Thanks for this, Raimund. Fascinating stuff!
On 05 Jun 2012, at 19:39, Raimund wrote:
> <But every now and then there's moments where the wind lies down and the
> flies stay away and it's silent. Not quiet. But silent. I'm sure that anyone
> who's ever driven into the Australian outback or desert know what I'm talking
> about. I can highly recommend it>
>
> Peter,
>
> I think I know what you are talking about. I experienced that stunning
> silence several times shortly after sunset while camping in the Sonoran
> Desert (Arizona).
>
> There is a simple explanation for that kind of silence: A strong temperature
> gradient in the air above the ground creates a sonic shadow region for each
> sound source (the ground is still hot, but the air is getting cooler at
> night). See http://www.acs.psu.edu/drussell/Demos/refract/refract.html. So, I
> think there is still some noise around, but it just cannot be heard due to
> these refraction effects.
>
> Regards,
> Raimund
>
>
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