Pro Tools 101_ An Introduction to Pro Tools 11 ( PDFDrive )

Most professional digital recording devices today offer sampling rates of
44.1 kHz and 48 kHz or higher. The digital information on an audio CD is
stored at a standard sample rate of 44.1 kHz.
How Bit Depth Affects Amplitude Resolution
The useful dynamic range of speech and music is generally considered to be
from 40 to 105 dB. To capture this range, an A/D converter must be able to
accurately represent differences in amplitude of at least 65 dB; stated another
way, it must have a minimum 65-dB dynamic range. The relative amplitude
(or loudness) of a sample is captured through a process known as
quantization. This simply means that each sample is quantified (assigned) to
the closest available amplitude value.
Computers use binary digits called bits (0s or 1s) to quantify each sample
that is taken. The number of bits used to define a value is referred to as the
binary word length. The range of values represented by a binary word is
defined by the binary word length and is equal to 2 to the n th power (2 n ),
where n is the number of bits in the binary word.
Tip: The binary word length is also commonly referred to as the bit
depth.
A 4-bit binary word is able to represent 16 different numeric values (2 4 );
used by an A/D converter to capture amplitude, this 4-bit binary word would
record the amplitude continuum using 16 discrete amplitude levels. By
contrast, a 16-bit digital word could define 65,536 discrete amplitude levels
(2 16 ), and a 24-bit digital word could define 16,777,216 discrete amplitude
levels (2 24 ).
As such, larger binary words are able to quantify variations in amplitude
with much greater accuracy. Therefore, a 24-bit audio file will always more
accurately reflect the dynamic range of the original sound than its 16-bit
counterpart.
Tip: 32-bit floating-point files use only 23 bits to represent discrete
amplitude levels, with one bit reserved for the sign (the same as 24-
bit files). The 8 additional bits provide exponent biasing and allow for
headroom above full-scale 24-bit audio.
A very general rule of thumb can be used to calculate the dynamic range
capability of an A/D system. By multiplying the word size by six, you can