It does sound like something mechanical.

I once had a Toyota 4runner that made that noise. It had a head gasket replaced about a year beforehand and it turned out the mechanic had lost one of the screws from the cambelt cover. It had gone through the middle of the cambelt and the noise was it hitting the cover as it went around!

I'm not suggesting that's what's going on here, but the frequency is similar so I would be checking belts and pulleys. If it's nothing exposed, check the crankshaft pulley too. When was your cambelt last done?

Sorry, I thought you were saying it was a 2000 model. If it's a MK3, it could be the belt and it could well be the tensioner pulley on the belt - they have a limited lifespan.

I presume we're talking about the rhythmic chirping noise?

As above. All I hear is a ticking noise at what appears to be every revolution of the belt. I suspect a small piece of grit has embedded itself in one of the grooves. I have an old stiff tooth brush bent to 90 deg (by heating with blow torch) which I have used to carefully clean the poly-v channels. I still have all my fingers!