Below are 3 defects detectors by LLJ I have in 2006 and that work in 2010. The first two have a file named detmilepost.wav that you might be able to replace with a new recorded wav file of the same file name. For example "Union Pacific Railroad Hensley Arkansas Detector Milepost" instead of simply the current "Detector Milepost" message.
The third one for the Clinchfield RR is already more detailed. It includes a string table with recorded wav files for a number of different locations. I've recorded and added my own wav files to this table and they work. However, you may find it difficult to match the mechanical voices used in the rest of the wav files.
Defects detector, female voice,<kuid2:30671:23306:1>
Defects detector, male voice,<kuid2:30671:23307:1>
Defects detector, Clinchfield Railroad,<kuid2:30671:23308:1>