Research On Improvement Of The Motorcycle Noise Based On Sound Quality Evaluation

With the development of industrial technology of motorcycle and the improvement of people's life quality, there is an increasing focus on the NVH in addition to excellent performance and reliable quality when people choose a motorcycle. The noise problem directly influences the product image and consumer's purchase, so the research on sound quality has attracted great concern by majority of the motorcycle manufacturing enterprises. But the application of academic achievements of sound quality to guiding new product design is not a lot by now.In this paper, numerical simulation method was used to control the noise radiation of muffler to improve the sound quality according to related theory. And other measures such as optimizing the structure of cover were also used to improve the sound quality.The sound intensity test in various operating conditions was carried out, and the characteristic of noise radiation was studied, so the primary factor influencing its sound quality was confirmed and some programs were suggested according to the difference in psycho-acoustic parameters and the frequency spectrum. Then the sound power of cover was tested because it was possible to generate serious regeneration noise. The resonance problem was found as a result of the spectrum array analysis of accelerating signals. Different methods including spectrum analysis, envelope analysis and time domain signal analysis etc were applied to analyze the abnormal sound signal and, at last the abnormal sound was successfully diagnosed. At last some parts of the motorcycle were redesigned to improve its sound quality.Some quick, cost effective and easy implementation projects were adapted according to the above test results, then the target sound sample was discovered and the difference of acoustic performance between them was compared. Many schemes were made which interior structures were improved. The transmission loss was calculated based on the FEM. Compared with the programs on performance, the two improved silencer with better acoustic performance were adapted to be the product sample piece. The restriction analysis of the cover model was completed and some methods such as reinforcement, increasing the thickness and adding setting points were used to increase the natural frequency in order to diminish regeneration noise.The product sample pieces of improved projects were made. And objective and subjective evaluation tests were carried out when acoustic signal was acquired and processed. Statistical test results showed that subjective preference scores of modified schemes were significantly improved. In conclusion, the purpose of improving sound quality was achieved.