The Glacier uses an older Actions chipset, which has this background noise. It's caused by the LCD backlight, configuring it to turn off after a while (if it's the standard Actions menu you can do it in Settings -> DarkMode) will minimize this background noise when listening to music.
For movies there's not much to do unfortunately.
You may try putting the player in the freezer for a couple days (seriously, but put a piece of paper under it as the metal will stick to the freezer!) and then letting it return to room temperature very slowly before using it again (wrap it in a blanket and put it in the coldest corner of your house).
It may seem crazy, but people have reported much less background noise and better sound quality after doing this. On my old Actions player the sound quality wasn't significantly better, but all that annoying background noise, "hiss and cracks" was gone. This method has been discussed a lot in the MyMPxPlayer.org forum, and none of those which said it's impossible for it to work came up with any proof. :P
It's your call if you try "Operation Big Freeze" or just live with the noise.
PS. This won't void your warranty.
