Effect on optimum sonar frequency of different absorption-loss expressions

It is well known that an optimum operating frequency exists for a particular sonar system with a specified range capability. In this paper, the extreme importance of the frequency curvature of the acoustic absorption-loss coefficient used in determining the optimum frequency is illustrated. A lower bound on optimum operating frequency, independent of the expression used for absorption loss, is derived. Results are presented for both active and passive sonar systems, and for four different, generally-accepted absorption-loss coefficient expressions.