The guage for the oil pressure is in bars and might show some fluctuations. Usually the tell tale is loud variocam, since it is dependent on oil pressure to remain decompressed. From an engine prespective, you might still be able to make enough pressure past idle.

 

Well, I can tell you this much. The initial posts here reminded me of a similar noise I'd been hearing for the preceding 6 weeks or so, so I ordered new 'slippers' and took my car in. Had it towed, actually: AAA is free.

Here's what they found- chains and cams were fine, thank goodness.

 

I had 138,000 mi. on the car and had only had visual inspections of the slippers up to that point!