Unrelated Noise on second track

I downloaded Audacity, and started recording a concert on Radio 3 of piano music. I couldn’t get rid of a second track of rustling and bumping around as if someone was moving the mic in some other setting. It is on the recording - and I don’t know how to get rid of it - or avoid it continuing when I record anything else from the radio. Help much appreciated.

Turn off your computer microphone.