It's amazing and wonderful how much total knowledge lurks on this one list.  Brilliant.

I think also you've explained why white noise (which is mostly high frequencies) will block out other noises.  I just have to think about it a bit more.  (-:

Lindy

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Cedric Chang
Sent: Thursday, June 28, 2007 9:24 AM
To: Microcontroller discussion list - Public.
Subject: Re: [OT] Why do I only hear the bass drum? 

Let me provide some more examples.
Light is a much higher frequency than the 2.45 GHz used by
WiFi.  AM  radio is a much lower frequency than WiFi.
All three of these phenomena are Electromagnetic radiation.

You can see through kitchen strainer.  To high frequency light
the holes in the strainer look huge.  To lower frequency WiFi
and AM radio, the holes in the strainer don't look like holes
at all, but more like a solid reflective surface.  Now switch
to a chain link fence.  To light and WiFi radiation, the fence
is pretty transparent but to AM radio it looks like a solid reflective
surface.


Now try a different experiment.  Put a bb in front of a point light  
source
such as the sun.  The pea will cast a shadow indicating that the bb can
block light since the wavelength of light is smaller than the pea.
The bb cannot block WiFi or AM radiation because they have longer
wavelengths than the size of the pea and WiFi and AM easily "bend"
around the pea.

Now hold a pie pan in the air.  The pie pan will block radiation from
a directional WiFi signal and yet a directional AM signal will bend  
around
the pie pan and continue onward.

Cedric

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