We get plenty of questions asking how loud the SMX 4u UPS range is.
So we made a video!

https://youtu.be/mGsQ4iW9pwk

They are generaly quiet, with the low volume transformer hum. When the fans start its an obvious noise. These come on 1/ When running from cell power 2/ When the internal temp exceeds a threshold 3/ When initially charging after a long time running from cell power. No UPS is silent, but these are good when you want relative quiet. Note tht this applies to the 2200 and 3000VA version of the 4U APC SMX range.