Digital Sound & Music: Concepts, Applications, & Science, Chapter 5, last updated 6/25/2013
15
Figure 5.16 Dynamic range shown in dBFS
The equation for converting between dB and dBFS is given in Equation 5.4
For n-bit samples, decibels-full-scale (dBFS) is defined as follows:
( )
where is an integer sample value between 0 and .
Equation 5.4
Generally, computer-based sample editors allow you to select how you want the vertical axis
labeled, with choices including sample values, percentage, values normalized between 1 and 1,
and dBFS.
Chapter 7 goes into more depth about dynamics processing, the adjustment of dynamic
range of an already-digitized sound clip.
5.1.2.5 Audio Dithering and Noise Shaping
It’s possible to take an already-recorded audio file and reduce its bit depth. In fact, this is
commonly done. Many audio engineers keep their audio files at 24 bits while they’re working
on them, and reduce the bit depth to 16 bits when they’re finished processing the files or ready to
burn to an audio CD. The advantage of this method is that when the bit depth is higher, less
error is introduced by processing steps like normalization or adjustment of dynamics. Because
of this advantage, even if you choose a bit depth of 16 from the start, your audio processing
system may be using 24 bits (or an even higher bit depth) behind the scenes anyway during
processing, as is the case with Pro Tools.
Audio dithering is a method to reduce the quantization error introduced by a low bit
depth. Audio dithering can be used by an ADC when quantization is initially done, or it can be
used on an already-quantized audio file when bit depth is being reduced. Oddly enough,
Previous Page Next Page