2.3 The hardware system: single-sensor receivers and one source
From what is described above we guess a hardware system of acoustic tomography by several single-sensor receivers and one source. All the receivers and the source are placed above the thermocline (Fig. 5). The width and length of the monitored area in Fig. 5 are all about several km.
Fig. 5 monitors the internal wave and tide by single-sensor receivers and one source.
This hardware system has two advantages. One is that it is cheap because each receiver contains only one sensor. The second is that it is robust to the measure error caused by the receivers' depth and distances. Several steps have been done for realizing this idea. The propagation models of BDRM: and coupled BDRM theory have now been developed. The experiment for monitoring the tide had been conducted in Sep. 1997 in Yellow Sea. This experiment has gotten satisfied result. At the same time the bottom buoy systems for the purpose of acoustic tomography is being developed under the cooperation between China and Russian.
3. BDRM THEORY: THE FORWARD PROPAGATION MEDEL
The sound field excited by a harmonic point source can be expressed as a sum of normal modes
