Question about GoPro Hero 5 Black

I also bought the Hero 5 and with the Sandisk Extreme 90MB/s microSDXC (128GB, Class 10) I also had a lot of noise when I watched films on the Hero. The Samsung Pro Plus microSDXC (128GB, Class 10) had less noise, but there were sometimes error messages after video recordings. With the Sandisk Extreme Pro microSDXC U3 (64GB, Class 10) everything is finally OK.

The noise behaviour in a quiet environment (e.g. in a room) is higher and normal with the 5.
This is confirmed on various YouTube videos, but can be reduced relatively easily with an editing programme.

It's because of the SD card, not all are equally compatible

Do you export them to a video editing programme? Depending on that, the quality can change.