Full Scale (dB FS) Versus Full Scale

Full Scale (dB FS) Versus Full Scale

There exist two competing references for decibels in digital audio signals. One convention references dB FS to the largest positive and negative amplitude values obtainable from a given integer sample word size – e.g., ± 32768 for 16 bits – normalized to a range of ± 1.0, such that 0 dB FS denotes the maximum possible digital amplitude value. We will refer to this as “normalized Full Scale.” 

The second convention, preferred by the Audio Engineering Society (AES), references 0 dB FS to the RMS value of a full-scale peak-to-peak sinewave (i.e., 0.7071 normalized Full Scale, rather than 1.0). We will call this “AES Full Scale”. In Smaart, Full Scale decibel values are always referenced to normalized Full Scale, meaning that the RMS magnitude of a full-scale digital sinewave is -3.01 dB FS.

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