I have a 92mm H-1BX Panaflo that I got a year ago and have been using it on an XP90 ever since. It's rated for 56.7cfm at 35dbA and I never found the noise very loud even at full speed, just a sort of light whirring. Last week I got another panaflo, an 80mm M-1BX model (32cfm, 28dbA) from Sidewinder to add to my case, but to my surprise it was quite loud, easily louder than the 92mm one that is rated 7dbA higher, and had what seemed to be a sort of periodic rattle to it. Not sure exactly how to describe this. It was actually branded differently, saying NMB MAT on it instead of Panaflo, but the part number matched up. The sound is not too bad if I cut it down to 75% speed using Speedfan and the rattle goes away, but I expected much better considering my experience with the older 92mm one. I know the dbA ratings are generally not comparable but these fans are supposedly from the same manufacturer. I've heard of the differences between the Japanese and Chinese versions, but these actually both say made in China on them, so what's going on here?