In layman's terms, standing waves are created on a transmission medium when the physical wavelength of the transmitted frequency (as perceived by the transmitter) is not equal to the electrical wavelength of that same frequency, resulting in some of the energy not being transmitted, but rather...
Late response, but if you still need an Erlang C table, you can find it (and Poisson & erlang B as well ) at http://www.ittc.ukans.edu/EECS/EECS_663/LOCAL/erlang-table.pdf.