I've flown other multirotors equipped with a GoPro camera. The GoPro can record sound, so I could hear the motors of my previous craft when I watched the videos. Unlike the GoPro the P4 camera has no microphone, so all you get with the recorded video is silence. I wondered what the Phantom would sound like if it had a microphone. So I took my little 808 #16 Keychain camera and taped it to one of the legs. I turned on the Keychain cam and the Phantom's cam at the same time. I lifted off, climbed to 150 feet and then cruised over my 'back yard'. I took the video from the Keychain camera, stripped off the audio track and then added it to the video captured by the Phantom. If anyone is interested, here's a quick 30 second sample of what a P4 video would sound like if DJI had included a microphone.