Research On Active Control Technology Of Sound Quality In The Cab Of Heavy Commercial Vehicles

In the past,domestic commercial vehicles considered less of the sound quality problems in the design stage,resulting in high noise and poor acoustic comfort in the cab.In recent years,as the demand for commercial vehicles continues to increase and the automobile noise regulations are becoming increasingly sophisticated,consumers are increasingly demanding the sound quality of automobiles,especially for drivers who work longer hours,if they are in a highly annoyed environment for a long time,they will be very tired and even have traffic accidents.At present,acoustic design is mainly based on old models,and focuses on lowering sound pressure levels.Traditional passive noise reduction has significant effects in the control of mid and high frequency noise,and the method is simple and stable,but it is easy to cause problems such as excessive quality and cost.The key is that it does not play a good role in controlling the low frequency noise below 200 Hz,especially the low frequency period-order noise caused by the engine.In general,reduction of sound pressure level can not improve the driver's irritability to noise in the car,and active control technology can solve this problem.This article starts from the definition of the sound quality and expounds the influence of the human ear structure on the sound quality.Acquired sound samples in the cab of 6 commercial vehicles and conducted a subjective and objective evaluation test,the correlation between objective parameters and subjective values was analyzed,and a SAGA-BP subjective evaluation model for commercial vehicle cab sound quality was established,the model has high accuracy and speed.In the weight analysis,we pointed out that the objective parameters that have a large impact on the sound quality are the loudness and the A sound level,from which the objective parameters to be improved are determined.Through spectrum analysis of 70km/h sample,it is known that these two objective parameters have large values in low frequency period,thus providing a basis for the active control system to control low frequency components to improve sound quality.Secondly,the loudness and A sound level is mainly influenced by the engine induced low order frequency,and then determine the adaptive notch filter algorithm as control algorithm,Learn the active control single and dual channel algorithms.Based on the strong correlation between the noise peak frequency in the cab and the engine speed,a method of manually calculating reference signal by reading the engine speed is determined.Sub-channel identification ? single-channel and 1-2-2 feedforward dual-channel multi-frequency active control system models are built in Matlab.Determined the sampling frequency,the key parameters of the algorithm,the feasibility of the algorithm was confirmed by simulation analysis.Finally,actual vehicle signal of two channels at deputy driver's left ear and at the head of the rear sleeper under idle and uniform conditions as the model's original desired signal,artificially add a secondary transfer function and give compensation in the reference signal and the sound quality after control was evaluated using the established SAGA-BP sound quality subjective evaluation model.The results show that the frequency at the peak of the two channels has a noise reduction of 7.0-10.7d B and 3.4-6.6d B respectively when simulated by the idle speed and constant speed test signal.The loudness values of the two channels have a maximum decrease of 2.7sone and the minimum is 2.1sone,A noise level has a maximum decrease of 2.5 d B(A),and the minimum is 2d B(A),subjective assessment of irritability levels at the two channels increased by a maximum of 1.6 levels,and subjective assessment of irritability levels increased by a minimum of 1.4 levels.