I bought this unit about 3 weeks ago. LOVE how great it seems to collect everything out of the air. After the first week alone the pre-filter was quite visibly dirty. Low mode it runs pretty quiet. Medium, just a tad louder. But, we run it on high and it is very loud. That is the only reason for 4 stars. If you'd like an air purifier & white noise machine all in one, then this would be your 5 star machine.... lol....