Creeking Rear Wheels

I'm looking for an explanations and suggested solutions to a problem that has developed in two of my rear wheels. After about 10 miles into a ride a creeking noise develops and becomes progressively louder for the rest of the ride. I used to believe it was the bearings but have replaced, cleaned and repacked them several times. Now, I believe it must be the spokes.

Here's some more back ground information that may help: both rear wheels have Campy Chorus Hubs (1999 or 2000), DT spokes (14/15 on one and 14 straight on the other), Mavic rims on both. No matter how sever the creeking noise is, it disappears if I stand and put weight on the bars. It will also disappear if I stand on my right - driveside pedal and intensifies when I stand on my left pedal. Both wheels have about the same amount of milage on them, probably over 3,000.

Thank you for any constructive comments.

 

Try looking at your bottom bracket or cranks, also quick releases. Sound is like water; sometimes hard to tell where it is coming from.