I hope this gets more scientific discussion, but I'm very sure this effect happens. When I lived in MN if I'd go outside on the absolute coldest days, like -30F sort of days, the one thing that always struck me was how loud everything seemed, from the crunching of snow under my feet, or even neighbors at the end of the block talking in a normal speaking voice and yet still being able to hear what they were saying.

Edit: Did some Googling, and apparently the explanation about refraction is correct? Essentially the ground air is extremely cold but there's a layer of warmer air above which effectively ends up bouncing the sound waves back towards the ground allowing them to carry much farther than normal