Insert Silence

To insert silence open Edit/Insert Silence menu. In the window that will show up choose the necessary duration of silence.

This function generates silence (entered in seconds) from the current playback cursor position, pushing any following audio back in time, and thereby lengthening the duration of the waveform.

With the help of this function you can also replace any selected area. Unlike deleting, or cutting, a selection (which splices the surrounding material together), Silence leaves the duration of the selection intact, and simply zeros the amplitude within it.