I used this air filter for the first time in my bedroom last night. I definitely woke up this morning with less congestion, so it must be working! I suppose it is fairly quiet but the sound is still quite noticeable, as is the light from the power on/off button. I put a quarter over the button to hide the light, but it comes out through the vents, too. It would have been convenient if it came with a power block, not just the USB cable.