RDB 975427 was an acoustics test vehicle converted from a MetCam Pullman car M323E in 1975

In November 1972 it was used to monitor noise levels and in order to accomplish this instrumentation consisting of microphones and pressure measuring devices were affixed to both the interior and exterior of the vehicle. In order to further these studies, and since the locomotive noise would be detrimental to the acoustic measurements, arrangements were made to attach the vehicle to the rear of the 08.16 from Derby to York (07.30 from Birmingham NS). On arrival at York the vehicle was detached and re-attached to the rear of the 15.20 to Derby

Martin Allen