if the static occurs when the volume is high, then you probably have a blown speaker. You need to find out which speaker has static. If all your speakers have statics with high or low volume, your audio signal is being interrupted by your phone's signal or another signal. Don't place your phone near the stereo system.
If you have a blown speaker, just go to advance auto parts or o'reilly or autozone and buy a sealant or super glue. That's what i did to my blown speaker. The speaker works perfect now. cheers!!!