Ian, fair question

I am unaware of any scientific tests that have been carried out. If you read the claims of all manufacturers carefully, they are worded very well. They all claim that their products reduce the affects of RFI in the system. I really don't care what they are doing if they make my system produce more enjoyable music. If the difference is marked when using a double blind test, I don't see the need for anything else. In the Shunyata's case, it was. Now in the overall picture the differences might be considered small by some. But it's getting the little things right that turn a good system into a great one IMO.

Now food for the nay sayers, and I'll probably get pilloried for this (but I tell it as it is ). Experiment with Tact. Take measurement and apply equalization. Then add various mains acoutrements. Not the improvements in levels of hash, bass extension etc etc.

Now perform another measurement with cables in situ and apply same EQ. Shockingly, the balance of the sound will revert to as it was prior to the mains tweaks to my ears  So, I would have to deduce that the cables are adding rather than subtracting something

I don't really care too much, as I find the music far better with them in circuit, and they do stand up to blind comparisons.