I have been using the GoPro in the Seven since I got it in December, but this was my first track day I have used it and it picked up a strange "chirp" sound while changing gear only when flat out. I didn't pick up on the noise, maybe because I wear ear protection, and I didn't feel anything funny or different with the gear changes.
The car is a 2011 ex academy car, open sierra diff, 5 speed type 9, with a 150 kit fitted.
My diff is not the quietest, and I am not worried about that, I think it could be a case of TADTS, or some weird resonance picked up by the GoPro, but I just wanted the BC community to confirm this.
Video here
PS The video was taken on the last session of the day, but all flat out changes from the day have this noise, also the second quiet gear change was done on the cool down lap from this session and the noise was not picked up on any gear change on the 100 mile journey home.