[axxl]

My thought on the general "loudness" of cold months was due to reduced noise blocking or absorbing greenery like tree leaves, grass, etc. Which is then altered by a significant snowfall leading to sounds being softened again.

[soulofmischief]

No one here has mentioned temperature inversion [0] which is responsible for a lot of the cold-induced amplification perceived in urban areas. It's quite a fascinating effect.

[0] https://wisconsindot.gov/Documents/doing-bus/eng-consultants...

[xerox13ster]

Cold air is also more dense, less momentous, and can transfer sound energy more efficiently between particles than hot air where the particles are spread out and have their own momentum to maintain rather than the sound's.

[xattt]

The volume of water flow should/would also vary at different times of the year, based on how much the water table is loaded.

Not sure how much of this would be complimentary to the acoustic effect of temperature. Either way, it’s not a simple single-solution explanation.

[ffsm8]

Shouldn't that be an inverse relationship though? Without leaves on the trees you should get less reflection, consequently more of the noise should radiate upwards. Unless you're standing at the other side of a bush/greenery. In that case it definitely absorbs a lot

[CrazyStat]

Lots of small unaligned surfaces, like leaves, scatter the sound and make it interfere with itself. Reflection only makes the sound louder if you have large smooth flatish surfaces.

[CoastalCoder]

I want to make a joke about the "three leaf" problem in acoustics, but I can't find a way to make it funny. Dang.

[BurningFrog]

My guess is that frozen terrain is harder, which reflects more sound and makes hitting it noisier.