pavucontrol shows input coming from unplugged device

[Skaperen]

in the tab section "Input Devices", pavucontrol shows a menu with a choice of 2 microphone inputs. one of the includes "(unplugged)" suggesting that it is the microphone input jack on the side of the laptop. however, when i select it, unmute it, and adjust the level up. it shows audio activity. it can hear something. it "hears" the music i am currently playing which could get in there many different ways. is it really hearing something acoustically or is there some kind of coupled leakage in the laptop audio electronics, or some issue in PulseAudio or some software bug?

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[HermanAB]

Note that the hardware of a particular computer model is not necessarily built exactly in accordance with the general convention...