Today I travelled Down from Euston in the DMF of -009, which was the wrong way round so 1st was at the front. There's been reference to resonance causing an issue with over-bridges. Is this the same as the resonance, similar to very loud, deep in note, steady wind noise, that permeated this car once speed has built up? It only seems to occur when the pantograph is carrying a load. I haven't noticed anything even remotely similar on East Coast or G.W.R. I.E.T.s.
Together with the sharp 'crack' when passing neutral sections 1st is no longer a quiet environment, but perhaps it only happens when the pantograph is leading.