People upwind can hear you hollering into a breeze, but it's hard to hear yourself:
Shouting into the wind isn't so ineffective after all.
The idiom is commonly used to describe an unsuccessful attempt to communicate. But it's not actually more difficult to shout upwind, says acoustics researcher Ville Pulkki of Aalto University in Espoo, Finland.
Sending a sound upwind, against the flow of air, makes the sound louder due to an acoustical effect called convective amplification. Sound sent downwind is quieter. So, if you're yelling upwind, a listener standing in front of you should have no problem hearing you — contrary to popular belief.
The misperception has a simple explanation, Pulkki says. "When you yell against the wind, you hear yourself worse." That's because, in this scenario, your ears are downwind of your mouth. That means your own voice sounds quieter to you.
[...] A similar effect occurs when an ambulance goes by. Most people are familiar with the sudden change of pitch of the siren's sound due to the Doppler effect (SN: 8/2/13). But the siren is also slightly louder when moving toward a stationary observer than it is when it's moving away. When you're bellowing upwind, it's not the source of sound that's moving, but the medium in which the sound travels.
Whichever way the wind blows, acoustics can explain it.
(Score: 2) by Rosco P. Coltrane on Monday May 15, @03:30AM (1 child)
Why the more silent, the worse a fart smells.
(Score: 2) by DannyB on Monday May 15, @02:16PM
I have never before given any thought to your question which is if grate interest to all of humanity.
Pondering the subject, I have a theory. Suppose the flatulence has two components, a less offensive smelling gas and a much worse smelling gas.
Now suppose that earlier in the digestion both gasses accumulate at a faster rate than later in the digestion process when gasses accumulate at a slower rate. Furthermore, suppose that earlier in digestion the less smelly gas accumulates at much greater volume such that a a discharge of gas early in digestion is both louder because there is more volume of gas which accumulates more quickly creating greater pressure, and that gas has a higher concentration of the less smelly gas. The greater pressure of early digestion gas makes it noisy, and the higher concentration of the less smelly gas makes it not smell so bad.
At a later point in digestion, gasses accumulate at a lower rate, thus having lower pressure when there is a need to expel them, and thus they are quieter or even silent. However at this point in digestion the worse smelling gas is now a much higher percentage of the expelled gasses. Thus the quiet flatulence has a much worse smell due to the higher concentration of the worse smelling gas that has accumulated over the longer digestion period. That gas may contain components which smell worse due to how much longer the digestion has proceeded to this point.
This is a subject that is experienced by all of humanity. Not just some rare minor subset. Therefore this should be deemed worthy of a healthy government grant for more study. The research project would need to seek out and pay two groups of volunteers. The digesters and the smellers. Both groups would need to fill out questionnaires during the experiments.
Gasses would need to be collected and analyzed for their molecular or elemental components. The collected gas samples could be stored and labeled by subject as well as at what stage of digestion the sample was collected. Small samples could be drawn from the collected gasses to be judged by the group of smellers. Probably no single research volunteer should be permitted to be on both the digester and smeller group to eliminate potential bias in the data.
Another significant factor which must be studies, and which thus significantly expands the size of this study, is what foods are consumed.
The results of this study would need to be published in an open access journal such that the results could diffuse to all people on Earth.
How often should I have my memory checked? I used to know but...
(Score: 5, Insightful) by Barenflimski on Monday May 15, @03:41AM (2 children)
We have some soccer fields about 1/4 mile away. The only time we can hear the folks cheering is when the wind is blowing from the field towards our house.
I would imagine, that if air is where sound waves travel, that your voice would travel further in the direction the wind is blowing.
I would imagine that while the Doppler shift may make the sound louder while yelling into the wind, and quieter away, that distance is what matters to most. I may be louder for the first 10 feet, but the distance ones voice goes is minimized. One would be trading the energy for distance for the energy to increase the frequency.
A great analogy for those of us that still get outside is something we teach our kids. If you piss into the wind, you'll have super wet shoes as about 95% of the liquid ends up in about the same spot a it "piles" up due to the incoming wind. Conversely, if you piss downwind, you'll mist the entire side of your barn.
I'm not going to read the full article, but based on my life experiences paying attention to echo's, yodeling and trying to not hear the neighbors fighting, I'm going to guess that this guy who wrote this is talking about a very specific case with some hard distance limits.
(Score: 4, Informative) by darkfeline on Monday May 15, @10:33AM (1 child)
Human intuition is sometimes wrong, because you're using the wrong model. Sound isn't matter being carried by the air like your piss, sound is the compression (and decompression) of air. If the air is traveling in the same direction, it's attenuating the compression.
Air travel != sound travel. When you shout across a football field, it is not the air from your lungs traveling across the field.
Join the SDF Public Access UNIX System today!
(Score: 1) by khallow on Tuesday May 16, @02:20AM
Except that it's not attenuating the compression it's a background motion that doesn't have effect on the compression of airwaves.
My take is that there's multiple effects reducing strength of sound waves - it's diverging (energy spread out) and it's attenuating as some energy of sound waves goes into heating air. Consider your situation of shouting across a field. A stiff wind would be like 2% (say ~20 MPH or 30 km/hr) of the speed of sound. Shouting into the wind versus shouting with the wind effectively lengthens and shortens the field by this amount. So there is roughly a 4% difference in audio length between the two. When you consider the divergence of sound energy, that's effectively equivalent to an 8% drop in sound energy. And that additional length also means additional exponential decay from the moderately greater length.
Now consider also that there's higher background noise from the wind meaning that it won't take as long for sound to drop to the point where it is inaudible. I think this is a real effect.
(Score: 2) by Thexalon on Monday May 15, @11:06PM
Shouting into the wind might do nothing, but it's a lot better than trying to piss into the wind.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.