Before going to bed in my B&B in Schipluiden near Rotterdam (The Netherlands), I opened the front door of my little house and wanted to take a breath. To my surprise, there was some weird deep sound pressure that came from the direction of the A20 highway – which is laying 4 km (!) away from the place I was standing when I took the picture.
The B&B is close to a little river in a wide-open landscape in the vicinity of Rotterdam. As far as you can see, there are grasslands, trees, canals, cows, and a few houses. That’s it. Great. Beautiful landscape, getting rarer and rarer in the heart of Europe, which is crowded with houses, and industry, and highways.
Tonight, one of those highways, the A20, was clearly visible and “hearable” from a long distance in the open fields. Again, the lights in the picture are 4 km away, and the red little dots are signal lights to avoid planes flying into high obstacles. That’s also why the sound was not loud, in the sense of making it hard to talk, or sleep. The sound was more like an omnipresent air pressure. A deep and low bass sound, that felt like if someone was putting a huge pump in the air that put pressure on both ears. A very weird feeling that was. It did not get into the house though, so it did not keep me awake at night.
(map based on google maps)