this is a LH drive 2003 (i think) diesel estate. A deep penetrating sound but no shaking or other physical manifestation. I've checked google and although 'vibration' gets plenty of attention I haven't been able to match up with my particular problem.
On opening the hood and to the left there is a large black plastic duct followed by a covering cowl and one vibrates against the other at between 1550 to 1650 revs only - otherwise nice and quiet. A light finger pressure on either one will silence the noise instantly. From my handbook, I don't see any identification so here is a pic of the trouble spot under the black arrow :-
Help appreciated.