Hydroacoustic waves are used to experimentally transmit binary numbers underwater. The numbers are first encoded into pulse sequences, according to the encoding scheme: two consecutive short pulses for a digit zero and two consecutive long pulses for a digit one. A clock period determines the timing of the encoding pulses. The influence of the clock period duration on the number of correctly transmitted binary numbers is tested in 30m deep coastal seawater, at a 1500m distance. The performance is compared at three different periods of the clock: 10ms, 20ms and 40ms. Increasing the clock period of the encoding pulses leads to an increase in the number of correct transmissions. At the longest tested clock period of 40ms all the transmissions of binary numbers are successful. Certainty of correct transmission increases at the longer clock periods of the encoding pulses due to attenuated interference from reflected signals.
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