At any rate, some leagues to the windward there must be some noisy phenomenon, for now the roarings are heard with increasing loudness.

无论如何， 上风几里远一定有什么吵闹的现象，现在轰鸣声越来越大。

And that's not all, studies have also shown that the dust level in the air can be as much as 75% lower on the sheltered side of the tree as compared to the windward side.

这还不是全部，研究还表明，与迎风面相比，树的遮蔽面空气中的灰尘含量可低 75%。