I have just fitted one of these:
OOPPEN 6’’ Inline Duct.
It appears to be a perfect knock-off of the Affinity that everyone in the US is using, except the affinity costs about $300 in the UK whereas this was about $100.
I also fitted 6in insulated ducting too.
Wow, the difference to the noise level is astounding!!! I knew that rear fan was noisy and the pitch seems centred right on the centre point of my hearing. But with the fan turned off it’s barely more noisy than a fan heater or laser printer. Absolutely gobsmacked.
The external fan gives a low rumble - I’ve mounted it on hard and soft foam, rather than screwing to the floorboards to help cut any rumble down. Again, no more noisy than a small fan heater.
Overall, I have gone from an evening of forging being very tiring on the ears (even with noise reducing headphones) to “noise? What noise? Is this thing on?”
In UK prices I spent £100 fan, £16 two sets of hose, £8 hose clips, £6 4 inch to 6 inch connector. Total £138 - I would guess the same in US dollars.