This volume contains invited and contributed papers presented at the 9th International Summer School "Neural Nets E.R. Caianiello" on Nonlinear Speech Processing: Al- rithms and Analysis, held in Vietri sul Mare, Salerno, Italy, during September 13-18, 2004. The aim of this book is to provide primarily high-level tutorial coverage of the ?elds related to nonlinear methods for speech processing and analysis, including new approaches aimed at improving speech applications. Fourteen surveys are offered by specialists in the ?eld. Consequently, the volume may be used as a reference book on nonlinear methods for speech processing and an- ysis. Also included are ?fteen papers that present original contributions in the ?eld and complete the tutorials. The volume is divided into ?ve sections: Dealing with Nonlinearities in Speech S- nal, Acoustic-to-Articulatory Modeling of Speech Phenomena, Data Driven and Speech Processing Algorithms, Algorithms and Models Based on Speech Perception Mec- nisms, and Task-Oriented Speech Applications. Dealing with Nonlinearities in Speech Signals is an introductory section where n- linear aspects of the speech signal are introduced from three different points of view. The section includes three papers. The ?rst paper, authored by Anna Esposito and Maria Marinaro, is an attempt to introduce the concept of nonlinearity revising several nonl- ear phenomena observed in the acoustics, the production and the perception of speech. Also discussed is the engineering endeavor to model these phenomena.