The feasibility of detecting a large plume of oil drops using low‐to‐mid frequency active sonar.

The use of long range active sonar in the frequency range 1–10 kHz is considered with regard to its potential for detecting large quantities of submerged oil drops. In the scenario considered, the drops are modeled as fluid spheres of radius of order 1 cm, for which the acoustic wavelength is large compared with the oil drop radius. This means that the volume backscattering strength of a cloud of oil (of given volume fraction) increases rapidly with increasing frequency. The implied requirement for the use of high frequency sound is balanced against the preference for low frequencies in order to reduce absorption in seawater. Detection performance is simulated for a background of bottom reverberation and ambient noise. It is shown that the optimum detection frequency depends on drop size, coverage distance, and ambient noise level. At the time of writing, the authors are exploring the possibility of carrying out measurements during the summer of 2010 to test the modelling results. If available in time, re...