The scientific and technological field of this project is acoustics/noise measurement.

Noise measurement is a necessary step in sound source evaluation and noise reduction. The layout method of noise measurement points should be selected or formulated according to the purpose of noise measurement and measurement conditions. The position and number of microphones and the measurement distance are the most important factors influencing the uncertainty of noise measurement. In today's most advanced technologies and requirements in the field of noise measurement, the arrangement of measuring points is only qualitative and not quantified. It does not clearly define the relationship between the arrangement of noise measuring points and the measurement uncertainty required by its corresponding accuracy level, that is, it does not include noise measuring points. The measurement uncertainty caused by layout factors is quantified and limit requirements are proposed.

This project focuses on the method of determining the layout of noise measuring points based on the mean deviation under the specified measurement accuracy level. By calculating the standard deviation of the average value of sound pressure levels measured at all microphone positions, it can meet the corresponding accuracy level. Uncertainty requirements specified. The uncertainty in sound power level measurement caused by the layout of noise measuring points can be quantified and effectively controlled. Therefore, the uncertainty of noise sound power level measurement results can meet the uncertainty requirements specified by the corresponding accuracy level. For example, for the measurement of Level 2 accuracy level, the position and number of initial noise measurement points are determined according to the accuracy level of noise measurement and the obtained measurement surface, and a microphone is arranged at each measurement point. If the calculation result of the mean deviation of the sound pressure level at the measurement point is less than or equal to 1.0 dB, the measurement results arranged according to the specified measurement points meet the uncertainty requirements of the corresponding accuracy level; If the calculation result of the mean deviation is greater than 1.0 dB, the measurement results arranged according to the specified measuring points cannot meet the uncertainty requirements of the corresponding accuracy level, and the measuring points can be rearranged according to the method given in this project:

The first method is to increase the measuring distance and/or increase the number of measuring points;

The second method is to reduce the measuring distance or not change the measuring distance but increase the number of measuring points.

After rearranging the positions of the measuring points, measure again, and calculate the mean deviation of the sound pressure level at the measuring points until the measured value of the mean deviation is less than or equal to the mean deviation threshold (1.0 dB), then the layout of the measuring points is completed. The above is the main technical content of this project. The technical problem to be solved by the present technical invention is to provide a method for determining the layout of noise measuring points based on the mean deviation. By determining the layout of noise measuring points based on the mean deviation at a specified measurement accuracy level, the uncertainty of the measurement result of noise sound power level can meet the uncertainty requirements specified by the corresponding accuracy level. This technical invention method has applied for an invention patent of the People's Republic of China and was authorized on September 24, 2014. The patent number is ZL201310122447.1. At present, this noise measuring point arrangement method has been widely used in the measurement of engine noise and intake and exhaust noise, and corresponding international standards and national standards have been formulated to provide a basis and standardization for noise measurement related to internal combustion engines. Standards that have been formulated include the international standard for exhaust noise measurement ISO 15619, the international technical specification for intake noise measurement ISO/TS 19425, the national standards for engine noise measurement GB/T 1859.1 (engineering method), GB/T 1859.2 (simplified method), GB/T 1859.3 (semi-anechoic chamber precision method) and GB/T 1859.4 (simplified method using standard sound sources) being developed. The series of standards for noise measurement of internal combustion engines invented and formulated by using this technology fully considers the current situation of noise measurement of internal combustion engines in my country, saves resources, makes noise measurement methods more advanced, scientific and operable, and brings huge economic benefits to the country and enterprises. At the same time, the technical invention method is applied to guide the development of SAIC Motor's independent commercial vehicle V80 and G10 products, improving the NVH performance of the vehicle, improving work efficiency, saving development costs, and contributing to the timely launch of products.