Sensory Adaptation

My parents, my brothers and I lived in small town railway stations for years. They were our home. In the fifties we lived in a station on the mainline of the Canadian National railway and there was a train whistling through every couple of hours day or night. In our little town the trains usually went by at full speed and they whistled twice for the level crossings. 400 yards  and 200 yards from the railway station. The track was about 25 feet from the station, separated by the platform, and our rooms shook when the trains whistled through. Many were very long freight trains and the shaking would be minutes long. The two transcontinental passenger trains both came thundering through at night as well. Over time, we never woke up with the shaking and thundering  noise at night. My mother, who was light sleeper under some circumstances, rarely awoke.
      The station caretaker came into the station at four AM. lit the fire in the potbellied stove in the waiting room below the boys bedroom, met the way-freight, unloaded the mail and manhandled the jangling cream cans on the platform attached to the station and we never woke up. Sensory adaptation.
        However, when the running employees went on strike and the trains stopped running for a few days the silence was eerie. We all woke up repeatedly during the night. Habituation,  no matter how chaotic
told you everything must be alright with the world. We adapt to the familiar , however unusual, but change, seemingly innocuous, brings sensory adaptation to a halt. Unconsciously alert to danger. There is little control of part of the autonomous brain which serves protection.