If, like me you suffer from the occasional bout of insomnia then it's entirely possible that at some point, while lied awake in the early hours you may have heard the distinct sound of a far off train. I first noticed this phenomenon some years ago, as I remember being struck by the thought that the nearest train track was perhaps ten or more miles away.
In the stillness of the night the ability of sound to travel is enhanced, and the sound of a low rumble seemingly combined with a distant sigh has for years reminded me that the overnight mail train was passing, and that yes, I was still awake to hear it! It's a sound that I'm completely familiar with, but one that I've only ever heard in the circumstances described above. Until now that is.
As I begin to familiarise myself to this 'new' rebuilt version of my old 2cv there are lots of things that I'm noticing, for example the way that I can now take a certain corner at speed, and yet remain on line, the tendency to drift wide into a bollard due to the old worn suspension giving up the unequal struggle has gone.
Another area that I made an effort with during the rebuild was that of soundproofing. I've put sound deadening underseal inside the chassis, added rubberised material to the top plate, stone chipped and undersealed both the body and floors, and added neoprene panels behind the door cards. All of this, combined with my absolute hatred of metal to metal fixings without some kind of gasket, fibre or rubber washer has given me quite a smooth and quiet ride.
Imagine my surprise then, when driving I began to hear a sound that I can only describe as the 'mail train' sound from those early sleepless hours. It sounded far away, yet it was inside the cab. It was the typical low far away rumble, accompanied by what I earlier described as a distant sigh, which is a sound best reproduced by forming an 'O' with the mouth then breathing (not blowing) out. First though - wheel bearing!
I couldn't understand how that could be but the diagnosis seemed to fit the bill, and as I drove I tried to focus in on exactly where it was coming from. The relative quietness of the car was now highlighting this odd noise, making it appear more intrusive than it might have otherwise been, and far more annoying. Was it vibration? It wasn't directional in that I found it impossible to tell whether it was coming from in front, behind, or to one side of me, the noise was just 'there', it didn't seem to have a specific place from whence it came.
I began touching things, items of trim that is to see if the damping effect of my hand stopped or diminished the sound, it didn't. After a few miles of this I was getting annoyed with it, after a few more I was livid, bystanders could have been forgiven for thinking that they had just seen a 2cv driving touretts victim as I hurtled by rapidly touching things and swearing out loud when it wasn't the right bit! the problem seemed right under my nose...and it was.

I had changed the late model plastic steering wheel for the 'Quillery' type shown above, and the centre cap for this type of wheel is of much thinner plastic. More by luck than judgement I had placed my hand onto the central cover and the noise had stopped. There followed a 'hand on - hand off' session to confirm that I'd found the source of the noise and by heck! -I had.
The hollow steering tube was behaving like a hollow steel tube does, acting as a megaphone, or behaving like Rolf Harris's digeridoo by passing up road noise in an echo-ey distant sort of way. The plastic cap, being only thin wasn't able to muffle the sound sufficiently.

The steering column has now been fitted with the above modification, i.e. it's been stuffed with four inches of sound absorbing foam, thus restoring peace and tranquility to the Old-Nail's daily drive. Silencing that late night mail train however, may be a tad more difficult.