Garrets are loud on ground, but can't say I find them very loud inside.
Adam
I flew a 690B with Garrets and every time the noise was horrendous. As stated like a machine gun going off and worse in the PAX area
The owners went to a lot of trouble with soundproofing and clever gismos which improved matters.
Apart from that a great performing and strong aircraft with an amazing climb rate and loved by many
Pace