Abstract: Traditional linear acoustic theory assumes that airflow from the vocal folds propagates through the vocal tract as a plane wave. According to Teager’s studies, however, this assumption may not hold true since the vortices are distributed throughout the vocal tract. Based on the nonlinear phenomena, a more popular AM-FM modulation model is proposed by Maragos and it has been successfully used in many fields of speech processing. In this paper, the background of the AM-FM modulation model is firstly introduced, and then its theory is explained. Finally, the applications of the AM-FM model and especially its potential prospect in the stressed speech analysis are discussed in detail.