CECS21-2000标准中关于混凝土不密实区和空洞检测的数据处理及判断，是建立在声学参数的平均值及标准差在正常范围内的基础上进行的，对于标准差过大或过小时，采用该标准进行判别易导致漏判及误判。通过工程实例的应用，建议CECS21-2000标准明确规定标准差的适用范围，而在标准差过大或过小时依据混凝土等级高低和整个工程的声速范围，采用固定临界值进行判别。

Data processing and judgment on the less dense area of concrete and cavity detection in CECS21:2000 standards, is based on that the mean value and standard deviation of the acoustic parameters is in the normal range. But the judgment from the standard should easily lead to omission and miscalculation if the standard deviation is too large or too small. Through the application of engineering examples, it is suggested that the scope of standard deviation should be defined in CECS21:2000 standard if standard deviation is too large or too small and fixed critical value should be used to judge the defect according to the concrete grade level and sound velocity range of the project.