i tried a gerni and it still wouldnt shift the crap built up under the cowl covers. so i took the drastic effort of removing the cowl covers to investigate. this requires removal of the wiper arms and also the strut brace so it's not a quick task.

cleaned up all the crud built up (leaf matter, dirt, sand, etc) and scraped it all off. I put a 10mm wide strip of self adhesive neoprene along the edge of the windscreen as a decoupler to prevent 2 hard surfaces hitting each other. noise has been gone since i did this :)
clark rubber had the neoprene but it was quite thick so replacing the cowl covers took a lot of effort.

there is...

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site:the370z.com Windshield cracking noise :hello:

My G37s had this problem every time I hit bumps, and there was a DIY on myG37.com on how to prevent this....it was the passenger side had no adhesive to prevent the cowl from staying put, so the G37 guys took it apart and applied their own and the problem went away