Could be lots of things. Have you done the obvious tests to isolate the fault? For example, have you removed the red/white cables and plugged them into a TV to see what the audio is like. If it is poor the problem lies with your set top box or the cables, if it is fine, the problem lies in the Slingbox.
Was working perfect for about 2 years. Now the audio has become awful. A lot of static. I have never touched the RCA cables from day 1. I checked to make sure they are good. I then reset the Slingbox. I am still having the same audio issues. Video is perfect. Any advice would be appreciated. Thanks.