No complicated explanations required. Throughout Little Aden the refinery could be heard. Unless the wind was louder or in the wrong direction. So when you went into Silent Valley, the silence was palpable. It was like a pressure on your ears.
I experienced a similar thing in the North of Saudi Arabia wher we had a dry lake which went to the horizon in all directions.

At sunset on a windless day you had, in all directions, at your feet a flat powder sand to the horizon, and above you a clear blue sky to the horizon. Only your tyre tracks disturbed the perfection. The silence was again a pressure on the ears.

When the sun went down the sky transformed into a myriad of stars with constant. rain of comets. Totally unforgettable

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