Buzzing only during speech

Windows 10, Audacity 2.0.6.

I am recording speech, but even after I use noise removal, I still get a kind of low buzzing/rumbling sound in the background, but only while I am speaking. In the silent parts, there is nothing but complete silence. Does anyone know why?

Post some of the work before you do anything to it. Raw capture clip.

Use this as a general guide.