An expression used to compliment a blank, retarded facial expression.
If used on its own, 'ehhh' is a show of confusion or uncertainty. However, it can also be used as part of a sentence, even multiple times, when immitating a person of inferior intelligence, or someone who is slow on the uptake.
"And Jonny was all like 'Ehhh, I is ehhh, wanting to know if you is wanting to buy my car."
An expression typically used by trance junkies, when they hear a decent track.
Sometimes it can be used in the ironic sense, and needn't be associated with a track of outstanding musical merit. For example, upon hearing 'Tiesto - Traffic', while hardly a work of genius, omg choon would still be an appropriate reaction, because, well...it's 'Traffic' innit.
It is a metaphor for the "storm" of adrenaline caused when a DJ plays a string of consecutive uplifting, energetic trance anthems in a short space of time, leaving the listener in a dazed mental state as they struggle to cope with the sheer power of the hooklines.