## 4 Results
### Evaluate the Influence of the Intersecting Area between PZTs--Test Model 2  
The study meticulously examines the influence of the intersecting area between PZTs on acoustic energy transfer. To ensure the accuracy of our findings, we designed a precise experimental setup. Two parallel metal plates were instrumented with PZTs in specific positions, as per the schematic diagram in Figure 6. These plates were then submerged in water, similar to Conf.2, and positioned at a distance of 100 mm. The intersection areas were varied in alignment percentages from 100%, 40%, 12%, to 0%, with 100% representing perfect alignment and 0% indicating complete misalignment.  
These aligned regions, a key aspect of our study, are visually represented in Figure 6. Furthermore, Figure 10 provides a clear visual of the variation in the S21 signal for the other intersections, enhancing understanding of the results.  
The first thing to observe in Test Model 2, compared to Test Model 1, is the decay in the S21 signal when the water barrier is added. The signal close to \(-1\) dB before is now \(-13\) dB for the region with the intersection of 100%, as shown in Figure 10. This value for parameter S21 is considered a not-so-good value because the closer to 0, the better the relation between S11 and S22. However, it is still possible to observe the signal transfer with the communication between transmitter and receiver, even with two steel barriers and a large water barrier. These factors are interesting as they ind  
Figure 10: The values that maximize the signal of S21 for the Test Model 2 for SP1 and Conf.2, where there is a water barrier between the test specimens, are identified by each black mark. These marks represent the value that maximizes S21 for each intersection percentage, guiding us in finding the optimal signal.  
Figure 9: Graph of the values that maximize the signal of S21 for Test Model 1 and SP 1. Each red mark represents the value that maximizes S21 for each temperature. Moreover, the variation in \(\Delta\)dB is marked on the right side.  
communication between the transducers, proving the data transmission theory with more than one physical barrier, which in this case, is three physical barriers.  
Another consideration is the intersection of areas. Communication between transducers is optimized when the transmitter and receiver are perfectly aligned horizontally. The data in Figure 10 show that the signal decreases as the intersection decreases. Parameter S21 is close to \(-13\) dB at the 100% intersection. For the 40% intersection, it is around \(-15\) dB. However, there is still communication between the transducers. For the 12.5% intersection, the signal starts to diffuse close to \(-19\) dB, and for the 0% intersection, the result also maintains this value. The result is then considered no longer to have good ultrasonic communication for these values. In addition, it proves that the more horizontally aligned the devices are, the better the ultrasonic communication and data transmission. The red line on Figure 10 emphasizes a linear relationship between parameter S21 and the intersection of the area, showing a uniform decay of S21 as the misalignment of the transducers worsens.