Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: Low vibration a BIG problem

Found these marked down 75%, from $200 to $50, so how could I go wrong? Very disappointed. Fit and comfort are great but there is a persistent low frequency hum in my left ear when NC is turned on. Figured out that it happens when I am wearing my glasses. The hum goes away almost entirely when I remove my glasses. I guess I will keep them because I got such a great deal, but come on Sony! You can do better than this! I would be furious if I had paid full price for these things.