Simple question. My wife feels that traffic noise is louder on cloudy days than clear days. Since we can talk perfectly well in a fog, ISTM that clouds should be transparent to sound, but what do I know?
I googled your exact thread title and it turns out it’s a pretty popular question on the internet with people saying exactly what your wife said. Traffic (and airport noise) seems louder on cloudy days. Very quickly glancing at a few of the articles, clouds, in and of themselves, don’t reflect sound. However, clouds form when in the atmosphere when it’s cool enough for water vapor to condense. The switch from warm to cool air, and more specifically, less dense to more dense air, causes sound waves, not to reflect, but to refract back down to earth.
TLDR, correlation, not causation WRT more/louder ambient noise and hearing clouds.
PS, it’s entirely possible I didn’t get that all correct, but like I said, she’s not the first person to ask that question.
Also, clouds/water vapor would serve to absorb sound waves, I’d think.
Not sure, but I thought high or low air pressure helped make sounds seem louder or softer as well (don’t remember which).
Snowfall eats sound for breakfast but I assume that’s because of the fluffy nature of the snowflakes. You can still talk just fine to someone in snow, but the difference, as with fog, is that you’re only a few feet from each other, whereas when we’re talking about clouds they can be miles up and just as thick. The physics change at that sort of scale.
Once the Mythbusters were planning one of their explosions, and expert Frank Doyle said they had to wait because there was a deck of stratus clouds above. I think Adam asked “won’t the explosion just blow through the clouds?” and Frank laughed and said no way. But they never really explained why. I assume as @Joey_P said, the clouds themselves aren’t the issue, but the temperature differential(s) in the atmosphere that caused the clouds is the actual reflecting/refracting of the pressure wave.
Living in Memphis, I’m used to hearing the FedEx jets flying over at night. Some nights you hear them, some nights you don’t. Most people think it depends on cloud cover and air pressure. Then there are the rare nights where you can hear them taxiing to take off and it’s really loud. And I’m a good 15 miles from the airport. I’m not sure what weather combination causes that. People ask about it all the time on NextDoor because they were up at 3-4 a.m. and wondered what the hell that noise was.
One year, while living in the flight path of planes at SeaTac Airport, I called the airport noise hotline (they were seeking citizen input re noise and flightpaths in anticipation of a new runway). I told the person on the phone that airplane noise was much louder that summer. He told me, “It’s not actually louder this time of year, it just sounds louder.”
To refract is to bend the path of something, e.g. when you put your hand in water and the image appears displaced. Refraction is not something bouncing back to the source.
Do clouds reflect sound?
Only duck quacks…
Anecdotally, when I was surveying, there was a definite difference in sound out in the field if I was working in heavy fog versus a clear day. I spent sometimes weeks at a time in the same area (in a developed oilfield, say) where a certain regular background noise level was normal, and those heavy fog days were oppressively quiet.
Refraction can bend waves back towards their source. Especially when “their source” is something as big as the entire ground.
I didn’t mean to imply that if you honk your car horn, you’ll hear it echo off the clouds. I meant to imply that if you’re hearing ambient traffic noise, it’s probably coming from a few miles away not that it’s noise from your immediate area echoing off clouds directly above you.
Refraction is exactly what is happening:
A google image search for “atmospheric sound refraction” provides numerous illustrations of what’s happening.
From this site:
At night or during periods of dense cloud cover, a temperature inversion occurs; the temperature of the air increases with elevation, and sound waves are refracted back down to the ground. Temperature inversion is the reason why sounds can be heard much more clearly over longer distances at night than during the day—an effect often incorrectly attributed to the psychological result of nighttime quiet.
Depends on whether you/they are talking about the sound as emitted or the sound as perceived. The laws and traffic management policies regulate emissions, not perceptions.
But yes, the argument sounds funny.
Isn’t this precisely how rolling/reverberating thunder occurs?
I think rolling thunder is more often echoing off of buildings, mountains, or other terrain.
It’s scientifically explained in this paper :
The Attenuation of Audible Sound in Fog and Smoke
The Journal of the Acoustical Society of America 20 , 849 (1948);The Attenuation of Audible Sound in Fog and Smoke | The Journal of the Acoustical Society of America | AIP Publishing
https://asa.scitation.org/doi/abs/10.1121/1.1906448
Depends on the size of droplets forming in the cloud (which in turn may depend on pressure ) and the frequency of the sound (noise)
Cite : http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1048.4570&rep=rep1&type=pdf
“ Different types of clouds have been selected. Quantitative evaluation shows that, for low audible and infrasound frequencies, absorption within clouds is several orders of magnitude larger than classical absorption”
“ Sound absorption in clouds is mostly sensitive to the radius of water droplets and the total water content. For frequencies above 0.01 Hz, clouds with small droplets and high water content absorb more because they maximize the total surface of droplets. Sound absorption in clouds is much less sensitive to altitude.”
This is probably not related at all, but when I get annoyed at the neighbor’s dog barking at the wind while I am enjoying my porch, I will turn the misting system on. It really seems to make the idiot dog sound not quite so loud and barky. Or maybe its just because I enjoy the feeling of the 300 PSI mist floating around me and get so relaxed that I can ignore the idiot dog.
Demolition range activities were restricted with low cloud cover at three of the sites I worked at. The commanding officer (through the switchboard) would get nasty-grams/calls/editorials in the local rag from citizens who disliked having their porcelain shook/shaken? off the walls.
Better to cancel for a day than absorb the wrath of irate grandmothers 
Does the addition of smoke particles from a wildland fire add to the noise transmission?
There is a fire that has created clouds dark enough to seem like a partial solar eclipse. It is a 100,000 acre fire about 30 - 40 miles away. I thought i could hear the roaring, but there is a lot of background noise from an Interstate and a 150,000 population city twixt us and the fire, so it is probably the extension of that noise.
I think the smoke particles themselves aren’t really a factor, but the warm combustion gases that drove that smoke up to high altitudes creates the sort of thermal inversion that tends to refract sound down toward the ground. Not the sound coming from the ground directly below that warm cloud - but the sound from ground level on the far side of that cloud (relative to the observer).