Yes, you can turn the keyboard typing sounds off by doing the following.
Exit kiosk mode by tapping all four corners in a clockwise fashion, starting with the top left. Enter the password 8026. This will close the kiosk application and bring you to the windows login page.
Slide up on the screen to bring open the login prompt, and click on XTL Admin user. Enter in password XTLKiosk80! and hit enter to log in.
Tap on the Windows Startup Menu icon on the bottom left of the screen
Tap on Settings > System > Devices
Under 'Touch Keyboard', tap on 'Play Key Sounds as I Type' to toggle OFF