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.

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.

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.