2004 Nissan Altima • 61,800 miles

From couple of days back, I have started hearing noise inside my car (around passenger seat end but not 100% sure) when I accelerate the car. More acceleration creates more noise. When I slow down and put breaks, then noise reduces and will be completely gone when I stop the car. I'm not sure whats going on. Can someone please let me know what could be the issue?
January 5, 2013.

It could be the CV axle on that side. Also, the motor mount could have failed on that side and the engine is out of alignment causing a noise. You will have to replace all motor mounts and tranmsion mounts at the same time. The stock mounts are very expensive. Try iinovativemounts on the internet to get some good aftermarket replacements.