Jay73, the Shunyata site has a YouTube video where they use an Entech Powerline Noise Analyzer to sonically and numerically demonstrate what you are asking about. Watch the video. It explains itself. In part I purchased a Shunyata Hydra Denali unit, like the one they were testing with the Entech after watching this video, which seemingly demonstrably measured it’s effectiveness in reducing line noise. The Entach unit is found both used and new on Ebay and Amazon in the $25 to $79 range,
Mike