À atenção de Luís Filipe Menezes: Underwater Humming Sound in Portugal
"Hello, my name is P.R. and I'm writing from Vila Nova de Gaia, Portugal.
I read your website for some time and I saw several reports about "The Hum".
I have heard the sound for several times and I can't explain it because it can last for hours. When I hear the sound it starts about 11 PM and can last for three or more hours. I also notice that some times the sound is louder than others.
The first time I heard I thought it could be a plain, because my house is located on the airplane route to the airport. I thought it could be a train stopped with the motor running, the train station is near my house or a car but the sound didn't stop.
My only explanation is that could be something in the ocean and my house is located less than a mile from the ocean. It could be a ship but some years ago, a man took a picture of an UFO over the water on a beach during night on Oporto, that is a few miles north."
