I bought 2. It works like a fan with 3 speed settings and the lowest one is quiet. I did some research and read reviews which ending to own these great air purifier in my house, one on 1st floor and the other on the 2nd's. To have a true HEPA air purifier makes Mr feel safe during COVID-19 pandemic. Just try it today and learning that if write review can receive 2 replacement filter, so wish I am qualified, too.