It is silent while recording.

Please tap image073 button on main screen, it will have sound while previewing or recording. But it will prompt a warning when you try to record a video, select “That’s OK, keep going” to continue. But in this mode, it may be a bit subtle noise in recorded files, it’s a normal phenomenon.

https://s1.occld.com/image/ca/kb/image075.jpg

Updated : Nov 21, 2019.