I have the greatest of respect for Keith Oakley, and he has done remarkable things in creating a quiet integrated hovercraft, not something I would ever have thought possible. I do need to take issue with one thing though, and set the record straight. Keith says that there are now 3 "quiet" hovercraft out there. However, he has not taken into account the Otter!
We launched the first Otter in 2012. It has almost all of the design features that Keith recommends, but of course predates his video by several years. If you look closely you will see:
Rear mounted thrust fan
"Clean" fan inlets, with long shaft drive
500mm obstruction free inlets
Very low fan tip speeds
Low revving engine
Plus there are some features that are not mentioned in Keiths article.
All these factors were designed in from the start to achieve low noise, and thats what was achieved - in 2012. Since then, the MkII Otter (Nick and Kims) have an improved rear end to further clean up the air flow into the fans, and this has reduced noise once again.
So forgive me for pointing out that there are 7 "quiet" hovercraft in the world
Here's the noise test data:
[mmg]2963[/mmg]
[mmg]2964[/mmg]
[mmg]2965[/mmg]
And here's the video
https://youtu.be/gQZmgqgTRyw