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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.
對于那些生活在美國北部的人來說，也許與其它季節相比，冬季的環境變化更大。
Snow makes the world over so that it's hardly recognizable.
白雪使整個世界煥然一新，所以很難分辨事物。
The scenery isn't the only thing that changes during the winter season, though.
然而，在冬季風景并不是唯一的變化。
Today's Moment of Science is about how winter transforms the way the environment sounds.
今日時差N小時為你講述：在冬季，怎么去聽聲音的季節變化。
Before that first snowfall, when the ground has hardened from the cold temperatures, sound experiences its first winter makeover.
第一場雪前，因氣溫下降地面變硬，這時聲音開始第一次季節性變化。
Just as smooth, hard surfaces like glass reflect light, the smoother and harder a surface, the better it reflects sound.
就如同玻璃反射光線一般，地面越光滑，越堅硬，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.
早冬時節地面越堅硬，被地面吸收的聲音越少。因此聲波在地表進行反射時，會保留更多的能量。
As a result, early winter sounds are louder and clearer. Pay attention, and you might notice that everything sounds a little bit crisper.
結果你會發現，早冬季節的聲音聽起來更響更清楚。如果注意聽，你會發覺萬物聽起來都帶點清脆。
After the first snow, sound is made over again. The porousness of snow makes it absorb sound.
第一場雪后，聲音又發生了新的變化。積雪融化深入土壤，使地面吸收聲音。
Specifically, snow tends to absorb higher frequency acoustical waves.
具體來說，積雪傾向于吸收震動率高的聲波。
As a result, sound becomes quieter and somewhat distorted.
因此，聽到的聲音音量變低，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，你也能通過傾聽略微壓低的鳥叫聲和汽車開過的聲音判斷下雪了。
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.
如果持續下雪或者出現雨夾雪天氣，聲音會再次改變。雪會結成冰，因此會變得光滑，滲透性弱。
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，這就意味著結冰的雪會像其覆蓋的僵硬的地面一樣，很好地反射聲波。
Sound will once again be crisp and clear.
聲音又會變得清晰明了。
This winter, see if you can hear how the season transforms sound, as well as the scenery. 這個冬季在欣賞景色變換的同時，去聽聽季節是怎樣改變聲音的吧。
