sharp noise after 5 sec  ...   what can this be  ?

Not sure I'm hearing what you hear on the 5 seconds mark.. Just sounds as if its getting closer to the camera and the sound increasing.. Also looks like the carbon props, if that's the case, they do sound different.

Just to be safe, rotate the motors by hand and see if they feel different.

sploodge Posted at 2015-9-25 16:50
Not sure I'm hearing what you hear on the 5 seconds mark.. Just sounds as if its getting closer to t ...

+1 from me - cant hear anything strange