I should add: Degaussing is just a fancy name for demagnetization. Typical we degauss things when there is some degree of residual magnetization that we don't want. The most common variant of headphone is the dynamic headphone, basically a magnet, voice coil and diaphram. So the notion that you would want to go and "degauss" the headphone would literally mean that you are going to remove all of the magnetic flux from the magnet. The same magnet that makes the damned thing work in the first place! Doesn't make any sense to me at all.
What you really need to do if you've bought into this theory is to put the head phones on while you are playing this special signal and degauss your brain. That way, all of the stale remanent material in your gray matter will be eliminated and you'll be able to think more clearly the next time you see this type of promotion.