Re: Very quiet recordings

["Raimund" animalsounds]

<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