4

594 Part VIII Audio Mixing
Sample Rate
The sample rate is the number of times an analog signal is measured—or sampled—
per second. You can also think of the sample rate as the number of electronic
snapshots made of the sound wave per second. Higher sample rates result in higher
sound quality because the analog waveform is more closely approximated by the
discrete samples. Which sample rate you choose to work with depends on the source
material you’re working with, the capabilities of your audio interface, and the final
destination of your audio.
For years, the digital audio sample rate standards have been 44,100 Hz (44.1 kHz) and
48 kHz. However, as technology improves, 96 kHz and even 192 kHz sample rates are
becoming common.
Bit Depth
Unlike analog signals, which have an infinite range of volume levels, digital audio
samples use binary numbers (bits) to represent the strength of each audio sample. The
accuracy of each sample is determined by its bit depth. Higher bit depths mean your
audio signal is more accurately represented when it is sampled. Most digital audio
systems use a minimum of 16 bits per sample, which can represent 65,536 possible
levels (24-bit samples can represent over 16 million possible levels).
To better understand bit depth, think of each digital audio sample as a ladder with
equally spaced rungs that climb from silence to full volume. Each rung on the ladder is
a possible volume that a sample can represent, while the spaces between rungs are
in-between volumes that a sample cannot represent.
Audio sample rates When used
8 kHz–22.225 kHz These lower sample rates are used strictly for multimedia files.
32 kHz 32 kHz is generally used with 12-bit audio on DV.
44.1 kHz This sample rate is used for music CDs and some DAT recorders.
48 kHz Almost all digital video formats use this sample rate.
88.2 kHz A multiple of 44.1 kHz. This is useful for high-resolution audio that
needs to be compatible with 44.1 kHz. For example, if you eventually
plan to burn an audio CD, this sample rate is a good choice.
96 kHz A multiple of 48 kHz. This is becoming the professional standard for
audio post-production and music recording.
192 kHz A multiple of 48 and 96 kHz, this is a very high-resolution sample
rate used mostly for professional music recording and mastering.