Engine area has a rattling-knocking noise. It is getting louder and louder. At my last oil change, they said it could be the tensioner pulley going bad. Noise is not constant so I dont see it as an engine problem.

Any suggestions?

 

Make like a stethoscope by putting a tube in your ear. Without damaging your fingers holding the other end, put the tube near the engine and try to localize the the point of sound. Usually you can find the exact location of the sound if it's tensioner pulley.