Noise, distortion of sound from speakers PC.

Speakers aren't new, not used in 4 years years)). 2 speakers and 1 buffer. In General, the essence of the problem. If you do not play music, not play games and so on, in columns noise, interference, a background crackling. But if you turn the music on, ie to use any sound, but louder all the clutter disappear, they are simply not heard. At the same time, the sound is clear,no noise is not audible in the background music. Even the interference sound is not connected in any way. Like there are only simple. What kroetsya the problem?
Buffer columns as primary source is connected by cable 3.5 green to the back of your PC.
If you connect a 3.5 headphone to the rear panel, no noises heard. Te reason I think the buffer of the speakers or the 3.5 mm cable between device and PC. Either or... Or I don't know)