Continual audio alarm - Phillips Whirlpool 18M 50/50?

Completely defrosted it. No food put back in, so empty except for ice tray that has frozen within 4 hours, so its cold in freezer now. BUT audio alarm, at centre/base of freezer unit keeps going continually (except when door is opened). Have set thermostat in upper fridge to max/5. How can we stop alarm or will it go off automatically when it reaches the max/5 temp in the freezer? It is in our kitchen driving us MAD. PLEASE CAN SOMEONE ADVISE US? Thank you.