Does sound travel better at night?

My speakers sound better at night ;-) Is there any science behind this?
Less grunge in the electricity, you are more relaxed, I believe most of us perceive our systems sound better in the evening.
My system sounds better at night too and I have determined it must be the quality of electricity coming throught the wall. As the neighbors and the city use less electricity, my belief is it allows cleaner electricity to flow and allows for better quality sound. I can't back it with science, but some smart audiogon member probably can.
The electricity travels better at night.
Rephrasing G m c I'd say electro-magnetic waves travel better at night.
Since we're dealing more with sound waves that have more mechanical nature the sound quality solely depends on the wall's power outlets.
Yes, it does! Most definitely! I can hear more car alarms, dogs barking, door slamming, screaming, crying, moaning, howling, singing, etc. at night than I do during the day! What gives?

Sorry, as far as sound systems go, refer to the answers above! I would agree with them in the electricity issues.
From 2 to 4:00am is the best in my location.
Mine also sounds better in the evening. I believe that the electricity supply is cleaner also, however I also believe that the seismic activity is less due too less travels on the road and the general noise floor in the local area (other people asleep). Maybe our bodies have a lower noise floor when we are relaxed more??
Even though consciously, you don't really notice it, at night the ambient background noise everywhere is lower. Therefore you will hear more at night, I think. If you've ever been outside at night when there is a widespread power outage, the silence is deafening. Often we do not realize just how much background noise is around us during the day, but at night, it is much lower. Just my 2 cents.

Happy night listening.
In most cases the improvement comes from the combination of,
"less noisy" & more abundant power supply,
reduced ambient noise,
and our own relaxation.
You are very likely more deaf at night (people consistently do better in hearing tests given prior to confronting noisy traffic, noisy work environments, etc.).
The wine helps.
Definitely better as I stoke more j _ h. PLUS, the wife and kids have retired upstairs and I'm finally alone.
James 50 and Gregm hit the nail on the head. Yes, less ambient noise allows for more detailed sound from your speakers. When I lived in the sierra mountains, the nights were very quiet and my system came alive with inner detail. Now I live in Santa Barbara and the ambient noises at night are no where as quiet, and subsequently, my critical listening sessions have suffered from it.
Don't forget that your natural cortisone levels tend to be higher in the evening, leading to psychological and physiological chages that impact perception and mood.
no wonder sean and others of the "old guard" have abandoned this site. this topic has been repalyed more times than sex in the city. booooooring!

It's just the circle of life...

IT'S THE MAINS. The current cleans up considerably at night when every other power hungry so and so is fast asleep. Try running a power regenerator like PS Audio and you will likely hear the same. Enjoy!
The speed of sound is directly proportional to the speed of light. When it is dark, the speed of sound increases because it is trying to find the light which is not there. When you see the light, you will understand the truth of my statement... grasshopper!
I think I see the light you speak of,oh great one... Why, it's coming from tube amps! He, he, he! Enjoy!
Ok I know I can't be the only one that knows this but, at night there is more moisture in the air due to less heat. More moisture means more density in the air, more density means more sound transferance. That is why you can hear traffic at night at much farther distances, voices, and dogs barking.
Sorry ibehere, but although the relative humidity might go up when the air gets colder, that does not mean that there is more moisture in the air, just that the air is colder containing the same amount of moisture as before. Its dew point remains the same.
One can hear voices or dogs better at night because there is usually less background noise to drown out those quiter sounds. Nothing to do with moisture in the air.
Bob P.
No,No,it's definetly the light.Make sure you have all lights of in the house,and I have found it makes much difference with the curtains closed. I left one open once and could not understand why the sound had not improved that evening,then I noticed a window blind was left open and emitting a small amount of light from the moon I think. I closed the blind and immediately the sonics changed. Now I have come to believe the moonlight is much better than say streetlight,but I much prefer no light at all. But it's all in the light man!
Especially if one is playing the 'Moonlight Sonata'!
Only if your Clever lil Clock is set to "PM" not "AM" in which case it will sound better in the morning.
I have to poke fun at these subjects to keep my sanity. I most definitely believe their is a profound difference most evenings,and I do not drink or use any uncontrolled substances anymore. It may be a combination of things. I read in a forum somewhere that radio stations are required to power down at a certain time in the evening also,which could play a role. I also noticed recently during the day when it was rainy out that my system sounded better,but it is almost every evening that I can tell the biggest difference. I would like to say it has nothing to do with the mind playing tricks with different mood-etc.,but the mind does cause us to believe some crazy things I believe.Sometimes I come to bed late and the wife asks me what I was doing,I respond the stereo was doing it again to me. It could quite frankly be a certain time when the body releases a certain chemical that happens at the end of the day that actually allows the brain to perceive our sound differently.I don't really want to believe that,but in reality it actually makes the most sense to me. I recently was talking to a well respected man in audio regarding this and he told me he could not critically listen to audio within two hours after eating,that after a meal it destroyed his ability to enjoy the music.Whatever the cause or rationale is,it is not slight. I am far from having a golden ear,and would like to tell you I am borderline deaf,but the night hearing thing is a real one for me also.I really want to blame it on the grunge in the power,and possibly a few combinations as listed in other posts,but seriously believe we create many of these things in our heads. I mean in the evening is usually when we decide ok it's time to listen to the stereo. We put the other thoughts,worrys,distractions aside and then,it's the magic evening thing happening again. I think it may be like the person that is blind,is the hearing really better or is the hearing just used more proficiently? Can we actually perceive the sound we want to hear if we are up tight,hungry,have things on our minds,are distracted in so many other ways?I mean the guy that is blind is no longer distracted by the vision of different things,so does he hear better now? Maybe some people can deal with the distractions and still hear what they hear when not distracted. Does this better sounding in the evening thing happen because we subconsiously set ourselves up for it?Whatever the reason it is usually like switching a light bulb on for me when it happens.
I agree with the cleaner AC, but I do not think that it plays such a big part.

Less distraction, both visual and sonics, better concentration on the sound ''images'' as it takes up your whole space, and a certain release from the tension of the work day. In complete darkness, it ''sounds'' even better too.
I find that if I have a certain amount of good brew during the day, that my system sounds as rockin as it does at night...