I've got one on mine with Spoon 2-1 Decat and it's not loud at all.
Very nice purr low down and mid range, with an audible growl on FT and in VTEC.
It's louder than a Twinloop as that's the only other A/M exhaust i've had, but it does make a lovely noise.
For reference I'm 30 years old and drive around town a lot and it's my daily, so I don't want anything deafening.
For me it's the perfect solution.