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Title: lots of knocking sounds
Review: I don't know if it's just my unit, but mine makes a lot of "knocking" sounds from, what I assume, are all the bubbles forming from the boiling of the water. I do hear a light gurgling sound, which isn't so bad, but even the low setting causes a bigger knocking sound every 10 seconds or so. The high setting is just unbearable for me during the night as I am a very light sleeper. I do get a continual mist, which is great, but the noise from this unit is a big disappointment.
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