Butyl is essentially Bitumin with higher heat tolerance properties.. again, I won't argue here like what IQ5 said earlier and take the package as it is.
If you complain E90 bising, how would u rate the GTI Mark V
Nobody beats Lexus when it comes to this noise damping topic, even their engine is wrapped from top to bottom with thick spongee material.
Able to listen to the E90 engine and exhaust node is part of the joy of owning the BMW because even that, there's a department in BMW AG to specially tune the pitch of each model to be unique, no 2 BMW models sound alike, go figure.
There's no end to additional layers to Butyl in the doors, some use more than 1 layer and eventually, might as well drive with ear mufflers..

(kidding here..

)
Maybe we are really missing something here but its alright and thanks for sharing with us.
And again, that's individual preference... Megabuck38, good luck to your quest of Ultimate Cabin Ambience.. :top: