Decibel (dB & dBFS) Reference
What decibel changes actually mean — the amplitude, power and loudness rules of thumb, and how the digital dBFS scale relates to clipping and headroom.
| Change | Meaning |
|---|---|
| +10 dB | ≈ perceived as 'twice as loud' |
| +6 dB | ≈ double the amplitude (voltage) |
| +3 dB | ≈ double the power |
| 0 dB | reference level — no change |
| −3 dB | half the power |
| −6 dB | half the amplitude |
| −10 dB | ≈ perceived as 'half as loud' |
Digital levels (dBFS)
| Level | Meaning |
|---|---|
| 0 dBFS | Digital full scale — the loudest possible sample; anything higher clips. |
| −12 to −18 dBFS | A common average level to mix at, leaving healthy headroom. |
| −60 dBFS | Very quiet — near the noise floor of most recordings. |
| −∞ dBFS | Digital silence. |
Decibels are logarithmic and relative: +6 dB doubles amplitude, +3 dB doubles power, and about +10 dB sounds twice as loud. dBFS is referenced to digital full scale, so values are at or below 0.
How to read this
Decibels are always a ratio, and the reference point is what the suffix tells you.
amplitude: dB = 20 × log10(new / old)
power: dB = 10 × log10(new / old)
dBFS relative to digital full scale (always ≤ 0)
dBu relative to 0.775 V — analogue line level
dBV relative to 1 V
dB SPL relative to the threshold of hearingNotes & gotchas
- +6 dB doubles amplitude; +10 dB sounds twice as loud. Two different things, routinely confused.
- −3 dB is half the power, which is why filters are specified at that point.
- dBFS is negative by definition. 0 dBFS is the ceiling; aim well below it and leave headroom.
- 1 dB is about the smallest change most people reliably notice on sustained material.
- Comparing dBFS and dB SPL directly is meaningless — different references, no fixed relationship without calibration.