Head phone jack problems

I bought new sony headphones and have been using them for the past two days in my Iphone 4. Then all of a sudden today they didn't work. All i can hear is static until I turn the volume up about four clicks away from full volume. I tested the headphones on other devices and they worked fine. Also I tried my old pair of headphones (only one bud works) and it worked like normal. How do i fix this?