Instruct: Classify a given review as either positive or negative.
Query: Periodically makes loud thud sounds

My only real problem with this product is that it will periodically, about every 20 min, make a thud sound that is so loud it wakes me up. Useless for a sleep aid because of this. I've read another review where it complained about a "screeching" sound. What is the point of making a noise maker for sleep if it's going to wake you up every 20 min? Do no buy.