Does it affect if I ate rice for lunch? Maybe stronger effect

I've seen power cord tuning by laying power cables on pieces of wooden blocks. And these wooden blocks or tuning products, cost a bomb. If think you can feel the difference, be prepared for huge financial expenses.

What is inside the concrete wall?

they extend towards the ground. It is grounded.

All buildings must have ground anyway.

EDIT: Also, do read this for further info http://en.wikipedia.org/wiki/Permeability_(electromagnetism)

That is attenuation, wiki for it and you will know why the phone signal drop.
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There is some article about mass damping by using sand bag, but it work more on CD player where you have vibration. I personally didn't try it yet but looking at the different beans fill-up the amp or power inlet really 

People say cable is voodoo, I think this is more voodoo. But if you can hear it why not?

We do so because it's a different story for high speed signals.

AF is only 20-20000KHz. High speed signals do not apply to audio frequencies. AF and RF can be thought of separate entities. They handle differently.

EDIT: Here's something easy to digest: http://www.audioholics.com/education/cable...cable-resonance

Do the math and you'll realize how irrelevant resonance is when it comes to AF.

Also, try not reading up sources from cable commercial vendors. Whether you like it or not, people who are trying to sell you products will always be biased. Read up sources from engineering sources instead, they have real experts who deal with much difficult applications.

Yes.

I suppose for a free market, there is nothing wrong with selling placebos. I do not go against the will of demand and supply. But blurring the lines between fantasy and scientific fact should be discouraged as it impedes the understanding of science itself.

If your search is to attain placebo, then all the power to you.

You could try reading some books about hypnotism. Maybe free upgrades are on the way

I didn't say it's a trolling fact. Lol. I have tried tuning feet and sticker-like (wall tuner?) product. I did feel the difference. While my 'feel' could be a placebo, I'm certainly to say that the product is well marketed to affect the listener's perception.