Originally Posted by
sycamore
They are actually Karman -Hardon bass speakers which `anti-phase` the WOKK-WOK of the blades,so it is essentially a `silent` aircraft,hence the name....
I've got a feeling you might be right on the money there.
The majority in the blade overlap where most of the slap is generated, but apparently a pair pointing upwards just ahead of the rear pylon and two more pairs aft end of the pylon, pointing up and out (if indeed they are the same thing) pointing pretty much where the tip vortices interract.
Stalker struck me as being a pretty strange name for a Chinook of all things!