As someone who's office overlooked an airfield apron where an Andover and a Comet (both of a similar vintage to the Rotodyne) used to conduct engine runs I can confidently say that most aero engines of that vintage WERE NOT QUIET. Apart from the fact that the Rotodyne was dropped by Westlands on the 'Not invented here' basis, the Rotodyne concept should not be constantly dismissed over an issue which the additional 55 years of technological development could be used to resolve.