Instruct: Classify a given Amazon review as either positive or negative.
Query: Rattling sounds

I've had these headphones for about 4 to 5 months, and over that time, they've started to make a nasty rattling sound. It mostly happens during parts with boomy bass, but it's been happening more and more for a month or so, and now it sounds terrible. I thought that I had a defective pair, but the same thing has happened to my brother's pair of PX100's, too. The quality was incredible, but it's not worth having a rattling sound in the background most of the time.