This part of ISO 15186 specifies a sound intensity method to determine the sound reduction index and the element-normalized level difference of building elements. The method can be used as an alternative to ISO 140-3 and ISO 140-10 respectively. One important use is when the traditional ISO 140-3 method fails because of high flanking transmission. The reproducibility of this intensity method is estimated to be equal to or better than that of ISO 140-3. NOTE Some information about the accuracy with which this part of ISO 15186 can reproduce the sound reduction index measured according to ISO 140-3 is given in annex A.