I do not come to this forum very often because of lack of time....but I read some of the topic titles and saw a few I really want to comment on that are very old.
Many of you know me ads most, probably do not. If you do not like what I say or you do does not mean a lot to me but I think the truth needs to be out in this industry.
Absorption coefficients that are published are in "most" cases incorrect by up to 60% or more.
Scattering information also leaves a lot to be desired as well as most "fixes" to the data.
The way scattering information is used in simulation programs is as another" absorption coefficient".
People who tell you to "add" numbers to the scattering numbers in databases are "flat out wrong".
The recent research on this indicate that "scattering" IS another form of absorption... thus increasing the absorption coefficient.
In fact, The shape of the absorption in most cases increases the absorption of the material even when the area remains the same.... THUS the numbers you have ONLY apply to the actual sample tested and cannot be extrapolated for other shapes and areas.
If interested in the researchgo to
www.nwaalabs.com and download the papers on the front page.
Thr reason items like geometric (diffusion) devices do not have a scattering coefficients is because of what scattering is.
Geometric devices CANNOT be assigned a scattering number because the are NOT scatterers. They are specular reflection devices and CAN be modeled in the simulation programs and should be by using things like groups or objects.
These can then be ignored when the lower frequency limits of the device is reached. The LF limit is based on the smallest size of the device.
If interested in getting more info please email me or call me at
[email protected] or phone is 253-973-1018.
Ron Sauro
NWAA Labs, Inc