A Simple Ship Noise Canceling Method With Vector Transducer

For ship mounted sonar, the transducer received not only the required signal but also the ship noise. For distant signal, the ship noise is a strong interference. People try to use different means to eliminate the noise, such as adaptive cancellation, optimal array processing etc. But all these methods are complicated and expensive. A simple way based on vector transducer for noise reduction had been studied in this dissertation. The output of vector hydrophone contains the spatial direction information, in the other word, the output has different phase gradient to signal with different direction. We can compensate the phase difference and subtract at the direction of ship noise, then the noise can be cancelled. The merit o f this method is simple, stable and efficient. The main contents are:1. Introduce some common methods about noise canceling.2. Study the working principle of the vector transducer, mainly for two-dimensional pressure-gradient transducer. And the experimental results for direction pattern of two-dimensional pressure-gradient vector transducer are given.3. Upbuild the signal model for ship noise, deduce the relationship between sound pressure and particle velocity in plane wave. Demonstrate the theory of noise cancelling based on the vector hydrophone and point out the concept of the optimal delay. Deduce the estimation of DOA (Direction-of-Arrival) equations in the presence of noise.4. Give some simulation result about noise cancelling, find the optimal delay, then estimation of DOA with the narrowband signal and broadband signal at different SNR. The results show that the method is feasible.