I saw last week that Lockheed has announced the release of a new quadcopter called Indago VTOL Quad Rotor. http://www.lockheedmartin.com/us/products/procerus/quad-vtol.html They've got price sheets posted. It seems overpriced but what I found interesting in the specs is how quiet it is. Whisper Quiet - 62dB at 3m, 52dB at 10m At 10m distance, the acoustic signature of the Indago is comparable to the hum of a refrigerator. I own a Vision+ and it's loud. Are there aftermarket props that are quieter?