I had the same issue, a lot of hissing/beeping/interference, even with normal web browser, and in games is was really loud. I tried to replace cables etc, but no luck. Often this kind of issues are caused by power issues.
The solution for me was to connect the power cables of the speakers connected to the CI1, to an source other than my PC (even another power group). Invest in a good powerblock may also be a good idea. That completely fixed it: perfectly sound again. Hopefully this helps others.