Since we so often rescale our signals to suit various needs (avoiding
overflow, reducing quantization noise, making a nicer plot, etc.),
there seems to be little point in worrying about what the dB reference
is--we simply choose it implicitly when we rescale to obtain signal
values in the range we want to see. In particular, dB relative
to full scale (
), abbreviated
dBFS, is perhaps the most commonly used case in the digital
audio world. Thus, 0
dBFS means maximum amplitude, and typical
amplitude levels are negative in dBFS. In addition, there are a few
specific dB scales that are worth knowing about, mostly for historical
reasons, such as to understand VU meters in vintage audio gear and
virtual analog plugins.