Night time on the farm

This recording was taken from my front porch. The temperature was above freezing as you can hear the snow melting off of the roof. There was an interesting cloud coverage, visible from the city lights of Lambertville, NJ, Doylestown, PA, and the Lehigh Valley, PA. A plane went over the house in this sound clip. Toward the end of the clip, there is an interesting hum. I am not sure what the hum is from. It is not from a highway or planes. It is either the Delaware River or wind through the trees.