I have used it, then it made a photos with no sound. No an unpleasant sound has appeared (by itself) when it counts to three. How to get rid of that? On the menu (upper right corner where are apple is) there's no preferences or settings and so also with a right click.. What to do..?

If I take a picture with Photo Booth it makes a camera-click sound when the photo is taken -- it's not particularly unpleasant, and doesn't seem like a big deal to me. There doesn't appear to be any way to turn it off. I suppose you could probably turn off all alert sounds, but some of them are useful/necessary. It looks like you'll just have to live with it..