Abstract:
The development of high-power, low-frequency sound sources and methods of acoustical tomography has been enhancing the range of observation of underwater inhomogeneties in the ocean from local to global scale. In this way, the problem of the role of underwater mountains in sound field formation arises. It also looks attractive to apply a low-frequency sound for large-scale acoustic ocean mapping. The characteristic of sound reflection by underwater mountains has not been studied enough until now. A review of experiments made in the Pacific and Atlantic on long-range sound reflections from underwater mountains and continental slopes is presented. During the measurements, continental slopes were sounded by tone-burst signals of about 240-Hz frequency from distances of 600 and 200 km. Receiving systems deployed at 20--90 km apart from the slopes detected both the forward and reflected signals. The reflection coefficient was found to be about -(20--30) dB. This makes it possible to observe the reflections everywhere in the ocean. Different schemes of long-range ocean mapping based on low-frequency echo sounding and on coherent and incoherent aperture synthesis are discussed. [This work was supported by RFBR Grant No. 96-02-1944.]