Level, amplitude and decibels
Amplitude describes the size of a signal’s change from its centre. A DAW meter reports a level using a chosen scale and reference; audio meters commonly use decibels (dB). A decibel expresses a ratio logarithmically, so equal numerical steps do not represent equal linear changes in amplitude. The meaning of a reading depends on what is measured and the reference used.
Keep three controls distinct: a track fader changes a signal in the project, a master/output control affects the signal leaving the DAW, and a headphone/speaker control affects your monitoring. Their exact order and meter points vary between applications. A track meter is not a measurement of how loud sound reaches your ears.
Amplitude describes signal variation around a centre
Two schematic signals repeat at the same rate but differ in the size of their variation around the centre line.
Text equivalent
Both traces show the same number of cycles in the same interval. The upper trace varies less above and below its centre line; the lower trace varies more. No meter position, numeric level or listening loudness is represented.
LISTEN
Play the same short sound at two comfortable playback levels. Listen for how loud it feels, without making either level harsh. If the level difference is hard to perceive, use the change in the relevant DAW meter as supplementary evidence; it describes a signal point, not your room or listening level.
TRY
Move a track fader modestly while observing its meter, then return it. Adjust the monitoring/output control separately. Notice which meter changes and which does not. Reduce playback before deliberately exaggerated level tests, and restore it cautiously. Do not chase a number from another project or treat a peak meter as a universal loudness recommendation.
APPLY
Choose a comfortable monitoring level and note which control sets it in your current setup. In your brief, record one level observation with its context (for example, “track meter peaks lower after the fader change”), not as a target. What changed in the signal? What changed in monitoring? Why does that distinction matter?
Source: NIST Guide to the SI, Chapter 8 defines decibel as a logarithmic ratio unit and distinguishes level quantities and reference values.
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