Underwater sound channel in the northeastern East China Sea

In May 2015 a shallow-water acoustic variability experiment (SAVEX15) was conducted in the northeastern East China Sea. Surprisingly, an underwater sound channel that is typical for deep water was discovered in this shallow water waveguide (∼100 m deep) with the channel axis at around 40 m. For a broad-band source (0.5–2.0 kHz) deployed close to the channel axis, channel impulse responses observed by a vertical array exhibited a complex arrival structure with a large delay spread (e.g., 160 milliseconds). Most arrivals are found to be surface and bottom reflected, while a pair of high-intensity refracted arrivals are embedded in the early reflected arrivals. Broadband simulations based on a normal mode propagation model show good agreement with data.