07 Acura tl tapping noise

recently I started hearing this inconsistent tapping noise from inside the car. after looking at videos I was convinced it could be valve noise but the noise is not consistent and it happens after the engine is warm and audible only on idle and very little when the hood is open. from the video I provided you can hear the noise suddenly start and then stop, after I increased the rpm a little and come back and then go away after turning on the AC and then suddenly come back up but a little louder. the noise is confusing because from the inside it sounds like it is coming from the engine, but when I listen from the outside and towards the back of the engine you can barely hear anything until you put your head really in there. any ideas what it could be? (07 Acura TL 3.2L)