GB/T 6881.2-2002 in English

《GB/T 6881.2-2002声学 声压法测定噪声源声功率级 混响场中小型可移动声源工程法 第1部分:硬壁测试室比较法》由TC17（全国声学标准化技术委员会）归口，主管部门为中国科学院。
本标准给出的方法能在指定的固定传声器位置或沿指定路径测量倍频程声压级。用比较法确定倍频程声功率级；A计权声功率级可以从倍频程声功率级计算。不能确定的量是声源的指向特性和非稳态发射的噪声源辐射的时间图形。

Scope

This standard specifies a relatively simple engineering method for determining the sound power level of small movable noise sources. This measurement is made by placing the sound source in a hard-walled test chamber and using the comparative method to determine the octave-band sound power level of the sound source. The spatially averaged (octave) sound pressure level produced by the sound source under test is compared with the spatially averaged (octave) sound pressure level produced by a standard source of known sound power output, if the conditions of the two sets of measurements are the same , then the sound pressure level difference is equal to the sound power level difference. The A-weighted sound power level can be calculated from the octave band sound power level. Note: The precise method for determining the sound power level of small noise sources is specified in GB/T 6881.1 and GB/T 6882. 1.2 Types of noise The methods specified in this standard are applicable to the measurement of all types of noise within the specified frequency range, except for intermittent noise including isolated bursts. NOTE 1 See ISO 12001 for the classification of different noise types. 2 For intermittent noise sources, including bursts of short duration, the free-field method specified in GB/T 3767 and GB/T 6882 should be used. 1.3 Noise sources Noise sources can be machines, devices, components or accessories. The maximum size of the sound source to be measured is related to the size of the room used for the acoustic measurement. 1.4 Measurement uncertainty According to the measurement results carried out in this standard, the standard deviation of the reproducibility of the A-weighted sound power level is generally equal to or less than 1.5 dB (see Table 1). The sound power level value of a single noise source determined by the method of this standard may be different from the true value, and the difference is within the range of measurement uncertainty. Uncertainty in sound power level determinations arises from several factors affecting the results, some related to the environmental conditions of the test laboratory and others to the experimental technique. If the sound power level of a specific noise source is determined by this standard method in several different laboratories, the results will show dispersion. The standard deviation of the measured sound power level can be calculated (for example, see GB/T 14573.1--1993 Appendix B), which varies with frequency. These standard deviations generally do not exceed the values listed in Table 1. The values in Table 1 are the reproducibility standard deviations defined in GB/T 14573.1, which take into account the cumulative effect of the measurement uncertainty applied to this standard, but due to changes in operating conditions (such as speed, supply voltage) or installation conditions Except for changes that cause sound power output. The uncertainty of measurement is related to the standard deviation of reproducibility in Table 1 and the required confidence level. For example, for the sound power level of normal distribution, when the reliability is 90%, the true value of the sound source sound power level falls within the range of ±1.645σR of the measured value; Values within ±1.96σR range. See GB/T 14573 and IS0 9296 series for further examples.