Re: TV Ads
"double volume = 6db (i.e. double amplitude). double power = 3db. approximately, that is. I don't want to search for the unicode character for a wiggly equals sign"
Err... nope. I understand where your confusion arises but "power" there is in the mathematical rather than physical sense, i.e. exponentiation rather than wattage. For electrical power the +10 = 10x relationship still holds. +20 is primarily for radiating quantities: I suppose it could also be used with other quadratic relationships but examples don't come immediately to mind.
So yes, back to your lessons. Hopefully taking rather than giving them this time...