To my ears, the quietest helicopters at present are the MD series 'NOTAR' types. If they could produce one of these big enough to carry a viable load, it might be acceptable to re-establish services such as the Link, but the problem is, you'll always get NIMBY's who insist on objecting on principle in spite of all evidence that there will be no adverse environmental impact; they'll even produce their own 'evidence' attempting to contradict scientific studies and reports (usually from a retired scientist with no recent experience).
I did hear somewhere that someone was re-inventing the Rotodyne concept with an emphasis on developing it with low noise output; I must admit the one time I actually heard the Rotodyne (from my home near Bovingdon) I thought it was no louder than other transient types using Bovingdon such as a Hercules, but it was just a different type of noise. The 'tilt rotor' concept does produce objectionable noise of course, so would not be acceptable.