A large amount of the noise from the SP10 comes out of the PSU, particularly at highest speeds.
heres my advice:
1) use 200-250V power when possible. this is probably 10% quieter than on 120V
2) set the system fans to the lowest possible so that the exhaust temps are <70C. if undervolting you can go <40% using ssh.
3) undervolt. running at 100-400GH slower speeds can reduce power consumption by 150-500W
If you want the minimum noise, this is the best way:
use 200V+ outlet.
use SSH, login (root,root), and type:
hit enter.
in the file, press 'i' (enters insert mode) and change the file to:
FAN:25 625 625 635 820 50
. press 'esc', type ':wq', and it will bring you back to the ssh main terminal.
In the web browser, click the 'restart minergate' button on the main page and wait the 30 seconds. it should drastically drop in volume.
this will limit the system, causing it to run at about 1050-1100GH/780-840W and is about the slowest speed at which the device is stable. you may see one or two chips disabled on the stats page. if more than ~4 disable, change the file so that instead of 625mv starting, its 628mv. you can also go lower if you want a bit more efficiency, but <610 the system might try to reboot if too few chips initialise correctly. at the stats above I get 1090GH/810W and is reasonable for use in a basement or behind a closed door.
replacing the fans wont make much change, since the majority of noise is the PSU fan (its like 20mm or something insanely small)