the butterfly valve on the varex can be opened fully or semi or totally closed when it is fully or semi open u can hear the obvious difference in loudness but once it is closed it is totally silent so if u have a varex u will not need to worry about ur nabours as u can just close the butterfly valve all the way before u go home and have it fully open or semi again when you feel like goin for a spirited drive u can just open it all the way so varex gives u the best of both worlds