Not opinion. If you cannot distinguish between the two, you are tone deaf. I have photographed just about ALL Santa Fe SD40, SD45, SD45-2, F45, FP45 and remember when the GP60 came out it had a Different sound. It wasn't in my head, It is a different sound. I saw these both at idle and accelerating.
Tell me that these sound the same:
https://www.youtube.com/watch?v=lavPKAsDlp4
https://www.youtube.com/watch?v=dViB5ckrRdE