I'm always worried about noise output when selecting an air purifier. But I am able to rest easy with the VeSync Core 400S Smart True HEPA Air Purifier. It is so quiet. I barely notice its there. Couple that with all the other awesome features such as, the 3 ways to control it including through the app, the ability to set timers and schedules and the amazing air purification, this device is a winner! Highly recommend!