dBFS

A potential for ambiguity exists when assigning a level on the dBFS scale to a waveform rather than to a specific amplitude, because some engineers follow the mathematical definition of RMS, which for sinusoidal signals is 3 dB below the peak value, while others choose the reference level so that RMS and peak measurements of a sine wave produce the same result.

[8][9][10][11][12] The unit dB FS or dBFS is defined in AES Standard AES17-1998,[13] IEC 61606,[14] and ITU-T Recs.

[21] This convention is the basis for the ITU's LUFS loudness unit,[23] and is also used in Sound Forge[10] and Euphonix meters,[24] and Analog Devices digital microphone specs[25] (though referred to as "dBFS").

The measured dynamic range (DR) of a digital system is the ratio of the full scale signal level to the RMS noise floor.

)[26] As the dynamic range is measured relative to the RMS level of a full scale sine wave, the dynamic range and the level of this quantization noise in dBFS can both be estimated with the same formula (though with reversed sign): The value of n equals the resolution of the system in bits or the resolution of the system minus 1 bit (the measure error).

For example, a 16-bit system has a theoretical minimum noise floor of −98.09 dBFS relative to a full-scale sine wave: In any real converter, dither is added to the signal before sampling.