Objectives  Aiming at the optimum frequency problem of typical shallow water environment,

  Methods  the relationship between the attenuation coefficient and frequency of the single-order normal wave was derived based on the bottom reflection loss three-parameter model, and the optimum frequency was solved. The correctness of the proposed algorithm was verified through the comparison with previous formula. Moreover, the method was applied to study the influence of the basement compressional sound speed, attenuation rate power exponents and bottom roughness on the optimum frequency of single-order normal wave.

  Results  The optimum frequency decreases with the increase of basement compressional sound speed; the optimum frequency becomes less obvious with the increase of attenuation rate power exponents; the change of bottom roughness has a great influence on the best frequency of near-field after superposition of all normal waves, but has little impact on the optimum frequency of single-order normal wave.

  Conclusions  The calculated optimum frequency is realistic for marine environment, and is beneficial for the underwater acoustic communication and detection.