Queries Anechoic chamber(Plz help in this regard)

PLease could any one help.

1)The quiet zone in the anechoic chamber is where we called the relectivity is very low. But want to ask that How can we create quiet zone?What I understand is that in anechoic chamber the absorber is placed on walls and floors and the reflectivity is same in the chamber but I couldnt understand that how the quiet zone is created and what we have to do to set the boundaries of quiet zone?

2) I have read in an artyicle that "24 inch and 36 inch pyramidal absorber is used in the same anechoic chamber". I am confused that Is it practice to use two different height absorber in the same chamber.?

I'll be thankful if any one could clear my understanding.

regards

consider the shape of the anechoic chamber... there is a possibility of a quiet zone if there is more absorption at a site i.e. the edges and corners provided the walls are made of same material...

Thanks but i think i couldnt convey my query properly.

Hi Adnan

I have a different opinion about "quite zone". As we know the 'beam pattern' of an antenna is formed only at the 'far' end. Whereas in an anechoic chamber (usual not large enough for this..!), employs a 'parabolic reflector' (PR). If the source is kept at the 'focus' of this PR we get a 'flat wave-front' some 3-4 mtr away form it. This zone ('flat wave-front' zone) is called a 'Quiet Zone'.
Hope this question is answered.

Generally the shape & size of the reflector, the frequency in question, and few other such parameters decide the "size" of quite zone.

and Lastly...Please forward that artice or copy-paste relevent excerpts. let us know if you have got the answer...!( b'coz I too donot know...!:D)

Regards,
Sai

more comments plz