Abnormal Propagation - Ijyoudenpan

Japanese: 異常伝搬 - いじょうでんぱん

The phenomenon in which sound waves are reflected, refracted, or diffracted in the atmosphere by large temperature inversions, large temperature gradients, or small turbulent cells, allowing them to travel long distances without losing their power. An example of this is the sound that is heard nearby from a distance that is normally inaudible at night, which is due to the sound being reflected by an inversion layer.
→ Related topics Outer hearing zone | Inner hearing zone

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

大気中の著しい気温の逆転層，温度傾度の大きいところ，あるいは小さい乱流セルの存在するところで，音波が反射，屈折，回折して，音の勢力が衰えずに遠距離まで伝搬したりする現象。静かな夜間に通常聞こえない遠方の物音が近く聞こえるのはこの例で，逆転層で反射したもの。
→関連項目外聴域｜内聴域

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