Measurement of absorption coefficients at 80 kHz band for broadband underwater acoustic data transmission

To achieve high-speed acoustic data transmission, the use of a frequency band of 80 plusmn 20 kHz is being considered. However, the absorption attenuation coefficient in these frequencies only has empirical formula. Therefore, the absorption attenuation was measured using the frequency of 60 to 100 kHz within the propagation distance of 530 to 700 m at approximately 1,000 m depth. The transmission signal wave form was measured with conductivity, temperature, and depth (CTD) data. From these measured data, the absorption attenuation coefficient was calculated using several empirical equations. Calculated value of absorption attenuation coefficients by using measured signal were compared with calculated value by several empirical equations. As a result, a corresponding comparatively good for the empirical formula of Francois and Garrison.