Special Effects - Adobe AUDITION 3 User Manual

Special effects

Convolution effect (Edit View only)
The Special > Convolution effect multiplies selected audio samples by samples in an impulse (.imp) file. Impulses
function like amplitude maps. For example, if you apply an impulse of a single full-volume sample, the selected audio
data will be unchanged. Should the impulse be at half volume, however, the selected audio data will be reduced to
half volume. If several such impulses occur over time, each with descending amplitude, the selected audio data will
gradually and rhythmically become lower in volume.
This effect essentially applies the sound of one audio file to another. The result can resemble filtering, echoing, phase
shifting, or any combination of these effects. For example, modeling someone saying "Hey" with a drum track (short,
full-spectrum sounds such as snares work best) results in the drums saying "Hey" each time they are hit. You can
build impulses from scratch by specifying how to filter the audio and what delay rate to apply, or by copying audio
directly from a waveform.
With the proper impulses, you can simulate any reverberant space. For example, if you create a stereo impulse in your
favorite cathedral, and you convolute it with any mono audio, the result sounds as if that audio were played in that
cathedral. (To create such an impulse, you would place a stereo microphone in the cathedral, generate a loud
impulsive noise like a hand clap, and record the noise and reverberation. If you apply the resulting impulse to other
audio, it sounds as though it was generated at the location of the hand clap relative to the microphone.)
To get a feel for the Convolution effect, open and play with some of the sample impulse files in the Imps folder in the
Adobe Audition program folder.
Use convolution to sustain a sound for any length of time. For example, the sound of a person singing "aaaaaah" for
one second can be turned into thousands of people singing "aaaaaah" for any length of time by using dynamically
expanded white noise. Also, to send any portion of an unprocessed, dry signal back out, simply add a full spectrum echo
at 0 milliseconds. The Left and Right volume percentages are the resulting volume of the dry signal in the left and right
channels.
See also
"About process effects" on page 104
"Apply individual effects in Edit View" on page 107
Convolution options
Opens a previously saved impulse (such as the ones that come with Adobe Audition). The sample rate of an
Load
impulse affects the outcome of convolution. For example, if an impulse is created at 44100 Hz, and it is later reopened
and used on a 22050 Hz file, everything is stretched out 2:1. Filtered echoes are at half the frequency, and delays are
twice as long.
Saves an impulse.
Save
Clears an impulse completely.
Clear
Specifies how the impulse works with mono or stereo data. Mono impulses work with either mono or
Mono, Stereo
stereo data (the left and right channels are convoluted with the same impulse). Stereo impulses convolute the left and
right channels separately.
Sets the scaling factor to use when you add a highlighted selection to an impulse to determine its volume.
Scaled By
By default, Adobe Audition provides a good starting value. Lower this value to increase the amplitude of the impulse.
Note that any audio can be added to an impulse directly.
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