J
John Cochran
Here are a couple of pretty good sites concerning calculations for echos provided by cindy19335; thanks cindy!
http://www2.umdnj.edu/~shindler/eq2.html#basicm
http://www.echobyweb.com/htm_level2_eng/formulas&calculations.htm
http://www2.umdnj.edu/~shindler/eq2.html#basicm
http://www.echobyweb.com/htm_level2_eng/formulas&calculations.htm