الوضع الليلي
1:26:43 
2023-05-17 
1087
Science explains why shouting into the wind seems futile
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.
Pulkki’s first attempt at testing the effect involved him hollering with his head out the top of a moving vehicle as microphones recorded the amplitude of his voice. The results were inconclusive about the reason yelling upwind seems hard, so Pulkki and colleagues upped their technology game.
For the new study, the team put a simulated yeller — a cylinder and a speaker playing multiple tones — on top of a moving vehicle. Microphones measured sound amplitude at the location of the mouth and ears when the yeller was facing either upwind or downwind. The experiments together with computer simulations confirmed the source of the misperception, the researchers report March 31 in Scientific Reports.
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. 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.
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