power cord directionality

When we talk about A.C. power or POWER Cords, there is no Physical science that specifies "polarity"

Polarity on A.C. power is mainly for safety. In the off position the device can be safely serviced because there is zero power after the power switch. This is why the HOT side of the cord is directly connected to the power switch. 
As for a device not equip with a power switch be careful.

U.L (underwriter labratories) is the largest testing facility in the U.S. tasked with safety testing things like power cords. I would venture to say that in this era, inorder to get the U.L. listing a device not equip with a power switch would require a polarizes power cord.

Sorry, I thought the topic on this thread was related to "power cords"

not to be confused with "signal"

In a perfect world you should never hear power or its side effects.

You want the signal to be clean.

So let me understand. are you saying vibration can have a negative effect  on how electrons flow? If you shake/vibrate any wire enough, it is possible to change the position of an electron?

In my opinion vibration can have an adverse effect on a connection point of a wire.

example: if you have a low quality outlet the physical connection between the plug and outlet may not solid enough and you may have arcing. Also the more valuable precious metals used in the plating (gold/silver) may offer higher conductivity.