# Laboratory Test of a Vehicle Active Noise-Control System Based on an Adaptive Step Size Algorithm
## 4 Laboratory Experiment
### The ANC Experiments
It can be seen from the frequency response diagram that the proposed algorithm has an obvious noise reduction effect in the frequency range of 30-135 Hz, and the noise reduction range is about 3-8 dB, among which the maximum noise reduction effect is near 50 Hz. The overall noise reduction is 2.8 dB in the frequency range of 20-400 Hz. The FxLMS algorithm has a noise reduction effect of 1-2 dB in the range of 30-90 Hz, but the noise is enhanced in the frequency band above 90 Hz. The overall noise reduction is 0.1 dB in the frequency range of 20-400 Hz. Figure 14: Experimental noise reduction effect at 30 km/h over a speed bump. (**a**) The time domain, (**b**) The frequency domain. Working condition 3: The car runs at a constant speed of 50 km/h and passes over the speed bump. The experimental results of the vehicle's internal noise as a reference signal in the second working condition are shown in Figure 16. The time-domain response diagram shows that the proposed algorithm significantly reduces the amplitude of sound pressure after noise reduction, which has a good inhibition effect on impact noise. The amplitude of the FxLMS algorithm does not change significantly before and after noise reduction. It can be seen from the frequency response diagram that the proposed algorithm has an obvious noise reduction effect in the frequency range of 25-140 Hz, and the noise reduction range is about 3-12 dB, among which the maximum noise reduction effect is near 40 Hz. The overall noise reduction is 3.1 dB, in the frequency range of 20-400 Hz. The FxLMS algorithm has a noise reduction effect of 1-2 dB in the range of 30-80 Hz, but the noise is greatly enhanced in the frequency band above 80 Hz. The overall noise reduction is \(-\)0.8 dB in the frequency range of 20-400 Hz. Figure 16: Experimental effect of noise reduction at a 50 km/h constant speed. (**a**) The time domain, (**b**) The frequency domain. Figure 13.0 Experimental effect of noise reduction at a 40 km/h constant speed. (**a**) The time domain, (**b**) The frequency domain. Working condition 4: The car is driving at a constant speed of 60 km/h. The experimental results of the vehicle's internal noise as a reference signal in the fourth working condition are shown in Figure 13.1 The time-domain response diagram shows that the proposed algorithm significantly reduces the amplitude of sound pressure after noise reduction, while the amplitude of the FxLMS algorithm does not change significantly before and after noise reduction. It can be seen from the frequency response diagram that the proposed algorithm has an obvious noise reduction effect in the frequency range of 20-130 Hz, and the noise reduction range is about 3-12 dB, among which the maximum noise reduction effect is near 40 Hz. The overall noise reduction is 3.1 dB in the frequency range of 20-400 Hz. The FxLMS algorithm has a 1 dB noise reduction effect in the range of 40-50 Hz, but the noise is enhanced in the range of 120-140 Hz. The overall noise reduction is \(-\)0.3 dB in the frequency range of 20-400 Hz.