I always shoot with a good set of electronic muffs in place, so total noise this day and age is not a big issue for me - even when hunting... Yet, even with good hearing protection, I still notice difference levels of muffled noise.
But, at the rifle range where I shoot, others don't always wear good hearing protection (not my fault). I get more comments on the loudness of my 17 Remingtons than any other rifles I shoot.
The noise from a 17 Rem is a loud sharp high pitched crack like Jack mentioned. If you're getting less noise than with a 223 Rem, I would think you're not loading the 17 Rem very hot...
The 17 Mach IV/FB is definitely less loud than some other popular varmint cartridges, but I find it hard to believe the 17 Remington round ranks there too.
JMO - BCB