So. You're having a good time on your favourite Garry's Mod server. But whats this? An iratating noise? It sounds like some form of prepubescent humanoid. Or possibly some tasteless music. Looks like you've got a Mic Spammer. Look to the bottom right of the screen find see the cause. You should see one or two names down at the bottom. These are the names of those unwanted noise sources.

Now that you've aquired the name of the offending party, rember it. Press and hold your TAB key to open up the player list. Here you should see the names of every player connected to the server. The Mic Spammer's name should be among these. To the far right of the bar that contains their name, is a small speaker icon. Clicking the icon will change the icon to a small speaker with a red slash through it. Congratulations. You have successfully muted someone. To undo the mute, simply click the icon again.