For the in-use motor vehicle noise control, the inspector needs to perform roadside noise test in the urban area. Because it is not easy to find a proper test-site that can meet the standard requirement, and the background noise is often too high to do the test. The idea of applying an acoustical sound enclosure cabinet to measure the stationary noise of motor vehicle is proposed in this project. To assess the feasibility of the new test method (Hereinafter refered as sound enclosure cabinet method), this project take the following work items: (1) To setup the geometry parameters, construction materials and target acoustic performance of the sound enclosure cabinet, for the purpose of testing motor vehicle stationary noise. Then setup the test procedure then accessing the feasibility of the new procedure. (2) Compare the difference and the relationship of noise test results between current CNS 5799 method and sound enclosure cabinet method. (3) Review and access the feasibility of using sound enclosure cabinet method to be standard test equipment for measuring the stationary noise of in-use vehicle, and propose some drafts for related regulations. By applying the acoustic simulation analysis of four sound enclosure cabinet models, the better geometric cabinet type was identified and prototyping. The effect of construction materials were evaluated first. And then the interior sound pressure uniformity, interior temperature effect, microphone positions and the connecting tube were reviewed by using the sound enclosure cabinet to measure the stationary noise of four cars and four motorcycles. Moreover, 50 motorcycles were tested in the laboratory and another 4 motorcycles were tested in the practical urban roadside to evaluate the difference and relationship of noise test results between current CNS 5799 and the sound enclosure cabinet methods. The results show good relationship between the two methods. Nevertheless, for some cases the difference will greater than 3dB(A) and we try to review the reason for the particular cases. After design modification, the difference between two methods can be less than 3dB(A), but still need some improvement to be in line with acoustic theory, and to improve the conformity of the two methods. Above research conclusions as regards to the geometry parameters of sound enclosure cabinet, construction material, acoustic performance specifications and their verification procedures were summarized into some drafts and operation procedures. Which can be used as reference of measuring the stationary noise of motor vehicles by sound enclosure cabinet method. And if the assessment of feasibility is possible to apply the method as part of in-use vehicle noise regulation, above drafts can be used as the basis of technical specifications.

In-use vehicle noise control;Stationary noise test;Sound enclosure cabinet