Why can I hear such long distances in the mountains?
The other week me and my wife climbed into a Cwm/Corrie/Cirque in the lake district on the side of St Sunday Crag in the UK. I could distinctly hear someone talking. I could basically hear every word. I looked for this person only to realise they we're on the other side of the cwm. I checked my map, they we're about 0.5-1km away!
I was at X they we're at Y. Each Square on this map is 1km.
Whats the process that allowed me to hear this person over such a long distance? I've experienced this phenomenon several times. Always in Cwms.
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Even barring special circumstances like focal points and such you can in general hear sounds from further away in the mountains. Reason one is all the air between two points. On flat ground there is often lots of sound absorbing stuff near the path of the sound, like soil and plants. Open air carries the sound better. The second reason are rocky walls serving as deflectors. If you talk in front of a large rocky wall all the sound that would usually go backwards is reflected, increasing the amount of sound going forward. If the listener is also standing in front of a rock, some of the sound that misses them on the way in gets reflected back and still makes it to their ears. In very short: you hear better for the same reason there are echo's. If a valley echoes well, it probably carries sounds very far.
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Sound reflected by concave surfaces will concentrate in a narrow area rather like light passing through a convex lens. You were probably at one of the focal points for the sound being reflected in the cwm behind the person you could hear.
This post was sourced from https://outdoors.stackexchange.com/a/16760. It is licensed under CC BY-SA 3.0.
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