Audible noise when cabel is plugged into the input of PO-32

I get this annoying noise that is quite audible even in lower volume whenever I plug a cable into the input jack of my new PO-32. There doesn’t have to be any signal coming in. It starts to appear once the cable gets plugged. Is this common issue or just maybe faulty piece? If so I will return my unit.

Problem solved. It was due to a low battery. Switched batteries and problem is gone.