Instruct: Classify Amazon reviews into positive or negative sentiment
Query: background hum and repeated failures

I've purchased this item twice and had exactly the same problems both times. First, I had a constant background hum/buzz when using with either my Sony Walkman mp3 player or computer. It wasn't significant and generally not a problem, except during soft passages. Second, after a few months of use, I've experienced sudden and significant loss of volume in the left earpiece. Again, this has happened TWICE (I thought the first occurance was just bad luck on my part), in spite of very gentle treatment of the cords. Overall, I'm very disappointed, since my Sennheiser headphones are great.