雪对噪音的吸收能力很强。因为雪花之间有很多空隙对噪音有很大的减弱作用。

下雪后为什么感觉很安静

双语阅读

The whole world seems to get unnaturally quiet after a snowfall, but why?

一场雪过后，整个世界似乎变得异常安静，但这是为什么呢?

Have you ever noticed how, after a big snowfall, the landscape gets very quiet, and everything looks like it's covered in that insulation you find in the walls of houses? Things that had a distinct shape before — wheelbarrows, mailboxes, parked cars — all become muffled lumps, and the ambient noise we're all so used to is suddenly gone. Some of this has to do with the fact that heavy snow can result in folks staying inside, cutting down on traffic noise and the sounds of tag football games and such. But there's something else: Fresh snow actually iskind of like nature's blow-in insulation.

你有没有注意到，一场大雪过后，周围的风景变得非常安静，一切看起来都像被房子墙壁上的绝缘材料覆盖着一样?以前有独特形状的东西——手推车、邮箱、停放的汽车——都变成了沉闷的块状，我们都习惯了的环境噪音突然消失了。部分原因是大雪导致人们呆在室内，减少了交通噪音和橄榄球比赛等的声音。但还有另一件事:新雪实际上有点像大自然的吹进来的绝缘材料。

Contents 目录

1. Snow Creates Air Pockets 雪形成气穴
2. How Does Sound Travel? 声音是如何传播的?
3. Why Doesn't the Quiet Last Long After Snowfall? 为什么下雪后的宁静不会持续很久?

Snow Creates Air Pockets 雪形成气穴

Snow makes everything it falls upon look so lumpy because each snowflake is an irregular shape — a six-sided, crystalline structure that doesn't lend itself to stacking neatly atop other snowflakes. As billions of snowflakes fall on top of one another, they don't merge together and zip off the landscape like rain; instead they pile up on each other like a bunch of origami cranes, creating a material that has lots of tiny holes between each flake. This porous material smooths out all the sharp edges that make the things the snow falls upon distinguishable from each other. The little nooks and crannies between the snowflakes allow sound waves to enter, but then it strips them of their energy as they make their way through the fluffy material.

雪花让它落在的东西看起来都是凹凸不平的，因为每一片雪花都是不规则的形状——六面晶体结构，无法整齐地堆叠在其他雪花上。当数以十亿计的雪花落在另一片雪花上时，它们不会融合在一起，像雨水一样掠过大地;相反，它们像一堆折纸鹤一样堆积在一起，形成了一种每片之间都有很多小孔的材料。这种多孔材料可以抚平所有锋利的边缘，使雪落在的东西彼此区别开来。雪花之间的小角落和缝隙允许声波进入，但声波在穿过蓬松的物质时，会被剥夺能量。

How Does Sound Travel? 声音是如何传播的?

Sound travels in mechanical waves, and in order for something to make noise, physical molecules — gas, liquid or solid — must be jiggled around in order for sound to be transmitted. Temperature also affects how quickly sound waves can move: They speed up in warmer weather and slow down when it gets cold. Not only can sound waves in cold weather be a little sluggish, falling snow can interfere with them, making sounds in a winter wonderland seem muffled.

声音以机械波的形式传播，为了让某些东西发出声音，物理分子——气体、液体或固体——必须四处震动才能传播声音。温度也会影响声波的传播速度:天气暖和时声波会加速，天气冷时声波会减速。在寒冷的天气里，声波不仅会有点迟缓，飘落的雪花也会干扰声波，使冬季仙境中的声音看起来很沉闷。

A blanket of fresh snow also does a lot to dampen noise. Sound absorption is measured using a scale called sound absorption coefficient alpha (α), which measures how well a material absorbs sound on a scale from 0 to 1. The sound absorption rating for snow is in between 0.5 to 0.9, which means, at its most effective, a few inches of new fallen snow provides an impressive amount of acoustic insulation for a lot of different frequencies of sound. One study, published in 2016 in ScienceDaily, found that a couple inches of snow can absorb roughly 60 percent of ambient sound.

一层新雪也能很好地抑制噪音。声音吸收是用一个叫做吸声系数α (α)的尺度来衡量的，它衡量的是一种材料吸收声音的程度，范围从0到1。雪的吸声等级在0.5到0.9之间，这意味着，在最有效的情况下，几英寸厚的新雪对许多不同频率的声音提供了令人印象深刻的隔音效果。2016年发表在《科学日报》上的一项研究发现，几英寸厚的雪可以吸收大约60%的环境声音。

Why Doesn't the Quiet Last Long After Snowfall? 为什么下雪后的宁静不会持续很久?

The sound-dampening air pockets don't last very long after snow falls. The shape of the delicate snowflakes changes pretty rapidly once they settle to the ground — as they begin to snuggle in together or melt, the space between them shrinks, leaving fewer spaces for sound to travel and get trapped. In addition to that, once the sun hits a snowy field a thin layer of ice forms on the top almost immediately, so the porous material that traps noise in its first hours becomes a soundwave reflecting surface that turns a silent landscape into a sort of amphitheater.

在降雪后，这种能抑制声音的空气袋不会持续很长时间。精致的雪花一旦落到地面，形状就会迅速改变——当它们开始依偎在一起或融化时，它们之间的空间就会缩小，声音传播和被捕捉的空间就会减少。除此之外，一旦太阳照射到雪域，顶部几乎立即就会形成一层薄冰，所以在最初几个小时内捕捉噪音的多孔材料就变成了声波反射表面，将寂静的景观变成了一种圆形剧场。

So next time you hear that hush of new fallen snow, enjoy it! It probably won't last long.

所以，下次你听到新落下的雪的寂静时，享受它吧!这可能不会持续太久。