Road & Engine Noise Intrusion: w126

[kennysin]

I have recently noticed increasing external noise levels, which seems to be mainly emanating from the bulkhead, especially the central air-con vents. Closing the central vent seems to reduce the noise level.

I am considering stripping the dashboard to investigate and possible add some damping sheets or insulation. I am hoping that it is a problem with the ducting, and not corrosion. There is no water leak to suggest that though.

Any suggestions as to the cause? The noise level was especially apparent after I sat in a w124 which was very quiet in comparison.