Short answer: a decibel (dB) is a relative, logarithmic unit for comparing two levels. It is a ratio, not a fixed amount, so on its own a figure like 3 dB tells you how much louder or quieter one signal is than another, never how loud a thing actually is. It reads logarithmically because that is roughly how human hearing works, which is why small dB numbers can stand for large changes in level.
The rules of thumb below are approximate and hold across the ranges that matter for music. A decibel becomes an absolute measurement only once it is tied to a reference, which is exactly what dBFS, dBu and dB SPL each do.
A decibel is a relative, logarithmic unit for comparing two levels, usually two signal levels or two loudnesses. The important word is relative. A decibel is a ratio between one level and another, not an absolute amount by itself. If someone tells you a sound is "3 dB" they have not really said anything yet, because 3 dB only means something once you know 3 dB above what.
A decibel turns into an actual measurement the moment you tie it to a fixed reference point. That is the job of the named scales further down this guide: 0 dBFS marks the top of the digital range, dB SPL is counted from the threshold of human hearing, and so on. Give the decibel a zero to count from and it stops being a bare comparison and becomes a reading you can act on.
Audio leans on decibels so heavily because they squeeze an enormous range of levels into small, readable numbers. The quietest sound you can hear and a sound loud enough to hurt are separated by a factor of about a trillion in power, which is hopeless to write out in full. On a decibel scale that whole span fits into roughly 120 units. The decibel is one tenth of a larger unit called the bel, which is where the "deci" comes from.
A decibel is always a comparison. On its own it is a ratio between two levels, and it names an absolute level only when it is pinned to a reference, like 0 dBFS in your DAW or dB SPL in the room. That is why the same -6 dB can describe a fader move, an amount of headroom, or a drop in room loudness, depending on what it is measured against.
Decibels are logarithmic because human hearing is roughly logarithmic. Your ears respond to ratios between levels rather than to flat differences, so equal multiplications feel like equal steps. Doubling the power of a sound feels like about the same jump whether you started quiet or loud, and a logarithmic scale is built to match that.
There are really two versions of the decibel, and the gap between them is where the 3 dB and 6 dB rules come from. For power, decibels are ten times the base ten logarithm of the ratio, so doubling the power is ten times the logarithm of two, which comes out near 3 dB. For amplitude, meaning voltage or sound pressure, it is twenty times the logarithm, because power rises with the square of amplitude. So doubling the amplitude is about 6 dB, and that same move is four times the power. You do not need the formulas day to day, but they are why the numbers land where they do.
The logarithm is also what keeps the numbers small and comfortable. A hundredfold jump in power is only 20 dB, and a thousandfold is 30 dB. That is far easier to read on a meter and to talk about than the raw ratios, and it happens to line up with how large those changes actually feel.
In practice a handful of round numbers cover almost everything. A change of about 6 dB doubles or halves the amplitude, the height of the waveform. A change of about 10 dB is heard as roughly twice or half as loud. A change of about 1 dB is the smallest step most people can notice at all. And 3 dB is a doubling of power, which is a smaller move than it sounds, because power and perceived loudness are not the same thing.
Those figures pull in different directions, so it helps to keep three ideas apart. Power doubles at 3 dB. Amplitude doubles at 6 dB, since doubling the amplitude is four times the power. Perceived loudness, what your ears actually report, only roughly doubles at around 10 dB. All three are true at the same time; they simply measure different things. When someone says a change is "3 dB louder" they usually mean the power doubled, not that it sounds twice as loud, because it does not.
| Change | What it does to the signal | How it tends to sound |
|---|---|---|
| +1 dB | a small nudge in level | about the smallest change most people can notice |
| +3 dB | doubles the power | a modest step, easy to underestimate |
| +6 dB | doubles the amplitude, the height of the waveform | clearly louder |
| +10 dB | ten times the power | heard as roughly twice as loud |
| -6 dB | halves the amplitude | clearly quieter |
| -10 dB | one tenth the power | heard as roughly half as loud |
On a fader or a gain knob these numbers become your intuition. Pulling a channel down 6 dB halves its amplitude and is an obvious, decisive move. Nudging something 1 dB is a fine adjustment you can only just hear. The same scale runs the other way too: because your meters read in decibels below the digital ceiling, they also tell you how much room you have left before clipping.
+3 dB doubles the power but is only a small step to your ears. +6 dB doubles the amplitude. It takes about +10 dB before something sounds roughly twice as loud. Power, amplitude and loudness are three different measures, and mixing them up is where most decibel confusion begins.
They are all decibels measured against a fixed reference, which is what turns the ratio into a real level. dBFS is the digital scale, dBu and dBV are analog voltage references, and dB SPL measures loudness in the air. The decibel part behaves the same in each; only the zero point changes.
dBFS means decibels relative to full scale, and it is the scale your DAW meters almost always use. Here 0 dBFS is the ceiling, the loudest level a digital signal can represent, and everything else sits below it as a negative number. A peak at -6 dBFS is 6 dB below the ceiling with 6 dB to spare. Nothing sits above 0 dBFS, so cross it and the signal clips. How much room you keep under that ceiling is exactly what our guide on headroom is about.
dBu and dBV are analog references, used for the voltage levels running through hardware and cables. dBu is measured against about 0.775 volts and dBV against 1 volt, so they describe how hot an analog signal is inside a mixer, an interface or an outboard unit. You meet them mostly in equipment specifications rather than while mixing in the box, but they are why a piece of gear is rated to handle a certain level.
dB SPL, sound pressure level, is the one that measures real loudness in the air, counted from about the quietest sound a person can hear. Ordinary conversation sits around 60 dB SPL, and sustained exposure much above 85 dB SPL starts to put your hearing at risk over time. This is what a sound level meter reads and the number that matters for protecting your ears, and it is separate from your DAW meters, which are in dBFS. The loudness of a finished track for streaming is judged in yet another unit again, LUFS, which our guide on how loud a master should be covers.
dBFS counts down from the digital ceiling, dBu and dBV count from fixed voltages, and dB SPL counts up from the threshold of hearing. Because the zero points differ, you cannot convert one into another without knowing the gear and the monitoring level in between. The -6 on your DAW meter and the 85 on a room meter are both decibels, but they are not measuring the same thing.
Decibels are a reading, not the work. They start to matter once you have something playing to point them at, and writing and recording that is the harder job. The scale on this page takes an afternoon to learn; having music worth metering is the part that counts.
The Collection is our three instruments together, ARGISH, SILT and REHEAT, with three separate licence keys. This page is about reading levels in decibels, and that reading stays simple when what goes in is already sensible: our instruments output at clean, sensible levels, so the numbers on your meters stay easy to reason about from the very first track. ARGISH is a self-playing drone synth, SILT is a tape-loop instrument, and REHEAT writes acid lines, and whatever you make with them is yours to release. Each one ships as AU, VST3, AAX and a standalone app on macOS, signed and notarized, and a VST3 on Windows.
You can hear one free in your browser first, no install and no account, then decide.
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