There is a guy on YouTube claiming to be a "locomotive machinist" for a major US railroad. He's a complete jack-waggon, who goes around insulting and belittling commenters on some railfan videos.
Some of us were having a discussion about how modern locomotives are significantly quieter than diesels built before the noise regulations which mandated reduced noise from locomotives built after December 31, 1979. He called us a bunch of know-it-all railfans and claims that today's diesels are much louder than those in the past. He said that even the regulations governing the volume of horns have mandated louder horns. When I cited chapter and verse the Federal regulation which reduced maximum volume of train horns to 110 decibels at 100 feet ahead of the locomotive while leaving the minimum unchanged at 96 decibels, he responded with more vitriol and insults.
One of the more fantastic sounding claims he has made is:
".....because occasionally trains are operated with a minimum reduction applied to the brakes when going uphill so that if there is a break-in-two the brakes are already set up and can achieve an emergency application more quickly."