"This book applies four relevant concepts in acoustic phonetics and proposes a new approach for assessing the intelligibility of second language pronunciation instrumentally. First, the acoustic phonetic features of L1 and L2 are extracted, compared, and contrasted. Secondly, the acoustic distances between said features are calculated to determine whether or not internal or external masking occurs. Thirdly, well-established and scientifically proven Just Noticeable Difference (JND) thresholds are used to assess degrees of masking. Fourthly, relative functional load (RFL) calculations help to estimate the severity of unintelligibility or lack thereof"--