Summary

The aim of this project is to validate the 1D theoretical directivity functions obtained analytically and numerically with experimental directivity function measured using direct contact and immersion techniques. Numerical theoretical directivity functions consist of the finite length, Gaussian and Sinc shape theoretical directivity functions.

1D linear phased array transducers were used to investigate directivity function. For direct contact, the experiment was conducted using aluminium as solid specimen and coupled with a coupling gel. Immersion wise, the experiment was conducted using water as coupling medium. The data was captured using Full Matrix Capture technique. The experiment was carried out with different specimen thicknesses (for direct contact) and distances between array and specimen (for immersion) using two types of array transducer; small and big element size.

The data was post-processed to compute the experimental and theoretical directivity functions. The experimental directivity was calculated in frequency and time domain using fast Fourier transform and Hilbert transform to provide a better comparison.

All the experiments in direct contact and immersion yielded a close agreement to either type of the theoretical directivity functions.

In general, immersion method is better as it provides a better coupling. Also, there is a stronger correlation (correlation coefficient value more than 0.9) between the experimental and theoretical directivity for immersion. For direct contact, the larger array follows the analytical theoretical directivity function. While for the smaller array, the experimental directivity yielded a closer agreement to the Sinc theoretical directivity function.

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