What is the sound when tank is back to level?

I hear 4 or 5 sounds like “ga ga ga” happen every time when the peeling movement is over and the tank back to level, it happen in the early period of the print,  The sound disappear later, I am kind of worried about it because I saw many have their peeling motor thread disconnected with the tank holder and the peeling movement is disable. Are those "“Ga Ga Ga Ga Ga” normal? Or it is a sign that the peeling motor is about to lose its connection with the tank holder?

Okay I am now printing and I notice after 60 or 70 layers in 0.05mm setting the sound is completely gone and the peeling movement sounds clear, It only happen in the early 60-70 layers. But I am still wonder if this is normal.

I just noticed the laser movement was not all silent, when print some layer it produce a very high frequency and most of the time it is silent as whisper.