You can use the Noise Gate plug-in to remove signals below a specified threshold. This effect is used to remove noise from silent breaks in a sound file.
Select the sound data you want to process. If no data is selected, the synthesis will be inserted at the cursor position. For more information, see "Selecting data using the mouse."
Choose Process > Noise Gate. The Noise Gate dialog is displayed.
Choose a setting from the Preset drop-down list, or adjust the controls as desired:
Drag the Threshold fader to set the level below which signals will be removed. Noise levels are typically near –40 dB.
Drag the Attack slider to set the time it takes the gain of the gate to change from zero to one once the level rises above the threshold.
A low Attack time preserves percussive attacks. Higher values cause sounds to slowly swell up in volume.
Drag the Release slider to set the time it takes the gain of the gate to change from one to zero once the level falls below the threshold.
A long Release time preserves natural-sounding decays; otherwise long decays will be cut off.
Click the Process button