Turn on slow keys
Turn on slow keys if you would like there to be a delay between pressing a key and that letter being displayed on the screen. This means that you have to hold down each key you want to type for a little while before it appears. Use slow keys if you accidentally press several keys at a time when you type, or if you find it difficult to press the right key on the keyboard first time.
Click the icon at the very right of the menu bar and select System Settings.
Open Universal Access and select the Typing tab.
Switch Slow Keys on.
Use the Acceptance delay slider to control how long you have to hold a key down for it to register.
You can have your computer make a sound when you press a key, when a key press is accepted, or when a key press is rejected because you didn't hold the key down long enough.