If you rev the engine does the noise go an come back when you De accelerate if so i can 100% guarantee that it is the decoupledr pulley on the alternator. You can buy these on line.. I changed the tensioner first DIDNT NEED IT THOUGH... that seemed to work but not for long a week maybe....DECOUPLER PULLEY also called a clutch pulleyhttps://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F263281585361