Background hum when recording in Audacity

I’m getting a background hum when recording in Audacity. It’s not present when using the same microphone with other programs, such as Jitsi. How do I get rid of it? Filtering after the fact only reduces the hum a little, I’d like it to not be there from the start.

Record a sound test and post it on the forum.

http://www.kozco.com/tech/audacity/TestClip/Record_A_Clip.html

Look at the blue links. They’re very short.

Koz