# Analysis of the Impact of Vibrations on the Driver of a Motor Vehicle
## 4 Discussion  
Having analyzed the dominant frequency values thus determined (Figure 11), isolating for the sample time intervals in which considerable vibrations were observed on the steering wheel, one can draw the following conclusions:  
* The fundamental frequency of the vibrations is approx. 35 Hz (approx. 2100 rpm), and it is dominant, while the amplitude in the FFT spectrum is up to 3.5 m/s\({}^{2}\);
* The consecutive dominant frequencies are harmonically related to the dominant frequency of 35 Hz, coming to twice that frequency (approx. 70 Hz). Figure 11: Detailed frequency analysis (FFT peak) for the steering wheel vibrations in the directions X, Y, and Z. Given that the dominant frequency value of 35 Hz is found near the peak of the curve of the vibration effect on human hands (the 8-16 Hz range reflects the most harmful resonant frequencies in terms of hand vibration; Figure 12), this frequency is considered rather uncomfortable and, where one is driving under adverse forcing conditions, it becomes arduous and unpleasant. Following an analysis of the vehicle speed (Figure 13) in the phases of perceptible and major driving wheel vibrations, certain conclusions have been drawn:  
* These vibrations are observed at velocities ranging between 40 and 100 km/h, and most frequently at 70-80 km/h;
* These vibrations are observed when the vehicle speed increases, either in the phase of acceleration or once a fixed running speed has been reached;
* The acceleration dynamic in the speed increase phases corresponds to an increment of approx. 2 km/h within 1 s, which translates into an acceleration of approx. 0.7 m/s\({}^{2}\). Analyzing Figure 13, which presents the analysis of the vehicle speed in different phases when clearly noticeable steering wheel non-standard vibrations were recorded (marked at the Figure 13), several important trends can be observed related to the conditions of vibration occurrence. First of all, it is obvious that steering wheel vibrations occur at speeds from 40 to 100 km/h, but the highest vibration intensity is observed in the interval 70-80 km/h. This interval may indicate the resonant frequency of the vehicle, when certain components, such as suspension elements, tires, or transmission parts, reach a state in which the vibration amplitudes increase. This is especially important, since resonant vibrations usually cause greater discomfort to the driver and can have a negative impact on steering control. Another crucial factor is that steering wheel vibrations happen more frequently in vehicles speeding or running at a constant speed. This implies that the vibrations are linked to particular dynamic working modes of the vehicle, not random or chaotic. During the acceleration phase (when the speed increases by an average of 2 km/h per second, correspondingly creating an acceleration of about 0.7 m/s\({}^{2}\)), it can be assumed that the engine and transmission are subjected to higher loads, which can lead to an increase in vibrations. Figure 12: Magnitude of the frequency weighting for hand–arm vibration in all directions (based on ISO5349-1 [49]). Keep in mind that the vibrations do not show up all the time; they only become noticeable at certain intervals. This could indicate that the vehicle is experiencing mechanical or structural imbalances that become more apparent at specific speeds. For instance, if the vibrations become more noticeable at 70-80 km/h, it could be because of problems with wheel balancing, uneven tire wear, or even a peculiar resonance in the engine or gearbox. While vibrations in the steering wheel may be annoying at first, they pose a serious threat to the driver's concentration and stamina in the long run. If the vibrations are most  
Figure 13: Analysis of the vehicle speed in phases of perceptible and major driving wheel vibrations (broken down into fragments subject to analysis). noticeable at moderate speeds, they may be something you experience frequently behind the wheel.