Measurement and simulation of the channel intensity impulse response for a site in the East China Sea

A model for the channel intensity impulse response Ic(t) is presented that is generally applicable for source-receiver ranges less than ten water depths. The separate impulse response functions from each arrival, such as the single surface bounce or surface-to-bottom bounce, are modeled using bistatic scattering concepts and are incoherently summed for the total response function. The expression Ic(t) is equivalent to a time-averaged response and embodies the boundary scattering and reflection physics corresponding to the center frequency at which computations are made. To compare with observations, Ic(t) is convolved with representations of the 8- and 16-kHz continuous wave (CW) pulses, and an 8–16-kHz frequency-modulated (FM) pulse, that were used in the Asian Sea International Acoustics Experiment conducted in the East China Sea (depth 105 m). For the FM case the computation frequency is 12 kHz, the center frequency of the FM pulse. It is found that six primary arrivals dominate the response for ranges less than about 1 km. With modeling of Ic(t) limited to these paths, the basic structure of Ic(t) is set by bottom properties and acquisition geometry with some changes in intrapath time spreading that depend on sea surface conditions.