That's the kuid number underneath the new locomotive sound effects library v1.08c (build 2.9).
They've also updated the train effects library to v1.30 kuid2:45324:555200:19.
They only did these on 7th February, you have to keep up with these new developments chaps, otherwise, you'll be missing out on all the new whooping sounds.....:hehe:
If the other locos use the same FX library the sounds should be their. That popping noise is the automatic water purgers in the air system. They are meant to keep the moisture out of the air system and yes they pop off that often. It's just adding a little more realism to the JR locos.:Y: