Physics Q & A - How do acoustic boards work?
Tong Shiu-sing (Translation by Kwok Yee-shan)  

Silence prevails at a snowy night
Silence prevails at a snowy night.

How do acoustic boards work? Why does silence prevail at a snowy night?

Have you noticed that many concert halls, conference rooms and classrooms have porous boards on their walls? These walls are made of acoustic boards, which are used to absorb noise. After sound waves propagate into the holes of the board, they will hit the spongy inner wall and lose energy. The waves will be reflected many times and most of the energy is dissipated as heat. The acoustic board has absorbed the sound.

In snowy days, everywhere is covered by a thick layer of snow. Snow does not have rigid structure like ice. Instead, snowflakes are packed loosely leaving many voids. The structure is just like acoustic boards. The voids absorb sound waves, especially those with frequencies greater than 600Hz. Therefore silence prevails at a snowy night.