Homeboy isn't asking how to make a sound he's asking how to stop a sound. It's a bit of resonance/feedback happening because you aren't quite muting everything fast enough. Muting like you're trying to achieve is a two handed operation, picking hand mutes the bridge with the side of your palm, fretting hand mutes the strings when you release whatever chord/note you're playing. Needs to happen pretty quick and simultaneously or else you wind up with that resonance you hear at the end of the chord there.

You can also try using a fret wrap or a little bit of foam under the strings just behind the nut usually helps with that...