Why do my speakers make a static noise when my tv is on HDMI

Why do my speakers make a static noise when my tv is on HDMI

I have a sinotech 32inch tv and when I plug my speakers into the aux audio output it makes a static noise, it only works if my tv is on the usb or pc channel but on tv and hdmi just a static noise , I have tried 3 different speakers .. all the same result

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