Loud helicopter-like noise that intensely vibrated 2 homes.Nothing seen, just heard and felt. Sounded like a helicopter except that it got so loud and close to our house and our neighbor's house that the houses were vibrating intensely and conversation could not be heard for approx. 10 seconds. There were no lights in the sky, just the sound. Local Police had at least 5 calls about the sound. Total time of occurance was approximately 2 minutes.