Currently compressive strength of a brick is determined by destructive method. The drawbacks of this method which starts right from the accuracy in sampling. The sampled brick represents the entire lot. Few of the bricks are sampled randomly and they are broken down to check the homogeneity and compactness of the internal matrix and to ensure the absence of voids, lumps, holes etc. However these destructive tests cannot be carried out for all the bricks. Present invention provides a method in which simply by hammering a bagasse ash brick with pre-determined energies and measuring the generated sound frequencies enable determination of the compressive strength of said bagasse ash brick. It eliminate the need to break the bricks for observing the internal holes and voids. The methods of current inventions are easy, more reliable, simple and non-destructive and can be automated which can further enable testing of all the bricks.