I did some research, and it turns out the decibel is actually pretty interesting. So after years of pretty much taking the decibel for granted, I finally had enough. I would often catch myself thinking "I know they are getting it wrong, but I don't know why". As such, I'd feel uneasy when I overheard a lay-person talking about volume. The mixer section of Logic X (a typical DAW - Digital Audio Workstation)įor a long time I've been at least tangentially connected to the world of "pro" audio. The desk shows the loudest value as zero, all the way down to silence at "-96" (or sometimes even "∞"). But when I look at the volume meter on a mixing desk, things are different. "It's louder than a jet engine at 50 paces, man". Sound engineers do it too, when boasting about the power of their speaker-setup. Journalists do this when describing how loud a band is 1. Sometimes people use decibels as an absolute value where "0" is silence and anything over "120" is very loud. I hope these six points help you to clear up some of the question marks that you might have had about decibel.The decibel has always confused me. Instead, you'll get 93 dB SPL.Īs another example, if you have three sound sources that have outputs of 60 dB SPL, 75 dB SPL, and 80 dB SPL, the combined sound pressure level will not be 215 dB SPL, it will be about 81 dB SPL. When you put an identical loudspeaker next to it, you will not get 180 dB SPL. However, if it is power you are measuring then halving or doubling is a 3dB change.Īs you can see decibel calculations cannot be made by using simple addition and subtraction!Īs an example, let's assume that you have a loudspeaker that has an output of 90 dB SPL at a distance of 1 meter. This is because the dB scale is logarithmic and percentages are linear! 50% of 70 dBu is 64 dBu because dBu is a voltage and a reduction of a half or a doubling is a change of 6dB in voltage. Truth 6ĭecibel calculations cannot be made by using simple arithmetic or percentages!įor example, you cannot say that 80% of 70 dB is 56 dB. Since 0 dBu is referenced to 0.775 Volt, and dBV is referenced to 1 Volt, the readouts might be either positive or negative values, such as -2 dBu, +6 dBu, -12 dBV, or +3 dBV. The professional line level standard is +4 dBu (1.228 Volts) and the consumer line level is typically -10 dBV (0.316). Consequently, all dBFS readouts are negative values, such as -6 dBFS or -20 dBFS.ĭBu and dBV are used to measure voltage. The reference for this scale is 0 dBFS and nearly all the other values that are measured are below this point. As a result, all SPL readouts are positive values, such as 50 dB SPL or 85 dB SPL.ĭBFS (dB Full Scale) is used to measure digital signal levels. 0 dB SPL is referenced to 0.00002 Pa (the threshold of human hearing) and all the other values that are measured are above this reference point. There are many flavours of decibel! The most common ones in today's audio world are dB SPL, dBu, dBV, and dBFS.Īlthough they share the same prefix (dB), and the same system for measurement (comparing two values on the logarithmic scale), they are quite different from one another.ĭB SPL is used to measure sound pressure levels. On the linear scale, the change between two values is a difference, whereas on the logarithmic scale it is expressed as a ratio.įor example, the change from 1 to 2 is 1 on the linear scale, whereas it is a ratio of 1:2 on the logarithmic scale.Īs another example, the change from 3 to 9 is 6 on the linear scale, whereas it is a ratio of 1:3 on the logarithmic scale. To truly understand a decibel, one should understand how the logarithmic scale works. It is not a fixed unit like, for example, kilogram, mile, cubic meter, or Fahrenheit.ĭecibel is a ratio of one value to another value or a specified reference value. Truth 3ĭecibel has not a value of its own. Logarithmic scale makes it easy to compare values that cover a large range.įor example, instead of saying "the threshold of hearing is 0.00002 Pa and the level of normal conversation is about 0.02 Pa", it is much easier to say "the threshold of human hearing is 0 dB SPL and the level of normal conversation is about 60 dB SPL". Truth 2ĭecibel (dB) is a unit used to measure sound pressure or signal level by comparing it with a reference point on a logarithmic scale. Bel is named after Alexander Graham Bell. If you are one of these people, we hope that Ufuk’s 6 truths of the decibel will help to clear up some of your questions. Even though for most people, decibel is a familiar term, most of us aren’t 100% comfortable with them. Ufuk Önen thinks the decibel has an uncanny quality! What does he mean? According to Freud, the 'uncanny' refers to something familiar or known, yet foreign or strange at the same time, which results in a feeling of it being unsettling and uncomfortable.
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