I wanted to check it out and hey, my Glock, CZ, and SIG do make slightly different sounds when I rack the slide, and more so when I drop the slide lock. I usually have ear protection on and other shooters around when I drop / rack the slide and I can dry fire double actions without racking the slide so it wasn't something I paid attention to or noticed. Though you have to be listening for it to notice the differences, I think. Out in public with any handgun it would be still quite a distinct sound.