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For those of us who live in the northern part of the United States, perhaps no other season transforms the environment quite as much as winter.
对于那些生活在美国北部的人来说，也许与其它季节相比，冬季的环境变化更大。
Snow makes the world over so that it's hardly recognizable.
白雪使整个世界焕然一新，所以很难分辨事物。
The scenery isn't the only thing that changes during the winter season, though.
然而，在冬季风景并不是唯一的变化。
Today's Moment of Science is about how winter transforms the way the environment sounds.
今日时差N小时为你讲述：在冬季，怎么去听声音的季节变化。
Before that first snowfall, when the ground has hardened from the cold temperatures, sound experiences its first winter makeover.
第一场雪前，因气温下降地面变硬，这时声音开始第一次季节性变化。
Just as smooth, hard surfaces like glass reflect light, the smoother and harder a surface, the better it reflects sound.
就如同玻璃反射光线一般，地面越光滑，越坚硬，反射的音效就越好。
The harder ground of the early winter season absorbs less sound. Thus, acoustic waves retain more of their energy when they reflect off the ground.
早冬时节地面越坚硬，被地面吸收的声音越少。因此声波在地表进行反射时，会保留更多的能量。
As a result, early winter sounds are louder and clearer. Pay attention, and you might notice that everything sounds a little bit crisper.
结果你会发现，早冬季节的声音听起来更响更清楚。如果注意听，你会发觉万物听起来都带点清脆。
After the first snow, sound is made over again. The porousness of snow makes it absorb sound.
第一场雪后，声音又发生了新的变化。积雪融化深入土壤，使地面吸收声音。
Specifically, snow tends to absorb higher frequency acoustical waves.
具体来说，积雪倾向于吸收震动率高的声波。
As a result, sound becomes quieter and somewhat distorted.
因此，听到的声音音量变低，并有所歪曲。
Without looking out your window, you might know it snowed simply from noticing how bird calls or passing cars are slightly muffled.
即使不看窗外，你也能通过倾听略微压低的鸟叫声和汽车开过的声音判断下雪了。
If the snow lingers or it is topped with rain, winter sound will be made over once more. As snow hardens, it becomes smoother, less porous.
如果持续下雪或者出现雨夹雪天气，声音会再次改变。雪会结成冰，因此会变得光滑，渗透性弱。
As you can probably guess, this means that the snow will, like the hardened ground that preceded it, reflect sound well.
可以猜到，这就意味着结冰的雪会像其覆盖的僵硬的地面一样，很好地反射声波。
Sound will once again be crisp and clear.
声音又会变得清晰明了。
This winter, see if you can hear how the season transforms sound, as well as the scenery. 这个冬季在欣赏景色变换的同时，去听听季节是怎样改变声音的吧。
