Amplitude Processing
Amplitude processing includes
- Amplification - increases or decreases the volume of a
waveform or selection. May be constant amplification (in which the same amount
of gain change is applied throughout the audio file) or fade (in which gain
varies over the course of the waveform or selection)
- Channel mixing - create new stereo mixes using the existing
right and left channels as input sources. By recombining and inverting the
channels some very cool stereo imagining effects created. By adding the left
channel with the inverse of the right, and place the result into both channels
on music where the vocals are equally loud on both channels, the vocals will
disappear, or come close to disappearing.
Dynamics processing - varies the output level of a waveform,
based on its input level. We may limit or compress the dynamic range of a
sample so that the perceived loudness is kept below a defined limit, or so
that the waveform's overall dynamic range is kept at roughly the same level.
We can also expand or gate the signal so that low-level signals are reduced
in level, thereby increasing the perceived dynamic range, or so that signals
that fall below a certain threshold [i.e. noise] are eliminated.
- Envelope processing - controls which parts of the wave
are amplified, and by how much from a graphic of the motification to be made
to the amplitude to create more realistic sounding instruments and effects
- Hard limiting - drastically attenuate audio above a certain
threshold, while leaving all audio samples below that threshold alone. Permits
amplification of a piece of audio well beyond where it would normally clip.
Softens the regions that would otherwise be clipping, ensuring that the maximum
sample amplitude does not go above the given limit. Especially usefull for
an audio sample which has a few places where the audio is clipping, avoiding
normalizing down the entire waveform (which would reduce the volume of it).
Hard Limiting will bring down only those portions that are clipping.
- Normalization - Amplifies the selection to within the specified
percentage of the maximum level to achieve the greatest amount of amplification
that will not result in clipping.
- Pan/Expand - pan, or shift, the center channel of a stereo
waveform expanding or narrowing the stereo separation of the left and right
channels. Center Channel Panning makes use of the “surround” and
“center” channels of a stereo recording, where the “surround”
channel is the difference (L-R) of the two original channels, and “center”
is the sum (L+R) of them. Think of a stereo recording as having 4 channels
(left, right, middle, surround), and this effect will pan these channels around.
This type of panning can provide realism to original stereo recordings.
