Thanks for all answers. My audio system is original and donot play with wiring stuff. Love buy you a beer for powe-in line filter , Silver, unfornately I am in Brisbane. Anyway, powering off the audio system but the sound still heard. The zirrring sound is not heard when car stop or engine idle so probably something to do with engine but the sound still heard after engine warm up ( drive for 20 mins) some cases and sometimes goes away after a while! it is weird. Might chat with service next time to see their opinions Anyway, I tried to volume up the radio! and summer time now so I am happy for a while.