Listening.....at night outside?

Posted: Tue Feb 26, 2008 12:12 am

Why is it that when at night when all is silent, you can hear people that are 100 ft away talking. But the same situation in the day you can't hear anyone?

Is the speed of sound affected by night and day? I know it is affected by temperature. But I notice this happens at the same temp. The temp for me is zero degrees Celsius.

Posted: Tue Feb 26, 2008 12:14 am

Could also be the fact that all the ambient noise "animals, traffic, building noises 'ie. heaters, stuff of that nature' cease at night and leave with you a more unadulterated path for sound waves to travel

Posted: Tue Feb 26, 2008 12:25 am

As Multok mentioned, there is man-made less ambient noise at night.

Humidity (air density) also has a direct bearing, as does air motion (wind). Ever been to an outdoor concert on a windy day?

Another reason is that your eyes don't work as well in the dark so your hearing becomes more accute.

Posted: Tue Feb 26, 2008 3:57 am

You'd think that sound travels better in low humidity rather than high humidity. But sound & reverb sticks around longer in a higher humidity environment like at night than a dryer sunlit day. If you've ever worked for a church on a regular basis, you'd notice that reverb was better indoors in the summertime when it was more humid than in the wintertime when it's dryer.

Plus, it seems that mentally disturbed people like myself prefer the peace and tranquility of the overnight. In comparison to the more frenetic daytime hustle. That's only for normal people.

How does that insomnia anthem go again? Something for nothing da da da something?
Ms. Remy Ann David

Posted: Tue Feb 26, 2008 4:46 am

Halifaxsoundguy wrote:

Why is it that when at night when all is silent, you can hear people that are 100 ft away talking. But the same situation in the day you can't hear anyone?

Is the speed of sound affected by night and day? I know it is affected by temperature. But I notice this happens at the same temp. The temp for me is zero degrees Celsius.

Interesting question. There are at least two effects going on here. One is already mentioned, that the background noise levels are usually very much lower, so the AGC in your hearing system can wind up and hear things that would otherwise be masked.

The other effect depends more on where you are and the what the weather has been doing. During the day, the sun heats the ground and in the evening the ground retains the heat, warming the layer of air near it. The upper air cools rapidly. This temperature gradient acts as a tunnel for sound, and low incidence angle sound waves from the ground are reflected off the cooler air layer back into to the warmer ground layer. This reinforces direct sound, so you appear to hear sounds from a distance more loudly than you would expect. It's like a whispering gallery in a domed building. A similar effect with MF radio waves and the edge of the troposphere causes AM reception to have interference from distant stations after dark and allows short-wave communications to circle the globe.

Posted: Tue Feb 26, 2008 5:21 am

I'm sure glad we have some competent British guys that know what they're talking about. Other than my brain damaged lost synapses. Yeah, what he said. Almost vaguely similar to my own understanding. If that were possible. I don't even know Boswell but I can hear him groaning above my computer's internal clock noise. So do you have a masters or a Ph.D. in electrical engineering and meteorology?? No, I mean physics. It's obvious that the British and Canadians are superior in every way. Except when it comes to being wrong. There no good at that. That's where we win!

Go George W. with his 91 IQ. Now that's American!
Ms. Remy Ann David

Posted: Tue Feb 26, 2008 8:18 am

Yeah Boswell - spot on! The thermal inversion one sees at dusk is THE big thang. You can see it when the smoke goes up a bit and then turns horizontal. And if it's over water you get 2 reflection surfaces - thus you can hear a dang mile away...
Sheeut! I knowed that an im from southcarolina.

Posted: Tue Feb 26, 2008 11:26 am

Along those same lines, why do we turn down the radio when we're reading directions and trying to find someone's house at night?

Why do we park in the driveway, and drive on the parkway?

I'd rather set up at night with no one around than during the daytime when the crowds are making me nuts.

I hate chatter and lots of people milling around when I'm trying to concentrate. The voices in my OWN head are loud enough.

Twisted Evil

Posted: Tue Feb 26, 2008 1:06 pm

I thought the poll was kinda stacked so here's my real answer: I only wear sunglasses at night in the middle of summer. The rest of the year I wear 'em only when I'm asleep.
gb

Posted: Wed Feb 27, 2008 1:12 am

Well, I really didn't admit this but, I frequently use yellow driving glasses at night. Throughout the year, in the car, on the motorcycle. Great haze cutters and contrast enhancers, while reducing headlight glare with ring cataracts over 50.

Dark glasses at night? Makes you look like its 1968 and you just ate a windowpane? Yeah, that's cool. I remember when I.....What? Yes hole assifer? Why am I wearing dark glasses? So I'm not so bright?? Honest, I haven't had anything....Nooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo............

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