psw110 sub speaker noise

i bought psw110 on20/02/2018 . connected with my harman kardon 171.after setup while playin the movie i heard a different noise comming from the sub. like hum noise ,and the bass quit good. i disconnect the rca cable and the power cord on the sub and reconnect it. but the noise is still there. pls help me out from this how to fix that noise ,its like bad feeling when you using your brand new sub and you not confortable with this.