I had a recent experience with a timing chain defect (stiff link) and the symptom was a cyclical/periodic noise with a repetition rate about 1Hz. Yours seems to have that repetition rate also. That is about the time it takes for the chain to go around once at idle. There is nothing else on the engine that revolves at that speed (at least not on my engine). Do take the belt off to make sure.

In my case I had to change the chain. Mine is a M111.

Good luck

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra