Commercial Volume fluctuations some channels.

I recently upgraded to Contour 2 and am now using a Polk Audio soundbar with Samsung TV.  Due to the voice delay of Dolby Digital 5.1 running through the TV I am connected directly from the DVR to the Soundbar with optical digital.  On some of the Digital Cable channels specifically Spike since I watch it alot and sometime WGN, the commercial volumes are all over the place.  .  I did not have this issue when I had the old Contour DVR and used a receiver. My guess is that Cox may be changing the output of commercial between PCM and Dolby Digital on some of these channels, because I don't have the problem in other rooms using the TV sounds. . I do not have this issue on Major Network channels for the most part.  Spike is the worst for sure especialy watching some older shows like Cops.   Can anyone tell me why this is, or if there is anything I can change.  I do not want to change the sound output to PCM so that's not an fix in my opinion.