Attenuation of sound is the process of decay in the amplitude due to combination of absorption and scattering. Transmitted pulse is influenced by many factors for selecting the center frequency of active sonar. For example, for a fixed size transmitter array with constant radiated power, ambient noise decreases with frequency and the source level increases with frequency. These considerations would suggest the use of high center frequency. On other hand the absorption of the medium increases with frequency Here, in this paper the relationship between the range and optimum frequency is derived which helps in selecting the center frequency.