How to insert silence into audio track?

I want to insert a silence into the audio track, to match the duration of the black which I have inserted into the video track. I could simply leave a gap in the audio, but that is too prone to accidental changes.
Is there a simple way to insert silence of a fixed duration (to be decided by me) in the audio track?

File > Open Other > Color. Color clips are silent, and you can put clips with video or imagery into an audio track. Audio tracks simply hide video and provide a simple organizational tool.
Otherwise, no, there is not way to make a duration of a clip fixed and unmodifiable.

What if you lock the track once you’ve created the gap?

In some cases that works but not if I’m working on audio at some other location on the timeline.

Thanks! Who knew?