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Sound in Fog

Badly Shaved Monkey

Anti-homeopathy illuminati member
Badly Shaved Monkey
Joined
Feb 5, 2004
Messages
5,363
While Rolfe is exploring the moon illusion, let's have another.

Are sounds really louder in fog- possibly transmitted more effciently maybe more quickly in saturated air? Or do they just seem louder because you are concentrating on hearing when visibility is reduced?
 
Are sounds really louder in fog- possibly transmitted more effciently maybe more quickly in saturated air?
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Not much. Up to maybe 0.5% more efficiently. Temperature has a bigger effect, and the sort of conditions likely to produce fog involve wet, warm air in contact with cold water or earth. My answer is:

If sound travels faster in fog, it's not because of the fog.
 
I don't see that loudness has any tie to speed.
Humidity makes sound travel faster, but does water droplets? My feeling is that fog makes the world quieter. Did you ever wake up in the night and notice it was quiet, then look out and see fog? I would think that the differing speeds of sound through air or through water droplets would tend to muffle sound. Sort of like the way the latest generation of ear protection works, cancellation of a wave with it opposite wave? And, I think the added mass of the water droplets must dampen the vibes too, since it takes more energy to vibrate heavier media. What's the mass of fog, vs dry air?
 
Capsid said:
Does fog affect sound refraction?
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Again, not fog itself, but the same difference in temperature that can produce fog can produce refraction of sound waves.

If the air is cooler when it's foggy then we should hear sound more clearly (not necessarily louder)?
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Cooler than what?

I'd say louder and clearer are, if not exactly the same thing, at least strongly connected. Temperature has a much stronger effect on both speed and amplitude than does humidity. It tends not to be real windy when it's foggy, and as far as clarity goes, I'd also expect temperature to have more of an effect than the moisture content of the air.
 
Capsid said:
Is it cooler when it is foggy than when it is not foggy?
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Not necessarily. If warm, moist air moves into an area that had been blanketed in cold, dry air, then fog forms where the warm, moist air is cooled by the surface of the ground (or water). So it gets warmer and foggy. Air somewhere else (say further inland) may be even warmer still, and rising. As it rises, it pulls the (comparatively) cooler (and foggy) air in to replace it. So in some places, it will get foggy, and cooler.
 
Unrelated...but having to do with sound in fog...the topophone was invented so that in fog, when we no longer have the benefit of clear vision, we can compensate by enhancing the direction-finding ability of hearing, if artificially.
mayer1a.jpg

Just 'cause it's so cool.
 
Is it not merely that when in fog, we pay more attention to what we hear, because we can't see well and feel endangered?
 
All we need is a warm air vaporizer and a decibel meter, total cost $30.00 to solve this question instead of just using thought experiments.
 
apocalypse said:
All we need is a warm air vaporizer and a decibel meter, total cost $30.00 to solve this question instead of just using thought experiments.
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I got yer thought experiment right here:

c = (331.5 + (0.6 * T)) m/s

where T is temperature in degrees Celcius.
 
Dymanic said:
I got yer thought experiment right here:

c = (331.5 + (0.6 * T)) m/s

where T is temperature in degrees Celcius.
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That covers the temp/speed relationship, how about humidity/speed?

And, fog being condenced droplets, not amorphus molecules, how does the fog effect sound?
 
casebro said:
That covers the temp/speed relationship, how about humidity/speed?

And, fog being condenced droplets, not amorphus molecules, how does the fog effect sound?
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The first colloid-related acoustic effect to be studied was the propagation of sound through fog; contributions by Henry, Tyndall and Reynolds made more than century ago between 1870-80.

"Under the auspices of the Elder Brethren of the Trinity House, and as their scientific adviser, Professor Tyndall has conducted an investigation on the acoustic properties of the atmosphere. The instruments employed included steam whistles, trumpets, steam syrens, and guns. The propagation of sound through fog was proved to depend not upon the suspended aqueous particles, but upon the condition of the sustaining air. And as air of great homogeneity is the usual associate of fog, such a medium is often astonishingly transparent to sound. Hail, rain, snow, and ordinary misty weather, were also proved to offer no sensible obstruction to the passage of sound."

In short, fog and rain have little effect, since the scale of the disturbances is much smaller than a wavelength.
 
Dymanic said:
The first colloid-related acoustic effect to be studied was the propagation of sound through fog; contributions by Henry, Tyndall and Reynolds made more than century ago between 1870-80.

"Under the auspices of the Elder Brethren of the Trinity House, and as their scientific adviser, Professor Tyndall has conducted an investigation on the acoustic properties of the atmosphere. The instruments employed included steam whistles, trumpets, steam syrens, and guns. The propagation of sound through fog was proved to depend not upon the suspended aqueous particles, but upon the condition of the sustaining air. And as air of great homogeneity is the usual associate of fog, such a medium is often astonishingly transparent to sound. Hail, rain, snow, and ordinary misty weather, were also proved to offer no sensible obstruction to the passage of sound."

In short, fog and rain have little effect, since the scale of the disturbances is much smaller than a wavelength.
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Do you think Amazon will take back my vaporizer and decibel meter? I can't see anywhere on the returns form that says "Unwanted: beaten to it over 100 years ago".

Still, the original point was a valid one.
 
Badly Shaved Monkey said:
While Rolfe is exploring the moon illusion, let's have another.

Are sounds really louder in fog- possibly transmitted more effciently maybe more quickly in saturated air? Or do they just seem louder because you are concentrating on hearing when visibility is reduced?
Click to expand...

http://www.doctorproaudio.com/doctor/calculadores_en.htm

The answer is not simple. Enjoy the various calculators on that page. Check out the excess attenuation one, for instance.
 
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