Howling Wind

Last post
FoilDodo's picture
FoilDodo
Offline
Joined: 03/19/2008 - 23:50
Posts: 1836
Howling Wind

I know that sound is always motion of some kind. But what motion makes the sound of the wind? Molecules? When foiling I can hear the sound of the air over my sail. Open the window in a moving car and you can "hear the wind". Right now I can hear the wind outside, but what is it? That "freight train" sound of roaring wind in a tornado... it's not the airborne mobile homes making that noise, is it? It seems like all those sounds are the same frequency (pitch), just more or less loud. Here's some music to help you contemplate:

0 Like
webguy's picture
webguy
Offline
Joined: 12/31/2000 - 22:01
Posts: 8776
Re: Howling Wind

Vibrations of the wind molecules - usually from turbulence. That's why a foil that has a square edge has a whistling but one that has a beveled edge has less/doesn't. (Same concept even if the "fluids" aren't the same. )

IMAGE(<a href="https://static.wixstatic.com/media/a4ab0b_599a31cada8f4b81970f47496a975695~mv2_d_1724_1588_s_2.png/v1/fill/w_632,h_582,al_c,usm_0.66_1.00_0.01/a4ab0b_599a31cada8f4b81970f47496a975695~mv2_d_1724_1588_s_2.png" rel="nofollow">https://static.wixstatic.com/media/a4ab0b_599a31cada8f4b81970f47496a975695~mv2_d_1724_1588_s_2.png/v1/fill/w_632,h_582,al_c,usm_0.66_1.00_0.01/a4ab0b_599a31cada8f4b81970f47496a975695~mv2_d_1724_1588_s_2.png</a>)

https://www.windfoilzone.com/single-post/2017/07/13/WHY-IS-MY-FOIL-WHISTLING

When you hear the wind, it's because the wind is moving across some object from your ears to things like trees, etc. The turbulence creates pressure waves -> sound.

Similarly, the whole science of making jet engines quieter involves understanding and diminishing the turbulence of the exhaust flow: https://en.wikipedia.org/wiki/Jet_noise

Quote:

The jet mixing sound is created by the turbulent mixing of a jet with the ambient fluid, in most cases, air. The mixing initially occurs in an annular shear layer, which grows with the length of the nozzle. The mixing region generally fills the entire jet at four or five diameters from the nozzle. The high-frequency components of the sound are mainly stationed close to the nozzle, where the dimensions of the turbulence eddies are small. Further down the jet, where the eddy size is similar to the jet diameter, is where lower frequency begins.

btw, that cat, Cat, goes by a new name these days.

more wind noise

0 Like
FoilDodo's picture
FoilDodo
Offline
Joined: 03/19/2008 - 23:50
Posts: 1836
Re: Howling Wind
Quote:

more wind noise

Thanks Mr Wizzer!
Shok

1 Like
webguy
arrogantj's picture
arrogantj
Offline
Joined: 01/24/2012 - 14:11
Posts: 751
Re: Howling Wind

How 'bout some Howlin' Wolf?

Air going past his harp Wink

IMAGE(<a href="https://media.giphy.com/media/M8u09RcuTzSNO/giphy.gif" rel="nofollow">https://media.giphy.com/media/M8u09RcuTzSNO/giphy.gif</a>)

--- The Arrogant Jerk: Crabby and irritable since 1998.

0 Like
Randy's picture
Randy
Offline
Joined: 05/05/2002 - 10:38
Posts: 3013
Re: Howling Wind

The interesting thing is when you are moving under wind power you usually don't hear the wind that much. Sometimes you do hear it when it is picking up a lot sailing, but I seldom recall hearing it on the kite buggy. I suspect one thing you hear at the lake is the sound of the wind going through the trees. On the water you have visual cues from the water - dark patches, suddenly more whitecaps, etc. On land you don't have that and whatever you see and hear (esp. flying kites on long lines) can be misleading because the wind where the kite is can be a lot different from you think it would be.

There is no off season.

1 Like
FoilDodo