Because the North Booms rear goes over the outside of the main body it causes the wind to go through the tube and out the holes. I used to put duck tape over the holes which was a pain in the butt but fixed the whistle. So I swapped it for an Enigma and now it's so quiet ??
I use electrical tape, takes about 2 seconds to put on. I'm happy to do this and have the stiffest and lightest boom on the market. Also 75% on the guys on the PWA use North booms and I don't think they care about the whistling.
