Hi I have a focus st225 2006 could anyone tell me why on tick over there is a whine is this normal car runs fine many thanks

 

I had this I first noticed it turning left or right eventually it was there all the time. Then it started to flash on the abs and stability warning again when turning left or right. Then the power steering warning came on and It cut out completely. Wouldn’t turn over flat battery. Would start and run with a jump pack. Mine was the alternator and it’s a twat to change if you still have the standard air box set up