I run an EX3400-24T at home and its extremely quiet, at least to me. I upgraded from an EX3300 which was much louder. I have herd the EX4300's are pretty noisy, even at idle but have not herd them in a quiet room yet. My home PC is louder then it
Just to note, as most enterprise switches - it will sound like a jet engine at boot (for about 3-5 minutes) then get super quiet