Reference Guide

794 Editing audio
Advanced audio processing
Removing DC offset
Some models of audio hardware produce a DC offset while recording, which is caused by electrical
mismatches between the audio hardware and the input device or instrument. Although
imperceptible, DC offset may cause problems in further stages of sound processing.
To remove DC offset from existing audio
1. Select the audio data and choose Process > Apply Effect > Remove DC Offset. This launches
the Remove DC Offset dialog box.
2. Choose from the following options, and click OK:
• DC Offset Threshold (dB). You can set a minimum dB threshold. If the analyzed DC offset
is below this value, no removal takes place.
• Analyze Left Channel (dB) and Right Channel (dB). This field displays the DC offset
separately for the left and right channels. Press the Audition button to update the display.
• Compute DC Offset from first 5 seconds only. To speed processing, select the Compute
DC offset from first 5 seconds only check box. Only the first five seconds of a sound file will be
analyzed when measuring the DC offset. The only time that five seconds is not sufficient is if a
long fade-in or mute has been applied at the beginning of the file.
To remove DC offset during recording
1. Go to Process > Apply Effect > Remove DC Offset to open the Remove DC Offset dialog
box.
2. In the DC Offset Threshold (dB) field, set a minimum dB threshold, and click OK to close the
dialog box. If the analyzed DC offset is below this value, no removal takes place.
3. Go to Edit > Preferences > Audio - Playback and Recording, select the Remove DC Offset
During Recording check box, and click OK.
This option filters out DC Offset according to the threshold value that you set in the Remove DC
Offset dialog box.
Applying fades and crossfades offline
SONAR provides several commands for applying gradual volume changes to audio data. The first
command, Fade/Envelope, lets you fade-in or fade-out, and lets you choose an envelope, a curve
that governs the rate of the fade. The starting envelope can be linear (straight line), exponential, or
inverse exponential. You can change the shape of the envelope before applying the fade.
The envelope in the Fade/Envelope dialog box is made of one or more connected line segments
(the linear curves are a single segment, the exponential curves consist of nine segments each).
Note: An easy way to spot DC offset is to zoom in to a silent section of your sound file. If the
silent waveform matches the centerline in the waveform display, your file does not contain DC
offset.