Secondly, the capability of
multipath interference resistance and the frequency choice decline were stronger. Thirdly, the capability of
decline-poor through the united coding of sub-carrier waves was stronger too. Finally the implementation of
DSP was easier because of the modulation and demodulation of OFDM through the using of IFFT and FFT. In
the underwater acoustic communication field these advantage of OFDM were the same as which was used in
the land wireless communication field. System hardware design and system software test had been completed,
finally the underwater acoustic speech communication system had been debugged. The pool test proves the
feasibility of this system. Speech effect is clear, can satisfy the hearing requirements.