A vessel is using a 180kHz side sonar exploring the marine environment. The active diameter of the circular sonar transducer is 3.5cm. The measured sound pressure 1m in front of the transducer is 10^11 microPa. A pulse is transmitted and an echo is returned from 200m range. The received echo strength single is 150 mircoPa.
(a) What is the source level (SL) is dB?
(b) What is the absorption at 180 kHz?
(c) What is the directivity index?
(d) What is the transmission loss in each direction assuming spherical spreading loss in the first 25m?
(e) What is the target strength (TS) o the target?
(f) What is the figure of merit (FOM) in a port environment with a background noise level of 100dB?