High resolution vertical directionality estimation using ambient noise data of shallow arabian sea

The information regarding seabed properties such as compressional sound speed, attenuation and layering are useful in transmission loss estimation for sonar application. Passive measurement techniques can be used to extract information regarding seabed and in this work time series ambient noise data measured in shallow waters have been used. Vertical noise coherence and vertical directionality of ambient noise field are related to acoustic properties of the seabed. Assuming Toeplitz property of ambient noise, higher resolution vertical directionality can be obtained by making array appear larger than the actual dimension and background theory is explained in a recent paper by Siderius et al.,^[l]. Using the above property and technique additional entries in the noise Cross Spectral Density Matrix(CSDM) can be made and which effectively creates synthetic hydrophones on an array. The new CSDM can be used to beamform resulting in high resolution vertical ambient noise directionality. The objective of this work is to achieve high resolution in vertical noise directionality using the above method.