# Evaluation of Noise-Reduction Techniques for Gas-Turbine Test Stands: A Preliminary Analysis
## 6 Results
### Pressure Loss and Self-Noise Assessment  
Table 1 presents the pressure loss for each analyzed configuration that used the Algrem [15] analytical method concurrently with the numerical method. The pressure loss was calculated at an inlet velocity of 10 m/s, resulting in an air velocity of approximately 30 m/s in the case of linear baffles and 40 m/s for staggered baffles. The pressure loss for  
Figure 14: Influence of flow on sound attenuation—FEM method [dB]. Figure 13: The influence of flow on the sound-pressure field: Mean air velocity ((a)—direct, (b)—inverse flow) [m/s], mean air density ((c)—direct, (d)—inverse flow) [m/s], and sound-pressure level ((e)—direct, (f)—inverse flow) [dB], fields. the staggered baffles was exclusively computed using the finite-element method (FEM) due to inherent limitations in the Algrem method. Linear configurations show lower pressure losses as compared to the staggered configurations. Staggered configurations generate significantly higher pressure losses due to the increased flow complexity and stronger interactions between the jets and deflector surfaces. Figure 15 shows the pressure and velocity field inside the attenuator. Figure 15: Flow fields inside the attenuator: (**a**) pressure field—Conf I; (**b**) velocity field—conf I; (**c**) pressure field—Conf II; (**d**) velocity field—Conf II; (**e**) pressure field—Conf III; (**f**) velocity field—Conf III; (**g**) pressure field—Conf IV; (**h**) velocity field—Conf IV; (**i**) pressure field—Conf V; (**j**) velocity field—Conf V.  
The single-baffled linear configuration shows the lowest pressure loss among all configurations analyzed. The close agreement conformity between [PERSON]'s and FEM results (124 Pa vs. 164 Pa) suggests a reliable estimation of pressure loss for this simple configuration. By adding a second baffle in a linear arrangement, the pressure loss increases slightly compared to the single-baffle configuration. The results from Almgren and FEM are again quite close (154 Pa vs. 175 Pa), indicating a consistent and predictable increase in pressure loss due to the additional baffle. When a third baffle is introduced, the pressure loss continues to increase, but the effect is not as significant as might be expected. The close match between Almgren and FEM results (184 Pa vs. 191 Pa) shows that the linear addition of baffles has a diminishing effect on increasing pressure loss. The double-baffled staggered configuration results in a significant increase in pressure loss compared to the linear configurations. The FEM analysis shows a pressure loss of 446 Pa, which is substantially higher than the double-baffled linear configuration. This indicates that the staggered arrangement causes more turbulence and resistance to airflow. The triple staggered configuration shows the highest-pressure loss at 737 Pa, as shown in the FEM analysis. This configuration introduces the most significant turbulence and obstruction of airflow, leading to the highest energy loss in all configurations analyzed. Square-edged baffles have a significant negative impact on the airflow or fluid flow. Their sharp-edged design causes flow separation at the deflector inlet, leading to the formation of recirculation areas and turbulence downstream of the deflector. This separation and recirculation contribute to energy losses in the form of heat and increase pressure losses. In a staggered configuration, deflectors are arranged in such a way that it forces the flow to follow a zigzag path. This creates multiple points of flow acceleration and deceleration, each point contributing to additional pressure losses, similar to the effect of steps. In addition to increasing pressure losses, the turbulence and recirculation areas, which are generated by square-edged deflectors and staggered configurations, have another important effect: noise generation. Turbulence creates vortices and rapidly changing pressure fluctuations, which are significant sources of noise.