10dBFS corresponds to a signal that is 10dB lower than the clipping point of the system.ĠdBFS (Full Scale) is the clipping point for a signal in a digital audio product. Therefore, dBFS values are always less than or equal to zero. In a digital audio system, 0dBFS refers to the maximum signal level possible, also known as the clipping point. dBFS is another dimensionless quantity, because it is just a number and cannot be converted to another unit. dB-SPL is also a unit, because it can be converted to other units of pressure, like pascals.ĭBFS, or decibels relative to Full Scale, is used to measure digital audio signal levels. 0dB-SPL corresponds to a sound pressure level that is barely audible to the average human. The V in dBV is capitalized to provide clarity between V and u when writing it down.ĭB-SPL is a measure of sound pressure level in the atmosphere, and is used to measure the amplitude of sounds (audio pressure waves) traveling through the air. To quickly convert between dBu and dBV note that dBu is always equal to dBV plus 2.21. dBV is dB relative to 1.0 volt such that 0dBV = 1.0 volt. dBu is dB relative to 0.775 volts such that 0dBu = 0.775 volts. Unlike the dB, they are actually units because they can be converted to an actual voltage value. The numbers grow very quickly: if you turn up a signal by 60dB, its amplitude will be 1000 times the original amplitude!ĭBu and dBV are decibel units specifically for measuring voltage. Another 6dB would put it at eight times the original amplitude. If you turn it up another 6dB, it will be at four times the original amplitude.
If you turn up the amplitude of a signal by 6dB, it will be twice the original amplitude. If someone tells you to "turn the signal down by 6dB", then they are asking you to reduce the amplitude of that signal by half.ĭecibels are useful because humans perceive sound levels logarithmically. If one signal is twice the amplitude of another signal, then it is 6dB higher. If those two signals are the same amplitude, then they are said to be 0dB apart. When they are being used to describe audio signal levels, they are often used to compare the amplitude of two audio signals. While decibels are most commonly associated with audio signals, they don't necessarily have to be. A decibel is a "dimensionless" value, meaning that it is just a number, not a unit. Some background is provided as a prelude to the article.Ī decibel ( dB) is a logarithmic ratio of two values. As a basis for the discussion it is important to understand the meaning of and differences between some of the common decibel units: dB, dBu, dBV, dBFS, and dB-SPL.
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