If your Mirc is beeping when someone joins a channel, connects to koach.com or parts a channel, here is a way to fix that.
1] go to Tools, select sounds, you'll see two dropdowns at the top right, first, click on the top one, titled "On Event, Play Sound" search the drop down for the event you want to stop.
2] Go to the lower dropdown, select "No Sound". click OK.
I have everything set to 'No Sound" and this may ne what you need to do, as well.