I think Phil Busardo was the first to coin the phrase "rattlesnake rattle". If my memory serves me correctly he first used it *while* showing the PWM of a device (Vamo?) on a *meter*, not holding it up to a microphone so it could be *distinctly* heard. I think a lot of users, after hearing various descriptions of this "rattle" automatically associate it with the Vamo in particular, even though most VV/VW devices use some form of PWM, and jump over the fence to join those who think it's a bad thing, an irritating *audible* effect, and perhaps even those who think it somehow produces an inferior vape. By coining that phrase, and it's wildfire like growth in use, he probably inadvertently did more to increase the sales of other mods, Provari's and mechanical mods especially, than anything else in recent times!
That said I've *never* heard it, regardless of tank/atty... not with an RBA, not with a clearo, not with a vivi, not with a dripper... not on my Vamo, my friends Vamo, my other friend's Zmax... and as a life long audiophile I think I am pretty good at "listening" (try and tell the difference between two similarly priced and designed phonograph needles some time!)
I think most people that bring this up are quite often hearing the snap, crackle and pop of a coil that is working well and some how reading into it a perceivable "rattle", something that happens at over 30 times a second. You know what a 30hz signal sounds like out of a loud speaker? It's not a rattle!