Sounds like you're shifting focus from the search box to a different area with a tab or something. If the cursor moves out of the search box, and you try and type, you would hear a ding. Are you hitting tab or could your keyboard be damaged and when you press a key close to the side of the keyboard where the tab key is, does the cursor move? Put the cursor in the search box and only type a few letters on the right side of the keyboard and see what happens. Then try numbers, etc and move yourself around the keyboard to see if a specific area is triggering it.
Most keyboards have keys "grouped" together on 1 circuit bunch, so any keypress in that "group" can trigger any other key in the group if it's been damaged.