Thank you for all of the responses.
My newsreader has a quirk that only showed Leon's first reply - the newsreader thinks everything else with that title is a duplicate - checked Google and there's a whole conversation going on.....
So I'm trying a first post using that method.

Anyway.

No intent to stir the pot. The Relative Humidity is so high where I live (south of some of the frequent posters here) that I really have to try for a while in the winter to generate enough static electricity to give the dog a buzz.

System is 6" metal to a wooden chip separator box, then 6" metal to a Y reducer to 4 inch PVC that goes over head. The RAS, router, tablesaw, bandsaw, scrollsaw, drill press, and a couple utility outlets are all connected from chest or floor level 4" PVC drops via the common clear 2" or 4" wirewound flexible hose. PVC joints are caulk sealed.

I'm very happy with the way the system works. If I remember to open the appropriate blast gate the shop stays fairly clean. The only PITA was installing two 45s to make a very broad turn to come down the wall. The hose would have been nice here - friction loss or not.

Back to the topic - The question of whether the black hose/pipe had the slits in it was the first thing I double checked. The only penetrations are the 4" ones at each end of the hose. Good idea.

The is 4" (I've got some about 2" too) ribbed hard plastic. The sound seems to eminate only from the opening of the hose - there doesn't seem to be any sound along the length of the hose, regardless of how much I attach or how it's broken up, though some may be masked by the howl I'm describing. It makes no difference if it's on the floor or suspended or if 'pressure points' are applied along the hose that should stop any vibrations.

This is likely a case of using the right tool for the job, but I have this stuff, it would be convenient to use it, and I've seen what -looks- like it in various shop photos and videos.

If you made it all the way through this epistle, thanks. Ideas are welcomed. If you are using what even resembles this stuff, what is it?

-Joe