Frequency State / Music Production Reference Library · Volume 1
The decibel is a logarithmic way of expressing a ratio, but different audio scales use different references. The distinctions between dB SPL, dBFS and a simple gain change are essential when recording, mixing and monitoring.
In music production, it is used to describe:
Decibels can describe changes in electrical signal level or measured sound pressure, depending on the reference. A dB number alone does not reveal acoustic loudness; the unit must be interpreted in context.
Rather than measuring sound in absolute terms, the decibel expresses relative differences between levels.
What the Decibel Measures
Decibels describe ratios. For power the calculation is 10 × log₁₀(P₂/P₁); for voltage or sound-pressure amplitudes under comparable conditions it is 20 × log₁₀(A₂/A₁). Around +6 dB doubles an amplitude, while +3 dB doubles power. The reference and quantity must be identified before the numbers make sense.
The decibel compares one value to another.
In audio, this usually means:
A decibel gives the ratio between a measured quantity and a defined reference, or between two levels. It is equally useful for describing an increase or decrease in gain through a processing chain.
This makes it useful for describing changes in sound level rather than fixed values.
Decibels and Loudness
A given decibel increase does not translate into a fixed increase in perceived loudness in every situation. Our ears respond differently across frequencies, and listening level, duration and spectral balance affect the impression. Digital signal meters do not measure the sound-pressure level at your ears.
In practical terms:
Higher sound-pressure levels will generally seem louder when other conditions are similar, but perceived loudness also depends on frequency, duration and spectral balance. An increase of a given number of dB does not have one universal perceptual effect.
However, the scale is not linear.
A small numerical change in decibels can represent a significant change in perceived loudness.
Common Reference Points
dB SPL expresses sound pressure relative to 20 micropascals in air. dBFS compares a digital sample with full scale, where 0 dBFS is the sample ceiling in a fixed-point representation. A value of −12 dBFS is not equivalent to 12 dB SPL. Sound-level measurements may use different weightings and averaging periods.
In digital audio:
In fixed-point digital audio, 0 dBFS represents full-scale sample amplitude. Digital samples cannot exceed that representation without clipping or limiting, although many floating-point DAWs can temporarily represent signals above nominal full scale internally. This distinction is crucial when interpreting meters.
Typical working ranges:
Engineers sometimes use −18 dBFS as a calibration reference for particular analogue-modelled plugins or level conventions, not as a mandatory peak target for every track. A peak near −6 dBFS leaves less margin than one at −18 dBFS, but neither number is automatically correct without considering the signal chain.
The Logarithmic Scale
The decibel scale is logarithmic, not linear.
This means:
A gain change of approximately +6 dB doubles voltage or sample amplitude, while −6 dB approximately halves it. This should not be confused with power ratios, where a change of approximately 3 dB represents doubling or halving power.
This reflects how human hearing perceives loudness.
Decibels in Music Production
Floating-point DAW processing can tolerate internal levels above nominal 0 dBFS in some stages, but converters, fixed-point exports and individual plugins can still clip or distort. Leave sensible headroom through the signal path. True-peak meters estimate peaks between samples, making them useful at the final delivery stage.
You will encounter decibels when:
In a DAW, decibels appear on track faders, input meters, gain controls, equalisation bands and compressor thresholds. Each display describes a particular part of the signal path, and not every dB reading is referenced to the same zero.
Understanding dB helps you make controlled and consistent adjustments.
Gain and Level
Set a microphone preamp while the performer plays or sings the loudest expected passage. You want clean input with room for unexpected transients, not a meter driven permanently near the maximum. Read Gain Staging Fundamentals for a complete signal-chain example.
In a DAW, gain controls are measured in decibels.
For example:
Raising gain increases the signal level into the next processing stage; reducing it lowers that level. Gain before a nonlinear effect can change its distortion character, whereas gain after the effect may change only the output level.
Proper level management is essential to avoid distortion and maintain clarity.
Use the decibel explorer below to hear and see how level changes affect a signal.
In digital audio, 0 dB is the maximum available level before clipping. Negative dB values reduce the signal, often by much more than the numbers first suggest.
Why the Decibel Matters
Understanding decibels allows you to:
Understanding the decibel scale makes it easier to leave headroom, detect clipping, maintain sensible balance and recognise when dynamic range is being compressed. It also helps distinguish a true change of level from an apparently louder frequency balance.
It is a fundamental concept in both recording and mixing.
Related Topics
Continue with Frequency, Amplitude and Waveforms, Gain Staging Fundamentals and Sample Rate and Bit Depth Explained.
This article is part of the Music Production Reference Library, organised into volumes covering sound, theory, production, and release.
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Next chapter: digital vs analogue audio. Return to the Music Production Reference Library.