It’s been a while since I was outdoors at temperatures well below zero (like -10F, -20F). But my recollection was that things sounded “different” on those occasions, as if there were an exceptional level of clarity. In a parking lot a half-mile laterally from a runway approach path, jets on final approach sounded really crisp and clear, without particularly being louder than normal. The same could be said for cars just a hundred feet away in the same parking lot, or moving on the nearby road. Not really louder than usual, just more clarity.
Am I misremembering? Was I imagining at the time? Or is there really something about very cold ambient temps that affects acoustics?
Mostly because cold air is more dense than warm air, so sound travels more efficiently through the colder air.
Also, in the winter you often have colder air near the surface with slightly warmer air above it (since cold air sinks). Because the sound waves travel faster through the more dense colder air, the sound gets naturally refracted back towards the ground when it hits the boundary layer between the cold and warm air.
This is one of he many questions addressed in Jearl Walker’s wonderful book The Flying Circus of Physics. In the edition with answers it’s item 1.28 (the numbering in the original edition and the online edition is different). You can find it here:
Cold air also carries very little moisture, and so in addition to being more dense it also provides less damping of high frequency acoustic signals, so sound carries further without being muffled even compared with transmission in warmer air with low relative humidity.
Also snow will be more ‘squeaky’ when you walk on it. I think this is due to it retaining its very crystalline angular shape, and not melted at all (that’s a guess though).
You can tell how cold it is by the way the snow sounds.
I find it’s the quiet stillness after or during some snowfall that’s remarkable. Sounds that we do hear are more easily identified since everything stands out against the snow and leafless branches. The chirp of a bird, a rustle of dry reeds, the soft hopping sound of bunnies.
Of course, all it takes is a little breeze to make you &$%@&ing sorry you were born.
Way back in the day (1970s) I remember a friend and I discussing this one bloody cold winter day in Ottawa when, from Sir Robert Borden High School, we could hear aircraft, faintly but extremely clearly, taxiing at the airport, a distance of 4.5 miles. In our 16 or 17 year old scientific minds we concluded that that was because air molecules were closer together in the cold (yes, we were nerds ). It was pretty cool (no pun intended).
No, when there is a colder layer under a warmer layer, it’s called an inversion, by contrast with the “normal” condition where temperature decreases with increasing height above ground. What may be counter-intuitive is that the air is heated from below and not from above; the air is largely transparent to solar radiation.
). It was pretty cool (no pun intended).