Minimum Variance Distortionless Response (MVDR) technique is one of the signal processing ways for noise reduction. Its principle is to minimize the output power of the signal. This study simulated an underwater acoustic field using ray acoustic method. The acoustic field consists of a signal source, multiple noise sources and a line array hydrophones. The signal source is ship-radiated noise. The simulated combining signals received by the hydrophone array are used to restore the original signal source by MVDR technique. The study discusses the different objective functions given in MVDR in order to restore the original source. Then, the results are compared in computing time, effectiveness and adaptability. The results indicate that MVDR can be used to restore the original signal source with very high correlation coefficient up to 90% between the original signal and the restored one.
Time difference of arrival (TDOA) and time reversal mirror (TRM) are commonly used in acoustic source localization. TDOA has excellent results in free field, but fair results in multiple reflections environment. TRM is applicable in multiple reflections environment and for multiple sources localization. The study continues the advantage of TRM and combines MVDR technique of noise reduction in order to find source locations. The results indicate that the combined MVDR technique gives better noise reduction than TRM in multiple reflections environment. From the drawing of energy diagram of acoustic waveguide, the combined MVDR technique will focus energy on signal source and it also reduces the noise energy in the other region. Comparing between TRM and the combined MVDR for source localization, the combined MVDR gives better resolution than TRM does. In addition to give better resolution, the combined MVDR will find the source location by finding the maximum energy location, on the other hand, TRM is unable to reduce reflection interference effectively which might lead to misjudge the source locations. However, the combined MVDR needs more computing time than TRM does.
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