A Study On Automobile Engine Noise Measurement And Psychoacoustic Evaluation System

With the increasing of people's attention paid to vehicle quality,the problem of vehicle noises has getting more and more important. As known that vehicle noises directly affect passengers comfort, has a great impact on the psychological and physical of human beings. Engine noises are important sources of vehicle noises. An evaluation and measurement system for engine noises is developed, which can be directly used in engine noise testing, time-frequency analysis, and psychoacoustical evaluation, in this dissertationBased on the technologies of sound intensity measurement and computer interface, this dissertation made a hardware system and a corresponding measurement software for sound signal acquisition, therefore, completed engine noise acquisition procedure. For removing the hardware and background noises in the acquired signals, this work firstly applied the matching pursuit technology to denoise the vehicle sound signals, and compared with the common used wavelet denoising methods. The results showed that the former method is more effective and reliable than the later one for a vehicle engine noise signal denoising. For analyzing the time-frequency characteristics of the engine noises, this dissertation performed the short-term Fourier transform and the wavelet transform, respectively. The analyzed results suggested that both the methods can accurately express the signal energies flowing in the time-frequency planes. The two methods are equivalent for feature extractions of vehicle engine noises. According to the Zwicker psychoacoustical model, a calculation program for sound loudness, sharpness, and roughness was complied in this work. Furthermore, the objective assessments based on subjective feelings of the vehicle engine noises were performed,and compared with the evatuations by A-weitghting Sound pressure Level and some valuable conclusions were obtained in this dissertation.