Implements a Calculation of Railway Noise (CRN) calculation using the procedure described in The Department of Transport Calculation of Railway Noise 1995. Throughout this calc, horizontal distances should be input relative to the nearest rail (d), and vertical distances should be input relative to the top of the rail (h). Users of this calculation need to be familiar with the standard to understand how the various corrections apply. The CRN SEL Corrections Lookup Table needs to be loaded to use the CRN Sources part of the calculation. This includes the corrections given in CRN, and the additional values produced by DEFRA in 2007.