## 3 Results and Discussion
### Validation of Natural Frequency Parameter and Acoustic Power Calculation
Similarly, for a Case II plate, the maximum peak sound power level is obtained for taper ratio \(T_{x}\) = 0.75 and minimum peak is seen for taper ratio \(T_{x}\) = 0.50 for a plate with 2 rectangular stiffener patches combination. Also, for a Case II plate, it is interesting to note that peak sound power level increases for increasing value of taper ratio for plate with 1 rectangular stiffener patch combination and the peak is seen to be maximum for a taper ratio \(T_{x}\) = 0.75. However, for a plate with 4 rectangular stiffeners patches combination, the peak is seen to be at a minimum for taper ratio \(T_{x}\) = 0.75 and maximum for taper ratio \(T_{x}\) = 0.50. Furthermore, it is investigated that for case III plate, peak sound power level decreases for increasing value of taper ratio for all combinations of rectangular stiffener patches attached to a plate. For a Case III plate, the maximum peak of the sound power level is obtained for taper ratio \(T_{x}\) = 0.25 for a plate with 2 rectangular stiffener patches combination and minimum peak is observed for taper ratio \(T_{x}\) = 0.75 for a plate with 4 rectangular stiffener patches combination. From Figure 29, it is observed that for a Case I plate peak is maximum for taper ratio, \(T_{x}\) = 0.75 for plate with 1 concentric stiffener patches and minimum for taper ratio \(T_{x}\) = 0.50 for 2 concentric stiffener patches. For a Case II plate the highest peak is seen for taper ratio \(T_{x}\) = 0.75 for 2 concentric stiffener patches. Similarly, for case III plate lowest peak is observed for taper ratio, \(T_{x}\) = 0.75 for plate with 4 concentric stiffener patches. However, from Figures 28 and 29, it is necessary to mention that for a Case II unloaded tapered plate the highest peak sound power level is seen for taper ratio \(T_{x}\) = 0.75. Furthermore, it is also observed that the peak sound power level increases for case I plate for taper ratio \(T_{x}\) = 0.75 and peak sound power level decreases for a Case III plate for taper ratio, \(T_{x}\) = 0.75. It is thus quite obvious that different combinations of rectangular and concentric stiffener patches have a significant impact on peak sound power level corresponding to the (0, 0) mode. Furthermore, different combinations of rectangular and concentric stiffener patches with different taper ratios provide us design options for peak sound power level. For example, for peak sound power reduction, taper ratio \(T_{x}\) = 0.75 with 4 rectangular stiffener patches and 4 concentric stiffener patches combination, as well as taper ratio \(T_{x}\) = 0.50 with 2 rectangular stiffener patches combination, for a Case III plate may be the options. Similarly, for sound power actuation, taper ratio \(T_{x}\) = 0.75 with 1 rectangular stiffener patch and 1 concentric stiffener patch combination for a Case I plate and 2 rectangular stiffener patches and 4 concentric stiffener patches combination for a Case II plate may be the alternative solution. However, for an unloaded tapered plate, it can be added that for taper ratio \(T_{x}\) = 0.75 for a Case III plate may be considered as a poor sound emitter and a taper ratio \(T_{x}\) = 0.75 for a Case I and Case II plate may be considered as the highest sound emitter. Figure 16:1 Comparison of peak sound power level (dB) for (**a**) Case I, (**b**) Case II, and (**c**) Case III plates having different parabolic thickness variations with different attachments of rectangular stiffener patches.