It's now 2018 and this little machine is still humming right along! totally love it!
there is a little control of the sound made by twisting the top as well as the side of this little machine, but it really doesn't chance the volume at all.  For me that is just find and dandy. I see some 1 star reviews say that theirs smell bad, is too loud or not loud enough. I have not odor issue, the sound it what I wanted, it's small so easy to take with me when we travel, and it is a steady constant sound that does not change or irritate.  Have had it a year now (got it last Christmas as a gift) and use it every night. No problems with it for the first 365 days of use.
Rating: 5 stars