical difference is (adding 5 dots to a starting 10 dots is more apparent than adding 5 dots to a starting 100). The decibel scale is a reflection of the logarithmic response of the human ear to changes in sound intensity: The logarithm to the base 10 used in this expression is just the power of 10 of the quantity in brackets according to the basic definition of the logarithm: Examples: Decibel calculation. To make this huge range easier to write down, a second scale of loudness was created called the. If you try to measure subjectively if a sound sounds twice as loud as an other, you have a bunch of other factors that come into play. The human ear is an amazing instrument that can detect intensities as low as 1012 W/m2 10 12 W/m 2 and can hear intensities as high as 103 W/m2 10 3 W/m 2 (although this is loud enough to cause damage to the ear). That's because some of the sound from each guitar cancels out the other guitar, unlike a duplicate signal, which has no phase cancellation. What's more is that, unlike a 6dB increase in "signal" you might expect, you actually get less. If you have 2 guitarists playing together, you could say that it is twice as loud, but you don't necessarily hear it that way. What makes it difficult to comprehend are the multiple effects that come into play. A logarithmic scale (or log scale) is a way of displaying numerical data over a very wide range of values in a compact way. Here are some properties you can use about sound:ĭuplicating a signal and hearing both together results in a ~6dB increase.Īdding 10dB increases the power of the wave by 10x.Īdding 20dB increases the amplitude by 10x. It's more useful to think in different terms when it comes to volume, like a negative decibel scale in digital audio, in reference to a 0 dB signal. Reason why it's confusing is that there's actually much more to it than you think.
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