NB Window Vibrations

[decayed.cell]

Hi guys I have been noticing a vibration sound which I haven't been able to pinpoint until tonight when I had the roof off and the windows up. The left window makes a lot of vibrations whilst the drivers side does not make any noise. When the window is down there is no noise. This leads me to believe that the seal or something is not tightened up near the window. Does anyone have any ideas how I could fix or reduce this? Putting my hand on the window stops the noise (obviously not a viable solution).