CAC,
your sarcasm is not really appreciated
I thought strake's answer was helpful and, in any case, sarcasm is the least of the insults one suffers on Prune
I also have the Sennheiser PXC450 which is fine.
It has a 'talk through' button although it may be perceived as more polite to slip an earpiece off.
There is an integral volume control.
There is a 'bypass' switch so that, if you run out of batteries (one AAA), they work as ordinary noise excluding headphones.
As strake says, they will not cancel all noise. Mine seem to cancel the low freq rumble.
With hindsight, I think I'd have been happy just with a soft ear-covering noise excluder.
p.s. If you go for any length of time between flights don't forget to remove the battery. Just had to clean one of my contacts - just noticed it before incurring more serious damage to an expensive headset.