Establishment And Applied Research Of Car Interior Sound Quality Evaluation Model

The popularity of car brings the convenient traffic to people, while its noise also has an increasingly serious impact on people's lives, jobs as well as physical and mental healthy, and has become the major noise source in modern cities. According to statistics, it shows that the traffic noise pollution accounts for 75% in urban environmental noise pollution. When the car exterior noise causes harm to the environment, its higher interior noise is easy to irritate and worry people, and even endanger traffic safety. With the development of science and technology, automobile manufacturers have recognized that the design of sound quality has become a selling point of product, which gradually forms the need for sound quality research of noise. The research of sound quality, on the one hand, performs in how to understand sound quality from the point of subjective perception attribute, and also in how to characterize the evaluation of sound quality from the aspects of physical and psychological acoustics, and get appropriate evaluation model of physical and psychological acoustics. The research is carried on in combination of the key project in Jilin province technology development programs,"The applied research of technology analyzing and evaluating car interior sound quality based on the model of hearing". On the basis of referring domestic and foreign research, the thesis develops an in-depth study on the analysis and implementation of subjective and objective evaluating car interior sound quality, and proves the accuracy, reliability and effectiveness of evaluation model by trial comparing.Firstly, in order to establish the prediction model of people's sound characteristic perception, the thesis discusses the hearing system's perception mechanism on sound, and gives the description of ear hearing mechanics. Then, on the basis of a single-channel hearing model, it summarizes some conclusions of hearing psychoacoustic research, mainly including the most commonly concerned hearing characteristic in psychoacoustic research such as masking effect, critical band and hearing loudness.Secondly, the thesis introduces the basic concepts of four parameters (loudness, sharpness, roughness and fluctuation intensity) used to objectively evaluate sound quality in psychoacoustic research, and gives their mathematical models as well as software design process framework. According to models and design process, the program based on MATLAB to calculate four parameters of sound quality objective evaluation is independently developed. By comparing with Denmark B&K Company's PULSE Sound Quality Software Type 7698 system, the results show that this thesis's independently developed program has higher accuracy and reliability. According to system requirements, based on VB and MATLAB mixed programming, objective evaluation and analysis system of sound quality is developed.Then, several commonly used subjective evaluation methods of sound quality are comparatively analyzed, and a subjective evaluation experiment of sound quality is conducted, choosing pairing comparison and organizing an evaluation team of 20 people. After related analysis and multiple linear regression analysis between subjective evaluation results of sound samples and four corresponding objective evaluation parameters, the mathematical model of sound quality that objective evaluation parameters quantitatively describe subjective evaluation results is established, through a variety of tests. The results show that sound quality is mainly impacted by two objective evaluation parameters of loudness and sharpness, and the role of loudness is more prominent.Finally, the sound quality of tested car interior noise is analyzed and evaluated with the established mathematical model of sound quality, which verifies the conclusion that engine noise is the main source of car interior noise with the main of low-frequency components. Against the weak suction and absorption noise problem of firewall between cab and engine compartment, the passively reducing noise measure of suction and absorption is taken to the tested car choosing ultra-fine glass wool by the experiment of standing wave tube method measuring suction noise coefficient. Through the analysis and comparison of car interior sound quality in different conditions between the sound quality before taking noise reduction to the tested car and the one after, the result shows that after noise reduction loudness and sharpness of car interior noise have significant improvement, and the SQ value of subjective evaluation index is improved about by 14%, so noise reduction measure has yielded satisfactory results to improve, and further proved the effectiveness of objective quantitative model of sound quality which is established in the thesis.