## 5 Field Test Results and Discussion  
All tests in this study were conducted under consistent conditions, maintaining the same trench dimensions, load source position, and accelerometer locations. The impact energy generated in manual hammer tests, being a man-made vibration source, can be influenced by various factors that may lead to energy losses post-impact. Therefore, a total of 17 tests were conducted, with at least three tests for each scenario, both with and without barriers. The distribution of these tests is as follows: No Trench (3 tests), Empty Trench (6 tests), BCCB Trench (4 tests), and Styrofoam-filled BCCB Trench (4 tests). A single impact  
Figure 23: A general overview of the experimental measurements: (**a**) No Trench, (**b**) Empty Trench (c) BCCB Trench, and (**d**) Styrofoam-filled BCCB Trench. test's acceleration-time responses of all cases in three directions for each accelerometer are presented comparatively in Figure 24.  
Figure 24: _Cont._  
It is known that the vibration data generated by the impact loading usually has a sudden and short-term character. Spectral magnitudes change in direct proportion to the intensity of the impact. The higher the impact magnitude, the higher the spectral amplitudes become. The energies of the vibration data also change in direct proportion to their amplitudes. When examining the acceleration-time histories in Figure 24, which are plotted by taking a single sample from the impact tests, it is observed that they exhibit a behavior similar to the general characteristics of the vibration responses measured in general impact tests. In more detailed terms, the acceleration data from the sensor (M129) right in front of the load source reaches a peak value in a very short time (0.01-0.02 s) and is damped within a short duration of time, as under conventional impact. This duration during which the vibration energies are concentrated is approximately 0.6 s. The variations in the amplitudes of the vibration data over time in the NS and UD directions, which are parallel to the directions where the vibration direction is dominant and where the hammer application is applied, exhibit approximately the same characteristics in four impacts. These characteristics are also similar in the vibration data of the other impacts. There are small differences in the maximum amplitudes of the vibrations in Figure 24. These differences arise from the difficulty in producing an equivalent magnitude of energy for each impact test. Some adjustments, which will be explained in the subsections, will be made to approximately equalize the energy levels. The slightly different vibration data obtained from the other accelerometer in front of and behind the barrier is related to the presence and characteristics of the barrier. In order to quantitatively measure the vibration reduction performance, the concept of Amplitude Reduction Ratio (ARR) proposed by [PERSON] (1968) is widely used [53]. This ratio is defined as the ratio between the maximum spectral amplitude obtained at a specific measurement point in the presence of a wave barrier and the amplitude of the same measurement point under free field conditions. [PERSON] also suggested a maximum Amplitude Reduction Ratio (ARR) of 0.25 for an effective wave barrier. Nevertheless, it is possible that a higher or lower ARR may be more appropriate in certain circumstances. [PERSON] and [PERSON] (2011) proposed that the effectiveness of a barrier can be evaluated based on displacement, velocity, or acceleration data [1,31]. ARR values are calculated according to the formula given in Equation (4). In order to qualify the percentage of vibration mitigation, Vibration Mitigation Performance, VMP, values calculated according to Equation (5) based on ARR values were used.