I am very sensitive to noise so most air cooling equipment keeps me awake even when set on the lowest speed. The "pink noise" of the 45i does not keep me awake. It actually helps me sleep more soundly. The sound is very quiet. The color indicators reflect the particulate matter in the air...as evidenced when I burnt my dinner several rooms away and the 45i reflected that fact with its purple circle. I purchased a colored front plate to match my bedroom and was very pleased to see the front plate attaches with magnets. Just pull off the front plate, no sweat, no mess, and the new one attaches with a magnetic pull. Couldn't be easier. I have the FL-40 Silver Carbon filter.