well, i never really thought much of this noise but when i recorded my inspire my iphone really picked up on it.... Like a frequency... Maybe thats lightbridge doing that? wierd. My fan is also going out in the same area. I have a seperate post with video attachment.

The sound you are describing is most likely the sonic sensors VPS system. Pretty normal to pick this sound up on recording equipment and cameras
Rich

Just to clarify, is it recgarding your other thread?

http://forum.dji.com/thread-76801-1-1.html