Cure for front end popping!

I have been experiencing the infamous popping noise coming from the front end since I owned her. So today I pulled my cowl off to check the tightness of my strut tower brace; hoping to find a loose bolt which would cure the pop. While my bolts were NOT tight, they now are. But still no progress on noise. So...after cleaning cowl area, and siliconing every moving part I could, I had given up again. As a last ditched effort, I started thumping this general area with my palm, trying to duplicate the noise of course...FINALLY, I could duplicate what I had been hearing. The very middle and bottom part of the windshield seems to be not secured. When the heal of my palm strikes this area, the exact noise I hear while driving is duplicated! WTF? The windshield doesnt leak. But when thumping to the left or right (VERY bottom of the windshield) there is no noise at all. Can somone go out and thump their windshield?? I am probably hitting with 15lbs of force. I maybe on to something here... OHH also, will my car leak if I keep the cowl off when it rains?? THANKS

OK we can make this easy...what is the responsibility of the cowl?

Well I could take pics....but it looks just like yours would if you took the cowl off. I hear the noise while driving. From the inside it sounds like it is coming from the area where the dash meets the windshield, directly in the middle. This is where I can thump the glass and the noise is duplicated. The only moving parts in that area is the wiper motor unit. So I wont ruin anything if I keep my cowl off when it rains? Seems like my ac blows WAY harder now.

Progress...I took her to an auto glass shop today. The guy confirmed the bottom, middle of my windshield had broken loose from the resin! Soo, being that I had been chasing a busted bushing, mount, etc...I am fairly confident replacing my windshield will fix this thud. BTW, the guy said this was not the first time he had seen this, the other time was in a mustang, which also had suspension mods...