# Research on Propagation Characteristics of Tire Cavity Resonance Noise in the Automobile Suspension
## 4 Power Flow Analysis of Tire Cavity Resonance Noise Propagation in a Suspension System
Figure 11: Strain contour of a suspension system under different loads. (**a**) Strain contour under 2500 N load. (**b**) Strain contour under 3000 N load. (**c**) Strain contour under 3500 N load. (**d**) Strain contour under 4000 N load. (**e**) Strain contour under 4500 N load. Figure 10: Stress contour of a suspension system under different loads. (**a**) Stress contour under 2500 N load. (**b**) Stress contour under 3000 N load. (**c**) Stress contour under 3500 N load. (**d**) Stress contour under 4000 N load. (**e**) Stress contour under 4500 N load. It can be seen from the stress and strain contour of the suspension system under the above five different load conditions that the areas with high stress are located at the steering knuckle, lower swing arm, and shock absorber. The resonance noise energy of the tire cavity acted behind the rim, spread to the inside of the wheel, and finally spread to the steering knuckle, lower swing arm, and shock absorber through the spokes, resulting in high stress and strain in these three places. Therefore, it can be concluded that the energy transmitted to this area was concentrated, and the structural sound intensity was correspondingly large. With an increase of load, the stress and strain of our suspension system increased. Similar to the steps in the previous section, the structural sound intensity of a suspension system under different loads could be evaluated, as shown in Figure 12. It can be seen that there was a large degree of structural sound intensity near the rim edge and hub. With an increase of load, the structural sound intensity of suspension system increased. Figure 12: Power flow contour of a suspension system under different loads. (**a**) Power flow contour under 2500 N load. (**b**) Power flow contour under 3000 N load. (**c**) Power flow contour under 3500 N load. (**d**) Power flow contour under 4000 N load. (**e**) Power flow contour under 4500 N load. For the suspension system under different loads, we calculated data such as the sum of the structural sound intensity and cross-sectional area at each point of the wheel input surface and three output surfaces. The power flow was obtained as shown in Table 5.  
It can be seen from Table 5 that the total power flow of the three output surfaces of the suspension system under different loads was quite different, and different loads had obvious influences on the transmission of power flow. Additionally, the output power flow of the suspension system decreased slightly with an increase in load. It was this increase in load that led to an increase of input energy. In the process of energy transmission, damping consumes a great deal of energy, but the output energy is lower. Based on the sound pressure amplitude distribution of the tire cavity resonance noise under different inflation pressure conditions under a load of 3500 N and at a speed of 50 km/h, as shown in Table 4, the power flow results of the input surface and three output surfaces of the suspension system were calculated, as shown in Table 6.  
From Table 6, it can be seen that the difference of the total power flow of the three output surfaces of the suspension system under different inflation pressures was small. Additionally, the influence of different inflation pressures on the transmission of power flow was not significant. The inflation pressure was 0.22 MPa, and the output power flow