sorry the confusion,
it was a tiny slim cable which was hitting a little window inside the case by fans air flow.
your answer led me to check everything inside and I found it! thank you again #DSzymborski
I spent using this pc over 6 months with no problems regard weird noises, and then next day powered up the machine I hear this noise all time with no stop if idle, when I am playing gaming or doing heavy work, lets say playing bf4 after like 10m I started hearing the noise keep fading, sometimes...