acer E14 E5-475G fan got consistent weird grinding noise

i bought this laptop at Jan 2017. I used after around one week and realised there is some grinding sound come out from the bottom left hand side. It really annoy me and I use it in a quiet environment, so I can hear the sound sharply, and the worst things is the grinding sound is consistently although I didn't run any programme. I send to "Acer AFTER SALE service center in Malaysia" for 3 times!!! First time they said is fan noisy, and replaced me a new fan, but the problem persist, and second time they said cannot diagnosed the problem from their diagnostic system, I went there and test in front of counter, and the receptionist open a new case ID for me and diagnose again; which is third time. Then the engineering team called me and said still can't diagnosed the problem that I descripted, and changed a new speaker for me ask to try test the problem, and if it still persist require me video it and make a further step. So what can I do? I really disappointed with Acer. I just want to solve this problem, and give me back a silent environment without grinding sound, it is harmful for my hearing!!!!