Get your alternator clutch pulley checked. I have a similar issue where I had replaced the tensioner and belt, but the noise came back 7-8months later. Realised that the clutch pulley was jammed. This causes extra stress on the tensioner pulley and causes it to wear prematurely. For me the sound is a very pronounced intermittent tappett noise in the cabin. Kinda subsides in neutral and under a little load