Instruct: Classify Amazon reviews into positive or negative sentiment
Query: smooth, rattle-free, compact, and actually works

The idea is quite simple, almost so simple that I felt slightly idiotic paying $45+ for it, but I must say that it is worth it. The concealed fan is steady, meaning I don't hear any rhythmic clicks or other noises being emitted. I've used window size fans for the same purpose for many years, even during winter months; they all eventually start rattling, unlike this compact machine. It's also nice to realize that the marpac creates comparable if not better 'white noise' than a window fan, but must consume only a fraction of the energy due to its size. Highly recommended!