Rebel mic refuses do shut u... (weird thing)

I not just turn the slider off, but I also pressed the button that make a "smal forbbiden like road signal" (red transversal strip inside a circle) over the drawing of a speaker, to try to cut 100% the sound, but didn't work.
The webcam configuration don't allow me to complete cut the sound, but just reduce the sensibility.

The only thing that last it's to go to COntrol Panel and disactevate the camera.
Well I did it, and I still can hear the mic, and if I speak close it still make sound. 

I suspect some wire near the mic plug imput on the PC it's "leaking" some electricity and invading somehow the speaker imput connection. Maybe some tiny metal wire touching the cabinet's steel near the other imput plug.

Anyway computers always cursed me in all ways. I can't remamber a single tme where something runned fine at first try.

Check if you have the output right.. if it applies to your system - There's maybe "HeadPHONE" out and "HeadSET" out? If you're using the headset plug, it's maybe keeping the camera mic alive (glitching because it's confusing its native driver for the camera's mic driver or such-like issue).

In control panel/sound, in the "communications tab" "When Windows detects communications activity" try setting to "Do nothing" - maybe it's set to something like "Reduce the volume of other sounds by 50%".

I'm not saying your "volume" is at issue - but - because a 'communications' service attached to the cam's mic may be interrupting, causing other drivers to hang and just stay open.

Only other thing coming to mind right now is, maybe that cheap cam has drivers designed for XP or something's just not working as intended for some hardware-level reason.

If the cam is old, maybe try running it in 'compatibility mode' for say XP? (maybe a reboot after making the setting) - that way it might be fenced off from causing such issues.

Or/and - check if it runs at start up - disable that if you can then reboot.

Hope something here helps.

It's the only mic installed. No other device with mics. I tried a month ago to test phone (3 rings plug) that also work as a mic, but the sensibility was so low that the problem wasn't noticeable when I had cut the mic's sound function in the panel.

I'm almost sure it's electric signal leaking, since the mic and phone plug are vewry close.

It's funny, but not as funny as in one occasion I was capturing radio signals, hearing the radio (amateur probably) in my piano speakers, despite it had no kind of radio receiver to sintonization. I asked a PC tecnician and he told it was impossible, but another one, more familiar with sound devices, told me it also have happened with hin when soneone with amateus transmissor radio was near his home. 
And that was how I found how the legends of superstition fools who claims God talk with them, in their TVs or sound systems, happens.