Wow, great tip, thanks! For me, I would get the "electric snap" sound when changing channels on the cable box. Not with every channel change, just some channel changes. Solution for me was slightly different as "sound leveling" was already off. I turned it on, then turned it off, and that seemed to work. Here are my steps:
1. While viewing the Cable Box video on the TV, press * button on Roku remote. Roku options screen appears
2. Scroll down to find the Volume option. In my case, leveling was "off". I turned it on, and then turned it off.